Good replacment for BB OPA 2604/604

moving_electron · 2005-02-12 12:59 am

Re: Deal?

carlosfm said:
Would you trade those for some "hand-selected" JRC op-amps?

If anyone has any JRC 4558 op amps where the numbers stamped on them are 4 digits (rather than 5) I seriously would be interested in trading.

If you have a clock radio made in Japan in the 80's you can take it apart and look.

There is a good chance there is one in there.

The application is recreating a vintage guitar effect box.

moving_electron · 2005-02-12 1:06 am

ericpeters said:
Hey Carlos,

I know it matters where to put the bypass, but how important is the quality/size of the cap used?

I just used what I had laying around, and it improved my project dramatically. I'm now wondering if a high quality/right size cap will even improve that.

http://www.diyaudio.com/forums/showthread.php?s=&postid=532582&highlight=#post532582

ericpeters · 2005-02-12 1:10 am

carlosfm said:
It does.
Search this forum and you'll find my hundreds (thousands?) of posts about that.
I suppose it's easy to find.

Ok, one thread I knew (VSPS) and I found a few others (So thousands or even hundreds is a bit :devilr:

)

anyway between 22 and 100uf it should be according you (I have 470uF now). Cannot find a quick mentioning of quality so I'll get some decent but not extremely expensive.

Thanks moving elctron, I just found it at the same time you poste.

carlosfm · 2005-02-12 1:58 am

ericpeters said:
Ok, one thread I knew (VSPS) and I found a few others (So thousands or even hundreds is a bit )

And the ones you didn't find?
Ok, tens.

Check out what I say about the bass.
Doesn't matter, put the right caps on the right places and full speed ahead.

Gaucho · 2005-02-12 3:29 am

No it's not.
You just don't know how to use it.
And yes, I KNOW what you're talking about. You've hit the spot.
Hint: PSU bypass.

Sorry try again. I have the bypass caps right at the pins: 47uF electrolytics with 0.1uF films from the supply pins to ground. Perhaps you are influenced more by datasheets then by your own ears.

moving_electron · 2005-02-12 3:40 am

Gaucho said:
Sorry try again. I have the bypass caps right at the pins: 47uF electrolytics with 0.1uF films from the supply pins to ground. Perhaps you are influenced more by datasheets then by your own ears.

Anything between V+ and V- ?

Gaucho · 2005-02-12 5:05 am

Anything between V+ and V- ?

Yep, I put 27uF across the supply pins too.

Perhaps LM317/337 simply don't get along well with the 2132.

carlosfm · 2005-02-12 12:38 pm

Gaucho said:
Perhaps you are influenced more by datasheets then by your own ears.

Quite the reverse, actually.
Most datasheets say the electrolythics can be shared between the op-amps and at some distance, with small caps on the pins. This is completely wrong, it sounds nasty.
You have a problem with the layout and/or the PSU and you think it's the op-amp.
The OPA2132 is quite demanding at that, as is the OPA627/37.
Try the LM6172 on that circuit.

carlosfm · 2005-02-12 12:43 pm

Gaucho said:
Yep, I put 27uF across the supply pins too.

27uf?

Gaucho · 2005-02-12 8:28 pm

Most datasheets say the electrolythics can be shared between the op-amps and at some distance, with small caps on the pins.

I agree the best sound is achieved by putting the electrolytic/film caps at the pins. I use bypassing on the in/out pins of the regulators too.

Gaucho · 2005-02-12 8:30 pm

You have a problem with the layout and/or the PSU and you think it's the op-amp.

Well at least your half right.

Gaucho · 2005-02-12 9:17 pm

Try the LM6172 on that circuit.

That's good advice and I have indeed tried the LM6172 in this circuit. I have used the LM6172 with the OPA2132P together in my phono stage with pretty good results.

Have you ever heard the AcousTech PH1-P? Although a favorite with reviewers it suffers from similar sonic short comings I experience when using the OPA2132 by its self.

carlosfm · 2005-02-12 9:21 pm

Gaucho said:
I use bypassing on the in/out pins of the regulators too.

What cap(s) do you have right after the LM317/337 regs?

