Page 1 of 2
#1
Pre-scriptum: Actual pics on page two.

Hey everone,

Some of you may recall me asking some questions in this forum regarding this project, but I think it could really use its own thread now.

I've been drawing schematics for the past 2 hours and I've got a truly epic headache.
I've also got these schematics done.

Hope you guys don't get a headache as well looking at them.

http://i16.photobucket.com/albums/b7/KillerMonkey386/Tube%20Amp%20Project/PowerSupply.png (note: old)

http://i16.photobucket.com/albums/b7/KillerMonkey386/Tube%20Amp%20Project/Preamp.png (note: old)

http://i16.photobucket.com/albums/b7/KillerMonkey386/Tube%20Amp%20Project/TMBPIPwr.png (note: old)

Still gotta calculate stuff for the poweramp. Preamp is based on my modded VJ, which I am very happy with right now. Just needed moar gain/br00tz, so I adjusted it a little. The "Tightness" pot is something I added today to the VJ and I liked it so much I added it to this project as well. It basically forms an RC highpass filter with the coupling cap. It cuts bass and slightly reduces gain. It worked better than I could've hoped for.

Everything will be mounted in a steel 2HU 19" rack enclosure.

Most components will be supported with sheet metal plates, probably aluminum.
Here's some Sketchup pics:

Top (tonestack, PI & poweramp):
http://i16.photobucket.com/albums/b7/KillerMonkey386/Tube%20Amp%20Project/Top.jpg (note: old)

Bottom (most of the preamp):
http://i16.photobucket.com/albums/b7/KillerMonkey386/Tube%20Amp%20Project/Bottom.jpg (note: old)

Now I really need some rest, and some aspirin.

ps: photobucket compresses the images a bit, sorry about that.

Update! New pics:

Preamp 1
Preamp 2
Relays

Separate tone/volume controls. Clean TMB is Fendery, OD is Marshally. Will tweak them somewhat, but that's the general idea:
Tonestack

Poweramp's still not finished:
Poweramp

Power supply:
Not sure if I'm gonna go with separate relay supply. I'm actually not sure if I can get away with 28V into 24v relays.
Power supply

Sketchup renders of planned lead dress (just the first stage, rest should be fairly similar), not quite finished yet. Brownish cylinders are resistors, green are caps. Should be fairly self-explanatory. Wires colour coded for your viewing pleasure.
Red = anode, blue = cathode & heaters, green = grid.
Lead dress
Lead dress 2

Update (13/10), now with proper references!

Preamp 1
Preamp 2

Reworked the relay switching, added a new tone control that allows the clean channel to bleed into the OD channel at the PI.
Relays

Tonestack

Poweramp's still not finished:
Poweramp

Power supply:
Power supply

Update (15/10):

Pretty sure I haven't changed anything about the relays and preamp. Here they are anyway.
Preamp 1
Preamp 2
Relays

Haven't tweaked the tonestack yet. That's probly up next.
Tonestack

Poweramp's pretty much done!
Poweramp

Power supply, now has bias supply and possibly something for a fan to cool the tubes.
Power supply

Update (15/10):

Preamp's done.
Preamp 1
Preamp 2
Changed the bleed/blend control, was wired wrong. Some other minor changes too. Is done.
Relays

Still haven't tweaked the tonestacks.
Tonestack

Poweramp's done.
Poweramp

Power supply's done.
Power supply
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Nov 2, 2010,
#2
There are not enough rack mounted pre/power amps out there. I've been thinking of doing something similar but my electronic skills only just let me build a ruby so I'm not quite there yet

Looking forward to see how this turns out.
,___,
[O.¬] - WTF?
/)__)
-"--"-
#3
Thanks

I just really wanted to make something fairly compact, and while planning the layout the 19" form factor seemed ideal.

