#1
Well, to start, I'd like to build my own amp; something that can work better for me than anything store-bought.

I do not know much of tube circuitry but I have been reading up on many sites (ax84, Eurotubes, the valve wizard, & end_citizen's amp building resource thread, to name some) and feel confident that I could assemble one with moderate help from people I know, (hopefully some people on here as well) and continuing to gain knowledge via online resources.

On ax84 they strongly recommended their beginner kits, to get experience from working with this sort of thing before attempting something bigger, and while I realize the significance of this I simply can't afford to make a smaller tube amp just for practice. From what I've been told & have read myself tube circuitry appears to be fairly straightforward & simple, (as opposed to solid state and/or digital circuitry) and doesn't take much to yield a good tone. All the while the chance of succeeding may still be slim, I'm willing to still make an attempt. With proper guidance, of course.

So far, for the basic idea of what I was planning, was a bi-amped power section. Originally I wanted to use two 100w Marshall JCM 900 power sections, but I want to use EL34's in one and KT88's in the other (It won't be bi-amped in terms of highs & lows, necessarily, but rather two different tones). I couldn't decide between which of those tubes to use so decided I could use both. I'm not sure about using the JCM 900 schematics, still, (I was only using them because they were readily available online) but really anything that is high gain (that doesn't sound like generic death metal/pop metal or pop rock/hard rock that is too prevalent in today's mainstream)

The price I'm not too concerned about, this is a long-term project. I'm hoping to have it done within a year, and not spend more than USD$1000

I don't want 200w of sound wave rape, per se, (I'm using speakers rated at around 102db) so I was thinking wiring it for 200w, but pulling 2 power tubes (to use 2 instead of 4 for each power circuit) to essentially get 100w with overly-saturated power tubes. Unless there is a simpler way to do it, or if it's impossible altogether, I'm open to suggestions. Though I would like to have the possibility of having 200w (just for fun, of course, since it'd be impractical anywhere else). If possible, I was thinking having a switch of some sort to use either of the power sections (KT88 and/or EL34, to have one of them or both combined). I'm using transformers from Hammond, so I can get whichever I need, hoping to spend no more than 200-300 on them. (for the output transformers, at least)

I also want to put in a reverb, namely one from Evatco, since that's the only place I've found them available.

For the preamp, I want a one-channel high gain pre, with as much EQ control and gain stages as possible. I want the EQ active if enough simplicity permits for a first-time build, but keep in mind I can easily wire anything from a diagram, regardless to whether I know how it works or not.

The chassis is being built for free by a friend who has access to sheet metal & cutting and bending tools.

The head cab I will build myself but that can be worried about later on, right now I'm worried about the layout & wiring.

As I said before I don't know much about this, but I'm determined to build my own amp. Any help I receive will be greatly appreciated, as I have no hope of building this entirely by myself ...


Thanks.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#2
Bump(because I posted this at 1:30 am when nobody was awake) + updates.

After doing more research, I've decided, for the pre, to have 3-4 individual gain stages, each with a gain/volume pot to control the distortion of each, and to drop the tone stack altogether. (unless I can manage to find some sort of active EQ, and add a "flat" switch to bypass it). Or possibly run seperate gain stages (instead of all in series) and run them in parallel? Maybe with a combination of different tubes? Still open to suggestions.

I'm considering something similar with each of the power amps as well. Maybe a gain/volume control for each of them.

& after lurking on other amp building threads, I decided to use Edcor transformers instead of Hammond, with them being much cheaper.


Also, if anybody would be willing to help me out with resistor values & layouts & the like with my overall design (for now I have the schematics from end_citizen's amp building resource thread (which helped a lot, thank you for writing such an informative thread) copied [crudely] into Bancika's DIY layout creater, but will continue to add to it as I learn more on my own & from suggestions)
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#3
Quote by ice condition
Well, to start, I'd like to build my own amp; something that can work better for me than anything store-bought.

I do not know much of tube circuitry but I have been reading up on many sites (ax84, Eurotubes, the valve wizard, & end_citizen's amp building resource thread, to name some) and feel confident that I could assemble one with moderate help from people I know, (hopefully some people on here as well) and continuing to gain knowledge via online resources.

On ax84 they strongly recommended their beginner kits, to get experience from working with this sort of thing before attempting something bigger, and while I realize the significance of this I simply can't afford to make a smaller tube amp just for practice. From what I've been told & have read myself tube circuitry appears to be fairly straightforward & simple, (as opposed to solid state and/or digital circuitry) and doesn't take much to yield a good tone. All the while the chance of succeeding may still be slim, I'm willing to still make an attempt. With proper guidance, of course.


