OP rolling

yayage · 28th November 2020, 11:00 AM

Hi,

I want to change the OPs in my vintage Kenwood PreAmp .
Some Modifikations were discussed here years ago.

The goal is to place good sounding OPs with less DC-Offset at the outputs.
I guess i have to choose low input bias current types.

In the schematic Output there is a JRC 5532DD which causes 150mV Offset.

Is there OPA2132 / OPA 2134 a good choice ?
Or maybe a LM4562? The input current is higher, but about 20mV Offset would be acceptable.

The input buffers are JRC4580DD with 100mV Offset and a very low slew rate.
Maybe there are the LM4562 a good choice too ?

Jay

Mooly · 28th November 2020, 11:17 AM

The offset is not a problem in that design, and if anything I would say it defines a known and stable small voltage across the coupling caps.

The OPA's would generate near zero offset but as mentioned that isn't an issue anyway.

The LM4562 is possible replacement for the 5532 but I would advise that whatever you fit that you check any residual offset and reposition the coupling caps accordingly to suit any change in polarity of offset.

analog_sa · 28th November 2020, 11:24 AM

Quote:

Originally Posted by Mooly

I would advise that whatever you fit that you check any residual offset and reposition the coupling caps accordingly to suit any change in polarity of offset.

Do you think that at a 100mV polarity makes a difference? In what way?

Mooly · 28th November 2020, 11:34 AM

100mv offset and its polarity makes a difference to electrolytic coupling caps and I would rather have 100mv with correct polarity across such a cap than have it reversed.

Any DC offset in an AC coupled circuit has no impact on audio quality whatsoever.

yayage · 28th November 2020, 11:36 AM

I want to get rid of the coupling Cs ��

Mooly · 28th November 2020, 11:40 AM

That could be misguided but its your choice

You will have to study the circuit in detail and see what the effect of such changes will be.

yayage · 28th November 2020, 01:14 PM

Therefore I posted the schematics to get an opinion from the pro's ;-)

Michael Bean · 28th November 2020, 01:22 PM

Quote:

Originally Posted by yayage

I want to get rid of the coupling Cs ��

Yeah...Silly manufacturers are always putting extra parts in their products that don't need to be there.../s

Question: Why? Do you have a reason...or just a belief?

Mike

Fast Eddie D · 28th November 2020, 04:24 PM

As long as you don't stack the poles, coupling caps have zero impact on audio reproduction (if sized correctly).

28th November 2020, 11:17 AM	#2
Mooly diyAudio Moderator Join Date: Sep 2007	The offset is not a problem in that design, and if anything I would say it defines a known and stable small voltage across the coupling caps. The OPA's would generate near zero offset but as mentioned that isn't an issue anyway. The LM4562 is possible replacement for the 5532 but I would advise that whatever you fit that you check any residual offset and reposition the coupling caps accordingly to suit any change in polarity of offset. __________________ Installing and using LTspice IV. From beginner to advanced.

28th November 2020, 11:34 AM	#4
Mooly diyAudio Moderator Join Date: Sep 2007	100mv offset and its polarity makes a difference to electrolytic coupling caps and I would rather have 100mv with correct polarity across such a cap than have it reversed. Any DC offset in an AC coupled circuit has no impact on audio quality whatsoever. __________________ Installing and using LTspice IV. From beginner to advanced.

28th November 2020, 11:40 AM	#6
Mooly diyAudio Moderator Join Date: Sep 2007	That could be misguided but its your choice You will have to study the circuit in detail and see what the effect of such changes will be. __________________ Installing and using LTspice IV. From beginner to advanced.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Rolling off woofer with HF absorbent material in front of it.	Circlotron	Multi-Way	17	29th June 2002 06:15 PM
Anyone rolling their own horns?	DrewP	Multi-Way	4	27th January 2002 08:55 PM
Rolling your own inductors...	JoeBob	Multi-Way	2	13th December 2001 05:28 AM

New To Site?	Need Help?
Register to Participate Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th November 2020, 11:36 AM	#5
yayage diyAudio Member Join Date: Dec 2011	I want to get rid of the coupling Cs ��

28th November 2020, 01:14 PM	#7
yayage diyAudio Member Join Date: Dec 2011	Therefore I posted the schematics to get an opinion from the pro's ;-)

28th November 2020, 04:24 PM	#9
Fast Eddie D diyAudio Member Join Date: May 2010 Location: Skokie Il	As long as you don't stack the poles, coupling caps have zero impact on audio reproduction (if sized correctly).