TS-9 Modification Advanced "Texas Blood Special" The Secret of Original TS-9

On the novice class page, I modified reissued TS-9

  1. Replaced OP amp with NOS JRC 4558D
  2. Changed output resistors as TS-808 specification

But it was 70 % of 1982 original TS-9. Original TS-9 has brighter, tighter, wilder and more powerful sound. So I checked the detail of inside of the original TS-9 with comparing reissued TS-9. Before that, I returned two output resistors value to TS-9 specification. Because I think Stevie Ray didn't change them for his TS-9.

TS-9 circuit is Here

1982 original TS-9

1892 original TS-9 2000 reissued TS-9 Description
OP amp Smooth surface 4 digit serial JRC4558D TA75558P NOS JRC4558D is a super rare item now
JFET 2SK30A O rank (Might have GR rank value in fact) 2SK30A O rank (O rank actually) low gm value makes the sound darker and foggy
Clipping diodes Toshiba 1s1588 Not sure Toshiba 1s1588 was discontinued
Film caps Only input stage 203 and clipping stage 473 seem to be polypropylene film caps. All film caps are polyester with see-through outside Clipping stage 473 cut unnecessary harmonics before clipping.
tantalum caps Reddish brown caps (model not sure) Yellow caps (model not sure) The cap for the tone control cut high frequency of distorted sound.
51pF ceramic cap Yellow brown cap (model not sure) Green cap (model not sure) The cap round the edge of wave form cut by clipping diodes to emulate tube over drive.
50V 1uF non polar caps Tall shape 1980s Nichicon caps Small shape Nichicon caps The caps cut DC and low frequency at input and output stage of effect side.

Changing JFET 2SK30A, rank O to rank GR

Modification on the novice class page made the same circuit as original, but we couldn't got the same sound. I found the rank of JFET is O (Orange) when I was checking the board carefully. They are used as switches to change Through mode and Effect mode. Low rank JFET has big resistance and disturb the sound going through. Original TS-9 has O rank JFET as well, but 1980s 2SK30A O rank had near value as GR (green rank) in fact. I replaced O rank JFETs with GR rank JFET. GR rank 2SK30A removed fog and made the sound brighter. Modified TS-9 was 90% of original.

Replacing clipping diodes with Toshiba 1s1588

Left side is clipping diode for reissued TS-9, right side is Toshiba 1s1588 same as original. 1s1588 has blue line for showing cathode. Toshiba 1s1588 was discontinued, however we can still buy them at Akihabara.

At "Clipping diodes" on the photo left side, two diodes are placed parallel with opposite direction. Replacing them with Toshiba 1s1588 makes the distorted sound tighter and powerful. It was still 93% of original.

Replacing film caps

All film caps of reissued TS-9 are yellow, see through outside, polyester type like left side of the photo. Original TS-9 has the same polyester film caps except input stage and clipping stage. Film caps for input stage and clipping stage are green polypropylene caps (or high grade polyester for audio filters) like right side of the photo. I think the circuit for original TS-9 is not special, because it uses only ordinary parts in early 1980s like JRC4558D, 2SC1815, 2SK30A and 1s1588. They were common for electronic engineer in 1980s. But those two caps are special. The designer for TS-9 might work hard for deciding those two caps. 0.047uF cap before clipping stage must cut high frequency not to make the distorted sound muddy. But the polyester film cap on reissued TS-9 does not cut high frequency enough and makes the sound muddy. I replaced the yellow polyester film cap with green polypropylene film cap. I could remove mud form its sound. 0.02uF cap for input stage shaves mid and low frequency from signal from guitar. Yellow polyester 203 can not shave mid frequency enough and the sound is not tight for low position chords. I replaced it with 203 polypropylene cap. The sound for mid frequency is like original TS-9. It could reach 95%.

Changing tantalum caps

Tantalum caps for reissued TS-9 are yellow one like left side of the photo. The caps for original are reddish brown one. I am not sure which company made them. I tried to replace the caps on reissued TS-9 with NEC's 1980s tantalum. Tantalum caps are used for tone control after clipping stage. Max level of tone control on reissue TS-9 is around 9 of 10 on original TS-9. I felt that tone control on reissue TS-9 could not open perfectly. I wanted to turn the knob more. After replacing the caps with NEC's tantalum, effect of tone control is the same as original one. I tried film caps instead of tantalum as well, the tone became too dark and too calm down. 1980s tantalum caps are the best for this part. Reissue with 1980s tantalum reached 97% of original. Bright harmonics from distorted wave form don't come out yet.

Replacing 1uF non polar caps with 1980s one

When we play low frequency string with reissued TS-9, the low frequency sound is not clear, not tight but loose. Left side of the photo is a 1uF non polar cap for reissue and right side is a same value normal size cap in 1980s. (This one was made by ELNA. Caps made by Nichicon are on original TS-9) These caps are used for input and output stage to cut DC and extra low frequency. After replacing them with ELNAs, the sound became clear and tight for low frequency. (Also I tried hi- end MUSE caps for expensive Hi-Fi audio, the sound comes too crispy and too thin. Sometimes, the best Hi-Fi audio parts are not the best for musical instrument)

Changing 51pF ceramic cap.

The sound of modified reissue TS-9 came closer to original one. But the harmonics on distorted sound are not rich and the sound is not shiny. I doubted 51pF ceramic cap. This cap round the corner of the wave form clipped by diodes and emulate tube sound. But I thought the cap on reissued TS-9 rounded too much on the wave form and lost harmonics. Reissue's one is green like left side of the photo and original one is brown. I tried some ceramic caps and the right side of the photo was the best for this part. The sound got harmonics and came rich. I used the same value 51uF, but smaller value such as 47uF might be good for this purpose. At last, the reissue TS-9 came 99% of original TS-9.


Reissued TS-9 sound Causes What to do
Dark and not vigor OP amp Replacing with vintage JRC4558D (Don't use reissued JRC4558D)
Not clear totally FET Replacing 2SK30A O rank with GR rank one.
Not powerful for attack Diodes Replacing clipping diodes with Toshiba 1s1588
Muddy sound for attack Film cap Replacing 473 for clipping stage with a polypropylene film cap 473 (Or, hi grade polyester film cap for filter circuit)
Not slender for mid and low Film cap Replacing input stage 203 with a polypropylene film cap
Can not open tone control Tantalum caps Replacing tantalum caps with Japanese 1980s tantalum
Not tight for low 1uF non polar caps Replacing 1uF non polar caps with (Nichicon's ) 1980s standard size caps.
Not rich harmonics 51pF ceramic cap Replacing 51pF with a same value another ceramic cap or smaller value.

I did it ! Now I know the secrets of original TS-9. I could re-create original TS-9 almost. There are lots of work to reach the original sound. But it is valuable to do that to come closer to SRV sound !