SimontY · 2005-02-12 9:49 pm

Hi everyone,

I'm excited to see a fresh thread on this topic, as I've been considering trying alternatives for the OPA2604 in my Marantz cd63ki.

I replaced the original JRC2114 (NJM2114) and whilst the OPA2604 offers more apparent detail, clarity and strong bass, I can't help thinking I've been suffering harshness as a trade-off. It often just can't manage to sound relaxed and natural :bawling:

Can the op-amp master (carlosfm

) help me? I do have 220nF polyester from v- to v+, and nothing else added.

Will adding a socket to swap them around for testing ruin the sound?

regards,
Simon

carlosfm · 2005-02-12 10:04 pm

SimontY said:
I replaced the original JRC2114 (NJM2114) and whilst the OPA2604 offers more apparent detail, clarity and strong bass, I can't help thinking I've been suffering harshness as a trade-off. It often just can't manage to sound relaxed and natural

It does.
Not a bad op-amp comparing to most used on commercial gear but the OPA2604 does tend to sound harsh and unprecise.
It has high distorsion, and it clearly affects midband and treble.
The OPA2132 sounds much better. Distorsion is also much lower.
But it is very demanding with the PSU.
That 220nf from V+ to V- is ok, now add electros at 22~100uf from each PSU pin to ground.
Then try the OPA2604 again and compare with the OPA2132.

Btw, the 63KI has the HDAM modules, right?
I've heard reports of big improvements when they are bypassed.

Gaucho · 2005-02-12 10:48 pm

Will adding a socket to swap them around for testing ruin the sound?

I believe there are some varying opinions about this but the op-amps that I've tried I have heard little difference when socketed compared to soldered. Use a good quality dual leaf socket like Aries Electronics part no. C9108.

Gaucho · 2005-02-12 11:37 pm

What cap(s) do you have right after the LM317/337 regs?

10uF electrolytics and 0.1 uF MKPs, I will try 27uF and 0.01uF bypass caps. What are your prefered caps and values? I will try those too.

SimontY · 2005-02-12 11:49 pm

carlosfm said:
It does.
Not a bad op-amp comparing to most used on commercial gear but the OPA2604 does tend to sound harsh and unprecise.
It has high distorsion, and it clearly affects midband and treble.
The OPA2132 sounds much better. Distorsion is also much lower.
But it is very demanding with the PSU.
That 220nf from V+ to V- is ok, now add electros at 22~100uf from each PSU pin to ground.
Then try the OPA2604 again and compare with the OPA2132.

Btw, the 63KI has the HDAM modules, right?
I've heard reports of big improvements when they are bypassed.

Carlos,

Thank you for informing me, and so quickly too!

When you said "It does" were you agreeing with my impression of differences between JRC2114 and OPA2604?

I do often find moments of "harsh and unprecise", regardless of many other system changes. Maybe OPA2132 is the light at the end of the tunnel.

"22~100uf from each PSU pin to ground" will be fairly hard to fit under the pcb, but with the right caps I'm sure it's possible.

63KI indeed has those HDAM modules, which I have not yet tried to bypass. Do they not help 'drive' the pre-amp though? I am using just a pot into LM3886 at the moment. I will try a buffer there sometime, but it works fairly well without - good enough for now

I searched for bypassing the HDAM on this forum, but with no luck yet :xeye:

carlosfm · 2005-02-12 11:50 pm

Gaucho said:
10uF electrolytics and 0.1 uF MKPs.

Try this: remove the electrolythic.

Another thing: do you use the Cadj. cap? What value?

carlosfm · 2005-02-12 11:55 pm

SimontY said:
When you said "It does" were you agreeing with my impression of differences between JRC2114 and OPA2604?

I was talking about your description of the OPA2604's sound.
Very accurate.

SimontY said:
63KI indeed has those HDAM modules, which I have not yet tried to bypass. Do they not help 'drive' the pre-amp though?

Nah...
The op-amp is enough.
Don't worry, too many times I take out too many unnecessary parts on commercial gear.

And then it sounds better...

Good replacment for BB OPA 2604/604

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