A bold approach, but it can be done if you take it slow.



So far, for the basic idea of what I was planning, was a bi-amped power section. Originally I wanted to use two 100w Marshall JCM 900 power sections, but I want to use EL34's in one and KT88's in the other (It won't be bi-amped in terms of highs & lows, necessarily, but rather two different tones). I couldn't decide between which of those tubes to use so decided I could use both. I'm not sure about using the JCM 900 schematics, still, (I was only using them because they were readily available online) but really anything that is high gain (that doesn't sound like generic death metal/pop metal or pop rock/hard rock that is too prevalent in today's mainstream)



It sounds like you think that hi-gain sounds come from the poweramp. Hi-gain amps get their tone from having very strong poweramps that are not going to saturate. The gain will be mostly generated in the preamp. Also, a bi-amped tube amp seems like a strange idea. You'd have to keep a speaker load on both sections. You'd also have to have 2 output transformers, and a rather large chassis.


The price I'm not too concerned about, this is a long-term project. I'm hoping to have it done within a year, and not spend more than USD$1000

I don't want 200w of sound wave rape, per se, (I'm using speakers rated at around 102db) so I was thinking wiring it for 200w, but pulling 2 power tubes (to use 2 instead of 4 for each power circuit) to essentially get 100w with overly-saturated power tubes. Unless there is a simpler way to do it, or if it's impossible altogether, I'm open to suggestions. Though I would like to have the possibility of having 200w (just for fun, of course, since it'd be impractical anywhere else). If possible, I was thinking having a switch of some sort to use either of the power sections (KT88 and/or EL34, to have one of them or both combined). I'm using transformers from Hammond, so I can get whichever I need, hoping to spend no more than 200-300 on them. (for the output transformers, at least)



First off, four KT88s will be producing closer to 200w than 100w. Also, 200w is only 3db louder than 100w. You'll just have more headroom at 200w. This will make it quite hard to overdrive your power section. Your price range seems to be close for 1 amp. With a second power section, you'd be cutting it quite close.



I also want to put in a reverb, namely one from Evatco, since that's the only place I've found them available.


You seem to be complicating a complicated design. All these features would be quite time consuming for someone with a lot of experience to get right. For you, I think it'd a frustrating ordeal.


For the preamp, I want a one-channel high gain pre, with as much EQ control and gain stages as possible. I want the EQ active if enough simplicity permits for a first-time build, but keep in mind I can easily wire anything from a diagram, regardless to whether I know how it works or not.


One channel is definitely the way to go. High gain on your first build would be a difficult challenge, but if you have some friends with experience and take it slow, this part can be done.


The chassis is being built for free by a friend who has access to sheet metal & cutting and bending tools.

The head cab I will build myself but that can be worried about later on, right now I'm worried about the layout & wiring.

As I said before I don't know much about this, but I'm determined to build my own amp. Any help I receive will be greatly appreciated, as I have no hope of building this entirely by myself ...


Thanks.



Bottom line, you seem to have a lot of ideas. I'd strip away the pioneering ones, and get down to bare essentials on your first amp.

I'd suggest 2 KT88s for around 100w of power. No reverb, and a simplified version of the JCM900.

Side note: I don't enjoy telling people to simplify their designs. It's just that I recently rebuilt my second amp. I know much more now than I did when I built it. Some of the things I did were just dangerous. Now I have a better sounding and safer amp.

You can leave some empty chassis space to maybe add in your reverb and second power section later. Right now, just focus on building an amp.
#4
Quote by end_citizen
It sounds like you think that hi-gain sounds come from the poweramp. Hi-gain amps get their tone from having very strong poweramps that are not going to saturate. The gain will be mostly generated in the preamp. Also, a bi-amped tube amp seems like a strange idea. You'd have to keep a speaker load on both sections. You'd also have to have 2 output transformers, and a rather large chassis.


I know they use mainly preamp distortion, but that was just an idea about using power amp distortion as well. Just an idea inspired by looking up EVH's tone from mainly power tube distortion & some preamp tube distortion.

I have the speaker load, (using two sets of 8ohm speakers, essentially two 4ohm loads)

The chassis I'm limiting only to the size of the top of my 4x12, minus an inch or so on either side for the head cab.


First off, four KT88s will be producing closer to 200w than 100w. Also, 200w is only 3db louder than 100w. You'll just have more headroom at 200w. This will make it quite hard to overdrive your power section. Your price range seems to be close for 1 amp. With a second power section, you'd be cutting it quite close.


