Request: BK Butler Tube Drive

Posted by on 13 August, 2012 31 comments

This one was requested a long time ago. Here’s an overdrive pedal that uses an actual preamp tube, which is quite exciting.

Based on Bajaman’s schematic I created a layout with wiring for the tube pins (since I can’t imagine a tube socket fitting neatly on a piece of vero board). I left as much space as I felt was necessary for the large supply caps, but I’m afraid it could still end up being a bit crowded. The effect uses a preamp tube of type ECC83 / 12AX7, and I guess you would need some ventilation in your enclosure. The wiring explanation is a bit convoluted as well, sorry. I really should draw a proper diagram for this.

Do note that this effect requires 12v AC power and not DC like most other effects. Use a small mains transformer or a good 12v AC power supply, and be careful when playing with mains power. Don’t do it if you’re not sure how to do it safely.

Update (09.09.2012): Thanks to several of you for verifying this one!

There’s also been reports of this being quite noisy, and I’m happy to pass on coi2001′s suggested fix; leave the heater resistor off the board since that’s the main noise source. Run the 10 ohm resistor (R16) from the 12VAC source (probably a trafo in most cases) straight to the heaters.

Update (09.05.2013): Here’s my own build, in a slightly taller 1590BB enclosure I got from smallbear (I think they call it the 125BB) which gave just enough room for the tube. Left the heater resistor off the vero board, as was previously suggested, and set it up to receive 12VAC external power (no room for a transformer and power socket obviously).

TubeDriver buildTubeDriver gut shot

Sounds great and there’s very little hum, just a small amount when drive is full on! :)

Request: ROG Uno – Mesa Boogie MkI emulator

Posted by on 3 May, 2013 3 comments

JFET approximation of the Mesa Boogie Mark I preamp. Probably sounds nice :)

UnoMarkI

Update (05.05.2013): Now verified as working, both by myself and Derek. Thanks Derek.

Amp #2

Posted by on 1 May, 2013 10 comments

I finally got around to finishing my second amp build, and as I promised here are the details.

Amp2 outsideAmp2 inside 1Amp2 inside 2Amp2 inside 3Amp2 inside 4

I’m reasonably happy how the internals ended up given that it was all laid out more or less as I went, though I am a perfectionist at heart and this really is far from good enough. Gives me a lot of room for improvements for my next amp, though :)

Amp2 Schematic

So this all began several years ago when a colleague lent me a Bad Cat Xtreme-tone preamp effect (the one with tubes inside) which I liked a lot. I got my feet wet converting the same preamp circuit to a JFET variant some time after that with the thought of eventually building a full amplifier for myself. To make a long and boring story shorter and less boring I started reading books on the subject, and ended up adding to and modifying the original idea to what you see above.

I’d like to bring your attention to a book that, more than any other, helped me understand a lot of this stuff. “Designing Tube Preamps for Guitar and Bass” by Merlin Blencowe is a surprisingly well written and downright enjoyable book made to help novices like myself getting into this great hobby/addiction (I can also recommend his book on power supplies). I found a lot of the changes and modifications here.

So the basis for the amp is the Hot Cat 30, which again is , I believe, based on a Matchless, which again is based on a Vox AC30. So it has the AC30 power section lacking the typical negative feedback that many other amps have.

I replaced the clean channel with a gain stage borrowed from the Dr. Z Carmen Ghia (a favorite of my friend). Then following this I added a standard BMP tone control with two added switches giving the option of a mid- scoop or boost (or a frequency shift towards bass when both are engaged) that I arrived at by experimenting with Duncan’s Tone Stack Calculator.

For the gain channel I replaced the tone stack with a Marshall one (bass, mid, treble), and followed it by an active parallel/serial FX-loop I got from Merlin’s book. I also got rid of the “edge” control and consolidated the two gain controls into one dual pot. And lastly I replaced the odd first gain stage with a more standard cathode biased one.

The schematic lacks a proper symbol for the output transformer and the following wiring, as well as the input power socket wiring, the heater wiring, the indicator LED + resistor, and the humdinger trimpot. There are also small tweaks to the power supply section as well as a “tube rectifier emulation” switch, all of which was borrowed from Merlin’s book (as far as I remember).

