Dod 250 ic idea question

[jimbob]

A while back I think there was someone around here who figured out how to switch between  2 different IC's. I was thinking about putting together a dod 250 and be able to switch between an lm741 and a jrc 1458 rather than building 2 diffrent ones.

Has anyone seen a layout for this around here. I already checked the "search" with no luck.

Thanks

James aka jimbob

[Mark Hammer]

I strongly doubt you would hear any audible difference.  The 1458 *is* a pair of 741 op-amps in a single package.  As such, it's a bit like asking for advice on how to switch between a 20k resistor, and a pair of 10ks in series.

[tungngruv]

Couldn't you socket the original op amp on the board set up for a single opamp, then mod a second socket to insert into the original? So if the original socket on the board was set up for a single opamp, connect pin 1 to pin 6 on the second socket (for the dual opamp) , then connect pin 8 to pin 7. Use a single op amp normally, then with the dual, stack the modded socket on the original socket. Probably best to use the sockets from small bear that actually have round pins. I do agree with Mark though, "if" you do hear a difference, it will probably be minimal. Here's a qoute from Aron's FAQ:

To use a TL072 instead of an LM741:

The connections that connect to Output pin 6 of the 741 connect to pin 1 on the TL072

The connections that connect to V(+) pin 7 of the 741 connect pin 8 of the TL072

The rest of the connections are the same.

[jimbob]

Oh- I see. Ok. Thanks

[JHS]

I built the grey 250 and wired two 8 pin sockets parallel, one set up for a single opamp, the other for a dual opamp, so those opamps can be swapped w/o rewiring.

There is a audible difference in sound between the 1458 and the uA741, the 1458 will give more gain, treble and a tighter bass, in short it's way more open sounding. IMHO the uA741 sounds quite dull, compressed and lifeless so I tried a Philips 741. The Philips 741 is very close in sound to the 1458. The frequency response of the uA741 is quite inconsistent, so I recommend to buy a few and select one good sounding IC by ear.

JHS

[oldrocker]

You're better off switching diode schemes.  Asym and GE and SI setups.

[Mark Hammer]

I built the grey 250 and wired two 8 pin sockets parallel, one set up for a single opamp, the other for a dual opamp, so those opamps can be swapped w/o rewiring.

There is a audible difference in sound between the 1458 and the uA741, the 1458 will give more gain, treble and a tighter bass, in short it's way more open sounding. IMHO the uA741 sounds quite dull, compressed and lifeless so I tried a Philips 741. The Philips 741 is very close in sound to the 1458. The frequency response of the uA741 is quite inconsistent, so I recommend to buy a few and select one good sounding IC by ear.

JHS

Then what you're saying essentially is that it likely isn't the single vs dual thing that matters, as much as the manufacturer, and the particular unit.

Personally, I suspect it is the whole damn circuit, and that component values can be selected to make the one chip "sound" like the other.  Of course the task of figuring out what changes to make in which components is an onerous one, so we tend to just take the socketed component out and try others, don't we.  I.E., we tend to confuse what is expedient with what is important.  If whipping one chip out and slapping another one in changes things, then we figure that the chip is the most important part.