Yeah, I see now ...
two KT88's like you suggested seems good, I'll leave room to put in the other power section later on if I still feel the need to.

I can go without the reverb, eventually I want to put it in but I see what you're saying.


So, simplified version of JCM900 driven by two KT88's?
(I'm not positive about using the JCM900 just yet, I'm still considering my options with other amp models, in terms of what will sound the best & being the most simple)


EDIT: I have found a schematic for a Marshall JMP 2203 , and think if I simplified the overall design a little bit (take out the low-gain input, and the tonestack, and left it with the 3 ECC83's & add a simple volume control to the end of the 2nd gain stage) it would work out well for my purpose ... and leave me with room in my overly large chassis to add a multitude of things as I gain more experience.

If I can make it out, I don't think it would be too hard to follow ...
any other suggestions to make it simpler?
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
Last edited by ice condition at Jul 27, 2010,
#5
Okay, another bump.

Since tube circuitry is all seemingly continuously mod-able & you can always add on things, I was considering giving in to ax84.com and building one of their kits, and adding on to it (more gain stages, bigger power section, reverb, etc.)

So, to save money (since I have limited funds), I was thinking about making my own turret board (since it's $20 less if you use your own) by putting rivets onto some sort of plastic or cardboard.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#6
it IS continuously modifiable, but only to some extent. it will be quite messy to add more gain stages, it will be quite messy to change quite a bit of the circuitry. changing resistor values and capacitor values will be easy. however, changing the layout is quite difficult and messy. i would at least come up with a block diagram, something like gain stage 1, volume, gain stage 2, volume 2, gain stage 3, tone stack, gain stage 4, master volume, phase inverter, dual KT88 power section.

something like that. i would strongly suggest adding at least a voltage divider between gain stages, or a volume control since things get out of hand easily with a high gain amplifier. it's fairly easy to get a nice warm clean tone from a DIY tube amplifier. it's not too hard to get distortion out of it too. however, to get a "high-gain" metal sound out of a DIY tube amplifier, it's not that easy. when things aren't good "enough", sound gets fuzzy, fizzy, flabby, unclear, etc. at least add a slot for a voltage divider/trim pot to give yourself some room to put them in. if you just want it full blast, you can just bypass it anyway.


i would agree that the 2203 design would be very nice for your design. three gain stages and a cathode follower. i think it'll be great as far as stability of the overdrive goes. or maybe even gut out the SLO preamp and stick it in there? your possibility (at least for now) is endless. here are some of the "classic" amplifiers designed to amplify a signal with distortion (and clean for some):
-Marshall JCM800 2203
-Soldano SLO 100
-Trainwreck Express
-Dumble "Overdrive Special"


just examples. those amps are all push-pull amplifiers with a long tail phase inverter, so you might wanna see the differences/similarities in those amps. also, i think the JCM800 goes gain gain gain gain CF tone, SLO goes gain gain gain tone with a crazy buffered effects loop, wreck goes gain tone gain gain, and the dumble goes gain tone gain gain gain tone for the OD channel.


if you see the marshall, it drops a lot of volume after a gain stage, before it hits the next one. a 470k resistor before the 1M volume pot makes the HIGHEST point on the pot only 2/3 of the max output from the stage before. 470k/470k network after the second stage cuts the volume in half (except for highs that are bypassed by the cap).

if you see the SLO, od channel has a 470k resistor before the 500k pot to cut the max volume to half, 470k/1M network after the second stage to cut the volume in 2/3, etc.

wreck doesn't have a noticeable voltage divider in the signal path. this makes the amp go out of control if it isn't assembled and played right.

on the dumble, before it goes into the OD channel there is a trimmer that controls how much gain goes into the OD channel. surprisingly, the full output is about 1/25 of what comes out of the previous stage. on the lowest setting, it's 0.6% of the original signal. theres other stuff going on there, but u get the idea.


make enough room in the amp so it can be modified. i was so sad when i fabricated my board to only fit a few things on it. i wish i made my board a bit compressed, so i can add more components on it if i needed to.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#7
Quote by ECistheBest
it IS continuously modifiable, but only to some extent. it will be quite messy to add More gain stages, it will be quite messy to change quite a bit of the circuitry. changing resistor values and capacitor values will be easy. however, changing the layout is quite difficult and messy.


Well, I was figuring all of that, too, of course. If it was anything that required too much off a change I'd just scrap the original and redo that whole part completely.