So to sum up, it’s a two-channel clean/high gain amp with an FX-loop, running 5x 12AX7/ECC83 and a push-pull power section with 2x EL34. It’s very loud and very cool, though being a perfectionist there are things I would like to improve/change.

Initial thoughts/lessons learned:

  • It’s too loud for home use (I knew this though). Maybe an attenuator will help. Some kind of power scaling would have been nice.
  • The FX-loop, though fully functional, could probably be scaled down a bit/made simpler.
  • I didn’t get much out of the “tube rectifier emulation” so will probably just stick with plain silicon rectifiers next time.
  • The point-to-point-layout-as-I-go ended up looking less tidy than I would have liked. Maybe this amp was a bit too much for such a small enclosure (8″ x 16″). Bigger enclosure or less components next time maybe.

If there’s requests for it I’ll add parts list and voltages. I also welcome suggestions, advice and criticism on anything from schematic and design to building and what not.

I’ll add more pictures when the amp is fully dressed up in tolex etc.

Update (01.05.2013): Here’s a rough overview of the various sections within the amp.

section_breakdown

Request: Catalinbread Pareidolia

Posted by on 11 January, 2012 43 comments

There have been a few requests for this one. Let me know if you build it and it works. This should fit in a 1590B enclosure.

Update (11.10.2012): Revision 1; changed Q3 and Q6 to 2N5457s.

Update (22.01.2012): Revision 2; I had mistakenly labeled this as requiring 44 cuts while it only needs 43. Thanks to Nocentelli for spotting this.

Update (01.02.2012): Built this one tonight. Had to reorient the depth and rate pots (layout has been updated), but otherwise it worked like a charm.

Update (18.12.2012): Voltage readings from my build as requested:

Power supply: 8.88V

All pots fully CW.

IC1 IC2 IC3
1 +3.75V 0V +8.88V
2 +3.75V +3.75V 0V
3 +3.75V +3.70V +7.46V
4 0V +7.46V
5 +3.72V +3.72V
6 +3.72V +3.72V
7 +3.70V +2.80V
8 +8.88V +3.64V
9 +1.53V
10 +2.82V
11 ~+15mV
12 0V
13 +1.73V
14 +1.73V
15 +0.93V
16 +0.93
Q1 Q2 Q3 Q4 Q5 Q6
D +8.88V +5.71V +1.21V +8.88V +6.02V +1.21V
S +5.71V +0.90V +1.21V +6.02V +0.96V +1.21V
G +4.13V +2.7mV ~+4.3mV +4.21V +2.6mV ~+3.8mV

Update (30.04.2013): Just adding the schematic that I drew based on the trace made by KindaFuzzy over at FSB.

Pareidolia_1.1

Request: Boss CE-2 Chorus Ensemble

Posted by on 27 April, 2013 3 comments

Supposedly one of the better sounding choruses. This one has the tonepad mods included. At 34×20 I believe this will fit nicely in a 1590BB. Enjoy :)

ChorusEnsemble2

Update (30.04.2013): Now also verified, thanks to Irmin!

Request: Maestro Brass Master

Posted by on 30 December, 2012 17 comments

I don’t know what it does or what it sounds like, but it look interesting for sure. Let me know if you build it.

BrassMaster

Update (31.12.2012): First revision; I forgot to add a trace cut.

Update (25.04.2013): Now verified as working, thanks to Jimmie!

Wobbletron

Posted by on 22 April, 2013 No comments

This one is a bit unusual in as much as I’ve already built it and verified it as working. Here’s a vero layout for Tim Escobedo’s Wobbletron, I believe it’s a vibrato-thingy similar to what can be found in some old amps.

Wobbletron

The original schematic (search for “tim escobedo wobbletron schematic”, I’m sure you’ll find it) called for a J201, which I have plenty of. Problem was not a single one worked.

So I tried a few 2N5457s and found two that gave a slight wobble. What really worked (almost too well) was a J112 (all of the ones I had gave lots of wobble). Experimenting for a while I came to the conclusion I wanted to stick with the J112, but greatly lower the 220K resistor between “Depth 1″ and ground. Since the 2N5457 required a larger resistance here I figured I’d make it a trimpot.

