Vox - V830 Distortion Booster

sevinisthenumber · Post by **sevinisthenumber** » 06 Jan 2009, 22:39

I want to just do a simple diode clipping switch on this pedal but there are two sets of diodes on the board (d1+d3)(d2+d4). D2 and D4 are coming right off the middle two legs of the jrc488p (47pf cap in between diodes and ic).
D1 and D3 are going to ground after a resistor on the other side of the board.

Just curious what diodes effect the clipping so I can try some different ones out.

Any help is much appreciated.

RnFR · Post by **RnFR** » 07 Jan 2009, 00:41

you should really post a schematic. without it, it is hard to help you out.

but it sounds as if both sets might be used for clipping. on in a feedback loop, and the other to ground.

sevinisthenumber · Post by **sevinisthenumber** » 07 Jan 2009, 02:39

ive looked everywhere but cant find a schematic......

Dirk_Hendrik · Post by **Dirk_Hendrik** » 07 Jan 2009, 08:14

Draw one up and post it.

Post by **modman** » 07 Jan 2009, 10:04

sevinisthenumber wrote:the middle two legs of the jrc488p (47pf cap in between diodes and ic).
D1 and D3 are going to ground after a resistor on the other side of the board.

If your not able to trace the circuit and draw a schematic yourself, you could provide some pictures like these.

sevinisthenumber wrote:Just curious what diodes effect the clipping so I can try some different ones out.
Any help is much appreciated.

It's either of the two sets, of course, or both. I would cut out all the diodes and start from there adding diodes or LEDs or nothing... on your own risk. No risk in having a look at these threads though

Diode Selector on Overdrive
2 vs 4 Diodes

But as this circuit really's not yet available, it would be a great to have pictures or a premilinary schematic. Everybody around here will

you so much

sevinisthenumber · Post by **sevinisthenumber** » 07 Jan 2009, 14:56

Heres some pictures! (crappy cam phone)

Barcode · Post by **Barcode** » 07 Jan 2009, 22:58

now if you can give us the board side, we should be able to help.

sevinisthenumber · Post by **sevinisthenumber** » 08 Jan 2009, 18:58

hope this helps!

sevinisthenumber · Post by **sevinisthenumber** » 09 Jan 2009, 22:17

Any body know???

analogguru · Post by **analogguru** » 16 Jan 2009, 19:02

Sharper pictures of the track (solder) side of BOTH pcb´s could be helpful.

analogguru

sevinisthenumber · Post by **sevinisthenumber** » 16 Jan 2009, 21:54

Turns out d1 and d3 effect it drastically while the other two I cant really HEAR A DIFFERENCE.....

Cloud10 · Post by **Cloud10** » 24 Apr 2009, 22:33

Can anyone tell if this is based on another more popular circuit design?

sevinisthenumber · Post by **sevinisthenumber** » 25 Apr 2009, 01:09

Its a unique sound. I would like to know as well!

Greg · Post by **Greg** » 25 Apr 2009, 01:32

Is there any way you can take some better photos ?

If you do it'll be traced in no time and you'll have all the info you need to mod it.. and so will everyone else here..

sevinisthenumber · Post by **sevinisthenumber** » 25 Apr 2009, 04:28

No problem!! When i took these photos i had to use my phone. Ive gotten a good camera since. I will get them up soon!

daveg777 · Post by **daveg777** » 20 Aug 2009, 18:39

Anyone else perfromed any mods to this pedal?

Dave

sevinisthenumber · Post by **sevinisthenumber** » 20 Aug 2009, 19:39

I did a few but i realized i was using the pedal wrong. Its made for boosting an already (post) effect or a saturated amp.

wolfmason · Post by **wolfmason** » 29 Dec 2009, 15:59

Yeah, I'm afraid these photos leave out the second board (there are two in there). I took this beast apart for the first time last night. Not as complex as a boss pedal or anything similar, so it shouldn't be too tough to figure out. I'm going to recreate the board in Spice or some likewise diagramming app, then post results.

But yeah, this is a nifty creamy distortion pedal, and it seems like it could be really great if you could tame the glassy highs and restore a bit of low end to the signal. In due time...

SteveDallman · Post by **SteveDallman** » 29 Feb 2012, 22:02

I just found the schematic. I had to join a German forum to get it. I posted this on another forum discussing the 810 VS the 830

The 810 is a Tube Screamer. The 830 has many differences.

830 has no input buffer. While the 810/TS has one gainstage, and clipping diodes in the feedback loop of that gainstage, the 830 has TWO stages. The first is like the TS/810 stage, with clipping diodes in the feedback loop. The second stage has two dioded from signal to ground after the stage, like an MXR Dist+/DOD 250.

So you have a TS overdrive stage, and an MXR Dist+/DOD 250/Ratt distortion stage after it.

The TS stage has limited gain. Here's the interesting part, the gain control is a dual pot, with one half controlling the gain of the TS stage, and the other half controls the gain of the MXR/250 stage simultaneously.

The tone stage is next. The 810 has an active tone control that mostly adjusts the high end.

The 830 has a gain stage, followed by a Big Muff type tone control. One could mod the tone control the same as a Big Muff control.

In that tone control, at some settings, there is a cut in the midrange. It is far different than the tone control in the 810.

The extra stage, and the fact that the second distortion stage follows the first distortion stage, could cause noise.

One could change the two 4558 op amps to TL072, or some other quieter op amps to lower noise.

The second pair of clipping diodes have no capacitor bypass to lower the high freq's some, as the MXR Dist+ and DOD 250 do. A small cap across D3/D4 could remove the very high end, lowering noise and taming the excessive highs of the pedal some. I will try this on mine.
Vox V830 Schematic

Chugs · Post by **Chugs** » 01 Mar 2012, 08:49

To tame the high end you could also try placing a small capacitor in parallel with R24. Say 220pf.