Because some people change INPUT BUFFER TS-9 RESISTOR? 510K for 610k

[ANDYEFFECT]

Because some people change INPUT BUFFER RESISTOR. 510K for 610k, in the ts, what does that have effect in the pedal? 
thanks

andré

[twabelljr]

    Quote from Robert Keeley's "Baked Mod." description:

I raise one of the resistors that affect the input impedance a slight bit (510k to 620k). This allows your pickups to breathe and you have less "tone-drain" when off.

[ANDYEFFECT]

    Quote from Robert Keeley's "Baked Mod." description:

I raise one of the resistors that affect the input impedance a slight bit (510k to 620k). This allows your pickups to breathe and you have less "tone-drain" when off.

does this also work in the clones?

[R.G.]

I raise one of the resistors that affect the input impedance a slight bit (510k to 620k). This allows your pickups to breathe and you have less "tone-drain" when off.

does this also work in the clones?

I think a more pertinent question is... does it do anything noticeable?

It's a 20% increase in a resistor value that's already +/-5%. There are those that will tell you that anything less than 1M is bad. There are even those that will tell you that anything less than 10M is bad.

IMHO, it provides a neato outlet for the sheer urge to mod something, anything. If you want more pickup breathing and elminate tone drain (I'm guessing this means treble loss), then put a real buffer in there. A JFET mod ought to be easy to do and could well get you well over 1M of input impedance. 

[stm]

Let's put things straight: the audible effect of changing the input resistor from 510k to 620k is nothing less than questionable.

Looking at GGG TS-808 schematic http://www.generalguitargadgets.com/diagrams/ts-808_sc.gif you can see there are three relevant impedances in play at the input of the circuit:

1) R22 (1 Meg) before the input decoupling cap
2) R2 (510k) after the input decoupling cap
3) R3 (10k) times the forward gain of Q1 which can be estimated as 150, thus, this impedance is reflected as 1.5 Meg at the base of Q1

Taking into account the parallel of the three impedances above, we have 276k loading your guitar... yep, this sucks tone!
Now if we substitute R2 for 620k, we have 305k, which is an effective increase of only 10% and still tone sucking!
So, does this change make a significant effect?  No way!

Note: even if the original TS-808 doesn't have R22 (which I'm not sure), the impedance change is still quite small and the effective input impedance still in the 400k vicinity!

This lower-than-standard input impedance is not necessarily a bad thing for a distortion box, since it helps taming the highs, however in this case it is present also when the effect is off.  Now, if you really want to raise the input impedance to a noticeable value, then I would suggest that you:

1) Raise R22 to 4.7 Meg
2) Raise R2 to 1.5 Meg
3) Replace Q1 by a 2N5089 or other very high gain silicon transistor (eventually a JFET could do it, but it might color the sound and have less dynamic range).  Assuming an hfe of 600 for the transistr now we have a 6 Meg impedance referred to the transistor's base.

Taking into the account the above, overall input impedance should be now 956k, or roughly 1 Meg.  Now this should be audible and brighter!

[Mark Hammer]

Pretty much the last thing you want to do when plugging into a device intended to add harmonic content is to give it lots of harmonic content.  Harmonics of harmonics, unless treated in a more complex way (like with exciters and enhancers), can be *really* ugly.  Indeed, often one of the best things you can do for a distortion pedal is to deliberately roll off input high end above some point like 4-5khz, and often lower.

So, even IF the change from 510k to 620k achieved more of a change in loading than was articulately described and explained by RG and Sebastian, there is still the question of whether it is even desirable to do so.  If one's intention is to use it at lowest gain settings (i.e., a slightly coloured semi-clean boost) then I suppose a higher input impedance might be constructive.  But if one's intention is to use it with anything over a gain of 20 (the TS-808's min gain setting is around 12, and max is around 118), loading starts to become your friend.  Heck, guys like Eric Johnson even go to the extent of using bloody curly cords to accentuate the rolloff that comes from loading.

Of course, it is important to recognize the context in which the question was originally asked, and the mod suggested, and that is the effect of changing the loading in a pedal whose buffer is always in circuit, whether in bypass mode or not.  The projects at GGG and Tonepad assume one will use a mechanical true bypass switching scheme, such that the buffer is only in circuit when the effect is, and out of circuit when bypassed.  While loading things down to shave off some high-end (constructive tone-sucking) can be helpful when the buffer is always (and only) a part of the effect tone, improving the input impedance will be helpful to achieving a better bypass sound when several such pedals (e.g., a string of Boss) are part of one's signal chain.

I suppose that's one of the nice things about true-bypass: you don't have to strike a compromise in buffer design between what's good for the effect tone and what's good for the bypass tone.  You can just focus on what akes the effect sound good.