Increase "Volume" Electra Distortion

[DJPsychic]

How do I increase the "Volume" of this circuit? I have to crank  A100k pot to almost 9 to match the "bypass" guitar signal. The only way to match bypass volume is if I have gain at "5" and volume almost cranked. I'd like to be able to have gain dialed back at around 2-3 and and hear volume boost on 100k @ around "5".

(for those of you who have seen my posts, I apologize again for the text on schematic  )





Do i just increase value of R1 or R2?   My original build I used 1uf input and output caps, and I still had volume cranked, gain at 1-2 to get a usable tone

I think I'm going to try a .47uf input this time.

[Fancy Lime]

Hi DJ,

if you want less "gain" (by which I assume you mean less distortion) and more volume, that is fortunately very easy. Just use diodes with a higher clipping threshold, e.g. LEDs instead of silicon or silicon instead of germanium. Blue LEDs have the highest among the commonly used diodes, red LEDs are between silicon diodes and blue LEDs If you really like the sound of the diodes you have, you can also double the diodes, so that you have two diodes in series, where there is now only one (for  total of 4 diodes). Generally, it is a good idea to try out different diodes and diode combinations and see what you like.

Cheers,
Andy

[DJPsychic]

Hi DJ,

if you want less "gain" (by which I assume you mean less distortion) and more volume, that is fortunately very easy. Just use diodes with a higher clipping threshold, e.g. LEDs instead of silicon or silicon instead of germanium. Blue LEDs have the highest among the commonly used diodes, red LEDs are between silicon diodes and blue LEDs If you really like the sound of the diodes you have, you can also double the diodes, so that you have two diodes in series, where there is now only one (for  total of 4 diodes). Generally, it is a good idea to try out different diodes and diode combinations and see what you like.

Cheers,
Andy

Not necessarily less gain, I guess more volume. The 100k doesnt seem to even kick in until 6-7. Not sure if I'm making sense!

[idy]

Maybe there is something wrong with your build. This circuit should be pretty loud. Something shorting? Something wrong value?
Maybe you would like a "b" taper volume pot better if it's just a matter of the volume changing at the wrong part of ts travel.
Different clipping diodes would make it louder.
That one transistor is like an "LPB" or rangemaster or something, it should be enough to really give you a strong signal, and a diode-clipped signal is still loud, like an MXR distortion +.

[iainpunk]

in this circuit the volume is set by the forward voltage of the clipping diodes, if you always have the gain at 1-2 and want more volume, just put LED´s instead of diodes, you will have higher volume and less gain, so you can set the gain pot higher for the same amount of distortion but with more volume.

and is it an IEEE or an american standard, that A100K pot, because the IEEE says that ``A´´ pots are linear and ´´B`` pots are log, while the american standard has them the other way around.
if the response is weird, it might be because you used a Lin pot for the volume, instead of a log

[DJPsychic]

in this circuit the volume is set by the forward voltage of the clipping diodes, if you always have the gain at 1-2 and want more volume, just put LED´s instead of diodes, you will have higher volume and less gain, so you can set the gain pot higher for the same amount of distortion but with more volume.

and is it an IEEE or an american standard, that A100K pot, because the IEEE says that ``A´´ pots are linear and ´´B`` pots are log, while the american standard has them the other way around.
if the response is weird, it might be because you used a Lin pot for the volume, instead of a log

Pretty sure it's a Linear 100k yes. And a B10k for gain.

I've got 2 diodes for clipping, (like on schematic).

Could maybe going to just 1 diode , and the LED that's already in build do what you're suggesting?

[DJPsychic]

Maybe there is something wrong with your build. This circuit should be pretty loud. Something shorting? Something wrong value?
Maybe you would like a "b" taper volume pot better if it's just a matter of the volume changing at the wrong part of ts travel.
Different clipping diodes would make it louder.
That one transistor is like an "LPB" or rangemaster or something, it should be enough to really give you a strong signal, and a diode-clipped signal is still loud, like an MXR distortion +.

