Hermida Audio - Zendrive [ goop-alarm ]  [traced]

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ODwan
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Post by ODwan »

Hi!
I build this circuit yesterday and found it sound pretty close to my TS-Clone that has been modded to broader bandwidth. As to wether it achieves the Dumble-tone, I ABd it with my DIY Dumble ODS clone and I must say that there is a certain resemblance, though the amp is more lively and dynamic and cleans up better with guitarvolume rolled down. It IS a very nice pedal, though. I had a AD712 and an OPA2604 in there. Not much of a difference, but both are way better than 4558s.
By the way, I find that Gain-, Tone- and Volumepots should be audiotapered. Makes for a much more usable range.
That's my .02$
Greetings,
Timo

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ik6gpy
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Post by ik6gpy »

Just build one with an AD712 (winner Ic :thumbsup ) and BAT41 Schottky Diodes (with 0.33V forward voltage). This is just an average sounding overdrive with Strats and Teles and i found it a little bit "farty" on the Low-Mid frequencies especially when you put the Voice control between 7 and 2 o'clock, not very good sounding with neck pickups. I found that there's not much difference with an all-1N34A clipping circuit.
With Humbuckers it's just wonderful! A totally different beast. Very versatile, dynamic and amp-like.
I don't recommend it for strat-tele lovers, if you want smooooothness a well tuned ts808 (or one of the 1000 clones around :shock: ) is a better choice IMHO. For humbucker equipped guitars is definitely one of the best amp-like overdrive that i've played so far.
Just my 2 cents :)

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MKB
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Post by MKB »

I've used one of these on several gigs now (AD712 op amp, MBR040 Scottky diodes) and like it a lot for a bluesy light overdrive through a clean amp. It's very responsive to dynamics. I did stumble upon something that helped the sound a bit IMO. By mistake on the breadboard I installed a 33nF cap in place of the 3.3nF cap for C6, when I built the circuit into the pedalboard with a 3.3nF it didn't sound as good. So I put a switch in the pedal to select either value for C6. I actually like it with the 33nF more for some reason, the treble is more "amp-like" through a clean bright amp. The 33nF does help the pedal sound better with my Strat (mid-eighties Japanese Fender Strat 1962 reissue, with Hot Gold Lace Sensor pickups).

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Silent Fly
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Post by Silent Fly »

If anybody is interested, I draw the schematics of the Z-Drive from Deric's layout. I used the same component's IDs so if should be easy to follow/correct/modify.

I am still not convinced we have a final list of components. I included some comments about possible variations but I probably forgot something... :roll:
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Z_drive01.gif
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Silent Fly
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Post by Silent Fly »

...and if someone wants to edit the diagram, here the ExpressSCH file.
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Z_drive01.zip
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Silent Fly
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Post by Silent Fly »

pedalfan wrote:(...)
The Z_drive schamatic is like the Jeter Red but with the voice replaced by a switch and two resistors. Has anybody have the Jeter schamatic?
Pedalfan
BTW, does anybody know, sound-wise, what the voice control does?
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madbean
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Post by madbean »

Silent Fly wrote: BTW, does anybody know, sound-wise, what the voice control does?
It will simultaneously (and inversely) change the amount of gain and bass in the feedback loop. One way will add bass at the expense of gain, the other removes bass and adds gain.

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pamaz
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Post by pamaz »

here there are the main differences for zendrive 2.
1) substitute the diodes in the feedback loop and put the tubes instead with anode and grid connected together as one terminal and cathode as the other one. SYMMETRICAL CLIPPING HERE
2) use a 1MB pot for gain control
3)use a 0,22uF cap as the voice control cap
4) filament of the tube powered at 9v dc

Hope to have not made mistakes

Bye.
PM

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Torchy
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Post by Torchy »

Image

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lynessmy
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Post by lynessmy »

Thanks Torchy....but was there 10k resistor in series with the gain poti?
And, is C6 470n or 47n?

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Torchy
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Post by Torchy »

C6 is 470nF as stated in the parts list, there is a 1K resistor across the gain pot - none in series. The vero is as per the schematic underneath it. That schem matches the Zendrive I opened up (as far as I can tell). It certainly sounds like it.

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briggs
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Post by briggs »

Cheers Torchy. More great vero layouts to play with! I'm going to have to order myself a larger sheet of the stuff 8)
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Silent Fly
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Post by Silent Fly »

Torchy wrote:C6 is 470nF as stated in the parts list, there is a 1K resistor across the gain pot - none in series. The vero is as per the schematic underneath it. That schem matches the Zendrive I opened up (as far as I can tell). It certainly sounds like it.
Did you use audio and linear pots as in the schematics?
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Post by tlpruitt »

Hey Torchy,
The layout says 13 trace cuts at the top but I only see 12.

-Tim

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tuemmueh
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Post by tuemmueh »

you're right, cut under C6 isn't visible.

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pedro
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Post by pedro »

Great layout Torchy - thanks for sharing,
I've been hoping I could build a Zen since I sold mine last year after waiting 18 months for it then having a bit of a gear clearout. Now I can build my own - so thanks a million.

Question on the circuit/layout though....
Someone has pointed out to me that he feedback loop on IC1b is quite different from a TS style topology with the tone circuit network not being part of the feedback loop in the Zen circuit/layout. What difference does this make and is it worth trying the circuit both ways ? Was the feedback in the Zen intentionally done this way do you think ?

cheers
Pedro

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Torchy
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Post by Torchy »

Sorry, I obscured the cut when I placed the component number. Ive edited the graphic to show it now, apologies ...

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pedro
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Post by pedro »

First - thanks to the guys who have reverse engineered this - I sold my original Zena and regretted it pretty soon afterwards. :cry:
Many thanks to Torchy for the veroboard layout which I built yesterday - I had a load of vero just sitting waiting and all the stuff I needed in my parts bins, so when I saw the layout I had to build one up to see if it matched the Zen,

Anyway,
for anyone building this I found a bug which needs an edit on the layout - at moment the voice 1&2 connection gets shorted to ground so an extra trace cut is needed in strip I , hole 5; ( i.e. 9 strips from top of layout - 5 holes in from left )

This stops the 100n cap (c% ) and the voice control and pin4 of the op amp shorting to ground. So 14 trace cuts in all.

It took me ages to find it late last night but I got it now and pedal sounding great ! :D
FWIW I'm using TL072, 2n7000's and 2x 1N914 ( i think ) , and old CV8791 germanium.

I plan to mess with different op amps incl AD712 and schottky barrier diodes to get closer to the Zen sound - but its bloody nice as it is frankly !!!

I have an *umble ODS 50w clone I built so it will be nice to compare tones with the amp.

cheers all, glad i found this forum, and hope my bug find helps someone else building this circuit.

What shall I build next - OCD ?

Rgds
Pedro

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Torchy
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Post by Torchy »

Thanks Pedro - layout edited for the extra cut :)

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pedro
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Post by pedro »

PS - i also reversed D3 vs the layout - so its cathode is connected to pin 2 of Op Amp ?
cheers
Pedro

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