[sdiy] On the topic of BBDs...

[anthony]

> On Tuesday 20 November 2007 17:23, anthony wrote:
>> I have A/B tested actual AN6550's that came stock in a Radio Shack
>> Realistic "Electronic Reverb" against different versions of the 4558 and
>> they all outperform the AN6550 - which is not to say the AN6550 is
>> particularly crappy, but...
>
> What sort of testing are you referring to here?

Running a microphone or a guitar in turn at either input at various levels 
for the mic input. They all distort to an amazing degree in this particular 
piece of gear and what I meant by outperforming is that the quality of 
distortion is more euphonic from the various 4558's; the JRC4558DD being the 
best in my opinion (and BiFET opamps were no good here...). The BBD does 
contribute a lot to the distortion, so it may be that certain op-amps play 
nicer with it.

Follow any thread on a stompbox forum regarding Ibanez TS-808, TS-9 
Tubescreamers and the virtues of various 4558's will be opined - the general 
consensus being that the older JRC4558D with the 4-digit date code is the 
best op-amp to use in this box (The JRC4558DD being much less common ins't 
mentioned a lot). But others swear by the Japanese-made TI RC4558 (but I 
would guess that the Malaysian one and the NEC version would be just as 
good...).

But it should be understood that MY Realistic Electronic Reverb has also 
been highly tweaked and modified by me (though many alterations were 
returned back to stock - changing the transistors in the output filter to 
higher hFE ones isn't a good idea...), so YMMV.

I have a small stash of AN6550's and have used them in synth modules and 
stomp boxes with good results. In many audio applications I'd sooner use an 
AN6550 than a TL072.