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#1
So I decided to build an all tube amp that is small (1 watt) with an equalizer and relatively clean so that I can run my pedals in front of it. I admit that I did use the blackheart as a guide and that my schematic is not perfect... yet... still in prototyping. This is the original. Rev 1 should have a headphone jack and a switch to change between headphones and the 12" celestion I am going to run with it. Comments and suggestions welcome. Also... What am I going to name this sucker?


By bobdahaxor at 2008-08-03

I know I forgot the 6.3v Heater filament.... I'll get to that too
#2
Looks good. You could put in switches on the caps going to ground on the preamp tubes to allow further adjustment of the gain. I forget what they are called, it has been awhile since I looked at an amp schem. Just lifting the ground of those caps will decrese gain and help clean things up a bit and lower some volume. Even one watt cranked can be a touch loud for bedroom practice at times. Also, the power supply might need some more filtering.
#4
Quote by PainIsPower
Looks good. You could put in switches on the caps going to ground on the preamp tubes to allow further adjustment of the gain. I forget what they are called, it has been awhile since I looked at an amp schem. Just lifting the ground of those caps will decrese gain and help clean things up a bit and lower some volume. Even one watt cranked can be a touch loud for bedroom practice at times. Also, the power supply might need some more filtering.



Do go into greater detail. I can be rather retarded at times. Now is one of those times. I follow you and yet don't at the same time.
#7
won't it be not clean at all if its 1 watt?
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#9
Quote by ESP_Shreder
Do go into greater detail. I can be rather retarded at times. Now is one of those times. I follow you and yet don't at the same time.


He is talking about using a bypass cap over r11.
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#10
name it GERALDINE
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#12
Quote by Sam_Prillaman
won't it be not clean at all if its 1 watt?


This is true.. well kinda.... I want it to be super soft.... So at my super soft volumes, It'll be clean, but still have a tube tone since it is 1 watt. Now if cranked.... Then it'll bring in some distortion!

Rev 1... Now it's all in ExpressSCH and I added the bypass cap over r11


By bobdahaxor at 2008-08-04
What are your feeling son those names... btw
#14
This seems like a very cool idea.
I hope it sounds good.
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Quote by handbanana
wiliscool is just plain dumb
#15
Headphones and tube amps are two words that should NEVER go together.

You can add cathode bypass cap switches. Maybe use and On Off On SPDT with a 0.68mF (Marshall) and a 25mf (Fender) with the centre being bypass. Many companies do this and label the switch as a voicing switch. It doesnt affect gain as much as your cathode resistor but can really change your sound.

As your signal moves towards the output the harder it is to change it so to speak. If you did want to do a mod like this you would want it on the first triode's cathode.
#16
Quote by -MintSauce-
Why bother with a headphone switch? Can't you just use a stereo socket somehow, to make it switched?


This is true....Never thought of that! I guess that'll be another project.

Quote by kurtlives91
You can add cathode bypass cap switches. Maybe use and On Off On SPDT with a 0.68mF (Marshall) and a 25mf (Fender) with the centre being bypass. Many companies do this and label the switch as a voicing switch. It doesnt affect gain as much as your cathode resistor but can really change your sound.


What would this be for? To reduce the output or what?

That and for some reason I am partial to dethamator. Do I smell a dethklok reference? I am thinking a dethklok name based amp would be sick.
Last edited by ESP_Shreder at Aug 4, 2008,
#17
Quote by ESP_Shreder
This is true....Never thought of that! I guess that'll be another project.


What would this be for? To reduce the output or what?

That and for some reason I am partial to dethamator. Do I smell a dethklok reference? I am thinking a dethklok name based amp would be sick.


Haha, yes! .. even if it's just the Dethamp.
#18
Deathamator sounds like you're saying decimator with a lisp
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Quote by handbanana
wiliscool is just plain dumb
#19
Quote by ESP_Shreder
This is true....Never thought of that! I guess that'll be another project.


What would this be for? To reduce the output or what?

That and for some reason I am partial to dethamator. Do I smell a dethklok reference? I am thinking a dethklok name based amp would be sick.