I'm working on the layout of the circuitry now, doing that in sketchup is surprisingly easy. It's really helping me figure out a good lead dress/layout, getting everything orthogonal and stuff.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#4
Standby switch should switch the HT on and off. Your way can work but I'd use a DPDT to switch both ends of the HV winding.

Your CT fuse is wrong. Fuse should be in series with the CT to ground.

Heater balance/CT resistors should be 100R not 100K. A 200R pot is even better, you can dial in the balance.


Gave a super quick look at signal path. Looked ok, cathode bypass caps are small.
#5
Quote by kurtlives91
Your CT fuse is wrong. Fuse should be in series with the CT to ground.


Not sure if you mean HT fuse and not CT fuse. While putting the fuse in series with the Center Tap does work, it is not the most ideal place for the fuse. It is also considered bad practice to break the ground. While this will turn the amp "off", the HT will be at high potential.

The way that he has the fuse in the schematic is the best place for it to be.

What was said about the standby switch is correct though. It should be moved to the other side of the rectifier.
Last edited by XgamerGt04 at Oct 9, 2010,
#6
Quote by kurtlives91
Standby switch should switch the HT on and off. Your way can work but I'd use a DPDT to switch both ends of the HV winding.
Good idea, I'll use a DPDT.
Your CT fuse is wrong. Fuse should be in series with the CT to ground.

I don't have a CT on my PT. Do you mean the OT CT? If so, that doesn't make much sense to me... Was that a late night post or am I missing something?
Heater balance/CT resistors should be 100R not 100K. A 200R pot is even better, you can dial in the balance.
Good catch, thanks!
Gave a super quick look at signal path. Looked ok, cathode bypass caps are small.
Yup, that's deliberate. I like bright tone.
What was said about the standby switch is correct though. It should be moved to the other side of the rectifier.
Wouldn't that make for a much harder startup?
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#7
Quote by Kanthras

Wouldn't that make for a much harder startup?


Not at all. The switch would just go between the output of the bridge rectifier and the rest of the power supply.
#8
Quote by XgamerGt04
Not at all. The switch would just go between the output of the bridge rectifier and the rest of the power supply.
But if you flip the switch, you would get a pop and lots of inrush current.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#9
Put a cap and resistor across the switch. See ValveWizard for more info.

I put the switch right after the B+ caps. Keep the big guys charged while in standby, less inrush.
#10
You will get the inrush current regardless if you put the standby switch before the rectifier or after. I've honestly never had a problem with popping either.

What Chris says is a good idea, you should put the standby switch after your first filter cap, but in your case that would be slightly difficult with how you have the amp set up.

What you could do, is put another capacitor after the rectifier before you tap the power supply for the plate supply. You would then connect one side of the standby switch to the cap, and the other side to where you are drawing power for the power amp tube plates.

It may also be worth it to include a bleeder resistor in the amp so that the caps will discharge faster.
#11
Quote by kurtlives91
Put a cap and resistor across the switch. See ValveWizard for more info.
Well, Merlin advocates using no standby at all.
I'll do the parallel resistor thing, though. That sounds good.
I put the switch right after the B+ caps. Keep the big guys charged while in standby, less inrush.
What do you mean with after the B+ caps? Wouldn't that mean the valves will have high voltage across them in standby? Do you mean after the reservoir cap?
Quote by XgamerGt04
You will get the inrush current regardless if you put the standby switch before the rectifier or after. I've honestly never had a problem with popping either.

What Chris says is a good idea, you should put the standby switch after your first filter cap, but in your case that would be slightly difficult with how you have the amp set up.

