Minor Questions about TS9/808

[Baran Ismen]

Hey everyone.

I just finished the TS9/808 pedal from this link, works just fine. I've added the resistor mode with an ON/ON switch for going between TS9 & 808, which works as intended. The difference is not that big, though, as we all know. For transistors, I've tried 2n5088 but they seemed to be a bit stronger than I expected, and as not having any 3904 at hand, I've put 2sk30a's on both and it works just fine. Never seen this before, tho.  But I'll get 2n3904's asap.

Yet I have some questions.

- Tone pot (B20K) seems rather ineffective within its most range, I can feel its presence on both ends, but the vast amount of its travel seems weak. Some schematics say it's a G taper, but mostly it's used as B. I can't hear any audible difference. Solved, that's how it is, either will use a G taper or wear it as it is..

- I've added clipping mode with an on-off-on switch as two 4148 didoes on one side, and two 5mm red diodes on the other (3mm is suggested for the layout), and middle lugs go to the board. I feel and hear almost no difference between unclipped and led-clipped versions. Is it normal? I see the LEDS are responding to pick attacks. One of them lights a bit brighter, tho. What would you suggest for a clipping type between 4148 and no diodes?

- On 4148 mode, I hear the clean guitar signal blended with the overdrive. I've just made a quick look over the internet and it seems how the pedal actually works, but just wanted to double-check. Solved, its intentional.

- When I lightly touch the strings, I hear a faint fizz/hiss around 14-15khz. Is this also normal? I've used all the parts as they should be apart from the 51pf, for which I've used 56pf. Would it be the cause of this?

[antonis]

I've tried 2n5088 but they seemed to be a bit stronger than I expected,

Meaning..??

I feel and hear almost no difference between unclipped and led-clipped versions. Is it normal??

Quite normal..
(it happens due to relatively high LEDs forward voltage drop..)

When I lightly touch the strings, I hear a faint fizz/hiss around 14-15khz.

Does this happen for any Drive pot setting..??

[marcelomd]

- Tone pot (B20K) seems rather ineffective within its most range, I can feel its presence on both ends, but the vast amount of its travel seems weak. Some schematics say it's a G taper, but mostly it's used as B. I can't hear any audible difference.

I think the original uses a _W_ taper potentiometer.

- I've added clipping mode with an on-off-on switch as two 4148 didoes on one side, and two 5mm red diodes on the other (3mm is suggested for the layout), and middle lugs go to the board. I feel and hear almost no difference between unclipped and led-clipped versions. Is it normal? I see the LEDS are responding to pick attacks. One of them lights a bit brighter, tho. What would you suggest for a clipping type between 4148 and no diodes?

Try two 1N4148 in series =) Or 1 diode on one leg and 2 on the other.

- On 4148 mode, I hear the clean guitar signal blended with the overdrive. I've just made a quick look over the internet and it seems how the pedal actually works, but just wanted to double-check.

Lots have been said and written about this, but yes, the "clean blend" is expected.

[Baran Ismen]

Meaning..??

That means I haven't used them and replaced with 2SK30A's, komşi.

Does this happen for any Drive pot setting..??

I think so, yes.

[ElectricDruid]

- Tone pot (B20K) seems rather ineffective within its most range, I can feel its presence on both ends, but the vast amount of its travel seems weak. Some schematics say it's a G taper, but mostly it's used as B. I can't hear any audible difference.

I did some analysis of this, posted over here: https://electricdruid.net/designing-a-classic-overdrive/

In short, yes, the response of the Tone control in the 'screamer is *dreadful* if you use a linear pot and Ibanez/Maxon had to use some weird pot taper to compensate. In the article, I propose an alternative solution using a different topology to avoid the problem in the first place. I've tested it and it works well.

[Baran Ismen]

- Tone pot (B20K) seems rather ineffective within its most range, I can feel its presence on both ends, but the vast amount of its travel seems weak. Some schematics say it's a G taper, but mostly it's used as B. I can't hear any audible difference.

I did some analysis of this, posted over here: https://electricdruid.net/designing-a-classic-overdrive/

In short, yes, the response of the Tone control in the 'screamer is *dreadful* and Ibanez/Maxon had to use some weird pot taper to compensate. In the article, I propose an alternative solution using a different topology to avoid the problem in the first place. I've tested it and it works well.

As I remember from the Pot's Secret Life article, regular pots can be converted into other tapers, even S/G-types, right?

[antonis]

Meaning..??

That means I haven't used them and replaced with 2SK30A's, komşi.

Don't get me wrong, arkadaşım, but I'd like to know more about transistor strength..  