Quote by ECistheBest
i would at least come up with a block diagram, something like gain stage 1, volume, gain stage 2, volume 2, gain stage 3, tone stack, gain stage 4, master volume, phase inverter, dual KT88 power section.


That's what I was thinking originally too, but now I'm wondering how 2 separate cascaded gain stages would sound, i.e.,


/gain stage 1, volume, gain stage 2, volume\>master volume
\gain stage 1, volume, gain stage 2, volume/


basically: (from left to right) in, then the signal splits into two paths, essentially being two separate, cascaded (V1, volume, V2, volume) gain stages. Then, a master volume for both of those. After that, then either another gain stage, or to the phase inverter/power section.


Something similar to a two channel amp, maybe? Except all in one channel. I only say this because of how much V1 contributes to the tone, so, why not have two V1's, and two V2's to match? (but using different V1's in each 'channel', to color tone accordingly with them. I was thinking either 12AX7/12AU7, or 12AX7/EL84 combo's.)

I know this is probably overly complicated for a first build, but keep in mind I'm taking this slow, spending a lot of time on laying out & planning, and am using a HUGE chassis (approx. 28x13x3).


As for those amps you mentioned, what I got out of it was that unless you have the voltage divider after each gain stage, it'll have a ridiculous amount of distortion and basically just sound terrible (if not destroy your amp & such altogether). Which is why you need to be careful with the Wreck because it has no voltage divider and could go out of control?

Though all the other amps have the tone stack after 2-3 gain stages while the Wreck has it after the first (so it might not need that, necessarily? or at least the manufacturers didn't think they would) whereas (except the clean channel on the Dumble) they have it 2-3 gain stages after, (with each gain stage having a voltage divider) so it has less output (and therefore less of a chance of something bad happening)


So, with that information, were you suggesting I use a trimpot to change the voltage or just use something like a resistor to keep it at a fixed resistance? Whichever would work out better for me. (keep in mind I just keep my settings on max all the time, and use a high gain tone all the time).
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#8
Quote by ice condition
That's what I was thinking originally too, but now I'm wondering how 2 separate cascaded gain stages would sound, i.e.,


/gain stage 1, volume, gain stage 2, volume\>master volume
\gain stage 1, volume, gain stage 2, volume/


basically: (from left to right) in, then the signal splits into two paths, essentially being two separate, cascaded (V1, volume, V2, volume) gain stages. Then, a master volume for both of those. After that, then either another gain stage, or to the phase inverter/power section.
it would work, and i think it would be cool. BUT you won't get all the gain you want with this. for a metal guitar, i'd say you might want 3 gain stages... two would work, but JCM800 had two gain stages in the low input. two gain stages = plexi, as far as the number of gain stages go. for a metal amp you want, i'd suggest 3 cascaded gain stages, and option to add another one in either parallel (first stage would be cool like a '57 twin) or cascade it like a JCM800's input stage.


Something similar to a two channel amp, maybe? Except all in one channel. I only say this because of how much V1 contributes to the tone, so, why not have two V1's, and two V2's to match? (but using different V1's in each 'channel', to color tone accordingly with them. I was thinking either 12AX7/12AU7, or 12AX7/EL84 combo's.)
i think this is a two channel amp. you mean you're going to blend the outputs somehow? and it's fairly difficult to match a 12AU7 and an EL84 at the output.

I know this is probably overly complicated for a first build, but keep in mind I'm taking this slow, spending a lot of time on laying out & planning, and am using a HUGE chassis (approx. 28x13x3).
well, that might be TOO big. but it's your call.


As for those amps you mentioned, what I got out of it was that unless you have the voltage divider after each gain stage, it'll have a ridiculous amount of distortion and basically just sound terrible (if not destroy your amp & such altogether). Which is why you need to be careful with the Wreck because it has no voltage divider and could go out of control?
basically, yes. you need some gain dump (voltage divider) because if you don't, overloading it just sounds like square wave, and you're not making a fuzz pedal. you're making an awesome amplifier here. I messed up on the design of my amp to forget to incorporate this. i'm suggesting you don't. they can be a 500k trim pot though, after each channel, and you can set it accordingly. you'd want at least one volume control though, so you can fiddle around with it when you feel like more/less distortion. overloading the grid on a tube doesn't blow it up though.

Though all the other amps have the tone stack after 2-3 gain stages while the Wreck has it after the first (so it might not need that, necessarily? or at least the manufacturers didn't think they would) whereas (except the clean channel on the Dumble) they have it 2-3 gain stages after, (with each gain stage having a voltage divider) so it has less output (and therefore less of a chance of something bad happening)
wreck has the tone stack right after the first stage yes. it's not like it's crazy though. some amps have it after the first stage, like the fender blackface amps. they had that. i think for your application, you might want a few gain stages before the tone stack to make it a bit more useful.