I might try that. I guess that could be my issue. On most Distortion/OD's I like, You can set gain very low, and volume seems to kick in around 3-4.

On this build, the volume doesnt seem to engage until about 5.

[Mark Hammer]

The taper of the Volume pot could likely use a rethink, if only to improve dialability.
That said, choice of clipping diodes can have a number of consequences.  The clipping is a function of the "ceiling" that the diodes place on the signal.  The lower the forward voltage of the diodes the lower that ceiling and the lower the maximum amplitude of the output signal.  But additionally, the lower the forward voltage, the more easily the signal will clip, and the longer a portion of the note's lifespan the clipping will continue for.  In other words, it will sound fuzzier because the clipping won't be limited to just those first few instants when you pick the string.

Though I'm quite certain Andy didn't mean to imply this, DJPsychic's inquiry suggests he might draw some mistaken inferences, so I'll clarify. If you are presently using germanium diodes, using a back to back quartet (i.e., 2 Ge diodes in series on each leg) will get you more volume, but will NOT maintain the same quality of clipping, since the volume boost will come from raising the total forward voltage and clipping threshold.  You cannot get the benefit of the one (volume boost) without forfeiting the other (clipping hardness/intensity).

If you are fine with getting more volume at the cost of a bit less grind (i.e., your goal is to get grind from the amp, not the pedal), then use of more diodes or subbing LEDs for diodes is the right and simplest path to follow.  If you like the quality of clipping and don't want to give that up, however, I will suggest that your build add a second gain stage.  Feed your Volume control output to a second copy of the circuit, but omit the clipping diodes, and just use a 10k fixed resistor instead of the 10k Gain pot.  There's a good chance you'll have enough total output to warrant inserting a tone control before the final output.

I'm just curious enough at the moment that I might build that just to see how it sounds.

[iainpunk]

in this circuit the volume is set by the forward voltage of the clipping diodes, if you always have the gain at 1-2 and want more volume, just put LED´s instead of diodes, you will have higher volume and less gain, so you can set the gain pot higher for the same amount of distortion but with more volume.

and is it an IEEE or an american standard, that A100K pot, because the IEEE says that ``A´´ pots are linear and ´´B`` pots are log, while the american standard has them the other way around.
if the response is weird, it might be because you used a Lin pot for the volume, instead of a log

Pretty sure it's a Linear 100k yes. And a B10k for gain.

I've got 2 diodes for clipping, (like on schematic).

Could maybe going to just 1 diode , and the LED that's already in build do what you're suggesting?

well, i wouldn´t recommend using that LED for the clipping, but use a fresh led instead of a normal Diode, the LED already in the schematic is a status light so you can see if the pedal is on, which is very usefull (that LED shoud not go directly to ground but wired like this)

in almost all cases, the volume pot is LOG instead of linear, that explains why it does nothing up to 5 or 6.

[DJPsychic]

in this circuit the volume is set by the forward voltage of the clipping diodes, if you always have the gain at 1-2 and want more volume, just put LED´s instead of diodes, you will have higher volume and less gain, so you can set the gain pot higher for the same amount of distortion but with more volume.

and is it an IEEE or an american standard, that A100K pot, because the IEEE says that ``A´´ pots are linear and ´´B`` pots are log, while the american standard has them the other way around.
if the response is weird, it might be because you used a Lin pot for the volume, instead of a log

Pretty sure it's a Linear 100k yes. And a B10k for gain.

I've got 2 diodes for clipping, (like on schematic).

Could maybe going to just 1 diode , and the LED that's already in build do what you're suggesting?

well, i wouldn´t recommend using that LED for the clipping, but use a fresh led instead of a normal Diode, the LED already in the schematic is a status light so you can see if the pedal is on, which is very usefull (that LED shoud not go directly to ground but wired like this)

in almost all cases, the volume pot is LOG instead of linear, that explains why it does nothing up to 5 or 6.

Should I be using a linear B100k for volume?

