Vox - Repeat Percussion (V 809)  [schematic]

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Vox - Repeat Percussion (V 809)  [schematic]

Postby analogguru » 20 Jun 2008, 14:04

A self-proclaimed "All-Knowing Guru" is offering a "corrected" schematic of the Vox Repeat Percussion here:
http://www.diystompboxes.com/smfforum/i ... c=38473.40

There is at least one thing what the self-proclaimed "All-Knowing Guru" doesn´t know:
His schematic neither original nor is it correct - so it is more a fake.

For comparision purposes here is the (wrong) original schematic

and as FSB birthday present No. 2 is here a traced (and for this reason really correct) and tested schematic:

Vox - Repeat Percussion schematic

Happy birthday FSB,
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Re: Vox - Repeat Percussion (V 809)

Postby MoreCowbell » 20 Jun 2008, 16:39

I would DEFINITELY recommend buying several 2N2646 UJT's to try out in this circuit. Some will make the tremolo work great, others won't work at all.
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Re: Vox - Repeat Percussion (V 809)

Postby borislavgajic » 20 Jun 2008, 16:43

:hug: Mine works just great....Thank You mister Guru for the schematic............ :thumbsup
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Re: Vox - Repeat Percussion (V 809)

Postby Dirk_Hendrik » 20 Jun 2008, 21:51

Thank you m'r Boris ;)

Would it be an option to download pdffactory pro, at http://www.fineprint.com/, and use the trial version to prit that layout as a PDF, saving the non-expresspcb users that hassle of installing expresspcb???

But nevertheless, thanks! Good to see people not going the vero- road (no flame intended at any vero leyouters ;) )
Sorry. Plain out of planes.

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Re: Vox - Repeat Percussion (V 809)

Postby borislavgajic » 20 Jun 2008, 22:36

Thank you Mr Dirk :thumbsup

I will follow your sugestion :thumbsup
it is a good advice... :D
... I post the express PCB file also,so people could modify layout,traces.....

[smilie=a_takethatfoo.gif] the summer finaly begins!
Greetings to all nice people on this forum!
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Re: Vox - Repeat Percussion (V 809)

Postby RnFR » 21 Jun 2008, 03:07

thanks boris! been dyin to get this one goin.
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Re: Vox - Repeat Percussion (V 809)

Postby borislavgajic » 21 Jun 2008, 07:20

Don't you die man!!! :block:

I added little SW and now have 3 cap's ( electrolytic)-switchable in place of 10mF.....try smaller valyes(0.47mF....2,2mF) cap......so there is kind of ring modulator sound possible in high speeds
It is recomended to put socket's for tranny's so you could experiment ............

when I connect phaser there was ticking ....but just put input cap 2,2mF

that is all ......
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Re: Vox - Repeat Percussion (V 809)

Postby Gripp » 22 Jun 2008, 08:26

Thanks all!!

Newcomer to this forum here.
I have the RP on my breadboard right now ( has been there for 6 months or something), constructed from various schems floating around and it works.
But it'll be nice to see how it sounds constructed from a true known good schem.
What's more, I've build quite a few pretty complex boxes and can handle the electonic side of things but doing layouts scare me.
This Lo for the RP is just what I need, thanks again Boris!

Best!
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Re: Vox - Repeat Percussion (V 809)

Postby theehman » 23 Jun 2008, 20:54

analogguru wrote:A self-proclaimed "All-Knowing Guru" is offering a "corrected" schematic of the Vox Repeat Percussion here:
http://www.diystompboxes.com/smfforum/i ... c=38473.40

There is at least one thing what the self-proclaimed "All-Knowing Guru" doesn´t know:
His schematic neither original nor is it correct - so it is more a fake.

For comparision purposes here is the (wrong) original schematic


I originally made a corrected schematic using what turned out to be an incorrect 2N2646 layout. :oops: :slap: If you read further you'll find that I discovered the error and corrected it, offering the corrected schematic once again. It was traced from an actual unit except for my 2N2646 orientation.

analogguru wrote:and as FSB birthday present No. 2 is here a traced (and for this reason really correct) and tested schematic:

Vox - Repeat Percussion schematic


Yes, I'm sure that one works, however, I've been using the newest corrected version for my Trem-O-Matic pedals since I started building them and it works fine. You're also welcome to download it using the link at the DIY forum, Mr. "self-proclaimed guru" . :D
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Re: Vox - Repeat Percussion (V 809)

Postby analogguru » 23 Jun 2008, 22:44

offering the corrected schematic once again. It was traced from an actual unit except for my 2N2646 orientation.

