"Hikari" Drive, something original?

[GammaFlex]

So this is one that I've been working on for a few weeks now, I have utterly become obsessed with the sound of a rangemaster pushing a nice dark amp, that beautiful subtle distortion with the huge amount of upper harmonics... love it! However I wanted to try to get more of that wonderful distortion with some more interesting harmonic content, thus we have this pedal. The breadboard got alot of good use out of this one. It's essentially a two stage one knob "driver" with the first stage being almost exactly a Rangemaster, however instead of the usual -7v the first transistor is biased at a much lower voltage. The second stage uses something called reverse beta, if you're not familiar with it I won't bore you, there's tons of good articles on it on the intrewebs. google-fu!

The reverse transistor in this circuit provides a much different sound than your typical "drive". Besides being focused on the upper harmonics/upper mids, this configuration provides the circuit with a clipped sound that has a bunch of harmonics that is not present in any other pedal I've heard yet. Drives an amp very well and is extremely responsive to playing styles, harder picking gets you more distortion less is less etc... The overall gain of both stages is actually about where a standard rangemaster would sit.

The paintjob is pretty lame (not sure what happened with the white ink), but it was a journey and I'm happy I did it! If you want a schematic I'll post it, if not, then ok.

[diablochris6]

Sounds interesting. Do you have any audio clips?

[RobA]

Sounds interesting. Do you have any audio clips?

+1 to both of those sentences.

What transistors did you use?

[TGP39]

If you want a schematic I'll post it, if not, then ok.

I'd love to see the schematic for educational reasons. If you built a cool pedal that has a pretty unique sound, I would love to learn more about it. With your blessings of course. Thanks.

[Bret608]

This is a cool idea on your part...the intent is similar to the Keeley Fuzzhead but you were able to accomplish your goal with a lower part count. I'd be curious to hear it too.

[GammaFlex]

Here is the vero layout, pay real close attention to the location of the emitter an base of both transistors, they are marked with the E and C for both. Remember that Q2 is flipped on it's head so the emitter is functioning as the collector. Also note the jumper on the trimpot



And the schematic for those that wanted it...



Keep in mind that this is a bright pedal, you may find it lacking in output (with a 10kA pot unity is roughly 2PM) but keep in mind that it doesn't need to have a high amount of boost in order to do it's job, people often interpret "volume" as just being heard.

I didn't have any extreme examples of germanium to try, as far as which PNPs to use I found that for Q1 a hfe of around 80-90 and lkg of .10 to .14 sounded good with a Q2 hfe of around 94-100 and lkg of .17-.20 sounded best, I don't have a ton of transistors to try but experiment and see what sounds good to your ears. Both transistors in this one were AC125s

The trimpot should be adjusted to give 3v on the C of Q1. Less than that and you lose volume and the effect doesn't work well and you get a much nastier saturation. This will vary slightly depending on your choice of transistors and hfe's. I'll put up a short video demo later today hopefully.

[RobA]

Thanks much for the schematic. I just happen to have a bag of shiny new (well, old I guess, but shiny) AC125's that I'll have to try this out with.

[GammaFlex]

[midwayfair]

Where's Q2 biased?

[GammaFlex]

Somehow I always forget something important.

My notes say that Q2's E (acting as the collector) should be biased to -4.6

[jtn191]

Cool build and idea. The demo sounds kinda harsh SS-like on my phone but could sound different through another amp? Sounds unique tho, kinda underbiased

[GammaFlex]

it is bright, on an amp like an Egnater which has some serious bass it provides a nice balance. If it's too spiky I had some good success with subbing the .0068 input cap with a .01uf, still gives a good bit of treble boost but doesn't cut too much.