JFET swap

[FrankB]

HI Everybody,
   I recently have repaired, then modified a non working Soundtank TS5 to something very usable, It's become my favorite pedal to use with either my Music Master Bass amp 2X10, Or my 1977 SF Champ. I also use an old arion sod1 wich is entirely different.
   So, As I was trolling the internet reading about mods, using cool free online calculators to ensure one mod didn;t undo another mod, or compund any frequencies wich could cause weird sounds or negative results IMO, I stumbled across a really great site where someone seems to have broken down an original ts-808 isolating the parts to recreate that dry-sweet tone that Stevie Ray Vaughan captured with his 808 setup.
  What I like about his screamers is the dryness of their character,I am aware that the Vibroverb 1X15 is a huge component of that sound, though I have heard it in a deluxe reverb as well. It's a specific thing. I'm not willing to sell anybody parts to purchase a vintage 808 of wich there are several versions anyway, so it's pretty mucha crap shoot.
  The TS5 I have modded is really really close, I've replaced alot of the parts with higher quality parts, Metalized diodes, non electro caps, the fat band blue diodes, and have removed the tantalumcaps and replaced them with polyfilm.
  My curiosity about the Jfets used in the original stemsfrom this websites description http://www003.upp.so-net.ne.jp/yochan/TS808analyzeE.htm it's interesting and very informative.
The board of the TS5 is really becoming scary to look at due to it's lackof quality so desoldering and resoldering has resulted in lots of jumper wires... but hey, what can I do it's working and it sounds nice.
  My goals are to find acheive that dryness of the original or specific ts-808 then build one so I can run 2 of them for different applications. Im not into running them engaged at the same time, but to use them for 2 different gain settings.  I also use my volume knob on either my tele's or strat's so I have alot of variations to control my tone.
  But That dryness i'm hunting for has me by the throat and I'm hoping the Jfet swap could be it.
  The TS5 is equipped with K118 0 2H, and also C1815 BL 2C The website I'm referring to is stating that 2SK44 creates more dryness. I donlt know which Jfets to replace, or whether they will work with how the TS5 is designed.
   Thanks in advance for any help with my hunt.
   Frank

[Gus]

First The fets are used as switching devices 2SK30A

A 2sc1815 is a NPN Si transistor used as a buffer(emitter follower) in the TSs

SRV's  sound might have been more SRV playing skills than the TS used.  Some of us here have played with the TS circuit (from before the ampage early days)
and IMO some of the stuff you read on the web should be questioned and tested.

IMO the TS is one of the most web overrated boring effects and I laugh when I see all the TS clones and changed part TS "mods" effects being sold.

I have heard a few real 808s, two sounded different than any other TS versions I have heard (808,9,5,7,10)s.  From what I know it will be hard to get that 808 sound.  FWIW I changed parts in a TS7 for a pro player to try to match their "real" 808 had both at the same time with  the player and the amp and guitar. We were testing as I changed parts.  I could get close.  That said the sound change is only heard when the player is real good it is a "touch control" smooth to gritty change with guitar level.  On stage I don't think one could hear the difference between a stock 9 and 808.  I think it is more of a recording thing.

My question. People that post about 808s how many have tried a "real" 808?

  Some sound just like stock 9s and the JRC thing is fun to read about.

[FrankB]

Hi Gus,
  Thanks for the Reply. I've been paying guitar since I was 5 years old, I'm 43 now and have seen heard and worked with alot of different tpes of musicians, I agree SRV's tone was his own. I'm not trying to recreate his sound at all. I have heard 2 of those dry sounding 808's and I remember them disticntly, I even played through one for nearly 5 hours during a festival and it nearly left with me  . It was very different than my early 80's ts9 and my MXR distortion II which was my main box, wich also had that dry, sweetness to it.
  I'm merely just trying to get as close to a dry sounding 808 as possible, The chip I installed was in the MXR initially which is the TI4558p Malayssia chip. It does sound different than a 4558D wich I also tried, allof the dual op amp chips have their specific unique sound quality to them. After changing the parts I llistened to it, it sounded different as each change I made impacted the way it sounded. It peaked my curiousity to go further, being I wasn't a tube screamer disciple at all after trading my 77 deluxe reverb with my ts9 for a pBass. I wasn't impressed with the combination at all, Frankly it bored me.
   During a session an engineer friend of mine had an amp setup already for the session, so I grabbed one of my guitars and plugged it into the cable that was draped over the sofa.
"Wow, what am I running through?" the engineer replied, "your music master Bass amp and one of Dan's 808's"....
   I was forever changed. I walked out to the room and played, thinking it may be an eq thing but, it got better, it was just one of those momentsthat was incredible.
I'm really close with the TS5 and I'm happy with what I have acheived thus far, tweaking it just a little more would be more of a curiosity for me.

  Thanks for your reply Gus.

[Gus]

Don't let me slow you down with trying different things with a TS circuit.  From your post you have heard real 808s.  Words are funny because maybe what you call dry is different than what I think that sounds like.

I will look for my notes.  IIRC the 808s I looked at had jrc4558s and most of the electronic parts looked the same as a stock 9 on the PCB, nichicon and pan caps etc.  The output circuit resistor change might have small change.  One day I want to build a TS output stage(9 and 808 type) and a triode preamp gain stage fragment(changing the series grid resistor) and scope and/or hook up a spectrum analyzer and see if it does matter and if the triode can be driven into grid conduction.

[FrankB]

Gus,
  Here is what I have swapped out thus far.
1.) output resistors, to the respected  values and also upgraded to metal oxide after trying the standard, the metal oxide actually sounded better, less noise to my ears.
2.) All of the caps, including the 2 non polarized electrolytic caps.
3.) a few other resistors to metal oxide, didn't change the value.
4.) Changed one resistors value and quality to compensate for a cap value change and upgrade.
5.) Opamp. I have tried several so far. 2 jrc4558's 3 ta4558, a jrc 4558dd and some I forget. The one I'm stucking with is a TA4558P, it has a very nice sound to it, lots of clarity, less midrange weirdness or harshness, (call it what you will)...
  So, essentially I've changed after counting the parts, over twenty. yeah, I know it's like dressing up a pig, but it;s what I have to work with and so far, I'm beyond happy.
  Initially I just wanted to fix it, since I saw one go for $60.00 on ebay.... but now, I'm keeping it. I also repainted it, but I don't know how to post pictures on this site,or I'd have posted pics of what I swapped out and how it looks now.
The Jfet thing has me curious...