What you could do, is put another capacitor after the rectifier before you tap the power supply for the plate supply. You would then connect one side of the standby switch to the cap, and the other side to where you are drawing power for the power amp tube plates.
You mean just a capacitor, or an RC filter? An extra RC filter seems like a good idea, extra filtering is no bad thing. Just a cap would pretty much just increase the reservoir capacitance. But I kinda like the idea of a standby switch with a parallel resistor for a really soft start. I might do both.
It may also be worth it to include a bleeder resistor in the amp so that the caps will discharge faster.
The heater elevation also functions as a bleeder circuit.
I also had one in the HT supply, the 220K one. That's a leftover from its Valve Junior origins, and I've taken it out of the schematic recently. I'll see if I can upload newer schematics today.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Oct 10, 2010,
#12
I missed that you already had the two resevoir caps in the bridge rectifier.

Another option you have, instead of using a standby switch, is to use a thermistor. I'm looking for the notes I have on doing that. It basically mimics the behavior of a valve rectifier as it allows the voltage to ramp up slowly until it is warmed up.
#13
Hmm, a thermistor.. I like that idea. Fairly high-tech for a valve amp.
Wouldn't really need a standby switch at all, then.
Maybe I could then make a switch that actually puts the amp in a "stand-by" mode, rather than a "warm-up" mode.

Anyway, I got the pics uploaded, will modify the OP in a minute.

Okay, everything's up!

Starting to get a headache again.

edit:

I just noticed on the sketchup that one of the red wires is connected to the input grid. It should go to the anode of the first triode. And if you're wondering why that relay s sitting on its butt there in the corner, that's because I haven't figured out how to mount it or secure it somehow.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Oct 10, 2010,
#14
Something that I Just thought of.

If you are using a two phase secondary on the transformer, which means that you connect the center tap to ground, then you will need to fuse both sides of the transformer.

Fusing the center tap would work, but its bad practice. It means that your HT will be at some high potential.
#15
Quote by XgamerGt04
Something that I Just thought of.

If you are using a two phase secondary on the transformer, which means that you connect the center tap to ground, then you will need to fuse both sides of the transformer.

Fusing the center tap would work, but its bad practice. It means that your HT will be at some high potential.
I forgot to upload the power supply schematic yesterday. It's up in the OP now. The PT doesn't have a center tap, unfortunately.

I also figured out how to make photobucket stop compressing images, so it should be easier on the eyes now.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#16
If you are worried about the relays, find out what the excitation current is for the relays and then put a resistor in series with it to drop voltage.
#17
I managed to find a schematic for the relays:
http://stevenengineering.com/tech_support/PDFs/19MAIN_PCB.pdf

On page 3 it says Umax for the coil is 38V, minimum is 16V. So these things can tolerate quite a bit of voltage fluctuation. So they should be able to handle 28V. The resistance is 2880 Ohms, so they don't draw much current either (about 9.7 mA). I think I'll run them under-voltage, probably a 300R resistor in series. This should reduce voltage (to 22.5V) and current, therefore hum. Since the supply filtering isn't gonna be perfect, I will also be sure to wire the relays so that the OD channel is active when the coils are off. The clean channel should be less susceptible to any induced hum.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Oct 12, 2010,
#18
At 10 mA you probably won't have much magnetic interferance from the coils. You will also have DC power going into the coils, so the magnetic field will be constant while it is on. The only time you may have an issue is at the moment that the field is produced, or when the field collapses.
#19
Quote by XgamerGt04
At 10 mA you probably won't have much magnetic interferance from the coils. You will also have DC power going into the coils, so the magnetic field will be constant while it is on. The only time you may have an issue is at the moment that the field is produced, or when the field collapses.
Yeah, that's true. I guess it's just "good practice" to make sure the more sensitive channel is active when the relay coil is off. Since it's not gonna be perfect DC due to ripple.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#20
Another update. Reworked the channel switching and gave everything proper references.

Also added another tone control. It bleeds some of the clean channel into the OD channel. Bit of an experiment, will be interesting to see how that turns out.
Might sound like crap, might have a nice effect.

New schematics are in the OP.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#21
Got the poweramp pretty much finished now. Changed the power supply a bit.

