DIY Effects

[LukeFRC]

Question… and you may need to point me somewhere better to ask

 

i have a schalltechnik Vong Filterung pedal I built sounds great, utterly silent in use

 

i have a sushi box London Underground and a similar diy valve pedal, 200v plate voltage - sounds great and both pretty silent in use.

 

put them together, in any order and there’s a high pitched whine. Separate power units and still happens.

what’s going on and how can I bug fix?

if I stick another preamp buffer between I can partially, but not totally filter it out. 
I thought I was impedance but it happens either way around.

 

[LukeFRC]

1 hour ago, LukeFRC said:

Question… and you may need to point me somewhere better to ask

 

i have a schalltechnik Vong Filterung pedal I built sounds great, utterly silent in use

 

i have a sushi box London Underground and a similar diy valve pedal, 200v plate voltage - sounds great and both pretty silent in use.

 

put them together, in any order and there’s a high pitched whine. Separate power units and still happens.

what’s going on and how can I bug fix?

if I stick another preamp buffer between I can partially, but not totally filter it out. 
I thought I was impedance but it happens either way around.

 

It’s the charge pump in the Vong I think

[Woodinblack]

22 minutes ago, LukeFRC said:

It’s the charge pump in the Vong I think

 

Charge pump in the vong? Its just a simple op-amp filter running from just under 9v.

[tauzero]

34 minutes ago, Woodinblack said:

 

Charge pump in the vong? Its just a simple op-amp filter running from just under 9v.

 

Which uses a TC7660H, presumably to generate the dual rails. Has it got a TC7660 in it rather than a TC7660H? The H is high frequency (120kHz) versus 10kHz for the non-H version.

[LukeFRC]

20 minutes ago, tauzero said:

 

Which uses a TC7660H, presumably to generate the dual rails. Has it got a TC7660 in it rather than a TC7660H? The H is high frequency (120kHz) versus 10kHz for the non-H version.

I will report back

[Woodinblack]

so it has, I never noticed that. I have one, haven't used it for a while, I think because of hf noise with something

 

[LukeFRC]

So... 

I have the same noise into either valve pre with two pedals... both with charge pumps. 
One is a John K Mini XO that is all gain and fizz anyway so you can't notice it unless you're listening... 

Mini XO uses LT1054CP - freq between 15 and 35kHz - typically 25kHz  - so at the lower end that would be audible... 
The Vong came supplied with a ICL7660s which is min 5kHz, typically 8kHz ... 8kHz is about the sound I am hearing! 


so I need a TC7660HEPA or TC7660HCPA Mouser and Farnell have it - if anyone else has got a supplier that stocks them.... 

And given that I may have to pay a fairly large postage on one IC if anyone else with a Vong would like me to buy and post out to you... I mean the ideal is I test it first but...

 

 

[Woodinblack]

ok, looked in my vong and then realised why I was confused - mine is the mini-vong LP, so it has nothing other than the op-amp!

[tauzero]

TC7660S operates at 10kHz unless pin 1 is connected to +V in which case it operates at 45kHz.

 

https://www.microchip.com/en-us/product/TC7660S

[tauzero]

Also https://www.renesas.com/us/en/document/dst/icl7660s-icl7660a-datasheet - under Features, bullet point 4 - "Boost Pin (Pin 1) for Higher Switching Frequency" and the table on page 3 also includes that

 

Mine's also a 7660S. Will stick the meter on it tomorrow and see what pin 1 is at.

[LukeFRC]

7 hours ago, tauzero said:

Also https://www.renesas.com/us/en/document/dst/icl7660s-icl7660a-datasheet - under Features, bullet point 4 - "Boost Pin (Pin 1) for Higher Switching Frequency" and the table on page 3 also includes that

 

Mine's also a 7660S. Will stick the meter on it tomorrow and see what pin 1 is at.

Ah I read about that - you can jumper pins 1 and 8 

[tauzero]

Just checked and pins 1 and 8 are connected so it should be running at 35kHz.

[LukeFRC]

14 minutes ago, tauzero said:

Just checked and pins 1 and 8 are connected so it should be running at 35kHz.

literally just found the same thing 

I wonder what it is then, might ask on the sushi box thread on TB

[Bigwan]

51 minutes ago, LukeFRC said:

literally just found the same thing 

I wonder what it is then, might ask on the sushi box thread on TB

Have you tried the sushi box forum on PedalPCB.com?

 

https://forum.pedalpcb.com/forums/sushiboxfx/

[tauzero]

Just searching for 7660 on PedalPCB I found quite a few references, many mentioning the 7660SCPAZ. I've found the meanings of the suffix letters after the S - C is temperature range (0-70 deg C), PA is package (8-pin DIP), Z is Pb-free. So it's just the S that matters as long as it's an 8-pin DIP.

