Unexpected Bender

[juansolo]

Well I wasn't expecting to build one of these! Found a bag of PNP transistors so it'd have been rude not to build a Mk2 bender. One of which turned out rather awesome so got boxed up.

[bluescage]

Very nice!! Love the artwork!

[zombie_rock123]

Looks lush! Did you audition the transistors or did the germ gods smile on you?

[jimilee]

I was just thinking about building one of these.


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[jubal81]

Love it. Also disgustingly clean for a vero build. Damnation.


When you happen to dial in the right Ge, it's magic. Just a little off and it's just 'meh.'

[juansolo]

Yeah the other one we did we couldn't get close. But yeah, we meter them first, and fit a pair of bias pots (we've started adjusting two resistors rather than the usual one) set at around the right values to start off, then tweak from there. When it's where we like it we measure and replace the pots with resistors.

Vero... I don't do it often any more, but for this as it was initially just an experiment, it wasn't worth getting any PCBs done for it.

[Bret608]

Looks awesome as always! How did your transistors measure? I'm building my second attempt at a MkII soon and am curious what you thought about leakier/less leaky, etc. The first one I tried wasn't bad, it just didn't set my world on fire.

[Boba7]

I love the artwork. Always a pleasure to see your work!

[juansolo]

Looks awesome as always! How did your transistors measure? I'm building my second attempt at a MkII soon and am curious what you thought about leakier/less leaky, etc. The first one I tried wasn't bad, it just didn't set my world on fire.

It's a bit of a crapshoot. These had bugger all leakage on them. Q3 was in the 200hfe range, can't remember the other two but they'd be a lot lower. The remainder we had were all low hfe and nigh on zero leakage and made a horrible sounding thing. We've just stripped an old mk2 we made (full set of mullards in it), and are going to drop them onto the other board we made and try and bias that to see what we get. Gave them a quick meter yesterday and they're 70,80 and 100+. Lots of leakage on these. So could work ok... We shall see if there's a build report in a few weeks or not with another mk2 in it

[mrclean77]

Nice work, per usual. I imagine finding a bag of PNP trannies is well past the excitement level of finding a few extra bucks in your pants from last week....maybe only a little past coming home to discover your wife did NOT eat that last pc of pizza in the crusty box hidden in the fridge. Approximately.

Love it. Also disgustingly clean for a vero build. Damnation.

Agreed.

[Bret608]

Thanks for sharing the info! It will be helpful for my upcoming build. I was suspecting higher leakage is important. When I tried a Supa Fuzz/early MkII specs build, I really only had low leakage transistors at that point. The collector voltages would not get into the ranges found on vintage units by the D*A*M* forumites--way lower is what I was getting. I have a better stash of leaky ones now, so hopefully it will go better.

[AntKnee]

Great work, sir! As usual I like your graphic choice. Your graphic library is impressive.

[flanagan0718]

This came out fantastic! I has fw qrwstns...

Never built a "Tone Bender" circuit. I recently squired an ASS LOAD of pnp germ transistors. What were the values you started with? How hard was it to "dial in"? What is your favorite layout?

[juansolo]

That one is one of IVIark's (TagBoardFX) layouts. Nice and tight and has the voltage inverter on board so is neat.

Meter all your transistors... Conventional thinking is Q1-3 70,70,100hfe. However that all depends on the amount of leakage. No leakage and you'll get very little nice fuzziness. Too much and it's too noisy. So we've gone all over the place from there. As I say, the one above has a 200hfe transistor in Q3 and sounds amazing. I think this might have something to do with the way we bias them.

Socket the vero for the trannies, also socket the 8K2 and 100K that are in line on the vero (yeah, we're going off piste here with accepted thinking). Fit a 10k pot in place of the 8k2 resistor and a 100k pot in place of the 100k resistor. Load it up with transistors. Power it up then adjust the 10k pot until the collector of Q3 is around 8V. Adjust the 10k pot until the collector of Q2 is around 250mV.

Then see what it sounds like. Because depending on the transistors, that might still sound shit... I know the 6 trannies we were juggling today all did. If however it sounds good, have a tweak of the pots by ear until it sounds awesome... If you can get it sounding awesome, pop the pots off and measure them dropping resistors of equal value in their place, de-socket and solder in the trannies and you're done.

BUT, bear in mind getting a good set of transistors is a bit of a 'mare. It's also really good to have a reference mk2 bender that already sounds awesome to back-to-back it with. They're a sod to get really good. We've even told the bloke we built this one that if he sells it, we'll buy it back from him Because it's the only one we've built that gets close to our reference bender (it's nailed on).

EDIT: Hmm interesting, I thought I'd look back on my site and see if I noted what I put in the reference Bender. I didn't but I made this note: "It's using a completely random selection of transistors (an unknown Mullard, an AC128 and some Hitachi thing!) all with too much gain if you go with accepted knowledge. Yet it sounds fantastic and makes mine sound shit".

So again with the higher than normal gain... *rubs chin* worth bearing in mind.

[flanagan0718]

WOW, That's a ton of good info. I am assuming that you mean fit a 10k trim pot where the 8.2k is...correct? I might give this a shot in the very near future. Thanks for the hand holding  . I'll have to look up a video on how to test leakage, I'm sure all the ones I have can't be good. Sorry for the Hi jack.

Your pedals are always stunning. Keep up the good work!