[Fancy Lime]

Mark is of course right, doubling the same diodes will change the clipping threshold (which is the point of doing it) and therefore the sound. However, there are a number of different factors influencing how a clipping diode sounds (knee curve, open resistance, capacitance, reverse leakage...). So doubling the same diodes will give you a sound that is the closest to the original except for the higher clipping threshold, whereas other diode types will usually sound "more different".

No, you should not be using a linear pot for volume. But, as iainpunk pointed out, whether log or lin is A or B depends on where you buy your pots. The volume pot should definitely be log. Log pots "sound linear" because our hearing follows a kind of log curve. If the pot was linear, you would get most of the volume jump in the first few degrees of the travel. What you describe is the opposite, right? Nothing happens in the lower part of the travel. There is no pot characteristic that would result in that. Do you have a multimeter? If so, I would check the resistance of the pot (between the leftmost and the middle pin, looking down along the top of the shaft with the pins pointing toward you) at all hours of the clock. At 7 o'clock the resistance should be 0, at 5 it should be 100k. If the pot is linear, you should find 50k at 12 o'clock. If it is logarithmic, you should get somewhere around 10k to 15k at 12. If you get around 85k to 90k, your pot is revlog. But I doubt that that is the case. If you get something entirely different, your pot is broken. I suspect that that is the case.

Overall the symptoms you describe may well imply a broken vol pot. With the vol pot at maximum and gain at minimum, you should get a signal that is already well above unity in a standard Electra. If it doesn't, something is probably wrong. If it's not the vol pot, then it may be that the transistor is not biased correctly or broken.

Hope that helps,
Andy

[DJPsychic]

Mark is of course right, doubling the same diodes will change the clipping threshold (which is the point of doing it) and therefore the sound. However, there are a number of different factors influencing how a clipping diode sounds (knee curve, open resistance, capacitance, reverse leakage...). So doubling the same diodes will give you a sound that is the closest to the original except for the higher clipping threshold, whereas other diode types will usually sound "more different".

No, you should not be using a linear pot for volume. But, as iainpunk pointed out, whether log or lin is A or B depends on where you buy your pots. The volume pot should definitely be log. Log pots "sound linear" because our hearing follows a kind of log curve. If the pot was linear, you would get most of the volume jump in the first few degrees of the travel. What you describe is the opposite, right? Nothing happens in the lower part of the travel. There is no pot characteristic that would result in that. Do you have a multimeter? If so, I would check the resistance of the pot (between the leftmost and the middle pin, looking down along the top of the shaft with the pins pointing toward you) at all hours of the clock. At 7 o'clock the resistance should be 0, at 5 it should be 100k. If the pot is linear, you should find 50k at 12 o'clock. If it is logarithmic, you should get somewhere around 10k to 15k at 12. If you get around 85k to 90k, your pot is revlog. But I doubt that that is the case. If you get something entirely different, your pot is broken. I suspect that that is the case.

Overall the symptoms you describe may well imply a broken vol pot. With the vol pot at maximum and gain at minimum, you should get a signal that is already well above unity in a standard Electra. If it doesn't, something is probably wrong. If it's not the vol pot, then it may be that the transistor is not biased correctly or broken.

Hope that helps,
Andy

Thanks for the response.

My last attempt I swapped the silicon transistor with a 2n229 germanium, and used 2 germanium diodes. But I accidentally used .1uf caps, that might be why I was getting such low output. Bread-boarded it sounded fantastic, but I failed to compare bypass signal.

[Fancy Lime]

The 0.1u caps should probably be fine, but for the input cap it is difficult to say because it depends on the input impedance of the transistor. The input impedance of the transistor in turn depends on several parameters that have *very* big tolerances in germanium devices. So, using a 1u or even bigger input cap may be a good idea when using a germanium transistor. The Ge diodes may or may not account for your low signal volume. Some Ge diodes have a very low forward voltage (i.e. clipping threshold). But from the strange behavior of the Vol pot that you describe, it seems to me that the problem could be high leakage in the diodes. the reverse leakage of the diodes essentially works like a resistor that is parallel to the "theoretical" (i.e. ideal, non-leaking) diode in this configuration. That means that the high output impedance of the Ge transistor forms a voltage divider with the low resistance of the Ge diode leakage, which just dumps a lot of your signal to ground.