It boosts certain frequencies. A 25uF bypass cap reduced compresson and gives you a more open tone. Changing to a marshall style .64uF cap will boost upper midrange and treble while compressing the bass and lower midrange.

Oh yeah... You drew that added cap to R11 wrong. It's supposed to be parallel with the resistor not in series.
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#20
Rev 2.... with the r11 drawn correctly

By bobdahaxor at 2008-08-04

I am thinking the dethamp too.

What would a Mesa voicing be? ~33uF?

My retardedness is kicking in again as always.... I seem to be able to draw the schematic using others as basis, but I am new so bear with me. Would I put the voicing right after R3?
#21
Call it the Tiny Te.... the Little Gi....

How about the Baddest One Watt Motherf--er?
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#22
Your revision still shows the cap in the wrong spot. It is still in series, just moved to a different spot on the schem. Your voicing switch would be after C2, and you would put another cap in there right beside it. The switch would just control which cap went to ground, or if none did. Also, just as a Q, do you have any experience with building anything electronic before? such as a pedal or another amp? I can see you have been around for awhile but I don't spend too much times on these forums so am not too familiar with everyone. Also, I still don't understand what is going on with your input, namely C1 and R1. Looking at it now also, your EQ is going to eat alot of signal and you might end up with trouble distorting anything after it. Have you considered a ground lift switch for the EQ to get your signal back? You could also move your volume into the master volume location and then just use your eq for shaping and "gain" control, in this case how the midrange works mostly, and then have your MV after. I just thought it could turn out more versitile that was especially since we are dealing with such low power.
#24
Most of your resistors are over spec...not an issue just saying.

Your cathode biasing resistor for the output is a bit under spec..maybe not.

Amps run on DC...there doesnt seem to be any rectification.

The heaters centre tap just goes to the power transformers bolt, along with the cathodes, main and screen filter caps and any other centre taps.
(Some actually like putting the heater's CT on another point)
#25
Quote by PainIsPower
Your revision still shows the cap in the wrong spot. It is still in series, just moved to a different spot on the schem. Your voicing switch would be after C2, and you would put another cap in there right beside it. The switch would just control which cap went to ground, or if none did. Also, just as a Q, do you have any experience with building anything electronic before? such as a pedal or another amp? I can see you have been around for awhile but I don't spend too much times on these forums so am not too familiar with everyone. Also, I still don't understand what is going on with your input, namely C1 and R1. Looking at it now also, your EQ is going to eat alot of signal and you might end up with trouble distorting anything after it. Have you considered a ground lift switch for the EQ to get your signal back? You could also move your volume into the master volume location and then just use your eq for shaping and "gain" control, in this case how the midrange works mostly, and then have your MV after. I just thought it could turn out more versitile that was especially since we are dealing with such low power.


To the first question: I have never built a pedal or an amp. I have built other smaller things in electronics, but nothing this large. I have really just done with RC and RL circuits.. finding out the voltage and amperage and resistance, but nothing this complicated. I have been a while actually, just posting in the guitar builds... not the amp builds. One of my friends who builds his own amps will help me after I get most of the work done. He can easily fabricate it, but he knows little about guitar amplifiers. Most of the design is from a blackheart as I said in the first post.

I agree about the C1 and R1. Experienced people like you though point these things out to me. If it eats a lot of signal though.... Wouldn't I be able to drive the tubes harder without cranking the volume? Like I said, I can be retarded with electronics. I think if I want it to distort, I am going to use a pedal actually... so wouldn't it be better to have a clean signal?

I agree with the ground lift and EQ change. Here is Rev 3 trying to implement your ideas.

I assume you use the master volume as a Rheostat?

Quote by kurtlives91

Most of your resistors are over spec...not an issue just saying.

Your cathode biasing resistor for the output is a bit under spec..maybe not.

Amps run on DC...there doesnt seem to be any rectification.

The heaters centre tap just goes to the power transformers bolt, along with the cathodes, main and screen filter caps and any other centre taps.
(Some actually like putting the heater's CT on another point)


I know they are a bit over... but I don't mind.
I agree, I now changed it to 500Ohm 1W. DO you think that this is enough?
D'oh... will be in Rev 3!
and to the last thing... Noted. and changed.


