quick question on Tubescreamer gain mod?

[formerMember1]

Hi,
I want to do this mod i found in a thread i searched for and found on this forum.

I changed the 4k7/0.047uF attached to pin 2 of the opamp to 2k4/0.1uF, and changed the 51k resistor attached to the drive control to 22k. This gaves me less drive at the lowest setting, and (almost) double the drive at the highest setting, without changing the frequency response.

There is increased hiss and squealing with increased gain, so you might want to increase the 51p capacitor across the clipping diodes to about 100p if this is a problem.

My problem is i can't identify the original parts so that i could swap them out, Is there a diagram/picture anywhere?

I did the mod of changing the NP electros- to boxed metal film, and the one tantalum cap to boxed metal film,
and changed the 2 resistors for conversion to 808.  I swapped the chip to a JRC4558D from smallbear, but thought that chip sucked.  I preferred the stock chip(TA7555???)  I do want to try the burrbrown chip but can't figure out what BurrBrown means?
Keeley said to try the Texas INstruments 4558 chip, anybody use/try that chip?
I don't have enough room for a socket, becuase of the boxed metal film resistors. 

thanks 

***EDIT*** The above mod for higher distortion, is that the same mod Keeley does with the toggle switch, except he allows the option of switching between the mod and stock?

[Bernardduur]

What pedal do you have?

[MartyMart]

formerMember1,
If you're happy with the op-amp tone and somehow can't squeeze a socket in there
( I know it can be a tight fit ! ) then leave it.
You will probably  do some damage if you keep un soldering/re soldering there !!
Those parts should be easy to find :
Top of opamp has a "notch/dot"  so ...
The four pins from top down on left side are 1-2-3-4
and other side ( right upwards ) are 5-6-7-8
There you have found pin 2 so can find the 4k7/0.047uf cap
There's only one 51k resistor green/brown/orange/silver or gold ( four band )
or green/brown/orange/red/ silver or gold ( five band )

Done !!

Marty.

[gaussmarkov]

I swapped the chip to a JRC4558D from smallbear, but thought that chip sucked.  I preferred the stock chip(TA7555???)  I do want to try the burrbrown chip but can't figure out what BurrBrown means?  Keeley said to try the Texas INstruments 4558 chip, anybody use/try that chip?

interesting question.  keeley refers to the Burr Brown and Texas Instruments RC4558 as distinct things (see his description of his Boss SD-1 mods).  a little google research tells me that Burr Brown was acquired by TI.  so as far as new stock goes, i guess there is only one RC4558.  that's all that mouser has.  the JRC4558 is the current product of NJR.  R.G. comments in The Technology of the Tube Screamer:

By all reports, the current manufacture JRC4558D's sound just as good as the ones current with the manufacture of the original tube screamers.

did you try more than one JRC4558D in your box?

[formerMember1]

What pedal do you have?

TS9DX, <<<sorry i forgot to mention that, 

THanks MArtyMart, got it now, i appreciate the help. 

Yeah, i read all the articles on Keeley's site, and he does talk about the BurrBrown chip and the TI as two different chips, here is some more info on that i read in another post by frostwave:

It's suprising how little one hears about the history of BB, compared to other big semi companies.

"Tom Brown, one of the founders of Burr-Brown, died (oct 72). He was 75. Brown and his partner, Paige Burr, started out in business in 1956. Brown worked out of his basement in Long Island, while Burr did manufacturing and sales in his garage in Tucson, Ariz. The company hit it big several years later with operational amplifiers and later migrated into data converters, making it so attractive that Texas Instruments bought the company two years ago for $7.6 billion. That makes Brown's run one of the more successful in electronics history."
http://iis.eller.arizona.edu/eller_times/december2002/Tom_Brown.html

I think Keeley is referring to real vintage 80's era burrbrown chips, I think i am gonna try the Texas Instruments chip, just to see, that will be the last chip i try,

I didn't like the JRC4558D chip from SMallbear though, it was to muddy, and as soon as i switched it back out for the original, the "tone" I like was back again,  I only tried one JRC4558D chip though, and there is absolutly no room for a socket either.

Oh yeah, one thing i forgot to mention though is, i am not looking for that SRV tubescreamer tone, I actually run the tubescreamer with the tone nearly on full, if not on full,(depends on amp/volume of amp) i run the level on full, and the drive either on full, or on around 11:00 o clock.

I am looking for a Smooth, trebley, but not ear piercing, buttery overdrive, for lead work, where a high gain fuzz, or Rangemaster isn't needed.    I am close to that sound now, as the tubescreamer is.

  A music store in my area lets me borrow pedals to try, and return them the next day,(that way i could play for hours through my own rig, and not have someone telling me to "turn it down!!"  Anyway, i tried the New reissue TS808 by ibanez, and actually liked it,


IN  conclusion I think what i am gonna do is, buy the TS808 reissue and mod a few parts, and also for true bypass, and use that as my main pedal, and use the ts9DX i have now, for backup purposes.  Or maybe just keep it at my other location, for practice,

It is funny how one day i don't like a certain tone, and a few months later, i try to get that tone i originally didn't like. 

[formerMember1]

ok i found the 4k7 resistor(yellow purple red gold) but there are two caps i am not sure which one is  the .047uf,
there is a green ceramic and a yellow cap that looks like a polystyrene or somthing, Which one?