Insert J112 (or 2N5457, or some other JFET maybe), set frequency fully clockwise (faster) and depth fully counter clockwise. Now adjust trimpot to where you want your depth minimum setting to be (probably at no, or very slight wobble). Now you can try playing with the range of the depth pot; I had good results with a B250k, but maybe something smaller/larger will work better with your JFET.

Anyway, good luck :)

Bad Cat Hot Cat emulator

Posted by on 4 September, 2010 26 comments

Having built the Bad Cat Mini II amp, and given how happy I am about that one, I’m contemplating building a 30W Hot Cat amp as well since the schematic is available on schematicheaven.com. But, since these things are quite an investment when it comes to parts and labor I’ve decided to first build an emulator circuit, similar to what can be found on runoffgroove.com, and in the same vein as some of the layouts I’ve already covered (like the Dr. Boogey, JCM800 and Boogeyman).

Here’s my first attempt at drawing a schematic:

I originally ended the gain channel after the master pot, tuned it to a set of 2N5457 transistors, and reduced the output impedance by a factor of 10 similar to what was done with the Dr. Boogey layout according to gaussmarkov.net, but after building it I was barely able to reach unity gain with all pots maxed. I decided to add the final gain stage leading up to the phase inverter on the gain channel, but also decided to leave this out of the clean channel (as that one was loud enough to begin with). I also switched to and tuned a set of J201 transistors instead. And now it roars! I haven’t tried a real Hot Cat amp, but the gain circuit is quite high gain, and very cool.

I added a second 3PDT to switch between the two channels (gain and clean) wiring it to a dual-LED. Red is the gain channel and green is the clean channel. Here’s how I wired it:

This is the vero layout I created based on my schematic. I originally created a layout without the final gain stage on the gain channel, but after testing it I retrofitted the last few parts on a separate, small vero board. These parts have been added to the final vero layout.

And here’s the finished build:

Note that the board pictured is missing the final gain stage, as described above.

The right switch toggles the effect on and off, and the left switch routes the signal through either the clean- or the gain channel when the effect itself is on. The top-most row of knobs represent the gain channel, from left to right is “Gain”, “Edge”, “Level”, “Bass”, “Treble” and “Master”. The single knob on the second row is the “Volume” control of the clean channel.

Update (15.04.2013): A small mistake crept back into this old layout during spring cleaning. Corrected the cut count, hopefully for the last time now ;)

Request: Hiwatt DR103 preamp emulator

Posted by on 13 April, 2013 7 comments

JFET version of the Hiwatt DR103 preamp, with a few extra components to (hopefully) make it work. I added R14, C9, C10 and D1; not sure if C9 is big enough, but it’s probably fine. You can assemble it either as “normal” or “bright”. I’m not sure which one would sound better.

DR103preamp

Klon Centaur

Posted by on 28 February, 2011 88 comments

Here’s a layout I did for the Klon Centaur overdrive based on a schematic by soulsonic.

Update (28.02.2011): I finally got around to boxing the Centaur. This time I felt brave and decided to try an artwork technique courtesy of “frequencycentral” over at freestompboxes.org (described in this thread). I thought I gave it a good go being the first time and all, but needless to say from looking at the picture my only option was to leave it to dry outside in -20 degrees Celsius (that’s -4F for you Americans) and the result was less than optimal. Looking forward to spring and my next attempt.

Update (18.03.2012): I’ve had several requests for voltage readings from my build and here goes:

Battery at approx. +8.90v and all pots at zero.

IC1 IC2 IC3
1  +4.43V  +4.6V  +8.84V
2  +4.44V  +4.43V  +4.52V
3  +3.45V  +4.43V  0V
4  0V  -8.44V  -4.13V
5  +4.43V  +4.42V  -8.42V
6  +4.43V  +4.43V  +3.97V
7  +4.41V  +4.26V  +5.29V
8  +8.87V  +15.92V  +8.82V

I don’t know whether these are the “correct” voltages, but mine sounds good so…

Update (21.06.2012): Fixed an error on the layout where gain lugs #1 and #3 were swapped. Thanks to Dieter Brenner for pointing this out!