So, with that information, were you suggesting I use a trimpot to change the voltage or just use something like a resistor to keep it at a fixed resistance? Whichever would work out better for me. (keep in mind I just keep my settings on max all the time, and use a high gain tone all the time).
trim pot would be cool, if you can fit it on the board. they're small, just be careful with the eyelets. since you keep settings on max and use a high gain tone all the time, you can just adjust the trimpot the first time you use it, then forget about it and crank it away. however, i might think you'd start fiddling with the tonestack more after you make this amp. cause honestly, you can do so much with your OWN amp. that's why i love it.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#9
There is a VERY good reason why virtually every person with experience building amps recommends starting with a very simple circuit. It's because building an amp goes exponentially beyond understanding how the circuit works. There are a number of facets to amp building that only come with experience, some of which are troubleshooting issues (and there WILL be issues) and tweaking for tone/response.

Starting with a simple design may seem like an unnecessary expenditure, but imagine dumping what will probably end up being well beyond $1k into a circuit that is highly complex for a first build, and having issues that are well beyond the scope of your current level of comprehension render the amp useless. Hopefully this doesn't happen, and I'm not doubting your capabilities which may be great, but tackling something as complex and as likely to be extremely temperamental as you are proposing may prove to be an exercise in total frustration as well as a waste of money.

Want a great challenge? Take something like the ax84 Hi Octane and design your own layout. Don't buy the kit, just print out the schematic and BOM and source all parts yourself. Design and build your own turret/eyelet board(s). Plot out the lead dress yourself. Use only the available schematic and BOM, and do it your own way without referencing ax84 layout guides and docs. That will likely prove to be a HUGE learning experience in more ways than I can mention here and won't be so complex that you will throw your arms in the air at issues that may crop up. They have a great forum and know the amp, so you can consult them if need be.

Just my 2 cents, take it for what it is. Good luck with whatever you decide on! Have fun!
#11
If you do go the three gain stage route, you can always change the bias point of the gain stages so that you alternate between hot and cold. This will clip one side of the signal a lot more than the other, which leads to the higher gain sound.
#12
Quote by ECistheBest
it would work, and i think it would be cool. BUT you won't get all the gain you want with this. for a metal guitar, i'd say you might want 3 gain stages... two would work, but JCM800 had two gain stages in the low input. two gain stages = plexi, as far as the number of gain stages go. for a metal amp you want, i'd suggest 3 cascaded gain stages, and option to add another one in either parallel (first stage would be cool like a '57 twin) or cascade it like a JCM800's input stage.


Maybe something like this then?

signal A/gain stage 1, volume, GS2, v2, GS3, v3\>volume>
signal B\gain stage 1, volume, GS2, v2, GS3, v3/

(Signal a & b are both on the input of the amp (mono))

Possibly an on/on/on switch to switch between the top(a), bottom(b), or both signals? Something like having a two-channel amp where you can combine both of them? Though honestly I think I would stick with both most of the time, the added versatality could always come in handy for whatever reason. I'm sure this is only complicating the actual build, but I know I can handle it as long as I take it slow

i think this is a two channel amp. you mean you're going to blend the outputs somehow? and it's fairly difficult to match a 12AU7 and an EL84 at the output.


Two channels merged together to make one great one

As for the 12AU7 and EL84, I meant using them both as preamp tubes. For now I will stick with ECC83/12AX7's in the pre, KT88's in the power to keep things simple.

well, that might be TOO big. but it's your call.


As long as it fits neatly on my cab, it's fine with me. I want to add a reverb, and then maybe double that whole circuit (the pre we're working out, dual KT88 power, spring reverb) at some point


basically, yes. you need some gain dump (voltage divider) because if you don't, overloading it just sounds like square wave, and you're not making a fuzz pedal. you're making an awesome amplifier here. I messed up on the design of my amp to forget to incorporate this. i'm suggesting you don't. they can be a 500k trim pot though, after each channel, and you can set it accordingly. you'd want at least one volume control though, so you can fiddle around with it when you feel like more/less distortion. overloading the grid on a tube doesn't blow it up though.


A trim pot sounds like the way to go then, instead of fiddling with different value resistors to get the right sound.

wreck has the tone stack right after the first stage yes. it's not like it's crazy though. some amps have it after the first stage, like the fender blackface amps. they had that. i think for your application, you might want a few gain stages before the tone stack to make it a bit more useful.


