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Vintage threads from the first ten years

TS9 reissues.

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7/8/1997 10:03 AM
Tom	TS9 reissues. Anybody out there how the TS9 reissues compare with the original ones? I've read that they're exactly the same, but are they? Tom

8/18/1997 4:58 PM
Paradiddle	Well there is a difference in sound you get more sustain and the tone changes,....

8/20/1997 7:53 AM

There is a fairly wide variance in sound in these boxes, depending on the component tolerances. The notable ones are the .22uf tantalum capacitors in the lowpass filter, but there are others as well.

I recommend replacing the tantalums with film caps for this reason. This has a lot to do with the variances between units, even with the same schematic.

The other variations are in the dual opamp. Vintage enthusiasts will insist on a "JRC4558D" as in the original TS808 and TS9, but some of the folks that have built or modified this circuit tell me that you get excellent tone from some more modern opamps, notably the LM833 and some of the CMOS dual opamps.

8/24/1997 7:21 AM
Tom Herpich	RC, I found an RC 4558P in a fried peavy bravo. Is this one usefull?

8/25/1997 9:02 AM
R.G.	Useful - yes. All the "4558"'s will work. The "JRC4558D" is the one that was in the original pedals and seems to be what most people prefer.

8/25/1997 6:21 PM

Some more parts queries...

You stipulate the JRC4558D as the preferred dual op-amp for an "ideal" Tube Screamer. Does this mean that any other variant of an RC4558 (e.g., RC not JRC, 4558P not D, etc.) is NOT identical to the ideal chip?

Also, there are two other active devices in the TS9/808, namely the two 2SC1815 transistors. I got a bunch, and they test out at between 150hfe and 250hfe. I know from previous exchange with you that "ideal" Fuzz Faces use transistors with hfe of 100 and 150 (1st and second transistors). To the best of your knowledge, do the gain characteristics of the 1815's (or their equivalent) make an audible difference?

Mark

8/25/1997 11:04 PM

I don't know that it's ideal, it's just what was in the original, and what a lot of people swear by. The other "RC" variants get mixed reviews. I think the Raytheon RC4558 is pretty darned close, in sound at least. Other labels including "4558" are NOT the same device, not identical, and may have different (although not necessarily worse) quirks of their own.

The original was from the "Japan Radio Corporation", hence JRC. I think.

Near as I can tell, good sound in a TS application correlates to graceful recovery from overload. I rationalized to myself that there is a sudden gain change when the diodes begin/end conduction, so the recovery from overload might be a similar circumstance.

I do get reports that high bandwidth good hifi opamps sound good also, examples being the LM833 and some Burr-Brown devices. Also some of the CMOS devices, notably the TLC2202.

To my ears, the two transistors make substantially no difference to the sound. They are both used in unremarkable emitter follower applications here, and the difference between an hfe 100 device and a hfe 500 device in an emitter follower is small. It's possible that deleting the first transistor in favor of the high input impedance of the opamp would work just as well, and splicing the output loading resistors onto the final opamp output would also work as well, although I haven't tested this. The emitter followers act as input and output buffers for the jfet bypass switching in the original device, and might be expendable. Experimentation is in order here.

The Fuzz Face transistors are not used as emitter followers. The basic circuit there is the buffered voltage feedback stage, and the saturation characteristics of the first device (at least) are critical to how it clips.

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