Diezel VH4 Pedal  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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SoftPalate
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Post by SoftPalate »

Hey guys,

I'm new to all of this stuff and I recently picked up one of these boards and populated it and am ready to install it. I'm using a 1590BB (which is, I believe, what it was designed for) and after I got all the holes drilled I discovered that, while the pots all fit nicely, there isn't any room "beneath" them for the jacks to fit. All of your build pics look so nice and neat and I can't even find a way to squeeze those jacks in the enclosure. Am I doing something wrong?

Thanks for any help... :roll:

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caspercody
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SoftPalate
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Post by SoftPalate »

OK, thanks. This documentation is for a different board (Valhalla), which I realize is the same kind of clone, but I was referring to the drill template I found for the Wiezel, because that's the board I was building. That one has the pots so near the top, that the jacks won't fit without sticking out below the floor of the enclosure.

I'll make an adjustment and try to drill a new enclosure.

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syamilaliff
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Post by syamilaliff »

Putting it after a buffered did the trick. No more whistling noise.

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Daverem
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Post by Daverem »

I built one without the charge pump to test other voltages. Is it worth raising the voltage to + -15V?

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lead2203
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Post by lead2203 »

Optical wrote: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
I don't know if someone has pointed this out yet but the tone stack in the real VH4 IS wired Fender style. Peter does it this way in most of his amps and the mods I've seen.

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befey
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Post by befey »

I just finished building the pedal pcb Valhalla.

I used shielded wire on the input and output. Was getting some squealing on the highest gain settings before I put it in the enclosure.

Once it was boxed, it's super quiet even maxed.

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Daverem
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Post by Daverem »

some experiments.....i tried with 18+-, no oscillation with to much headroom and the tone feel was not like the original, 15+- feel good,but oscillation at 3 o clock, i came back to 12v be cause is a better tone for me.

I jump the buffer stage, take off 100k and it had 0 oscillation finally, the gain looked similar to the original but with a lilttle of lost of bite tones, not to much as put a clon buffer in front
(really bad sound), the buffer in the original give there some of personality and bite, but can jump it.

Im not and expert but my theory is: the buffer with the first high gain in the same op amp maybe create the oscillation in contact with 4th stage of tone control treble section....maybe some day i gonna build one with a insolated buffer and first stage, but without the buffer stage sound really good to me...

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Daverem
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Post by Daverem »

I finally build the same buffer in a insolated pcb and i canceled the original in the op amp... The oscillation is gone!!! And the tone is same as the original....maybe there was the problem, too much gain inside the same op amp... Now I gonna redesing the pcb, change all tl072 by opa2130 or jrc4580 for tube screamer flavor and return to the Icl7660 .... By the way, i took off the Insolated wires and still without oscillation, but with a little of ground noise, I gonna return at them for a better quiet tone...

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freshmex18
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Post by freshmex18 »

I just built this and I am having troubles. The pedal does not work at all when it is switched on. All I get is a high pitched whine even though I used shielded wire for the input and the gain. When the pedal is off, the gain knob somehow affects the bypass signal. When the gain knob is turned all the way down, the bypass works; if I turn it up, the signal disappears and is replaced with a whine/beeping sound. I have checked every component and they are all in the right place and oriented correctly. I have resoldered every connection twice. Anyone have any ideas?

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freshmex18
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Post by freshmex18 »

OK, I was wrong. One of the 2.2 electrolytic caps was off by one hole. Now that that's fixed and everything is verified in the correct place and resoldered, nothing works at all. No signal going through to the amp either when the pedal is on or off. I'm at a loss.

Does anyone have a pic of the offboard wiring? Wondering if I did something wrong there

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dfx_pcbs
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Post by dfx_pcbs »

befey wrote:I just finished building the pedal pcb Valhalla.

I used shielded wire on the input and output. Was getting some squealing on the highest gain settings before I put it in the enclosure.

Once it was boxed, it's super quiet even maxed.
Just built the Valhalla, works but same as you some high pitch whine with full gain, maybe it will quieten once boxed up!

