Westbury "The Tube" distortion pedal transformer

[Boy Howdy]

The Free Information Society - Westbury W20 Electronic Circuit Schematic

I have the Nady version of this pedal and I want to make some changes, but I don't want to modify this one. I'll build a new one instead. But I need some transformer advice.

The transformer in the pedal is pretty small. It measures 1.5" square. I don't know much about transformers. Where can I get one this small? What would I ask for?

Thanks, guys.

[J M Fahey]

As shown on the schematic: 6.3V 300 mA or more, center tapped; 200V 10 mA or more.
Anyway I don't understand very well why would anybody prefer it over other pedals, since the distortion comes from a pair of diodes, like on countless pedals.

[Boy Howdy]

Damned if I know, JMF. Must be something about the diodes in the feedback loop. It just sounds better and more natural (to me) than the SS pedals I've tried. I do hear that tube in there, and the diode effect is somewhat moderated somehow.

edit: That said, it does need some tweaking, IMO. I want to beef up the bottom a bit (larger coupling caps) and cut the treble (tone circuit). I currently have to use an eq between it and the amp.

Thanks for the info. Got any recommended brands or dealers? I don't know where to get one even. Sheesh!

[tboy]

I don't understand very well why would anybody prefer it over other pedals, since the distortion comes from a pair of diodes, like on countless pedals.

Since you're building your own, you could always replace the silicon diodes with tube diodes - maybe a 6AL5, or even a 12AX7 wired for diode operation.

[Boy Howdy]

Color me intrigued.

Can you elaborate, tboy? Where would I get a lesson (schematic?) on how exactly to do that? Got any links? I'm afraid I am, and will - despite the contradiction - always be, a newbie.

It's been my experience that without diodes there is no compression and/or sustain. Would these act the same as the silicon in that regard?

[J M Fahey]

Howdy, boy?
(sorry, I couldn't resist)
I believe you if you say so.
I fact, I *always* believe what musicians say about any given sound, although not always agree on what they *think* the reason is.
Anyway, I guess here the tube preamp response is not flat, at all, and pre-distortion EQ is important.
Don't know if the second triode clips . Even if it clips a little, it will add something useful.
I fear (may be mistaken) that increasing pre-distortion bass will add little body and much mush/mud, but test it anyway.
As usual: post your results, good or bad, we always learn from each other's experiences.
Good luck.
EDIT: forgot about the trafos: try all the usual suspects, it's an unusual combination, but somebody *might* have something similar. HV winding is not *that* critical, you can use a lowr voltage one, you can use a 100V one and a doubler.

[tboy]

Fuzz box builders are always trying different diode types (germanium, silicon, LED), and combinations of types (like one silicon and one germanium), to get different "flavors" of distortion; no reason to leave tubes out of the mix. You could even put in a switch (or two) to select various types and combinations, including tube.

You can use the two triodes in a 12AX7 as diodes by connecting the grids to the plates (connect pin 1 to pin 2, and pin 6 to pin 7). Power the filaments as you normally would from the 6.3v supply. Connect your two tube diodes back-to-back (pin 3 to pin 6, and pin 8 to pin 1) just as the silicon diodes are in the W20 schematic, and away you go.

[booj]

mouser, digikey, mcm, newark,... good luck!

[Boy Howdy]

Sounds easy enough. I think I'll give it a shot. Thanks, tboy.

[Boy Howdy]

Best not believe me too much, JMF, I change my mind like my underwear (what, monthly?).

This TD-1 has a sibling called the TO-2 which is very similar but with tone controls and less gain. I've done some experimentation with the TO-2 and the second stage (with diodes removed) distorts only slightly, but that distinctive tone that I referred to is there with or without the diodes. Sort of a glassy squeak.

I changed the second stage coupling cap on the TO-2 to a .01 which may be a bit too big, but I can dial it back since it has a bass control. I think a .005 would be about right. I think I'll go to a .002 on stage one. If too big it'll be simple enough to change out.


The only change I've made to the TD-1 is to remove that 470p cap before the second stage grid. I hated the blunting effect it had on the treble ... made it muddy, then crunched it back up in the second stage. Ugly.

[Boy Howdy]

Well the transformer is proving to be a PITA. Having trouble finding one that'll work.

I looked at the Matchless Hotbox - they used a hammond 269ex. Some diyers have used 369ex and 369gx. But these range in price from $48-74 and are awfully big for a pedal. Edcor said I might be able to use their xpwr082 EDCOR - XPWR082. What do ya'll think? Can I use that? It's priced right.

A couple more questions:

Can I just use a wall wart? I hate 'em but that may turn out to be my best option.

Do you guys know of any good surplus outlets where I might find something suitable?

What about a DIY tranny? Can I just make my own? Doesn't look like there's all that much to it.

[J M Fahey]

You can use the "Mac Tube" trick, using a small/cheap/available reverse connected 220(or 240)VAC<->12V AC transformer inside the pedal, to get b+ and an *external* 12VAC wall wart which powers filaments *and* the internal inverted transformer.

[HTH]

I've used a 240v-to-12v toroidal tx for a valve OD pedal and it works great. You use a 12vac wall wart into the 240v/12v tx with the 12v serving as the primary - you get approx 240vac out the other end.

With a bridge rectifier to get your DC voltage, you get around 290vdc once you account for losses - perfect for a valve OD pedal.

The toroidal tx's I've used also had 115v taps on the 240v winding, so I get a low voltage option too which gives approx 145v and makes for a softer sounding OD.

I got mine from Rapid in the UK, but I looked last week and they're not stocking them any more

[Boy Howdy]

Interesting ideas, guys. Thanks! But can someone confirm the Edcor? EDCOR - XPWR082
It looks like it would work fine. I just want to make sure, since I'm a babe in the woods about some of this stuff.

[J M Fahey]

It looks VERY good, it's the real deal.
Perfect for a preamp with 1 (one) 12A_7 and as many Op Amps as you like.
A real find !!
If it had a higher 6.3V rating (600mA) it would be even better.