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Hey there-
I've got one of the reissue TS9 tubescreamers (mid-90's), and wanted to mod it to the TS808 specifications. First I changed the two resistors in the output network as described elsewhere, and then I put an IC socket on the board in place of the TA75558P that was stock in my unit, to enable quick swapping.
Since the op-amps are so cheap, I figured I'd buy a bunch of different kinds and try them out. Note that a NOS 4558 was not one of my choices, because I stuck to what Mouser had to offer.
Some of the chips that I tried were not noteworthy, but the chip that I finally settled on was a TSH22IN, made by ST Microelectronics. This guy has a higher slew rate and much higher gain-bandwidth product than either the 4558 or the 75558. I make no assertions that this has anything to do with my liking it better. In fact, I didn't look at datasheets until after doing the sound test.
As anyone who has done chip-swapping knows, the differences in most cases are pretty subtle. What I was looking for was something that made the TS9 sound less compressed and with a little more clarity than the 75558.
Not only does the TSH22IN have better clarity, but for any given setting of the "DRIVE" knob, this chip gives a little more gusto.
The NJM4558D came in a close second place - almost as clear, but a little less gain at a given setting. I should note that I tried two different NJM4558D chips, and they did not give identical sound - I can't offer a reason for this. It surprises me that the tolerances chip-to-chip would be big enough to hear the difference in new chips, but I'm only reporting what I heard.
The RC4558 did not sound as good as either of the two NJM4558's that I tried.
I tried a couple of others. TL072ACN was a little better (less compressed, more clear) than the stock 75558. And the NJM2068D was no better than the stock chip.
If anyone is interested, I can try to provide a little more detail on the distinction between the chips, but it's so subjective, I wasn't sure it was worth it. Mainly just wanted to give a heads up on the TSH22IN for those who haven't tried it. Only $1.10 from Mouser.
I've got one of the reissue TS9 tubescreamers (mid-90's), and wanted to mod it to the TS808 specifications. First I changed the two resistors in the output network as described elsewhere, and then I put an IC socket on the board in place of the TA75558P that was stock in my unit, to enable quick swapping.
Since the op-amps are so cheap, I figured I'd buy a bunch of different kinds and try them out. Note that a NOS 4558 was not one of my choices, because I stuck to what Mouser had to offer.
Some of the chips that I tried were not noteworthy, but the chip that I finally settled on was a TSH22IN, made by ST Microelectronics. This guy has a higher slew rate and much higher gain-bandwidth product than either the 4558 or the 75558. I make no assertions that this has anything to do with my liking it better. In fact, I didn't look at datasheets until after doing the sound test.
As anyone who has done chip-swapping knows, the differences in most cases are pretty subtle. What I was looking for was something that made the TS9 sound less compressed and with a little more clarity than the 75558.
Not only does the TSH22IN have better clarity, but for any given setting of the "DRIVE" knob, this chip gives a little more gusto.
The NJM4558D came in a close second place - almost as clear, but a little less gain at a given setting. I should note that I tried two different NJM4558D chips, and they did not give identical sound - I can't offer a reason for this. It surprises me that the tolerances chip-to-chip would be big enough to hear the difference in new chips, but I'm only reporting what I heard.
The RC4558 did not sound as good as either of the two NJM4558's that I tried.
I tried a couple of others. TL072ACN was a little better (less compressed, more clear) than the stock 75558. And the NJM2068D was no better than the stock chip.
If anyone is interested, I can try to provide a little more detail on the distinction between the chips, but it's so subjective, I wasn't sure it was worth it. Mainly just wanted to give a heads up on the TSH22IN for those who haven't tried it. Only $1.10 from Mouser.
I'm definitely gonna order one when i get around to modding a ts9 for myself. Stratdeluxer I imagine will be very interested in this thread.
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