# Twin Face Fuzz - Hiss on the Ge Side



## Dirty_Boogie (Dec 23, 2019)

Hi friends.  I decided to re-box a Twin Face (Si-Ge Fuzz Face) build from last year.  I rebiased it, and the Si side sounds a lot better than I remember from a year ago.  However, there is a noticeable hiss on the Ge side that I can't pinpoint.  Anyone have any ideas on which component(s) might be the source of this hiss.  Using NTE158 Ge transistors, and BC108B Si transistors.  While not overbearing, it's enough to open the gate on my noise gate, and I would love to tame it.  Thanks.


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## benny_profane (Dec 23, 2019)

I'd check the power supply first. Can you try powering your circuit without the charge pump with a battery (be mindful of polarity!) and see if the problem is still there. If it isn't, try reintroducing the charge pump and again use a battery (be mindful of polarity!). You may have to increase some of the power filtering capacitance.


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## Dirty_Boogie (Dec 23, 2019)

benny_profane said:


> I'd check the power supply first. Can you try powering your circuit without the charge pump with a battery (be mindful of polarity!) and see if the problem is still there. If it isn't, try reintroducing the charge pump and again use a battery (be mindful of polarity!). You may have to increase some of the power filtering capacitance.


Thanks.  Only been running it with a battery - it's not (yet) on my pedalboard with the 9V power brick.  I'll look at the schematic to see where to introduce the -9V and bypass the charge pump.  Hoping for something simpler first to check.


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## benny_profane (Dec 23, 2019)

-9V in at the junction of R3 (470R) and R1 (33K); positive ground at a ground point. I just noticed you didn't socket your IC... I _think_ you should be okay putting -9V on pin 5 (Vout), maybe wait for confirmation from someone else before moving ahead. You definitely don't want to put out of tolerance voltage on the Vin pin. 

Where did you source the TC1044, by the way?


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## Dirty_Boogie (Dec 23, 2019)

benny_profane said:


> -9V in at the junction of R3 (470R) and R1 (33K); positive ground at a ground point. I just noticed you didn't socket your IC... I _think_ you should be okay putting -9V on pin 5 (Vout), maybe wait for confirmation from someone else before moving ahead. You definitely don't want to put out of tolerance voltage on the Vin pin.
> 
> Where did you source the TC1044, by the way?


Yeah, the one time I don't socket the IC... ;-)  Most likely Tayda for the TC1044


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## benny_profane (Dec 23, 2019)

I've had issues with charge pumps from Tayda (as have others). That's one component that I'd recommend sourcing elsewhere if possible. If it's a whine/high pitched hiss, I'd suspect the charge pump and go about powering the circuit while bypassing the charge pump. If you're hesitant to do so, rule out other issues by providing transistor voltages for the Ge side of the circuit to see if there's a bias issue.


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## Dirty_Boogie (Dec 23, 2019)

benny_profane said:


> I've had issues with charge pumps from Tayda (as have others). That's one component that I'd recommend sourcing elsewhere if possible. If it's a whine/high pitched hiss, I'd suspect the charge pump and go about powering the circuit while bypassing the charge pump. If you're hesitant to do so, rule out other issues by providing transistor voltages for the Ge side of the circuit to see if there's a bias issue.


Will do - thanks Benny


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## Chuck D. Bones (Dec 24, 2019)

Ge transistors themselves can be noisy and are susceptible to heat damage when soldering.  I've heard that NTE transistors are low quality, but have no hard data to support that notion.  Those cheapo bias pots are also suspect.  If you eliminate the charge pump as a cause of the noise, then I'd install sockets for the Ge transistors and try some others.  Bourns makes quality trimpots that fit the footprint on the board.


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## Dirty_Boogie (Dec 25, 2019)

benny_profane said:


> I've had issues with charge pumps from Tayda (as have others). That's one component that I'd recommend sourcing elsewhere if possible. If it's a whine/high pitched hiss, I'd suspect the charge pump and go about powering the circuit while bypassing the charge pump. If you're hesitant to do so, rule out other issues by providing transistor voltages for the Ge side of the circuit to see if there's a bias issue.


Where do you suggest getting the charge pump IC's from?  I checked Smallbear, and their charge pumps are the same part number/same manufacturer that Tayda lists.


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## Nostradoomus (Dec 25, 2019)

I’d socket your transistors and play around with different types before I messed with the power supply! I haven’t had any bunk pumps from Tayda.


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## Chuck D. Bones (Dec 25, 2019)

If you have an audio probe or a scope, check the -9V supply for noise.  It should be quiet on the AP and there should be a little bit of high-freq ripple on a scope.  If that's good, then you can eliminate the charge pump as the cause.


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## benny_profane (Dec 25, 2019)

Dirty_Boogie said:


> Where do you suggest getting the charge pump IC's from?  I checked Smallbear, and their charge pumps are the same part number/same manufacturer that Tayda lists.


Mouser, digikey, Newark, etc. as well as small bear. Even though the part number is the same, the supply chain reliability, legitimacy of parts, etc. is better assured with the vendors just listed. Tayda certainly isn’t bad (for most things), but I’d avoid their charge pumps for sure since many people have had issues with those parts in the past.


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## sticky1138 (May 8, 2022)

I just built this and I'm also getting a hiss (kind of like a semi-audible high frequency sound) out of each side when the fuzz or bias is turned up, but it goes away when I touch both transistors at the same time. Does that sound like a grounding issue?


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## Chuck D. Bones (May 8, 2022)

Probably charge pump noise.  Maybe you want to start a new thread and post pictures.  Where did you get your charge pump and did you sub any parts?


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## sticky1138 (May 8, 2022)

Here's a pic. The only subs are 22u for 20u. I just remembered that the charge pump is from Tayda - maybe that's the culprit. Too bad it's going to be hard to get ahold of one from another source at the moment.


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## Chuck D. Bones (May 8, 2022)

Make sure the transistor bodies are not touching anything.  Sure looks like those Ruskie trannies are touching.


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