Sm Pro Audio PR8E?

[hugoderwolf]

The 4580 is pin compatible with most dual Opamps like the 5532. So you can try anything that fits into the PR8E.

 

[the19thbear]

thanks!
I'll order some LM4562's and put them in!
There are 2 IC's on the preamp circuit itself, and one near the output plugs , for every channel.. Do i need to replace the ones near the output plugs as well??

I understand if you dont know at all, but it might be the same design as with the pre8.
thanks again!

 

[hugoderwolf]

[quote author="the19thbear"]
There are 2 IC's on the preamp circuit itself, and one near the output plugs , for every channel.. Do i need to replace the ones near the output plugs as well??
[/quote]

There is no real need to do anything, just the possibility. And yes, you can replace the output ICs, too. At last, your ear decides if it's a good idea, I think it might be.

Remember that under certain circumstances replacing opamps can cause the circuit to become unstable in some gain ranges, thus causing oscillation. But if your unit is similar to the PR8E I think there is no problem like this, unless you begin removing caps.

 

[the19thbear]

thanks again!

I wont be playing around with caps.. but i will change the ic's.. i compared this preamp with others i have.. and didnt like the result, so its perfect that this unit can be modded!

I'll post here again when i have done it.
thanks

 

[the19thbear]

I have decided to go for the NE5532 instead.
But i can get:

NE5532AP
NE5532P
Does it matter which one?? I can get the NE5532P very cheap.
thanks

 

[TobWen]

Better go for NJM5532 ... best 5532s in DIP (the SIP ones are little better).

 

[the19thbear]

what about the NJM5532DD??
I can buy these in denmark ( where i live), and would save me shipping fees.

thanks

 

[Kaspar]

Hey the19thbear,

Any news on your EP84 project? I've been looking at that preamp. Seems like it must be close in design to the PR8E.

Kaspar

 

[the19thbear]

sorry... not yet... but maybe this coming month but keep bugging me! i will post info eventually!

 

[the19thbear]

just ordered some NJM5532dd's today.
will post samples sometime in june :grin:

 

[Kaspar]

Cool!

I went ahead and got one of these puppies. 4580s throughout. I haven't had a chance to compare the layout to the schematics of the PR8 or PR8E but at first glance it seems close.

Looking forward to your results.

 

[the19thbear]

modded one channel today with 3 x NJM5532dd.
I will post some audio clips, comparing one channel to another, later this month!

 

[the19thbear]

done!
soundfiles here:

http://www.mediafire.com/?ddnx2jj0svb

what can i say...
there is NO difference at all
listen for yourself!
maybe i should find other ic's? i'm thinking opa2604/2134??
anyone with suggestions?

thanks alot!

 

[Kaspar]

Did you clip any of the caps? On earlier versions, people seemed to get improvements removing some of the small value caps that come off of the op-amps.

The schematic on page 2 of this thread, <http://www.groupdiy.com/index.php?topic=344&start=15&postdays=0&postorder=asc&highlight=pr8>, shows caps 13, 14 and 15 on op-amp U2.A People had better results, when these were removed. I'm having a look at one of the preamp boards from an EP84 right now. I'm not an EE, just a hobbyist with limited skills but it looks as though the layout is very similar. There are two 100pf caps next to the op-amp closest to the XLR jack. These appear to be the equivalent of the two 470pf caps (13 and 15) on the older version. There is an electrolytic 47uf cap on pins 6 and 7. This is somewhat similar to the older version which had a 47pf cap in parallel with a 100k resistor.

I just got some OPA2134s to play around with. I'll substitute those and also try removing the two 100pf caps.

Will keep you posted

 

[Kaspar]

Did you clip any of the caps? On earlier versions, people seemed to get improvements removing some of the small value caps that come off of the op-amps.