I get it now. Though after reading some article about utilizing your guitar's and the tubes without the tonestack makes for a much fuller sound, if I do incorporate one it'll have a "flat" (bypass) switch.


Quote by CECamps
There is a VERY good reason why virtually every person with experience building amps recommends starting with a very simple circuit. It's because building an amp goes exponentially beyond understanding how the circuit works. There are a number of facets to amp building that only come with experience, some of which are troubleshooting issues (and there WILL be issues) and tweaking for tone/response.

Starting with a simple design may seem like an unnecessary expenditure, but imagine dumping what will probably end up being well beyond $1k into a circuit that is highly complex for a first build, and having issues that are well beyond the scope of your current level of comprehension render the amp useless. Hopefully this doesn't happen, and I'm not doubting your capabilities which may be great, but tackling something as complex and as likely to be extremely temperamental as you are proposing may prove to be an exercise in total frustration as well as a waste of money.

Want a great challenge? Take something like the ax84 Hi Octane and design your own layout. Don't buy the kit, just print out the schematic and BOM and source all parts yourself. Design and build your own turret/eyelet board(s). Plot out the lead dress yourself. Use only the available schematic and BOM, and do it your own way without referencing ax84 layout guides and docs. That will likely prove to be a HUGE learning experience in more ways than I can mention here and won't be so complex that you will throw your arms in the air at issues that may crop up. They have a great forum and know the amp, so you can consult them if need be.

Just my 2 cents, take it for what it is. Good luck with whatever you decide on! Have fun!


Your Hi Octane idea sounds good, especially if it would be practical to build the amp I've been planning off of here on to it, and using the high octane as a base.


Quote by XgamerGt04
If you do go the three gain stage route, you can always change the bias point of the gain stages so that you alternate between hot and cold. This will clip one side of the signal a lot more than the other, which leads to the higher gain sound.


What if I followed the new plan in this post (with 3 gain stages) and biased them how you suggested?


Quote by forsaknazrael


Well, what I'm planning is something quite different. The reason I had mentioned JCM 800's, 900's, 2203's and the like previously was only to use them as a base to work off of and build my own amp. Something that doesn't sound like every other guitarist and will make me stand out more with a distinct tone (hopefully )
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#13
OKAY!

For the EQ, I found this:

http://www.angelfire.com/electronic/funwithtubes/images/Amp-Tone-6-A-A.gif

Which is on this page:

http://www.angelfire.com/electronic/funwithtubes/Amp-Tone-A.html
(scroll down to "Three Band Tone Control? Maybe.", it's a little more than 3/4 down the page)

So, I was wondering, to make it into the 10-band EQ, do I just keep adding tubes to the bottom part of the circuit (off of more pots) before it gets to that last tube, and change cap. values accordingly to finish it?

I was thinking either a 9- or 10-band eq (9 because I would need one less tube), after all the gain stages (since it's active and wouldn't take away from volume i'm assuming) or add a 4th gain stage after it.

I was also thinking about modding my wah (just a simple crybaby) and changing the transistors out with tubes, and putting that circuit inside of this amp and using the wah pedal to control it (as opposed to keeping the circuit inside of the pedal). Any input on the practicality of that would be appreciated.

Of course, to start, I'm just doing a simple 3 gain stage pre + push-pull KT88 output, and continuing to build off of that. Unless I'm confident after planning everything out, that I can successful do it all at once.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#15
I'm just brainstorming right now ...
When I get to the build I'm not going to rush in to a million things that I won't be able to finish. It'll be added in later on once the simple regular amp is finished. That's why I'm getting such a big chassis, so there's plenty of room to add things in as I go.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#16
Okay, well, I have about $200, that's about enough for the tubes and the power transformer ... not including shipping. I still need the output transformer, tag board, tube sockets, caps, resistors, etc.

So, while I get the rest of the money I may as well start deciphering these JCM 800 schematics from drtube.com

JCM800 preamp section:
http://www.drtube.com/schematics/marshall/jcm800pr.gif

JCM800 power section:
http://www.drtube.com/schematics/marshall/jcm800pw.gif

Now, for the power section, I want to get 100w out of two KT88's, would I just replace the 50w transformer with a 100w transformer, (and change bias, maybe?) and proceed with the rest of the wiring as shown? Or would I need to make something completely different.

For the pre, what would I need to change to make that a one-input amp? Or could I just use one jack with an on/on switch to change between high- and low-gain?