There are a number of ways to fix this issue (if the issue is what I now think it probably is, give the information I have at this time). If you are happy with the sound you have and only want to fix the volume issue, I would say: Go with Marks suggestion and add a second stage. Just copy the arrangement: [ Q1, R1, R2, R3, C2 ] and insert it between the clipping diodes and the vol pot. Make R3 a fixes 10k resistor. I would use a silicon transistor for the second stage, because those are more stable and predictable and this transistor will have very little influence on the sound.

Hope that helps,
Andy

[idy]

The gain pot specified is "c" or reverse log taper. Another case of it being dodgy to get a nice range of low, medium, high gain sounds if you use linear or log.

[Mark Hammer]

Built, tested, works fine with more volume than you probably need.  I  initially included a Tone control, but found it was pleasantly warm enough without the need to cut any treble.  The added 220R resistor is just to set the maximum gain where it won't start going haywire on you.  The added electrolytic cap on the gain control can be omitted, or changed to achieve varying amounts of bass "thrust".  I used 33uf on mine but I think I'll want to drop it to 10uf or maybe even less, because there's more bottom than I personally want.  Don't forget the 1M terminating resistor on the input to eliminate switch-popping noise.

[DJPsychic]

Built, tested, works fine with more volume than you probably need.  I  initially included a Tone control, but found it was pleasantly warm enough without the need to cut any treble.  The added 220R resistor is just to set the maximum gain where it won't start going haywire on you.  The added electrolytic cap on the gain control can be omitted, or changed to achieve varying amounts of bass "thrust".  I used 33uf on mine but I think I'll want to drop it to 10uf or maybe even less, because there's more bottom than I personally want.  Don't forget the 1M terminating resistor on the input to eliminate switch-popping noise.

Wow very cool. Thanks for taking the time to do that! When I get a little more
Savvy I'll have a go at it. Very cool!

[DJPsychic]

So I ended up only using 1 germanium diode in clipping instead of 2, this solved the volume loss. (and it was easier because I can't read schematic yet, but thank you Mark Hammer!)

I also replaced R2 with a trim pot as I decided to go with a Germanium transistor and I increase the values of C1 & C2.

Not to toot my own trombone but this thing sounds amazing. The lack of sleep and possible lead poisoning might have actually paid off

I'd like to add a tone knob to the circuit, I think that would be the cherry on top. But I have no idea how to do that. I've been "painting by numbers" on this build, following the instructions on the pdf. I know it's kind of cheating but I'm still learning.

please excuse the rats nest, still getting comfortable with using shorter wire lengths 

[duck_arse]

Not to toot my own trombone but this thing sounds amazing. The lack of sleep and possible lead poisoning might have actually paid off

we can't toot it for you, so toot away! about the tone control, the simplest to try would be Mark Hammer/Jack Orman's SWTC, just a pot and a capacitor. you'll need to search, tho.

toot toot.

[Mark Hammer]

I have to say that, having lived with the suggested circuit for a week, I'm liking it a lot; indeed, more than I expected to.  And although I'm personally prone to sticking a tone control of some sort into an overdrive, I've found little need for one in this case. YMMV, of course.

A few words of advice, though, DJP.  I don't know if you did the machining or bought a premachined enclosure, but next time out you'll want to move both the footswitch and in/out jacks closer to the "front" of the pedal.  That will leave more space for a more "relaxed" layout.

[DJPsychic]

I agree that the pedal does hit a really nice sweet spot. Using a Germanium transistor along with a trim pot and the single diode clipping really tuned it in for me.

Being that's it's only my 2nd officially completed pedal (I have amassed a large circuit graveyard already) I'd like to eventually be able to add a tone control as I learn more.

I did machine the holes and I will take your advice thanks. I  have an enclosure graveyard as well