The schematic on page 2 of this thread, <http://www.groupdiy.com/index.php?topic=344&start=15&postdays=0&postorder=asc&highlight=pr8>, shows caps 13, 14 and 15 on op-amp U2.A People had better results, when these were removed. I'm having a look at one of the preamp boards from an EP84 right now. I'm not an EE, just a hobbyist with limited skills but it looks as though the layout is very similar. There are two 100pf caps next to the op-amp closest to the XLR jack. These appear to be the equivalent of the two 470pf caps (13 and 15) on the older version. There is an electrolytic 47uf cap on pins 6 and 7. This is somewhat similar to the older version which had a 47pf cap in parallel with a 100k resistor.

I just got some OPA2134s to play around with. I'll substitute those and also try removing the two 100pf caps.

Will keep you posted

 

[Kaspar]

Did you clip any of the caps? On earlier versions, people seemed to get improvements removing some of the small value caps that come off of the op-amps.

The schematic on page 2 of this thread, <http://www.groupdiy.com/index.php?topic=344&start=15&postdays=0&postorder=asc&highlight=pr8>, shows caps 13, 14 and 15 on op-amp U2.A People had better results, when these were removed. I'm having a look at one of the preamp boards from an EP84 right now. I'm not an EE, just a hobbyist with limited skills but it looks as though the layout is very similar. There are two 100pf caps next to the op-amp closest to the XLR jack. These appear to be the equivalent of the two 470pf caps (13 and 15) on the older version. There is an electrolytic 47uf cap on pins 6 and 7. This is somewhat similar to the older version which had a 47pf cap in parallel with a 100k resistor.

I just got some OPA2134s to play around with. I'll substitute those and also try removing the two 100pf caps.

Will keep you posted

 

[the19thbear]

great! thanks alot! i'm not a EE either, but you seem to know a bit more than me :grin:
let me know your results!
i'm sure this thing is moddable!

-and yes! KEEP ME POSTED :grin:
thanks

 

[Pentium]

I have had a lot more time to get to know my PR8E mods and there is interesting results. I put TI5532's, LM4562's, OP275's in there.

The differences were large not small, though this is not easy to quantify.
I also changed the caps from cheap ceramic to more stable NPO variety
and 1 channel has Polypropolene.

The 5532 has a slightly nasal quality about it though offers best bass performance, the LM4562 is the most linear in frequency response IMO
though I could have sworn I can hear slight distortion artifacts along with the OP275, you can download a speech file I recorded here......

I will have to do further tests with the LM4562 and OP275, can you hear the distortion on the words "powerful" and "time" ? which is not present on the Mackie preamp? The transformer reduces the distotion when in line (I used a mic splitter isolated out to give a transformer flavour variant)

I used a Studio Projects B1 microphone, no pad, no HPF (slight popping might be in the files though I used a pop shield)

This link only lasts for 7 days so download it ASAP.......

https://www.yousendit.com/download/Q01HcmxUSEJPSHl4dnc9PQ

1) 5532 NPO

2) OP275 with polypropolene caps

3) LM4562 NPO

4) Mackie XDR

5) 5532 with audio transformer

6) LM4562 with audio transformer

7) Mackie XDR with audio transformer

Please.... let me know your favourites......

 

[aortizjr]

Hey thanks for doing that!

It is hard to say which one I like best. Personally I find any of the mods to be an improvement over the Mackie.

What transformer are you using?

But at least to my ears, the NE5532's sound pretty good and are definitely the cheapest way to go. When I did my PR8, the NE5532's were a huge improvement. Going to an OPA2134 wasn't enough to justify the cost for all the channels. Although, that LM4562 does sound really clear and airy.

Was it only OpAmp changes and upgraded caps. Or were there other mods in there as well?

 

[MagnetoSound]

Great shootout, although I would suggest that the different factors (caps, transformer) wreak havoc with any chance of a definitive conclusion regarding the chips ....

... that said, number two is a clear winner for me being, to my ears, more intimate and open. I also detected a more forward low end, although I wonder if proximity played any part in it (or just better caps!).

The Mackie comes in last, sounding hard and middle-y by comparison with all the others.

My one pence. :wink:

Thanks for doing it!


Dan