There is increased hiss and squealing with increased gain, so you might want to increase the 51p capacitor across the clipping diodes to about 100p if this is a problem.

For the 100p cap  i guess i am gonna use a 100p silver mica cap,

[MartyMart]

It will be fairly small and have "473" written on it

Marty.

[Michael]

Are these parts (the ones for increasing the gain) found in the same places in a TS10 tubescreamer? i would like increased gain aswell... im allready on max gain setting on the knob. The sound is nice, i would like the ability to have more gain though.

Great pedal apart from that.

Michael

[gaussmarkov]

cool formerMember1.  thanks for all those thoughts.    i discovered the burr-brown thread after posting--but i appreciate that you pointed it out.

if you get the ts808 reissue, try putting it in series with the ts9dx.  two tubescreamers back2back:  double trouble, but not in an SRV kinda way. 

i have been trying to learn about RC filters.  for more treble, i think you could mess with the low pass filter after the clipping section and before the tone pot.  i haven't seen anyone suggest this, but R.G. explains that its roll off point is 723Hz.  replacing the .22uF cap with a .1uF cap would increase this to about 1.6KHz.  that may be too much.  i haven't tried it (yet ).  nor do i understand what else you might have to adjust to account for the cap switch. and i understand you might not want to do this in a commercial pedal.  it would be easier in a clone that you built  yourself.

[formerMember1]

It will be fairly small and have "473" written on it
Marty.

huh, thats funny i can't find a cap with 473 written on it. The green ceramic cap next to the 4k7resistor says  C   with   51   J
written underneath the C
                                                                                                                                                               
the yellow cap says    203k   
                                50C?

There is a yellow cap, on the other side of the board,(same side as rest of the components but i mean far away from the opamp,
it says 473K
          50D?

the ?'s above mean that there is a symbol that i can't make out. 


gaussmarkov:
yeah thanks for those tips. 

[wampcat1]

The ts9dx .047uf caps in question are on the circuitboard under the pots.


The mode switch changes the cap and the resistor IIRC as well as the diodes.

I have a diy kit for it if you get tired of looking for it.

Take care,
Brian

[formerMember1]

thanks!!

[formerMember1]

wampcat1 :

There is increased hiss and squealing with increased gain, so you might want to increase the 51p capacitor across the clipping diodes to about 100p if this is a problem

the green ceramic cap next to the 4k7 resistor, is that the 51p cap i am looking for?

thanks

***EDIT***
I looked at all the caps, and the only one it seems to be is the green ceramic cap above, i don't think the 51p cap is on any of the boards with the pots, 

[formerMember1]

More 2nd Harmonic Distortion
You could replace the original diode pair with a 1N914 on one side, and two (or more) 1N4148 in series on the other. LED's are worth a try, let your ear be the judge. I have used one silicon diode on one side and 2 on the other (mixture of types). This produces a more musical distortion, depending on your taste.

i found this mod on the net, but, What does 2nd Harmonic Distortion sound like?  more smooth and compressed? It says more musical distortion, but does that mean more smooth or crunchy?

there is other mods here ,

http://web.archive.org/web/20020824175704/www.guitarkit.com/distortion/GeneralHotrodding.html

thanks 

[formerMember1]

i didn't like the extra gain mods, i am gonna switch it back,  It sounded farther away from what i want,  I am trying to get a  overdrive sound, with a hint of chorus or something, and some delay,

Heres my reason,
I use a Korg Pandora PXR4 for recording, and in there is a digital preset called 80's, I liked it somewhat, but want that sound but more analog sounding,  I wrote a few songs using that preset, but i want to replicate that sound with pedals, the closest i  ever got was with a delay, slight chorus, and a stock TS808 reissue or TS9DX,

I guess i am gonna switch back the tantalum caps, and NP electros, and swap out the gain mods for stock sound, then start the modification over, or perhaps just buy a TS808 and mod it for true bypass, 

thanks

PS:Any pedals out there that anyone thinks will sound like what i am looking for, that i don't know about?
I heard the liquid drive from fuzzcentral is great, but never heard one. 

[Fret Wire]

Take a look at the Tube Reamer, it's a nice sounding ckt.

[Melanhead]

i didn't like the extra gain mods, i am gonna switch it back,  It sounded farther away from what i want,  I am trying to get a  overdrive sound, with a hint of chorus or something, and some delay,

No surprise .. I've tried it myself a while back and thought that it sounded mushy and not tight sounding like it should ... ... I should have piped up sooner, may have saved you some time ...

I usually switch both Tants and electros as well as change the input cap to .047 for a bit fatter tone .... Change one cap at a time and it's not that noticable but changing the 5 of them is... of course I also change the 2 resistors in the output section and the chip ... I prefer the TI chip.

[wampcat1]

I believe the 51pf is right next to the opamp, it isn't next to the other diodes on the other cb's. Sorry so late at posting!

You might also try subbing in some transistors in place of the diodes -- IIRC it sounded nice. My favorite combo (at the moment) is a red led and 1n4148 in series on both sides. I don't increase the gain on my personal ts but I do use a fuzz or distortion behind it for ultimate creaminess.
Hope that helps!