sound of discrete opamps - Page 4 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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
Reply
 
Thread Tools Search this Thread
Old 13th May 2011, 01:35 PM   #31
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
Fotios,

this has nothing to do with op-amp my friend. What size were your coupling caps? There will be no error if DC coupled, or if AC coupled, the caps are correctly sized.

At 50Hz, even the 741 will be perfect!
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/

Last edited by Bonsai; 13th May 2011 at 01:41 PM.
  Reply With Quote
Old 13th May 2011, 01:39 PM   #32
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by Bonsai View Post
I don't know SY - I am doing some work with the THAT mic pre right now, but I have not looked closely at the SSM2019. The THAT part is around 1nV/root Hz.
So is the SSM (I think it's about 1.4nV/rtHz). What kind of mike preamp are you working on? I was knocked out by how well the SSM worked for a ribbon.

Scott Wurcer was nice enough to send me an extra pair which are currently in a prototype MM preamp.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 13th May 2011, 02:05 PM   #33
coluke is offline coluke  Italy
diyAudio Member
 
Join Date: Mar 2009
Quote:
Originally Posted by fotios View Post
I don't know if there is any IC that could obtain
this.
With a 50 Hz square wave input? Quite hard to believe, unless you are trying to squeeze out of a poor ol'5532 a 10MHz BW with 40dB gain...

L.
  Reply With Quote
Old 13th May 2011, 02:23 PM   #34
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by fotios View Post
Inject a 50Hz square wave in input and you will see exactly the same square in the output. I don't know if there is any IC that could obtain this.
Nearly all of them can, it's trivially easy. You might revisit your test setup.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 13th May 2011, 03:15 PM   #35
Dave S is offline Dave S  United Kingdom
diyAudio Member
 
Join Date: Mar 2003
Location: Searchin' for Sweet Singletrack
When I tried Jung's nested feedback circuits I found they did not really sound any different to most op-amp circuits. The power supply and decoupling used has a massively larger effect on the sound than tweaking the figures with some clever feedback schemes IMO.

I don't have any problem with high feedback circuits, in fact the JE990 is a high feedback circuit. It's optimised for high gain and low noise with low input impedances, but it sounds very good at modest gain and with a 20K pot stuck in front of it.

Quote:
Originally Posted by CraigBuckingham View Post
Then there is the question of thermionic vacuum tubes. Those things have no equal in the discrete world let alone IC op-amp world when applied in the right manner and in the right places. But the problem is dwindling supply of those parts unfortunately.

Anyway, that's my findings.
I've built 2 or 3 highly regarded valve preamps. Although they give very impressive sound on first hearing them, somehow this becomes wearing on longer term listening. It's a mystery to me why one in particular (Rosenblit Grounded Grid), sounds like this when it's measurements are pretty much textbook.

Quote:
Originally Posted by abraxalito View Post
Useful observations, thanks. I've been wondering for a while if sound quality is mainly to do with the input stage's immunity to RF. As I recall the JE-990 has a unique feature - inductors to degenerate the input pair. Have you any experience with trying different inductors (values, styles) in the Re circuit? Does replacing just those two inductors with resistors make a difference to the sound?
The resistors degenerate the input pair and the inductors actually "un-degenerate" the LTP at lf. I think this is mainly done to keep the nf low. No I have not tried removing them or any other types, although just like you , the thought had crossed my mind.
  Reply With Quote
Old 13th May 2011, 03:28 PM   #36
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
One opamp type you should be carefull about is the RR input type. Analog devices has addressed this problem. Some RR input types has a crossoverrigion where the input biascurrent peaks or shifts rapidly..

Read the datasheet. If there is no graph in the datasheet of RR input types, showing input biascurrent versus input voltage type, then i would say they are no-go.

Just a little advice. Some types are very sensitive to input impedance, but so are all amps, and some more than others.
  Reply With Quote
Old 13th May 2011, 04:30 PM   #37
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
sonnya,

I would really avoid RR opamps for hi end audio. These devices are typically designed for LF signal conditioning, and not high performance audio. Just my 2 cents.
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 13th May 2011, 04:34 PM   #38
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
Quote:
Originally Posted by SY View Post
So is the SSM (I think it's about 1.4nV/rtHz). What kind of mike preamp are you working on? I was knocked out by how well the SSM worked for a ribbon.

Scott Wurcer was nice enough to send me an extra pair which are currently in a prototype MM preamp.
A dynamic mic pre - for my son. He's a recording engineer and has challenged me to produce something 'decent'. I'll either be a hero or its going to be a case of 'my old man just ate humble pie' . . .
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 13th May 2011, 04:49 PM   #39
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
Quote:
Originally Posted by Dave S View Post
When I tried Jung's nested feedback circuits I found they did not really sound any different to most op-amp circuits. The power supply and decoupling used has a massively larger effect on the sound than tweaking the figures with some clever feedback schemes IMO.
...
Jung's toying with Otala inspired inner loop feedback is ill advised in my opinion (really only in one instance - he has generally advocated several "multiloop"/composite amplifier topologies)
his use of gain in the output op amp of a multiloop/composite amp allows sub regulating the input op amp supplies - since the input op amp has little dynamic current demand even simple Zener shunt gives good regulation

the psrr is then boosted by both the excess loop gain and the subregulation



to address common mode input distortions I was pointing to the Sandman "feedforwad" as one example of power supply bootstrapping
the feedforward bootstrap can improve cm distortion if the bootstrapping amp is good - say a cascoded fet - and the main amp adds gain, possibly better noise (Funasaka used a discrete fet ps buffer amp) AES E-Library Feed Forward Floating Power Supply (High Response-Speed Equalizer Circuit)


Dimitri's floating ps bootstrap circuit does even better in that the composite amp input sees only the bootstrapped U1 input - effectively "cascoding" the entire input op amp
Attached Images
File Type: png dimitri2.PNG (67.3 KB, 532 views)

Last edited by jcx; 13th May 2011 at 04:53 PM.
  Reply With Quote
Old 13th May 2011, 04:59 PM   #40
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
Quote:
Originally Posted by Bonsai View Post
sonnya,

I would really avoid RR opamps for hi end audio. These devices are typically designed for LF signal conditioning, and not high performance audio. Just my 2 cents.
Well. You will be surprised how many good lownoise and high speed RR I/O there is on the market.

I use the AD8692 from analog, it is by far not the best opamp in the world but it is very decent and cheap.

Look at the specs and tell me if you can do it better from a +5V supply only.

G = 1, RL = 600 Ω, f = 1 kHz, VO = 1 V p-p 0.0006% - This is at +5V supply and the distortion rises to only 0.002% at 6KHz.

at RL = 1KOhm it is below 0.0008% at 6KHz.

at RL = 100KOhm it is below 0.0004% at 6KHz.

Voltage noise is 8nV/SQ(Hz) at 1KHz.
Current noise is 50fA/SQ(Hz) at 1KHz. A good candidate for MM pickup input.

Match it with a good powersupply decoupling with low noise and ripple and you can have a good and cheap MM RIAA amp.
AD8692 | Dual, Low Cost, Low Noise, CMOS Rail-to-Rail Output Operational Amplifier | Operational Amplifiers (Op Amps) | All Operational Amplifiers | Analog Devices
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
low noise discrete opamps robmil Solid State 0 7th May 2010 08:24 AM
Are Discrete components better than Opamps ? jsa_ind Everything Else 51 20th December 2006 09:23 AM
discrete vs. IC opamps? has anyone tried the pass labs design? dorkus Pass Labs 22 28th June 2001 02:02 AM


New To Site? Need Help?

All times are GMT. The time now is 06:17 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2