Maxon OD-808 Original Opamp

[soupbone]

I have a Maxon OD-808 Re-Issue that I love.Doing some research,I found a schematic from a Japanese site by Matsumin.The opamp that's in my re-issue is a JRC4558D.Looking at Matsumin's schematic(od-808 ver.#1.2) it uses a MC1458(D?) I have that opamp in an old dod pedal that I can yank out and put in my od-808.I'm just wondering if changing this opamp would get it to original spec's?It doesn't help to ask,does it?lol

[Seljer]

It might be original spec, but could you really hear the difference?

http://www.youtube.com/watch?v=bpTv2jAree8

[soupbone]

It might be original spec, but could you really hear the difference?

http://www.youtube.com/watch?v=bpTv2jAree8

If I had ears like Eric Johnson...Yeah,Probably. 

[Johan]

The only difference you will hear is the difference your mind decided you must hear after going through the trouble you did. ..and you might end up ruining a good opamp out two
J

[JebemMajke]

Personally I will always take 1458 over jrc4558. 4558 sounds a bit more boomy than 1458, and i think that it has a bit more gain. But the difference is so small that you would need two 808's placed next to each other to notice it.

Bottom line is no need to change it, because it's not going to transform your 808 into a magical vintage sounding unit .

Better mod would be true bypass.

[YouAre]

Personally I will always take 1458 over jrc4558. 4558 sounds a bit more boomy than 1458, and i think that it has a bit more gain.

Boominess, I can understand. Widened bandwidth could do that.

But more gain? How would we quantify that? The gain is set by the ratio of the gain pot to the shunt resistance, and the output is eventually clamped by the clipping diodes. Do you mean it has more headroom?

[JebemMajke]

In 808 it's hard to tell the difference, but in the high gain circuits like Shredmaster or Riot you really can tell that its gainier with two 4558's than with two 1458's.

808 with 4558 is easier to palm mute into heavier sound than 808 with 1458.

You should socket the damn thing and than try different opamps to find the best one for your ears. But the biggest difference is made with those capacitors, their values and the material.

[soupbone]

I think I'm going to put a socket in,and swap them out just for the hell of it.For Tube Screamers,my favorite opamp is the TL072CN,which I can't find anymore.

[JebemMajke]

You live in USA and you can not seem to find Tl072cn? 

Dude, try small bear and other big stores that are mentioned here on diystompboxes ... hell, if you can not find it there try farnell ( http://www.farnell.com/ )

I mean it's the most wide spread opamp there is. It's easier to find 072CN than high quality JRC4558D

[soupbone]

You live in USA and you can not seem to find Tl072cn?  

Dude, try small bear and other big stores that are mentioned here on diystompboxes ... hell, if you can not find it there try farnell ( http://www.farnell.com/ )

I mean it's the most wide spread opamp there is. It's easier to find 072CN than high quality JRC4558D

Thanks for the link!I've tried the main two distributors i use.(Mouser & Digikey) and both of them said that part is obsolete.So,I thought they didn't make them anymore.I'll check out your links.Thanks!

[teemuk]

Boominess, I can understand. Widened bandwidth could do that.

But more gain? How would we quantify that? The gain is set...

...by the negative feedback loops. And essentially so is the bandwidth of the circuit, along with usual passive signal coupling circuitry. At least if any kind of RC filtering is used.

In case of OD-808 we can safely say it is used.

Unless someone can portray some valid test data about these OpAmp differences, other than "I heard it", I'm dubious towards any kind of "information" presented by threads like this. The high levels of negative feedback in OpAmps should practically level out any difference that could appear in their open loop performance.

And no, OD-808 has no stages which could be subject to exceeding input common mode range of the chips so we can rule that out too before anyone throws that theory around to explain differences.

[soupbone]

Boominess, I can understand. Widened bandwidth could do that.

But more gain? How would we quantify that? The gain is set...

...by the negative feedback loops. And essentially so is the bandwidth of the circuit, along with usual passive signal coupling circuitry. At least if any kind of RC filtering is used.

In case of OD-808 we can safely say it is used.

Unless someone can portray some valid test data about these OpAmp differences, other than "I heard it", I'm dubious towards any kind of "information" presented by threads like this. The high levels of negative feedback in OpAmps should practically level out any difference that could appear in their open loop performance.

And no, OD-808 has no stages which could be subject to exceeding input common mode range of the chips so we can rule that out too before anyone throws that theory around to explain differences.

Interesting stuff!

[armdnrdy]

TL072CN

http://www.taydaelectronics.com/tl072-low-noise-j-fet-dual-op-amp-ic.html