Schematics are in OP.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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~ BUM: For all things extinguishing

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#22
Hey guys,

I'm pretty much done designing now, except for one small thing. The screen grid resistor. I'm not sure how much resistance is needed, if any is necessary at all. Anyone have any idea?
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#23
Right, pretty much done with the design part. You could basically order all the parts and complete the amp before I do, now.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#24
Yes, updates!

The package from Musikding arrived a few days ago, big box with about 300 parts inside.


Here it is all sorted:


As for stuff I've already done in between learning for exams, I've already made the footswitch.

Behold, the cutest footswitch in the world!


It's wired up as a simple on-off switch. Kind of a tight fit, but it works.

Also made the board for the first two preamp tubes:

I think I'm gonna go with smaller coupling caps next time... Height-wise, these will barely fit in the amp.
Well, at least they won't get overvoltaged, they're rated at 630V.

And the underside:

Gonna redo some of that wiring on the left maybe. Not quite as neat as I want it to be.

Enjoy the eyecandy. There should be more to come in the weekend!
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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#26
Quote by salgala2000
Pictures!! Something i can finally understand

lol

I guess this thread has been kinda heavy on the theory. That's definitely gonna change now.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Nov 2, 2010,
#28
Oh nice! Looking pretty good!

As for the cutest footswitch in the world, it's pretty cute for a metal box. You could probably add some paint and some cat ears and...

owait, pit is thataway.

All kidding aside, that's looking nice! Can't wait to see how it'll turn out!
Amps
Randall RG50TC, Roland Cube 15x

Guitar
LTD MH-100QM, Washburn X12

Effects and Etc.
Ibanez Weeping Demon, Boss FV-500H, Ibanez TS7, Ibanez PH7, dbx 31-band EQ, ISP Decimator
#29
Kawaiiiiiii!!!!

But seriously.

Nice work man, solid theory under your belt too! Congratulations!
Quote by SlackerBabbath
My ideal woman would be a grossly overweight woman who would happy go jogging, come home all sweaty and let me put my dick under her armpit while she shuffles a pack of cards.

Stay classy, pit.
#30
Small update, finished the power supply board today. Enjoy the pics.



Making those rectifiers was pretty fiddly. I managed to squeeze diodes between the tags to keep things nice and compact.

The stuff in the middle with the trimpot is for balancing and elevating the heaters, to lower the hum. It also prevents the cathode follower from arcing internally, because the cathode is at a pretty high voltage there and the heater/cathode insulation may not be good enough. Elevating the heater makes the voltage difference smaller.

On the backside there isn't much to see, of course. All those wires coming together on the the left are going to be the grounds for the filter caps & stuff. Trying to keep things as star-grounded as reasonably possible, right up until the base of the reservoir cap.
You can also see the reservoir cap and its star ground for the low voltage supply on the right. This is for the relays, bias supply and cooling fan (still have to order that).

Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#33
Hey guys, finally an update! And it's a big one.

Better grab some popcorn.

You might recall from the Sketchup pics that I wanted to divide a 2 height unit 19" rack into numerous spaces, separated by metal sheets. Well, today I finally got the chassis stuff done. It was the first time I did any kind of serious metal working. It was pretty cool, but it was also a hell of a lot of work. And because I wasn't entirely sure what I was doing, I had to be very careful. I was continuously doing a routine of measure, fit, remeasure, refit, mark where I have to drill, make sure I marked the right spot, carefully align it on the drill press, then carefully drill and finally check if I did it right. Fortunately, I got it right, save for a few exceptions. And I managed to correct those fairly inconspicuously...

Another delay was caused by the fact that the steel I had in the first place was rubbish, and it started to rust pretty quick (even though it was nearly drenched in WD-40) and it wasn't cut very evenly. Well, that last thin would be my fault, it was my first time using an angle grinder for precision work, so it wasn't pretty. I decided to get some better steel and redo it, and I'm glad I did. It turned out great the second time.

Here are some pics of the three plates. All drilled and sanded and shiny.



