Tech 21 Double Drive

[aziltz]

Has anyone built one of these?

I have an original and I'd like to make a replacement that is True Bypass, a bit more robust, and possibly in a smaller box than the original.

i found this schematic/pcb in the gallery: http://www.aronnelson.com/gallery/main.php/v/Gila_Crisis/Double_Drive/

does any one have any suggestions for "improvments" other than simple value changes?

[Bucksears]

I just finished this today and has ZERO sound. Can't for the life of me figure out why.
Gotta be trace somewhere, but the build on this was pretty straight-forward.
Has anyone built the DD with this PCB/layout?

Given that you have the original, is this worth building? Is the sound of the original any good? I was hoping to get a Vox-y meets Marshall sound out of it.

Thanks,
- Buck

[sevenisthenumber]

i would like to try this....    is it verified at all?

[new]

I've found some errors  on the pcb/layout  as shown in the picture.

[Bucksears]

I've found some errors  on the pcb/layout  as shown in the picture.

Don't see an image - problems attaching?
I'd LOVE to get this working....not enough Class A (Vox-ish) DIY distortions/ODs out there, if you ask me.

[aziltz]

I just finished this today and has ZERO sound. Can't for the life of me figure out why.
Gotta be trace somewhere, but the build on this was pretty straight-forward.
Has anyone built the DD with this PCB/layout?

Given that you have the original, is this worth building? Is the sound of the original any good? I was hoping to get a Vox-y meets Marshall sound out of it.

Thanks,
- Buck

sorry i never responded bucksears...

I'd say this is definitely worth building and tweaking.  I'm thinking about adding a bass cut at the first clipping stage. I've only build it on breadboard and it worked quite well.

i'm mainly looking to build it to get ride of all the buffers and get it in a more robust box, but its a great sound.  i tend to use it for some class A grind, like the Bad Cat  - Vox kind of sound.

The tone control is just a high roll-off, meaning there's no tone stack, and I was thinking it might be nice to replace it with a Vox tone stack.  Maybe in a version 2

[Bucksears]

Did you use this schem for your breadboard version? I'm trying to figure out what's wrong with the PCB, if it's just a minor adjustment or needs a complete redesign.

[aziltz]

i've been using this one:

http://www.axiomdrift.com/schematics/


i was planning on making my own board layout when i do get around to it.

[Bucksears]

What JFETs & diodes did you use near the end of the circuit (lower right corner of the schem)?

[aziltz]

i skipped that entirely.  that's how they do the bypass, its similar to FET switching found in BOSS and IBanez.

That's what I mean by improving the circuit...  Dropping all that extra stuff at the input and output and making it true bypass.

[Bucksears]

I'd love to see a PCB if you get around to it. I'm tempted to hunt down a DD myself just to play around with.

- Buck

[aziltz]

I'd love to see a PCB if you get around to it. I'm tempted to hunt down a DD myself just to play around with.

- Buck

it may be a while before I get to designing a PCB.  Its next on my list but I haven't etched PCBs yet.  the originals aren't being made nowadays.  they have a programmable version currently, but the originals pop on ebay every now and then for ~$60.

[Bucksears]

Have you played the programmable version? If so, any sonic differences between that and the original?

[aziltz]

i haven't played it, but it has a 3-band Eq instead of a simple roll-off.  judging by the Sansamp Schematic, its probably a Bandaxall plus Mid Control.