 

Ah, just found this: "Use your digital multimeter to make sure you have a connection between pin 1 and pin 8 on your charge pump IC. If that is connected and you are hearing a whine you likely have bad chips and can fix your problem by replacing them with something from another source." Can't post a link to it (it's verboten, don't know whether by BC or PedalPCB) but if you search for 7660 it's a topic called "Problem IC Sunflower Fuzz". So maybe you have a duff 7660. I haven't really used mine so don't know if I have the same issue.

 

[LukeFRC]

On 19/06/2023 at 12:41, tauzero said:

Just searching for 7660 on PedalPCB I found quite a few references, many mentioning the 7660SCPAZ. I've found the meanings of the suffix letters after the S - C is temperature range (0-70 deg C), PA is package (8-pin DIP), Z is Pb-free. So it's just the S that matters as long as it's an 8-pin DIP.

 

Ah, just found this: "Use your digital multimeter to make sure you have a connection between pin 1 and pin 8 on your charge pump IC. If that is connected and you are hearing a whine you likely have bad chips and can fix your problem by replacing them with something from another source." Can't post a link to it (it's verboten, don't know whether by BC or PedalPCB) but if you search for 7660 it's a topic called "Problem IC Sunflower Fuzz". So maybe you have a duff 7660. I haven't really used mine so don't know if I have the same issue.

 

So…

Did the power filtering “fix” on the sushibox pedal…

 

and then tried swapping the 7660s for a 7660h 

both of them silent on their own, high pitched whine together… wired either way 

oddly switching either the HPF or the polarity seems to reset the whine and it does a Star Wars like power up sound before returning to the same frequency 

very strange 

[bobbass4k]

The capacitors you're using can affect the noise, modern design rules actually recommend ceramic caps for switched cap charge pumps. Personally I've had issues with the 7660,  I tend to use the LT1054. It's pin compatible except it runs at 25khz by default, so pin 1 isn't boost and needs to be isolated from.V+ if you're replacing a 7660s.

[LukeFRC]

8 minutes ago, bobbass4k said:

The capacitors you're using can affect the noise, modern design rules actually recommend ceramic caps for switched cap charge pumps. Personally I've had issues with the 7660,  I tend to use the LT1054. It's pin compatible except it runs at 25khz by default, so pin 1 isn't boost and needs to be isolated from.V+ if you're replacing a 7660s.

I have a LT1054 I can try 

my thinking is though that if 7660s and 7660h both have a similar sound… and pressing the phase button makes it sound like a cap charging to a point/freq … that it might be something else in the circuit that causes something audible when combined with the sushibox 

 

I think it must be on the ground rather than the power. 
Awkward thing is that it’s the one pedal you get as a kit without having the schematic 

[bobbass4k]

49 minutes ago, LukeFRC said:

I have a LT1054 I can try 

my thinking is though that if 7660s and 7660h both have a similar sound… and pressing the phase button makes it sound like a cap charging to a point/freq … that it might be something else in the circuit that causes something audible when combined with the sushibox 

 

I think it must be on the ground rather than the power. 
Awkward thing is that it’s the one pedal you get as a kit without having the schematic 

Most pedal designers use the same reference design for the 7660s, if you check the schematic for the pumpernickel i would imagine the charge pump section is identical. if you use the LT1054 make sure you isolate pin 1, either cut the trace on the pcb (bit dramatic) or carefully bend the leg so it doesn't go in the socket.

[LukeFRC]

8 hours ago, bobbass4k said:

Most pedal designers use the same reference design for the 7660s, if you check the schematic for the pumpernickel i would imagine the charge pump section is identical. if you use the LT1054 make sure you isolate pin 1, either cut the trace on the pcb (bit dramatic) or carefully bend the leg so it doesn't go in the socket.

This then 

 

[LukeFRC]

Vong is built as per guide, no duff solder I can see… squeeeell different chips can change the freq slightly but something just isn’t right with it when combined with the sushibox. 
not sure what next - probably decide not to use the valve pedals, sell the Vong or put it in a drawer somewhere- which seems a shame  

 

@tauzero I’ll get that sticker in the post tomorrow- its been a super busy week.

[tauzero]

Thanks for that.

[Badscrew]

Gathering my will to restart my electronics adventures. If all is working out like I expect it will, I'll be subjecting y'all to my electronics experiments soon

Nothing original most probably (but what new can you possible invent in the transistor real these days!)

[LukeFRC]

1 hour ago, Badscrew said:

Gathering my will to restart my electronics adventures. If all is working out like I expect it will, I'll be subjecting y'all to my electronics experiments soon

Nothing original most probably (but what new can you possible invent in the transistor real these days!)

Depends what you’re aiming for! 

[Badscrew]

1 hour ago, LukeFRC said:

Depends what you’re aiming for! 

Have ideas for buffers - DIs - EQs - boosts (maybe not all in the same device!)