I also have a question about power transformers,
Do you need one for the whole amp, or one each for the pre/power?
Later on I'm hoping to add in another pre (exactly the same as this, and put it in parallel with this), would I need a separate power transformer? or can I just use the first?

The KT88's I'm getting from Eurotubes handle about 700v, whereas the 12AX7's handle about 300v, do I need a 700v AND a 300v transformer? or can I just use a 700v with a separate 300v out?

Please don't take me as a noob and be like GTFO LEARN YOURSELF, I've been all over the internet and can't figure that one out. Everything else has made sense so far & I think this will turn out pretty well.

Also, if I'm posting too much with bumps, it's only 'cause I'm desperate for feedback about my ideas.
Quote by Steve46
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#17
Not GTFO you n00b but I think you need to seriously reconsider your project and scale it down a lot. The questions your asking are kinda basic and show you don't have much experience with this stuff.

I really suggest you start with something simpler. Maybe a cool SE design.
#19
Well, say I started out with a single-ended design, later on would it still be practical to change it out with a push-pull output?

Could I still use the JCM 800 preamp?
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#20
Quote by ice condition
Well, say I started out with a single-ended design, later on would it still be practical to change it out with a push-pull output?

Could I still use the JCM 800 preamp?
This seems like a bad plan to me. Adding another output tube and a phase inverter isn't all that bad, if you reserve enough real estate on the chassis in the initial design. It's a bit silly, but possible. But changing iron is expensive. And unless you build ANOTHER amp for the SE OT, you're wasting money. A sizable chunk of money. Not to mention the chances of the two transformers mounting the same are unlikely. So more machining on the chassis.

imho, you're best off to decide what you want for your power supply and output section and stay with that. If you wanna punch some extra holes for 9pin tube sockets and install covers so you have some options at a future time, that seems reasonable. Changing your preamp architecture or even changing between cathodyne and LTPI is not unreasonable. But changing from SE to PP is.
Meadows
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#21
So, are you saying I should stick with the JCM 800 plans? At least, with the push-pull output?

I understand how it works, in a basic sense, at least ... I still have plenty of time before I start the actual wiring.

The out of the preamp goes into the phase inverter, which gives the power tubes an uneven amount of input, causing one to push power into the transformer, while the other pulls from the output transformer. By doing that, it significantly increases efficiency compared to a single-ended output.

The chassis I can get punched to have all the components I need to (My friend at a tech school is making it for me) which is the reason why I want to have everything planned out (the preamp, power amp, reverb, 10-band EQ, etc) so that I can have the chassis punched for that so I don't have to keep bringing it back.

It's being made out of sheet metal, the kind they use on air ducts (my friend is in HVAC) if just drilling into it would be suitable, I could do it myself, too. Only for the sake of not putting a million holes in it that I can't end up using.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#22
Quote by ice condition
So, are you saying I should stick with the JCM 800 plans? At least, with the push-pull output?
I'm not saying that at all. If this is your first build, you might be much better off with the simplicity of a SE design. I'm saying don't plan to change that part later, in this amp. You can always build more amps.

If you build a modest little SE amp first and build a big push-pull later, you haven't wasted anything in the first build. It's still there. It still works. And you learned something.
Meadows
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Quote by SK8RDUDE411
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#23
i agree with that too. make a simple 2~4 tube single channel amp, then next amp maybe go big if you succeed on the first amp.
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#24
mm, yeah, maybe. That's starting to sound like a better idea.

The only thing is the money, I'm relatively POOR and don't have much income. As SYK said, Changing Iron is expensive.

Maybe, If I get a PP transformer, could it be used the same way a SE is?
Quote by Steve46
thanks alot ice condition!! your the breast!


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#25
Its possible to use a Push-Pull output transformer as a single ended transformer, but it requires more circuitry. A single ended transformer will always have a "high" current flowing through it relative to the net current flowing through a push pull transformer. This is why if you had two identical transformers except for them being push-pull or single ended, the single ended transformer would be much larger.

In order to use a Push-pull transformer in a single ended design, you have to minimize the net current flow in the transformer. One way that you could do this is to use a transistor current mirror that receives its bias current from the power tube, and then draws current from the second tap of the transformers. The only problem you will have with this is that the transistor pulling current from the transformer needs to be rated for the same power dissipation as the power tube that you are using, and its better if you use a much higher power dissipation as it will cause the transistor to be more linear overall.

