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Vintage threads from the first ten years

JRC4558D in Vox Valvetone?

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11/12/1999 4:09 AM
Doug	JRC4558D in Vox Valvetone? has anyone tried replacing the original IC in the Vox with the JRC4558D . Does it make the same improvement that it does in the Tubescreamers?

11/12/1999 7:17 AM

The Vox Valve-tone has an RC4558 chip which is just fine. I would assume the JRC4558D would be ok, but the key is that many dual op amps work fine in these TS style pedals and guess what? MANY op amps sound good and in fact some sound better! It depends on your ears.

I speak for myself but I encourage people to move beyond the weird (to me) mojo surrounding the JRC chip and try other alternatives.

You may find, as I did, that the JRC is not the ONLY component and others sound as good or better.

11/12/1999 2:45 PM

Absolutely correct. The JRC part is not by any means the only good sounding dual opamp. Even in the Tube Screamer circuit, you can do at least as well, if not better.

Try a TLC2272 CMOS opamp for instance.

Never discount mystic mojo in musical electronics though - in the people involved, not the parts. The human psyche seems to need a reason for why things happen, and will gladly invent "reasons" for events or conditions where they don't know the real ones. Where they only know a little, they will cling to any shred of fact they have. That's really what's happening with the JRC4558's - people with little or no way to test alternate opamps found that they liked the "old original" pedals with the JRC4558's better than the new ones with the other numbers - so the concept of looking only for the JRC4558 got to be part of the myth.

It's better than nothing, in that the JRC's really do sound better than the later 7xxxxx duals, but the idea that ONLY the JRC's can sound good is faulty.

People!

11/13/1999 8:59 PM

quote:
"Never discount mystic mojo in musical electronics though - in the people involved, not the parts. The human psyche seems to need a reason for why things happen, and will gladly invent "reasons" for events or conditions where they don't know the real ones. Where they only know a little, they will cling to any shred of fact they have. That's really what's happening with the JRC4558's - people with little or no way to test alternate opamps found that they liked the "old original" pedals with the JRC4558's better than the new ones with the other numbers - so the concept of looking only for the JRC4558 got to be part of the myth. "

I think what also helped contribute to the 'mystique' of the JRC4558 is the rumor that only the 'vintage' JRC4558s sounded good. I think this mainly came about because of the way NJR uses part numbers and how it differs from the way they mark the actual parts. When people started looking for JRC4558s they couldn't find them. Only because NJRs part numbers all start with NJM (for bipolar monolythics anyway) but they mark the parts starting with JRC.

Nothing makes a thing more desireable than knowing it's no longer available.

--johng

11/12/1999 3:27 PM

I have modded 3 VVT's the TI rc4558 and the 1uf np elec's(the VVT used good caps IMO) give it as Aron says a darker sound. 1 has an old jrc4558 more 808 sounding, one has an NE5332 sounds like more gain brighter but not harsh, One has a good fet dual opamp (Aron it is in the DIGIKey cat.)IMHO it has it all. The best test I have found is a strat into the effect into a tube amp with the tone and gain all the way up if it sounds good there it is good IMO. In my testing and modding of TS type effects different ICs change the tone the most as well as the .22uf cap in the lowpass section more bite use a tan less bite use a film change to taste. FWIW I have modded for one friend 1VVT,2 TS10,2ts 9,1 ts5 all to sound different. Also I had emailed Aron about using a rat before a ts for a good sound.

11/13/1999 11:45 PM

Lets see, knowing Gus, thats gonna be a- LF353N
Seriously, I did an Opamp shoot-out this past August,
Buffered signal generator- 0.1v input into each Opamp,
with 500k "drive" pot in the feedback loop, no clipping
diodes of any kind, and watched the output with my DSO.
very interesting-
If anyone wants to know ,I can provide an explanation about
why the JRC sounds so sweet, which is quietest, who has the best drive capability, widest freq. response etc.
I know you EE's know all this stuff, from data sheets, but those data sheets assume that we're gonna use this stuff
as the designers intended. And we know we're not doing that.
Ed Rembold

11/14/1999 5:32 AM
Aron	Very nice Ed. The unfortunate part is that as R.G. said, "the devil is in the details". Once you put that op amp in a circuit, the "details" take over and boy does every little thing affect the sound. Actually I wonder if anyone did a survey on how possible it is to make consistent pedals that sound alike.

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