By bobdahaxor at 2008-08-05

My questions are in the schematic. I am new to electronics, but I feel I understand it well from my E&M Physics course as we did a lot of RC and RL circuts. r11 is now in parallel. I work late at night usually (I am lucky I got some daytime hours) so sometimes I have brainfarts.

Oh... and still open to ideas for the name!
Last edited by ESP_Shreder at Aug 5, 2008,
#26
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#27
You got some pretty funky stuff happening with your cathode on the output...look into that...its got issues.

The diodes can be 1N4007... Might wanna add despiking caps... Just an idea.

Wait why did you rectify the heaters but not the B+? You don't even need to rectify the heaters really.

I think your C5 coupling cap is a bit big. Most tone shaping happens early on imo. Stuff that happens at the beginning passes through lots before it hits the output. Its harder to shape something at the end when it has been amplified so many times and shaped already.

What program are you using to make this schem?
#29
I am using ExpressSCH. Works great. Love it!

What specs should I look in the rectifier and the fuse?

I think I got it right. Would it be bad to use a common set of resistors and capacitors for both Triodes?

I also reduced the c5 value.

I got rid of the diodes and just used the rectifier. I don't see the need for the diodes anymore.


By bobdahaxor at 2008-08-05
#30
The cathode is still worng...they dont both need induvidual resistor/cap.

That 4700mF cap will blow the second you start the amp up... It is also backwards.

WHy did you add another fuse?
#34
I have ExpressSCH too but how did you get the tubes in there. Is there a newer version or something or did you make them in the program yourself?
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#35
I downloaded a pack that has tubes....http://home.pacifier.com/~gpimm/downloads.html The first one and then just put it in the component directory and restart ExpressSCH. Works like a charm.
#36
Nice...thanks a lot!
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#38
Under connectors. I use what they call "wall jack for transformer" and it looks like a phono jack. That cathode is just kicking my ass.
#39
Any chance I could score a copy also? or a link or where to get it?

Also, P5 is in the wrong spot, should be after the 12ax7b. I believe right after C7 with one end going to ground, a 500k log pot should be sufficient, some one correct me if i am wrong. I would go check another schem, but I just got home form work and feel lazy.

Your cathode resistors off of your power tubes are feeding into you tube input, not ground, that should be corrected, they need to go to ground. I can't see any purpose in C8.
1N4007 I believe will work for you rectifying diodes.
Your input still confuses me some what, though it looks cleaner. Just take the ground and sleeve and take them straight to ground, no resistors. And put then 1M resistor to ground coming off of the hot signal. You use 1.5M which will work, that will just give you a bit more signal going to the first tube. Normally High and Low channels refer to the resistor that R2 is. 1watt is WAY over kill for that resistor. It will be lucky to a few volts with a couple mili-amps. Anyways, High Channel normally use a 2M resistor, where as Low channel uses a 1M resistor, the difference being that the High channel has a higher impedence and sends more signal through, and the low does the oposite. I head of some one using a resistor in parralell with a cap of some value that I can't remember and getting what they called a Mesa sound. If you end up with lots of radio interference before the input of the amp, you can also put a very small cap going to ground from your hot signal to ground out the radio.

You might want to check your power supply, I think you might of mixed up your B1 and B2.

Also, C6 can be the same 22uf as the other cap on the first half of the preamp tube.
#40
Quote by PainIsPower

Any chance I could score a copy also? or a link or where to get it?

Your cathode resistors off of your power tubes are feeding into you tube input, not ground, that should be corrected, they need to go to ground.
You might want to check your power supply, I think you might of mixed up your B1 and B2.


Check Your PM's

My cathode resistor is not connected to the power tube. It connected to ground. I just cannot make that "hump".

I made a hump to signify that they are not connected if that's what you mean. I cannot see what else is wrong with it. If there is still something wrong.... I blame my lack of tube knowledge on it!

Also this ExpressSCH is amazing. It did an updated BOM for me which was amazing. I think I will use that to for my final BOM.


By bobdahaxor at 2008-08-05
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