So is it possible? Yes. Is it practical? Depends on if you believe having transistors in your amp will ruin the sound. The other thing that you will see with this. It also limits you to biasing the power tube via a negative voltage at the grid, fixed bias, and not a cathode resistor.
#26
Quote by XgamerGt04
In order to use a Push-pull transformer in a single ended design, you have to minimize the net current flow in the transformer. One way that you could do this is to use a transistor current mirror that receives its bias current from the power tube, and then draws current from the second tap of the transformers. The only problem you will have with this is that the transistor pulling current from the transformer needs to be rated for the same power dissipation as the power tube that you are using, and its better if you use a much higher power dissipation as it will cause the transistor to be more linear overall.


So, I'm using the transistor to limit how much output the transformer would have? Essentially lowering it down enough to be used with only one tube?

I'd probably have to lower it by half, right? a KT88 trying to do 100 watts wouldn't last too long ....


If I have to go through all that, would it be THAT much different from just doing it in push-pull? Especially with trying to find a transistor capable of that?

Would it be more/less expensive?

What do you think I would be better off doing?
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#27
Its not really using the transistor to limit the power that you get, its using the transistor to balance the net current flow in the transformer. You won't get 100 watts out of 1 KT88.

You could get up to 42watts with 1 KT88, but your going to need a transistor that can dissipate 42watts of power at least, and it'll be better to get higher than that.

The difference between the two possibilities is that you will have to have a phase inverter in a push-pull amp where as in a single ended amp you do not.

Building a smaller, simpler Single Ended amp first is a good way to get started, that is not to say that given the time and effort you would not be able to build a more complex one. But you don't learn some of the nuances of building amps when you try to dive in head first. An 18 watt Marshall style amp would not be a bad first build project, and many people have successfully done that, but to try to make a very high gain amp with a push pull output section your first time is likely to end up pretty bad.

A high octane kit from AX84 is a good place start honestly. For less than 300 dollars you can get a nice 5 watt amp that sounds quite good too. Its a great place to start. You couldn't make it a push-pull amp without spending a lot of money though. You could also get an 18watt kit and change some of the cathode resistors on gain stages to get a sharper sound out of it. My first build was one of the ax84 P1 amps. I blew a transformer the first time because I was in a hurry to get everything done and shorted the heater wiring. Now, a few years later and a number of other builds, I can build just about anything I want to, when money permits. I learned a lot from that P1 build that just reading up on things wouldn't have taught me. You can't learn how to wire an amp very tidy from reading, it comes with practice.
#28
So, then, is it just going to be a SE-PP hybrid, that uses a transistor as the second tube? It doesn't require a phase inverter because the transistor and tube are already unbalanced?

What If I just focused on building a tube-powered preamp then? (Well, more of an overdrive/distortion pedal, I suppose), but I already have a 100w solid state paging amp that my sound engineer rewired to work as a power amp for instruments, there is SOME room, I'd say enough to fit 3 preamp tubes and a power transformer ... even if it would be a little cramped.

I only have one pic:



It's at my bassist's house, so I can't take pics of it right now ... I'll try to within the next week when we have practice.

The chassis is 5 rack spaces tall, and approximately 2-3 inches deep. It has two huge transformers on the back (only one of them is in use, if I HAVE to it can be removed, I think, I'd rather keep it for looks though ) and there is room where the original in's and out's were (screws mounted on fiberglass tagboard).

I'm thinking only something very basic, of course, 3 gain stages(that's not too complicated, right?), no tonestack, (maybe some trim pots on the inside to change gain accordingly) and a volume for the pre, and one for the power amp (on a concentric pot to replace the original volume in the top left corner)

Would doing that be a better alternative to trying to build a whole big amp?
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.
#29
OKAY
another idea. My bassist is getting a new amp, because he has money and I don't. So, he's giving me his power amp. It's a 250w paging amp (similar to the one above, but it's about 25 lbs heavier and has rows of heat sinks on the side of it's perforated steel chassis that like to cut your hands open, also rewired to work as an instrument power amp) SO, guitarfetish has this guitar 'preamp'

http://store.guitarfetish.com/Guitar-Preamp-GainBassMidTreble-Our-Best-Unit_p_411.html

Right now, the Bogen (bassist's old power amp) just has a single volume knob. Could I put that directly in, before the power section, and it would work fine? Could anyone help me come up with a simple tube based high gain preamp? (and use the guitar fetish pre as the tonestack) that I could put in there (there's much more room in this one). Also, I have a Boss Metalzone (yeah, yeah, don't laugh.) are the Keeley mods worth it? Would it be a decent substitute to building a power amp? It's $75, worth it? Would a tube pre from scratch be more/less? I have $140, that's my budget for now.
Quote by Steve46
thanks alot ice condition!! your the breast!


The best bosom in all of UG.