Whats's the difference in tone between TS9 and OD808 resistors ?

[ChrisGS]

Hi Everybody ,

This is my second post , and once again It's more tube screamer questions...The subject title is my basic question .

Also , as I understand , a TS10 and an OD808 have one or two additional resistors at the input...What effect do the added resistors hve on tone ?

Thankyou For any advice ,
Chris.

[pi22seven]

Hey Chris, welcome to the board!

To answer your question in a round about way... there's more on the internet about the 808 and the other Tubescreamers and clones than any one person could read in a lifetime.

If you use the searchbutton and plug in "808" you'll pull up a whole mess of stuff to keep you reading for weeks!

Just a bit of advice, DIY effects can be rather addincting...

[petemoore]

Hey Chris, welcome to the forum
  If I recall correctly, [but I wouldn't count on it], not much, if we're discussing input buffer bias resistors.
  for me to give a better answer to 
  Whats's the difference in tone between TS9 and OD808 resistors ?,   
   a look at both schematics and designation of exactly which resistors we're referring to would be necessitated.

[ChrisGS]

Hey guys ,
I see what you mean about "808" and the search button .

As for the particular resistors in question, they would be the ones in what I believe is the output stage . There is a series resistor before a cap going to the output jack...on the 808 it's 100k , and on the TS9 it's 470k . The other resistor in question is attached after the afore mentioned cap , and goes from the output signal to ground ...on the 808 it's10k , and on the TS9 it's 100k .

I don't have a working amp at home right now... just abunch of disassembled and half assembled projects, so I'm trying to put the mods that I think that I'd like in before I go to my friend house to try out .

Thanks again ,
Chris.

[brett]

Hi
have a read of RG Keen's "technology of the tubescreamer" article.  Especially at the end, where he specifically discusses the resistors.

It is clear that there is no difference in the output of the two circuits, except that the 808 has lower output impedance (TS9 = 470 ohms + a bit, TS808 = 100 ohms + a bit).

Could output impedance be the difference?  Under certain circumstances, it has an effect.  One such situation is where tube preamps are driven into grid conduction.  However, things like grid stopper resistors (usually 68k) will affect the outcome, too.  Low vs high impedance sources for tube amps are discussed in RG's article on the Dallas Rangemaster (called the Austin Treblebooster by RG for obscure reasons).

So it's possible that there's a difference.  But personally, I think it's psychological.  People research this stuff and hundreds of people do the 9 to 808 conversion.  If they got no change, would they admit it?  The answer is clearly no.

cheers

[PaulC]

Actually there is a difference that can be seen on a scope.  The follower on the output section is to give a low imp signal, but it's not all that low.  The 10k shunt resistor in the 808 can load it down causing it to distort the signal a little when it's cranked up.  With the 100k value in the 9 it's not loaded down, and you don't get the loading distortion.  IMHO the difference in sound is not about how it's driving the tube, but how the buffer is holding up under drive. 

Later, PaulC

[JHS]

Soundwise the difference is very small, the 808 has a bit softer highend, on the 9 it's a bit harder.
Most early 808 have 4558P chips inside, later 808 have the 4558D chip as the early 9 models.

It's not only those 2 resistors, the difference in sound on a 808 with 4558P compared to a 808 with 4558D is way bigger than the difference between a 808 and a 9 with 4558D inside. In the early 808 the diodes are 1S1588, in the newer TS9 are MA150, the 1S1588 "blue band" sound clearer in an OD than the MA150.

JHS