Mini Chorus tone bleed when off and lack of headroom

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Mini Chorus tone bleed when off and lack of headroom

Beitragvon randomas » Mo 17 Jun, 2013 14:05

Hallo there, my apologies for not writing in German, but it would be even less comprehensible than my English ... :P

I have just bought and successfully built the mini chorus kit (3 pot version), and I'm very happy with it.

I do have a couple of questions though.

When I have the pedal in my signal path it kills the volume when in the off position, even though it looks like true bypass wiring (to my untrained eyes).

When I play chords with allot of strength I get some pretty ugly breakup noise is this normal can I do something to give the pedal more headroom?

I have wired the output jack ground to the central pin on the 3dpt switch (same ground as input jack), instead of the enclosure, could this be the culprit for the tone bleed?

TIA

Matt
randomas
 
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Re: Mini Chorus tone bleed when off and lack of headroom

Beitragvon Uwe K. » Do 20 Jun, 2013 14:55

HI,
if the pedal in TB mode (effekt off) . You don't must have any volume drop or changes of the sound. If all in a metal enclosure, the output jack doesn's a wire to ground. Ground becomes over the metal enclosure.
The ground wire goes from the shield input jack--> DC jack -- PCB and a wire from the DC-jack to the Lug 5 of the switch to give the ground for the LED. A little bit noise is normal,is the digital noise from the AD of the pt2399. At the minimum circuit is not a filter design.

regards Uwe
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Uwe K.
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Re: Mini Chorus tone bleed when off and lack of headroom

Beitragvon randomas » So 23 Jun, 2013 23:18

Thank you Uwe, I'll try and move the output ground, it's wired to the switch's pin 5 so that's probably why I'm getting the tonebleed.

On the other hand the noise I'm talking about is not background high or low frequency noise but peak breakup distortion when I play hard (particularly on the attack of chords) and signal from the guitar gets very strong.
randomas
 
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Registriert: Mo 17 Jun, 2013 13:56

Re: Mini Chorus tone bleed when off and lack of headroom

Beitragvon randomas » Di 25 Jun, 2013 09:59

I disconnected the output ground from pin 5 on the switch, but I'm still getting terrible tone loss when in TB mode, it sounds as if the tone pot on the guitar were turned down all the way.

Any idea of where on the circuit I could have a short that builds a low-pass filter in TB mode?
randomas
 
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Registriert: Mo 17 Jun, 2013 13:56

Re: Mini Chorus tone bleed when off and lack of headroom

Beitragvon Uwe K. » Di 25 Jun, 2013 11:23

Hi,
If the switch ready soldered inc. the in and outjacks, you have in TB modus a 1:1 connection from in to out. You can it measured with a dmm in resistor mode. The resistance must be zero.
you can tested, desoldered the wire from Lug 1 3PDT (in Effect) and lug 8 3PDT (out effect). The is the complete circuit down.


regards Uwe
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Re: Mini Chorus tone bleed when off and lack of headroom

Beitragvon randomas » Do 17 Okt, 2013 13:33

I've been doing some more testing and have partially solved the problem. First off the TB mode low-pass problem is solved by putting a buffered pedal before it in the pedal chain, this can happen and it's just that there's an impedance interface between cable and effect ... nothing to be done (could change jacks and connection wires, but buffer is easier).

Next when the effect is activated there was a noticeable volume drop, I have partially solved this by changing the resistance value of R15, from the circuit diagram that looks like a negative feedback Amp circuit so I raised R15 from 22k to 68k and then 100k. With 100k the volume is perfect, but the break-up/distortion problem with loud mid low frequencies has become allot more noticeable, I may have to roll it back to 68k.

I recorded a test run (before changing R15) with another delay pedal too here, using a guitar I built, and here is some random noodling with the full effect chain on (my playing is not very good, but you can hear the pedals).

Thanks for the help, and if you have any suggestion for giving the pedal more headroom I'd love to hear it.
randomas
 
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