Diezel VH4 Pedal  [schematic]

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Re: Diezel VH4 Pedal

Postby bmxguitarsbmx » 13 Sep 2017, 18:48

Both Presence and Depth should be C type (reverse log). It will give the controls something closer to dB/degree of rotation, making the sweet spot a little easier to hit.
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Re: Diezel VH4 Pedal

Postby Optical » 14 Sep 2017, 03:40

You can mitigate the issue by reducing the pot value or putting a resistor between pins 2&3 on the pot to change the curve to a more aani-log shape.
That's something I need to play with soon to figure out what values. Had the same issue building a tube VH4 amp
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Re: Diezel VH4 Pedal

Postby reichi » 19 Sep 2017, 09:48

Hey,

i don't know if this is allowed here but i've ordered a small batch of weasel v84 and now have 4 boards left.
I'm located in germany and would give them away for production cost + shipping (for germany/austria roughly ~5€ for one or ~7€ for two).
Sadly packaging + shipping costs are higher than the actual prodcution cost which is <2€.

If anyone is interested I'll calc the exact price (it's a bit less than stated, i was just too lazy to calculate it exactly).
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Re: Diezel VH4 Pedal

Postby Optical » 27 Sep 2017, 03:08

Bummer, just finished building two and the output is messy and lots of oscillation and motorboating :(
I must have stuffed something up, time to start tracing with a scope!

Actually im just using 9v to power them at the moment. Would a low voltage or current supply ability cause this?
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Re: Diezel VH4 Pedal

Postby alltrax » 27 Sep 2017, 08:44

Optical wrote:Bummer, just finished building two and the output is messy and lots of oscillation and motorboating :(
I must have stuffed something up, time to start tracing with a scope!

Actually im just using 9v to power them at the moment. Would a low voltage or current supply ability cause this?

Did you put the regulator ?
I'm using mine @9v but omitted the regulator to avoid the voltage drop and it sounds fine
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Re: Diezel VH4 Pedal

Postby Optical » 29 Sep 2017, 03:54

I tracked down the issues. I built two - one with a 12V reg and one powered direct from a 9V battery.
The one with the 12V reg had a jack issue - not making ground properly which caused oscillation.
The 9V powered re-less one - the battery voltage was too low, about 7.5V. Sent the circuit into oscillation.

Comparing the sound of 9V pedal to the 12V pedal, the 9V one has a little muddiness in comparison, lack of headroom I suppose. Not a huge amount but it's enough to want to make me want to power it from more volts...

Thanks for the PCBs Bajaaman! Now to do some recording and see how it compares to my tube VH4 :)
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Re: Diezel VH4 Pedal

Postby Optical » 29 Sep 2017, 04:03

Oh - I also want to address what might be a small error.

In the tone stack, the schematics show a Fender style tone stack with the mid pot wired as a rheostat. In the real amp the tone stack is Marshall style with the mid pot wired as a pot. The values are the same, but this change changes the tone shaping a lot! Much more bass and less treble with the Fender stack.

Can someone check the real pedal to confirm whether it is on fact fender style or Marshall style? It's an easy wiring reconfiguration to make and the PCB wont change.
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Re: Diezel VH4 Pedal

Postby Optical » 29 Sep 2017, 04:09

I think it should be like this:
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Re: Diezel VH4 Pedal

Postby Optical » 29 Sep 2017, 04:48

Sorry for all the posts :o

I checked the photo and the tone stack does appear to be wired Fender style. So the schematic is correct.
I wonder why they went that way instead of like the real amp... I think i'll try the other configuration anyway to see how it sounds
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Re: Diezel VH4 Pedal

Postby alltrax » 29 Sep 2017, 08:57

Optical wrote:I think i'll try the other configuration anyway to see how it sounds

Let us know :thumbsup
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Re: Diezel VH4 Pedal

Postby Optical » 30 Sep 2017, 04:23

Just tried the Marshall style mid pot wiring and it is definitely my preference. To me there more audible mid range harmonics and overall has more clarity.
Easy to do by swapping one wire across.

I also tested where the pedal starts to get muddy relative to the input voltage, 8V seems to be the limit. So I think a full 9V battery should be fine.

I also tried boosting it with some clean boosts and tube screamer type circuits. It takes a boost really well. Overall an excellent pedal!
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Re: Diezel VH4 Pedal

Postby J0K3RX » 12 Oct 2017, 18:50

Looks like UK-electronic is selling bajamans "Wiesel V84" board in their new Diezel VH4 amp sim kit which ironically is also named Wiesel V84 :hmmm:

http://uk-electronic.de/onlineshop/prod ... fdffa372ad

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Re: Diezel VH4 Pedal

Postby bajaman » 12 Oct 2017, 22:18

:shock:
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Re: Diezel VH4 Pedal

Postby bajaman » 12 Oct 2017, 22:36

Uwe has put together a complete kit of parts with an excellent pdf builder's manual too! :thumbsup
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Re: Diezel VH4 Pedal

Postby reichi » 13 Oct 2017, 14:55

@bajaman: i have high frequency "squealing" issues when turning the gain up to far (probably everything beyond 75%).
It's sounds like feedback to me.

I've pretty much narrowed it down to happen around the first TL072 ( the part with the z-diodes).
Does any one have any hint's what could be wrong here?

I took some "random" 5V6 z-diodes had still flying around (4734 to be precise) , could it be caused by those?
I'm a bit clueless cause i seem unable to track the actual issue down
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Re: Diezel VH4 Pedal

Postby reichi » 13 Oct 2017, 14:56

oh.. i'm using the v84 pcb from osh park (built elsewhere but that shouldn't matter i guess).
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Re: Diezel VH4 Pedal

Postby J0K3RX » 14 Oct 2017, 16:42

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Re: Diezel VH4 Pedal

Postby reichi » 16 Oct 2017, 06:03

As an Information for others that may encounter issues similar to mine (massive feedback when gain is turned up "too far").
I was able to suppress the feedback by increasing the feedback cap on the 3rd gain stage (IC2A, the one with the 1N5232 Z-Diodes) a LOT!
I opted for a quick trial & error with i had flying around here and had to go up to 560pf to eliminate feedback on full gain.

Could it be the caused by different Z-Diode capacitance (afaik they do have some capacitance, right?) ?!

It's nice to have a working Pedal now, but I hate not understanding the why on issues like this one ;).
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Re: Diezel VH4 Pedal

Postby sego91 » 05 Nov 2017, 14:50

My current status on the build
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When you have all the pieces, but you run out of the 1uf caps and the Tl072 :evil:
can't wait until tomorrow to get this things at the local electronic shops and test them!



Btw I have some extra boards if someone is interested :D
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Re: Diezel VH4 Pedal

Postby Optical » 05 Nov 2017, 22:30

Depending on the footswitch you use and the enclosure you put it in, you might want to mount tall components on the other side of the PCB.
On mine the electro caps hit the lid and wouldnt let it close
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