Sweet Thing booster and power section plus some whining noise

[matopotato]

I just breadboarded a Sweet Thing booster (overdrive (?)) by Doug Hammond based on Aron Nelson's Booster 2.5.
This schematic is what I used:


The power section seems to consist of a 4148 diode for polarity protection and an electrolyte cap of 10uF to ground.
But in other builds of pedals I've come across, there are usually more to the power section.
1. Should the 10uF be increase to 100uF?
2. Should there also be a 100nF Film Cap to ground as well?
Or would either of these changes impact the sound/tone of the build?

In other builds where I have Ge transistors and even Ge diodes for clipping, I can get a (not so nice) whining noise floating over the expected effect sound. If I put the build earlier in the chain it is at least diminshed (if not gone) to a level where I can't here it anymore.
3. The Sweet Thing is based around 5 JFETs, are they also sensitive to being late in the chain, and like Ge prefer to be close to the source?
(This is probably a generalization about Ge on my behalf, so there are most likely exceptions to this "rule", but at least to me it seems to hold quite true)

The whining was less if I put the breadboarded build earlier, but I find it hard to tell for sure until it is soldered and boxed if noise is due to the nature of breadboarding a circuit or if it is something with the circuit itself (that could be fixed before soldering).

[ElectricDruid]

1. Should the 10uF be increase to 100uF?

It might be a good idea, but if it's going to act as a proper lowpass filter for the incoming power supply, it needs a resistor in series with that diode. Try 47R/68R.
For slightly less voltage drop across the diode, you could use a schottky diode like 1N5817.

2. Should there also be a 100nF Film Cap to ground as well?
Or would either of these changes impact the sound/tone of the build?

Electrolytic caps tend to stop being effective at higher frequencies, so adding a 100nF in parallel makes the filter more effective for radio frequency rubbish.
None of these changes will change the sound of the pedal except to make it quieter.

In other builds where I have Ge transistors and even Ge diodes for clipping, I can get a (not so nice) whining noise floating over the expected effect sound. If I put the build earlier in the chain it is at least diminshed (if not gone) to a level where I can't here it anymore.
3. The Sweet Thing is based around 5 JFETs, are they also sensitive to being late in the chain, and like Ge prefer to be close to the source?
(This is probably a generalization about Ge on my behalf, so there are most likely exceptions to this "rule", but at least to me it seems to hold quite true)

The whining was less if I put the breadboarded build earlier, but I find it hard to tell for sure until it is soldered and boxed if noise is due to the nature of breadboarding a circuit or if it is something with the circuit itself (that could be fixed before soldering).

If you've got whining noises, it sounds like power supply noise. That could be from the actual power supply you're using, or it could be coming from something that's using a chargepump for higher headroom and then not filtering the output properly before sending to the other pedals. It's possible your germanium pedals are more sensitive to this, especially if they have filtering like shown above, and especially if the other non-ge pedals are mostly op-amps (which tend to have pretty good power supply noise rejection).
If moving the germanium pedals to the front of the chain fixes it, it sounds to me like you've just put them *in front of* rather than *after* the offending pedal.

HTH

[idy]

Several Times I've fought and fought, replacing charge pumps, adding caps, and finally found that the cheap power supply I use on the work bench was the culprit.
Usually with simper circuits, like Ge fuzz.
When I use a OneSpot trouble disappears.

[antonis]

I'd proceed as below:

[matopotato]

1. Should the 10uF be increase to 100uF?

It might be a good idea, but if it's going to act as a proper lowpass filter for the incoming power supply, it needs a resistor in series with that diode. Try 47R/68R.
For slightly less voltage drop across the diode, you could use a schottky diode like 1N5817.

Thanks, I'll add that, and yes the 1N5817 sounds more approprate than the 4148 for this part.

2. Should there also be a 100nF Film Cap to ground as well?
Or would either of these changes impact the sound/tone of the build?

Electrolytic caps tend to stop being effective at higher frequencies, so adding a 100nF in parallel makes the filter more effective for radio frequency rubbish.
None of these changes will change the sound of the pedal except to make it quieter.

Great, will do.

In other builds where I have Ge transistors and even Ge diodes for clipping, I can get a (not so nice) whining noise floating over the expected effect sound. If I put the build earlier in the chain it is at least diminshed (if not gone) to a level where I can't here it anymore.
3. The Sweet Thing is based around 5 JFETs, are they also sensitive to being late in the chain, and like Ge prefer to be close to the source?
(This is probably a generalization about Ge on my behalf, so there are most likely exceptions to this "rule", but at least to me it seems to hold quite true)

The whining was less if I put the breadboarded build earlier, but I find it hard to tell for sure until it is soldered and boxed if noise is due to the nature of breadboarding a circuit or if it is something with the circuit itself (that could be fixed before soldering).

If you've got whining noises, it sounds like power supply noise. That could be from the actual power supply you're using, or it could be coming from something that's using a chargepump for higher headroom and then not filtering the output properly before sending to the other pedals. It's possible your germanium pedals are more sensitive to this, especially if they have filtering like shown above, and especially if the other non-ge pedals are mostly op-amps (which tend to have pretty good power supply noise rejection).
If moving the germanium pedals to the front of the chain fixes it, it sounds to me like you've just put them *in front of* rather than *after* the offending pedal.