Here's the separator for the power supply section during the assembly, all bolted up and with wire protectors. At this point the plates had also gotten a few coats of clear lacquer, to help protect them against the elements.


Here is the chassis in a more assembled state. Also in a very blurry state...


Spot the difference!



Continued in next post...
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
#34
Some sweet looking pots here. The blue ones are for the clean channel, orange for overdrive. No script on the faceplate, unfortunately. I didn't want to use stickers (fugly) and I suck at engraving, so I'm just gonna leave it like this. It's not like I don't know what's what.

The blue is a bit too dark, IMO. Maybe I'll get some lighter knobs later.


I couldn't resist starting with the wiring. Here's some higher res shots of what I've done so far.
Twisting long wires together for the filament supply is a bitch, btw.



Right, that's it for today! Hope you enjoyed this update of epic proportions. There will be more to come soon.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#35
awesome.

'Nuff said!
Quote by SlackerBabbath
My ideal woman would be a grossly overweight woman who would happy go jogging, come home all sweaty and let me put my dick under her armpit while she shuffles a pack of cards.

Stay classy, pit.
#36
That looks awesome, I wonder how heavy it will end up being.

And if you still really want letters, get some clear decal paper, print out onto it, and making sure your steel is flat, put it in cut holes for the pots, then clear coat over it. I'm going to do that on one of my pedals, and I'd imagine it would work pretty good.


████████████
████████████








RBY CYOA
#37
You can get face plates made by BNP Laser. Just get Inkscape and design it and then save it as a pdf. They have pretty good prices and a good selection of things too.
#38
Quote by N_J_B_B
awesome.

'Nuff said!
Thanks!
Quote by MonkeyLink07
That looks awesome, I wonder how heavy it will end up being.
Right now it's 4.2 kg. Since most of the weight is in the trannies/chassis, I'm guessing it'll weigh about 5 or 6 kg in the end. That's probly about the norm for a 15 watt amp without wooden enclosure.
And if you still really want letters, get some clear decal paper, print out onto it, and making sure your steel is flat, put it in cut holes for the pots, then clear coat over it. I'm going to do that on one of my pedals, and I'd imagine it would work pretty good.
Unfortunately, the faceplate is pretty rough. I would either need to sand it down or spray a whole heap of clear coat on it. At this point, I'm not gonna do more painting, would be a big PITA. Letters will have to wait for the next project.
Quote by XgamerGt04
You can get face plates made by BNP Laser. Just get Inkscape and design it and then save it as a pdf. They have pretty good prices and a good selection of things too.
That looks very interesting, I didn't know there were companies that did that sort of thing for hobbyists. Something to keep in mind for future projects... Their international shipping is expensive, though. Maybe I can find a similar company here in Europe.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#39
Quote by Kanthras

That looks very interesting, I didn't know there were companies that did that sort of thing for hobbyists. Something to keep in mind for future projects... Their international shipping is expensive, though. Maybe I can find a similar company here in Europe.


Just look for a place that does laser engraving. If you give them a pdf file and the plate (usually plastic) they can do something. They may even have the plastic themselves.
#40
Update time! Got a fair bit of soldering done today. I'm starting to like the soldering fumes. Not sure if that's a good sign... Anyway, enjoy the pics!

Wired up the fuses and some other stuff in the power supply.


Behold... a noisegate! Yes, those two tiny diodes on that big fat switch, that's a noisegate.

It's the most primitive noisegate possible. It's an experiment really, I made it switchable because I might not like it. What it does is only allow the signal through until it's past a certain voltage. Since noise is pretty low voltage, if you stop playing it should kill the signal entirely.


Also added the grid stoppers. Was kinda fiddly to get those neatly in there.



And some relays. Partly wired up already to the pots and the supply for the coils. PCB relays are a bitch in a point-to-point build. Considering going at least partially PCB for future projects..


Here's a nice overview of the progress so far.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
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