This I can´t believe, since it is still incorrect:
The mistake is in the 820 Ohm resistor which in a real unit is 82k....
The difference between 5k6 and 4k7 is not so important

You're also welcome to download it using the link at the DIY forum...

I already downloaded it, for this reason I knew that it is wrong...

Mr. "self-proclaimed guru". :D


:hmmm: ...maybe yes, but for sure not the "All-Knowing" one...... :roll: :D

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Re: Vox - Repeat Percussion (V 809)

Postby theehman » 23 Jun 2008, 23:50

analogguru wrote:
offering the corrected schematic once again. It was traced from an actual unit except for my 2N2646 orientation.

This I can´t believe, since it is still incorrect:
The mistake is in the 820 Ohm resistor which in a real unit is 82k....
The difference between 5k6 and 4k7 is not so important



What I did was scan the original Vox schematic again and modify it. Apparently I forgot to adjust the value of R7 this time which should be 82K, as you pointed out. Thank you for correcting me, however I wish you had just emailed me about it. I'll make the correction once again and upload it to my site.
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Re: Vox - Repeat Percussion (V 809)

Postby analogguru » 27 Jul 2008, 22:55

Above this components is written: MOD like "modification".
The componenent numbers are identical to the original (below) and would replace them.

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Re: Vox - Repeat Percussion (V 809)

Postby Chugs » 29 Mar 2010, 10:38

I just built a Repeat Percussion from AG's schematic. It's a cool sounding pedal. I have noticed, however, that there is a bit of a volume drop with the pedal engaged. Is that normal? :scratch:
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Re: Vox - Repeat Percussion (V 809)

Postby analogguru » 29 Mar 2010, 10:52

You can reduce the value of the 3k3 emitter resistor (R13) to compensate for that.

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Re: Vox - Repeat Percussion (V 809)

Postby Chugs » 29 Mar 2010, 12:48

Great. I shall try that. Thank you. :applause:
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Re: Vox - Repeat Percussion (V 809)

Postby theehman » 29 Mar 2010, 13:48

Chugs wrote:Great. I shall try that. Thank you. :applause:



Try a 1.5K on the emitter.
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Re: Vox - Repeat Percussion (V 809)

Postby dperry » 31 Mar 2010, 18:35

I built this from the schematic too, and also noticed the volume drop.

A 1.5K on the emitter seems to only let the oscillator work in a very small range of the speed pot, so i presume something a bit larger? 2.2k?

Also...the depth knob acts more like a master volume, is this correct?
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Re: Vox - Repeat Percussion (V 809)

Postby R.G. » 02 Apr 2010, 15:21

Any tremolo-like device (this is one, just an odd kind of LFO) can be either cut-only, boost-only, or cut-and-boost with it's amplitude variation.

Boost-only doesn't get out much, as it doesn't offer the fade-to-quiet on the down variations.

Cut-only tremolos work by offering only reductions of level from the normal level. This causes an apparent loss of volume, because your ear hears the up-and-down volume variations and senses the lowered volume times as a reduction in overall volume.

Cut-and-boost tremos inherently hold the same "average" volume level, and are therefore simpler to deal with in a live playing setting. The volume doesn't go down when you hit the footswitch. But the circuit complexity of cut-and-boost is significantly more than cut-only circuits.

Cut-only plus a fixed boost is the compromise which happens a lot in the effects world. The repeat percussion does this style. The UJT and modulation transistor cut the incoming signal level; the transistor amplifier boost it back up to help make up for the apparent cut in levels. Cut-only-plus-fixed-boost can only approximately compensate for the change in apparent level. Changing the depth parameter also requires a change in the boost to make it come out the same apparent level. Works OK if you don't need to change depths while you're playing.
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Re: Vox - Repeat Percussion (V 809)

Postby Chugs » 20 Apr 2010, 11:37

I just built a second Vox Repeat for a friend who is a BIG Spaceman 3 fan but the speed pot only works in a small part of the pot's range and then, at the fast end of the pot's range, the effect stops "repeating" completely. I tried a couple of different 2N2646 transistors but that didn't seem to make much difference. Does anyone have an idea as to what could be causing this problem?

Is this the same problem you had dperry? I used 3k3 on the 2nd transistor's emitter as per the schematic.
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Re: Vox - Repeat Percussion (V 809)

Postby Dan N » 21 Apr 2010, 01:56

What taper did you use for your rate pot? This may be a case where audio or reverse audio could make a lot of difference.
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