[Dormammu]

For transistors, I've tried 2n5088 but they seemed to be a bit stronger than I expected

If we are talking about buffer transistors — their "strength" does not matter, they do not provide voltage gain, regardless of the type of transistors used.
In this case, the noise characteristics are more important, and for the input transistor — much more than for the output one.

[ElectricDruid]

As I remember from the Pot's Secret Life article, regular pots can be converted into other tapers, even S/G-types, right?

I thought so too, but unfortunately the curving you get from bending the taper with extra resistors goes the wrong way and makes the situation worse not better for this particular case. It came up in a thread here some time back, but it might take me a while to find it...

<edit>No, actually that was easy! Here it is:

https://www.diystompboxes.com/smfforum/index.php?topic=66471.msg1267222#msg1267222

[Mark Hammer]

1) As near as I can figure out, the change in output buffer resistor values was an attempt to make the bypassed sound a bit brighter.  The 808 values loaded the signal down a bit.  That was good was making the overdrive sound a little warmer/smoother, but at a cost of dulling the bypass a bit.  If your build uses a true bypass switch, instead of the classic Ibanez FET-switching, use the 808 buffer values.

2) I've built a few TS units, and the output level does seem to vary with the transistor used.  Not dramatically, but certainly enough that you can hear the difference.

3) One TS I built (and sold to one of Canada's best blues guitarists) included a "warp" control.  This was simply a 10k variable resistance in series with ONE of the clipping diodes.  This provided a continuously variable degree of asymmetry.  It also raised the output level somewhat, by raising the headroom for one half-cycle.  You may find it more useful that selecting between LEDs and silicon diodes.

4) The TS tone control can be varied in many productive ways. Perhaps Jack Orman's site can provide some useful ideas for you.  http://www.muzique.com/lab/tstone.htm

5) I contend that the basic design of the TS was intended to provide roughly similar clipping across the entire range of notes.  This is why it rolls off low end at the gain stage to make bass notes clip less.  If you increase the value of the .047uf capacitor, more gain will be applied to the low end.  That is often useful for single-coil guitars.

[Baran Ismen]

Don't get me wrong, arkadaşım, but I'd like to know more about transistor strength..

No, of course not. Maybe I'm using the wrong term for that. I.e; I've tried 2n2222 for both and the sound I got was smoother and more creamy. I think its something to do with the vfe or something of the transistors.

It came up in a thread here some time back, but it might take me a while to find it...

I remember this article, I was there too    Again a s.ity pot type that I can't find where I live    Either going to order a W taper from Tayda, or use a lower linear one as Rob suggested under that topic..

I wonder how the taper type is determined. What does it depend on?
 

[antonis]

2) I've built a few TS units, and the output level does seem to vary with the transistor used.  Not dramatically, but certainly enough that you can hear the difference.

But of course, Mark..
The whole story lies on that Emitter follower %^&*$ bias method, which strongly depends on both V_BE and h_FE of particular devices used..
Emitter bias (quiescent voltage) could exhibit a spread of more than 1.5V with all aftermath..

[Mark Hammer]

I wonder how the taper type is determined. What does it depend on?

It depends on the function one is trying to achieve.  W-taper is often used for graphic equalizers.  From the midpoint, it is logarithmic in one direction, and anti-log in the other direction.  This results in identical amounts of cut and boost for the same amount of wiper movement, whether slider or rotary pot.

Th tone control on a TS is not quite the same as a graphic equalizer, but it does provide boost in one direction and cut in the other.  As the tone pot wiper is moved towards the inverting pin in the second op-amp, the gain of that op-amp is increased.  And, because of how op-amps work, when using the ground leg for gain adjustment, the greater the gain, the higher the low-end rolloff.  In the case of the TS, when the tone pot is fully clockwise, the gain of the op-am is around 5.5x, for content above roughly 3.2khz, and less for content below that.  Rotate that same tone pot fully the other way, and the 2nd op-amp's gain is a small amount more than unity, and flat down to around 35hz.  Meanwhile, the .22uf tone cap gets added in parallel to the existing .22uf cap to ground on the output of the drive stage.  The 1k/.22uf pair rolls off content above roughly 720hz, and the added parallel cap adds to that.  Obviously the 220R resistor doesn't simply drop the rolloff point to half, but it does move downwards.

My point is that the control becomes more "dialable" and useful if it is a W taper.  A linear taper is also roughly symetrical, but a bit less dialable, since it reduces the adjustments of most interest into a smaller arc of rotation at each extreme.

Make sense?

[antonis]

I wonder how the taper type is determined. What does it depend on?

It depends on the function one is trying to achieve.

+1..!!

Look at "taper modifications" of an, otherwise classic, Baxandall  tone control..