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familybezerker
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Post by familybezerker »

Daverem wrote: 21 Jan 2020, 23:19 I finally build the same buffer in a insolated pcb and i canceled the original in the op amp... The oscillation is gone!!! And the tone is same as the original....maybe there was the problem, too much gain inside the same op amp... Now I gonna redesing the pcb, change all tl072 by opa2130 or jrc4580 for tube screamer flavor and return to the Icl7660 .... By the way, i took off the Insolated wires and still without oscillation, but with a little of ground noise, I gonna return at them for a better quiet tone...
I also am pulling out my hair trying to get rid of the oscillation from this Valhalla. @Daverem, I am interested in what you found by removing the buffer. Could you provide more info about exactly how you did that? I did try pulling out IC1 completely and there was still sound including oscillation. Would that then mean that separating out the input section as you did to another board wouldn't solve the issue for me?

Buffer pedal in front helped me with eliminating squeal but not oscillation. Shielded input and output wire did not solve oscillation. I've tried different TL072s. Only thing I have not yet. tried to replacing first TL072 with OPA2134. Could that be a way to solve oscillation?

I have a real VH4 pedal and it's spaced much further apart in there and I wonder if that's the key. I can't change my PCB but it seems others have gotten rid of oscillation somehow! Any other latest and greatest ideas that I haven't covered to solve oscillation?

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familybezerker
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Post by familybezerker »

I solved the oscillation problem! It was my switching power supply. Using a non-switching power supply fixed it.

I got the idea from one of bajamans earlier posts where he said his power supply whined.

I have no whine when the guitar is plugged in. If there is no input into the pedal, it will while above 60% gain but putting the Valhalla in front of a buffer pedal solves this.

I shielded the input and output wires but have no way of knowing without unsoldering what effect this had on the final result.

Now - since I have an real VH4 pedal, when comparing side by side they are very close. The character and sound is all there.
The real one is a bit more crisp - more hifi. I wonder if this is due to the Nichicon and Wima caps in the original plus they have an OPA2134 in IC1 and I have a TL072. I may try upgrading these components to see if it brings it close. The huge yellow Wima cap in the original may have to be bent in some way to fit inside the enclosure.

[I ordered this kit from Musikding. I realized after the fact that one difference between their Valhalla kit and their Benzin VH4 kit is that the Benzin VH4 kit includes the OPA2134. However Valhalla kit BOM has the correct C25k pots but I still received B25k with it.]

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Ichabod_Crane
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Post by Ichabod_Crane »

I don't know how much difference do those ICs, but consider that a C25k pot setted at 50% is about like a B25k setted at 90%.
In this circuits (if there's no other difference) with your B25k you should get lower Presence and Deep setting than the original one (or than a C25k pots one).

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avielnah
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Post by avielnah »

Bringing this up again.
I built the pcb guitar mania board and i face w problems
1. I get squeels, hiss, and noise whenever my gain is more than 12oclock. I dont get any though if i use TL072 in the first stage instead of the OPA2134.. how is that possible?

2.my presence knob acts more like volume

My wires are shielded,and pedal is boxed, but i cant get rid of the noise..

I will appreciate your help.

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bmxguitarsbmx
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Post by bmxguitarsbmx »

1) tl072 is a pretty forgiving op-amp to layout and power supply. Almost no consideration is needed to keep the 072 in line.

2) is your presence cap too big?

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avielnah
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Post by avielnah »

i double checked my presence cap,
but i am more worried about the feedback for now, with TL072 the pedal has less gain, and less saturation. it really lacks that extra drive. the OPA2134 gives it a crazy amount of gain.
i tried a buffer in front but it didnt help. in fact i get it with nothing connected to the input as well.
any ideas what to try to fight this?

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avielnah
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Post by avielnah »

i also dont really get it how come i see such a gain boost, the overall gain should be determined by the feedback network, and not the op amp itself.

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Post by avielnah »

did another test - i removed all the ICs expect the OPA2134 and the charge pump. i still get oscilation on the 2nd stage output, no idea how to solve it though

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