HTH

Good point, I will.make some detective work. Although the other pedals were all bypassed so no signal passing. But I am guessing thar even so, the power stage of a suspect pedal still introduce the whine as long as power cable is plugged in. And then I guess Ge pedals pick up on it easier. I have a BD-2 clone with a switch for Si vs Ge diode package and it whines quite more noticeable when in Ge mode.
(I adde the switch according to Brian Wampler's mod description just a week before he made a YT clip about BD-2 and says he no longer thinks diode selection matter at all...  . )
Should be fun to investigate.

[duck_arse]

Posted by: antonis

I'd proceed as below:

but you would explain the additions, wouldn't you? cause people will ask.

[matopotato]

Several Times I've fought and fought, replacing charge pumps, adding caps, and finally found that the cheap power supply I use on the work bench was the culprit.
Usually with simper circuits, like Ge fuzz.
When I use a OneSpot trouble disappears.

Good info!
I use Truetone CS12 and it is good with the others.
Simetimes a wall wart with no ground, but then I would already know the culprit.

[matopotato]

I'd proceed as below:

And a 1N5817 instead of 4148?

[antonis]

but you would explain the additions, wouldn't you?

Are you calling me a blubbermouth or what..??

[matopotato]

Posted by: antonis

I'd proceed as below:

but you would explain the additions, wouldn't you? cause people will ask.

Yes, please. Not sure why 47R 220uF should be doubled?

[antonis]

And a 1N5817 instead of 4148?

Personally, I'd use a reverse polarity protection shunt diode for no voltage drop but a series Schottky should be fine, also..

[antonis]

Yes, please. Not sure why 47R 220uF should be doubled?

To be honest, +9V and diode should be placed on J5 Drain, and RC filters between J5/J4 & J4/J2 Drains..

In the mean of current hungry descending order,,

[duck_arse]

blubb blubb. no, not accuse no-one of nuffink. just done enuff typing for a while.

first stage supply perturbations caused by the audio shenannigans are prevented from polluting the second stage by inclusion of the interstage supply R/C filter, allowing stage 2 to perturb to its hearts content. and in general, the values used are not critical, as long as you have some resistance to work against some capacitance.

[matopotato]

Yes, please. Not sure why 47R 220uF should be doubled?

To be honest, +9V and diode should be placed on J5 Drain, and RC filters between J5/J4 & J4/J2 Drains..

In the mean of current hungry descending order,,

So each 47R/220uF pair should be moved right one "notch"?

[antonis]

So each 47R/220uF pair should be moved right one "notch"?

[matopotato]

So each 47R/220uF pair should be moved right one "notch"?

Eucharisto!

[matopotato]

Sorry, fogot:
4. R19 at 2k2 is mentioned can be changed for more or less treble.
I tried a 10k trimmer and am now considering a B10k pot to control this from the outside.
I felt there was no issue even with the new 10k trim at zero, it just made the result quite dark.
I would say the extra pot decides what spectrum or sweep the Tone control at R18 B50k gets to work with, but to me at least the two pots seem to do the same or similar thing.
So my question is if both could be replaced by one pot all together, and if so how?
Or is the circuit such that they do different things albeit in the tonal part/block?

[antonis]

TONE pot mixes two LPFs where R19 alters the corner frequency of the upper one..
So, they do different things..

[Rob Strand]

Sorry, fogot:
4. R19 at 2k2 is mentioned can be changed for more or less treble.
I tried a 10k trimmer and am now considering a B10k pot to control this from the outside.
I felt there was no issue even with the new 10k trim at zero, it just made the result quite dark.
I would say the extra pot decides what spectrum or sweep the Tone control at R18 B50k gets to work with, but to me at least the two pots seem to do the same or similar thing.
So my question is if both could be replaced by one pot all together, and if so how?
Or is the circuit such that they do different things albeit in the tonal part/block?

The caps/frequencies in that tone control are voiced quite low.  You could try a lower value for the 100nF cap, say 68nF or 47nF.

You could even go further and change both cap values: like 12n/15n and 47n/68n.   This is where personal preferences and sticking to the original design start to separate.

Then there's the stupidly wonder tone control.   You could get it to work with a 10k + 50k tone pot with smaller caps (maybe none to 10n fixed and 10n to 15n wiper).  Small amount of signal loss (due to 100k volume pot loading) but you have *heaps* of signal to spare on those boosters.

https://www.muzique.com/lab/swtc.htm
https://www.muzique.com/lab/swtc3.htm

[matopotato]

You could even go further and change both cap values: like 12n/15n and 47n/68n.   This is where personal preferences and sticking to the original design start to separate.

I got that 47n/68n is to try for C9
And the 12n/15n is meant for C10, right?

Then there's the stupidly wonder tone control.   You could get it to work with a 10k + 50k tone pot with smaller caps (maybe none to 10n fixed and 10n to 15n wiper).  Small amount of signal loss (due to 100k volume pot loading) but you have *heaps* of signal to spare on those boosters.

Yes I noticed there was a lot more boost in there than I had thought at first.
Many thanks for the suggestions.