Zendrive... things have changed??

[claytushaywood]

So... I seem to remember my first zendrive build a few years ago.  bat41's, 2n700's, and ad712 were all i saw as parts recommendations.  I go to look at schematics again and now it seems like i'm seeing more people using the 1458 opamp and even 1n34a's as diodes.  Then I see 2 back to back bat41's with the other one a 1n34a...

Is there any general consensus or is it all unknown?  I'm curious because I just built my first one that doesnt sound good... I used 2 bat 41's (.32mv) , 1xnos germanium measured at .36mv, and 2x2n7000's and an ad712 that I paid $3.50 for. 

I never even thought about measuring forward voltage of mosfets but now thinking about it i'm using 2n7000's i ordered from tayda (I've gotten 1n34a's that measured a .75mv voltage drop haha)

I also feel like increasing the gain increases some dirty undertones... and going counter clockwise on the voice pot really affects how much gain i have... almost more so than the gain pot. 

I've tried several opamps and they do greatly affect the sound but none of them have made it great sounding.  it's not absolutely terrible and it works.  it's just not quite there.

any ideas would be appreciated!

[cooder]

... nad to add to the confusion I've seen gutsshots of the latest version made under Lovepedal umbrella with NE5532 opamp in there (maybe because it's cheaper than AD712 ).
Haven't tried that or made comparisons myself yet, but would be keen to do so and have other people chime in as well what maybe a go.

[alanp]

Hate to sound rude and rough, but if sounds good, then fuck it. There are times when all the corksniffery gets annoying. How many people bitch about Jimmy Page's toan on old Zepp records, but then thoroughly enjoy the songs themselves? (discl:beer)

[midwayfair]

I also disliked the stock Zendrive, even when using the right chip.

Here's a few things I can suggest:

1) I like BS170s as clipping diodes. I don't think it's a big difference, but they just sound ... spongier, I guess. The knee might be different from the 2N7000s. This is true for me in a lot of circuits. But I wouldn't fuss about the diodes. I don't think there's any mojo there in a negative feedback circuit beyond the peculiarities of the MOSFET clipping. The others are just blocking diodes to prevent the MOSFETs from reverse conducting.

2) I think the Zen Drive sounds worlds better with an input buffer. I actually made mine buffered bypass with a FET buffer on the input.

3) You're right that the voice pot affects the gain a lot -- it's actually setting the range of the gain pot both in terms of frequency and amount of gain. At its lowest, the max gain is about 51x ... at its highest, it's 502x. That's a HUGE difference. What I would do is find the range you like, and then measure the pot at both extremes of those settings. Swap out the pot for a value close to those measurements (C taper is best) OR just strap a resistor across it to get to the right amount of resistance, and then adjust the resistor in series with the voice pot. (If you like the lower settings, you could recalculate the cutoff formed with the 100nF going to ground, increase the size of that capacitor accordingly, and then still use the smaller potentiometer so that you don't affect the gain range as much.) Alternatively, you could just modify it to have the Timmy's bass control instead ... the voice pot aspires to be a bass control, after all. (Apologies if this paragraph is a little confusing, I don't really have time to draw out a schematic with what I'm talking about.)

4) I can't think of what to do about dirty undertones. Are you talking about fizziness? Something else?

[Jabulani Jonny]

I swear it's like Miracle on 34th Street, every time Patton speaks, a pedal gets its wings.

I could probably fill a notebook with the great suggestions you've made for bettering existing circuits.


Sent from my iPhone using Tapatalk

[claytushaywood]

I also disliked the stock Zendrive, even when using the right chip.

Here's a few things I can suggest:

1) I like BS170s as clipping diodes. I don't think it's a big difference, but they just sound ... spongier, I guess. The knee might be different from the 2N7000s. This is true for me in a lot of circuits. But I wouldn't fuss about the diodes. I don't think there's any mojo there in a negative feedback circuit beyond the peculiarities of the MOSFET clipping. The others are just blocking diodes to prevent the MOSFETs from reverse conducting.

2) I think the Zen Drive sounds worlds better with an input buffer. I actually made mine buffered bypass with a FET buffer on the input.

3) You're right that the voice pot affects the gain a lot -- it's actually setting the range of the gain pot both in terms of frequency and amount of gain. At its lowest, the max gain is about 51x ... at its highest, it's 502x. That's a HUGE difference. What I would do is find the range you like, and then measure the pot at both extremes of those settings. Swap out the pot for a value close to those measurements (C taper is best) OR just strap a resistor across it to get to the right amount of resistance, and then adjust the resistor in series with the voice pot. (If you like the lower settings, you could recalculate the cutoff formed with the 100nF going to ground, increase the size of that capacitor accordingly, and then still use the smaller potentiometer so that you don't affect the gain range as much.) Alternatively, you could just modify it to have the Timmy's bass control instead ... the voice pot aspires to be a bass control, after all. (Apologies if this paragraph is a little confusing, I don't really have time to draw out a schematic with what I'm talking about.)

4) I can't think of what to do about dirty undertones. Are you talking about fizziness? Something else?

WOW!  Thanks again jon, the bs170's really made this thing come alive!  It helped with the fizziness on the decay of the overdrive immensely (that's what i was talking about with dirty undertones or whatver I said).  Much smoother with the bs170's for sure.

i think i may have had a short or something with the voice pot, gain pot interactions... it is working much better now, but I'm going to look at the timmy and see about implementing the bass control from it

THANKS!

[micromegas]

If you want something similar to the Zendrive, but a little more original and more usable (in my humble opinion) you should try the NOC3 Firefly (I shared the schematic here I think)