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Author Topic: Please tell me what op amps you guys have put in your MP-1's  (Read 15574 times)

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luffliffloaf

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I have an early MP-1.

Curious as to what op-amps you guys have put in, and did you only replace U4 and U9?

What about the OPA827, OPA2134, OP270EZ, LM833N, NE5532 instead of the TL072IN's?

Anyone?

Thanks!
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MarshallJMP

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U4 OPA2604

What U9 do you mean,on the mainbaord or on the midi board?
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luffliffloaf

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Main board, sorry.

Did you replace both the U4 and the U9 on the main board with 2604's?

My rear board already has an RC4559, which I kept in.

Thanks
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luffliffloaf

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Also, I did both noise mods 1 and 2 (all large lytics replaced and several resistors upgraded to 1/2 watt 1%), replaced all the 4004's with 4007's, recapped all the 33uf small caps on the tube board, and got 2 vintage usa 12ax7's that test strong on my calibrated Hickok.

And I replaced every jack in the thing (5 of the 7 were broken). That job sucked.

But it's still a bit noisy. Any other suggestions? I think I'll order a few 2604's next.

Loomis
« Last Edit: Time Format by luffliffloaf »
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MarshallJMP

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Leave U9 like it is,won't help you with reducing the noise.

Do you still have an original non modded mp-1?
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luffliffloaf

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I've already socketed and replaced (on the main board) U4 and U9, with the TL072IN.

I would like to point out that this unit is still stock basically. it is not modified per se. It has upgraded caps, resistors, and jacks, but it is basically stock otherwise. The op amps are socketed, so I can revert them if necessary.

I might consider switching to the 2604 but I read the current draw is much higher and it's not realistically a drop in replacement?

Do you guys replace the tube board mylar caps with orange drops?
« Last Edit: Time Format by luffliffloaf »
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MarshallJMP

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The 2604 works very well in a MP-1.At +-15V supply it draws 23 mA,so no problem here.Why wouldn't it be a realistically drop in replacement?

The original NE5534 is a far better opamp then the TL072.

You can use orange drops or mallory 150's.Downside of the orange drops is that they are quite big.
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Dna^Yay

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Hey MarshallJMP

Have you ever tried stacking op amps/running them next to each other?

Came across an adapter on

http://www.monteallums.com/pedal_mods.html#CA

Was wondering what it would be like to run 2 op amps in the same slot
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BrokeDownSouth

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Hey MarshallJMP

Have you ever tried stacking op amps/running them next to each other?

Came across an adapter on

http://www.monteallums.com/pedal_mods.html#CA

Was wondering what it would be like to run 2 op amps in the same slot

I've tried this in a few OD pedals with no noticeable effect compared to a single opamp.  Marketing gimmick IMHO.
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MarshallJMP

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Hey MarshallJMP

Have you ever tried stacking op amps/running them next to each other?

Came across an adapter on

http://www.monteallums.com/pedal_mods.html#CA

Was wondering what it would be like to run 2 op amps in the same slot

I've tried this in a few OD pedals with no noticeable effect compared to a single opamp.  Marketing gimmick IMHO.

+1
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luffliffloaf

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Ok two OPA2604's just arrived, and will try them in place of U4 and U9 on the main board, tomorrow.
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MarshallJMP

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Put the original LF412 back into the U9 socket.
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Zsoli

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NE5532 vs TL072:

NE5532: (original MP-1)
http://youtu.be/jcCAvESZVu0

TL072: (noise mod)
http://youtu.be/H8-qdDzTXh8

JRC4558 (tube screamer overdrive pedal):
http://youtu.be/s21MmTQaGAc
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BrokeDownSouth

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NE5532 vs TL072:

NE5532: (original MP-1)
http://youtu.be/jcCAvESZVu0

TL072: (noise mod)
http://youtu.be/H8-qdDzTXh8

JRC4558 (tube screamer overdrive pedal):
http://youtu.be/s21MmTQaGAc

That's interesting b/c the NE5532 is marketed as a low noise opamp (vs. a JRC4558 AFAIK).  The TL072 is a JFET based opamp; I can vouch that It's fuller in the low and high freq. range vs. a JRC4558 in a TS circuit.  I'm going to check out those links ASAP.  Anyone experimented with Burr Brown opamps?  They're premium-priced but I don't notice a significant difference swapping in overdrive pedals. 
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WickedBlade

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First of all I have to admit that I didn't read the whole thread, lazy me.

That being said, here's what opamps I put in my MP-1. Basically I swapped U4, U11, U15 and U18 for OPA2604 (with sockets). According to my notes U4 was originally a NE5532 and the others were RC4559N. I kept U9 as is (almost, it was an LF412CN and I put an LF412CP, because I mistakenly swapped it for a TL072 in the first place and damaged the original opamp when I removed it).

I chose the OPA2604 over the OPA2134 because some said it was more tube-like whereas the other was more hifi, whatever that means. I'm sure the 2134 wouldn't be a bad choice either.

The bottom line is that I am more than pleased with the results, it's as if a blanket had been lifted (that's so cliché!) and I suddenly had some nice high end coming back at my disposal. And of course the noise went drastically down (but I also changed the caps as per the noise mod instructions).

I also felt that my gain went up too. Previously I had doubts and was considering a gain mod, but no longer now, I get the gain I need, and more (think Bettencourt gain).
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