The LM4562 in a phono stage. - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, 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 17th October 2014, 09:55 AM   #1
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
Default The LM4562 in a phono stage.

G'day all, I've been using the OPA2134 in one of my DIY phono stages (ESP P06) and today for a bit of a change/experiment I replaced the both of them with LM4562's.

Yes the LM4562's are noticeably quieter, but I'm not sure if they sound as 'nice' as the OPA2134's. Certainly there seems to be more musical detail evident, but it sounds more 'sterile' to my ears. Any thoughts or comments on the LM4562's in phono stages? Regards, Felix.

Last edited by fap; 17th October 2014 at 09:56 AM. Reason: Addition.
  Reply With Quote
Old 17th October 2014, 11:02 AM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
I'd look at three things-

1. Is one version of the circuit oscillating? That can be quite tricky to nail down since probing around with a scope can inadvertently quell things while you're looking and the frequencies can be quite high (VHF). This sort of thing is distressingly common when doing op-amp swaps.

2. Have you inadvertently changed the RIAA conformance or the circuit gain? Do a careful frequency response and gain measurement of both versions.

3. Is one op-amp more capable than the other in driving the reactive load of the RIAA network?

If "none of the above," I'd set up an ears-only test to see if the perceived difference is real.
__________________
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 17th October 2014, 11:15 AM   #3
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
G'day all, all points check out ok. I think that I've just become to used to the OPA2134 'sound'.

One thing is interesting in that with the OPA2134's in place the extended bass end of the ESP P06 seems much more noticeable, yet with the LM4562's the bass sounds 'tighter' without the almost 'bloated' bass sound of the OPA2134. Does that make sense? Regards, Felix.
  Reply With Quote
Old 17th October 2014, 11:15 AM   #4
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by fap View Post
Yes the LM4562's are noticeably quieter, but I'm not sure if they sound as 'nice' as the OPA2134's. Certainly there seems to be more musical detail evident, but it sounds more 'sterile' to my ears. Any thoughts or comments on the LM4562's in phono stages?
RF sensitivity was my tentative conclusion for kicking LM4562s out of a pair of active speakers I have. Same false detail evident. You might want to check your power supply cleanliness at beyond the audio range, also the grounding. Are there any common-mode currents flowing through the 0V connection - between input and output connectors for example, or between the mains supply and the output connectors?

Tighter bass could be that the PSRR at LF is much better on the LM4562.
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.
  Reply With Quote
Old 18th October 2014, 02:58 PM   #5
diyAudio Member
 
Join Date: Jan 2008
OPA2134 is probably the most coloured sounding operational amplifier I have ever heard. Behind its "made for audio" tagline is sweet, puffy, FET-like but muddled sound, particularly in midrange, and boosted bass region with poor definition. LM4562 is far more neutral and a good choice for RIAA circuit. The difference you hear with them is actually much more accurate sound. For RIAA applications, I would recommend LME49720 which, according to datasheets is nothing more than just a rebranded LM4562, but in listening is quieter and more analogue sounding, while retaining the 4562's neutrality.
  Reply With Quote
Old 18th October 2014, 06:08 PM   #6
diyAudio Member
 
Join Date: Jun 2011
Location: Arlington TX
One thing I learned when trying to use these newer high-performance op amps is that they really need more attention to layout and power supply decoupling since they are capable of working at much higher frequencies than the usual parts like NE5534. One attempt I did using the LME49990 resulted in oscillation in the 100MHz range; fortunately I was able to see this with just an oscilloscope. It did result in the chips running hot and drawing much more current than expected, along with poor sound quality. Fixing the decoupling scheme got rid of the oscillation and the sound quality was more in line with what I had expected. Don't be surprised if there is some oscillation or instability that results in a perceived change in sound quality.

As far as noise goes, depending on the impedance presented by the phono cartridge to the input, the LM4562 could be either quieter or noisier than the OPA2134. A low impedance cartridge (like, say a Grado) will run quieter with the LM4562. This I found out with the LME49990 experiment I stated just above. Quiet with a Grado, noisy as heck with an AT440MLa.

I'm doing another experiment right now with four phono stage boards, each identical except for the op amp used. The four parts are LME49710, LME49990, OPA1641, and NE5534. I just need to finish the cases for the boards, then get my measurement setup to show less power supply hum during testing (seems to be a ground loop problem; disconnect the phono stage inputs and the hum disappears from the spectrum display). Then I want to compare noise and distortion between the four op amps used in the same circuit, and do some listening tests. I don't expect to hear much difference apart from noise level, however.

I don't much believe in op amp "sound"; the "sound" appears to be caused by factors besides the op amp itself. Things like oscillation, instability, output load too low for a particular op amp, common mode distortion differences between op amps, or, in the case of JFET op amps, non linear input capacitance, although this, along with CM distortion would appear to be of limited concern at phono cartridge signal levels.
  Reply With Quote
Old 18th October 2014, 07:51 PM   #7
diyAudio Member
 
Join Date: Jan 2008
I agree with loepke72 that power supply and oscillations are two important considerations for op-amps, in spite of the popular "swapping compatibility" fashion.
On the other hand, as much as external factors do influence the sound of an op-amp, they do show very similar, often identical, own "fingerprints" on sound in various environments.
@fap, if your LMs do not tend to get hot and if you do not experience sharp or grainy high range, then most probably they are happy.
  Reply With Quote
Old 19th October 2014, 01:47 AM   #8
diyAudio Member
 
Join Date: Jun 2011
Location: Arlington TX
Some preliminary results from the phono stage "shootout" I described above:

I measured THD at 1kHz and 500mV rms out (gain of phono stage was 43.5dB) as well as noise level at 1kHz with a Shure M91ED connected to the input and ~400pF load capacitance. Distortion was .0008% on all op amps used except the LME49990, which showed a slight edge at .0006%.
Noise (I used 1kHz to get away from the effects of AC hum), however, was the deciding factor between the four op amps. Lowest noise (-114dB absolute) went to the NE5534, with the OPA1614 only 1dB worse at -113dB. The LME49710 showed a noise level of -104dB, and the LME49990 was worst of all with a level at 1kHz of -105dB, but rising to a peak of -100dB between 5-10kHz. The added load capacitance at the input is most likely responsible for a rolloff of noise with frequency; this was observed with all four units and could be altered on the spectrum display by switching out the input load capacitors.

The phono stage circuit is a conventional series feedback single op amp stage, nothing fancy.

The noise vs frequency characteristic observed with the LME49990 is evident upon listening to the noise alone through an audio system compared to the others.

The clear winners are the NE5534 and OPA1641, I'd give the edge to the 1641 due to it being a JFET part whose inputs draw negligible DC current and not requiring a coupling capacitor at the input for that reason. Nothing wrong with the other two besides they are not suited for best noise perfomance with the source impedance presented by the average moving magnet cartridge, and in the case of the LME49990, high enough to be noticeable when listening to a record in good condition. Now I cringe when seeing MM phono stages using low voltage noise parts like AD797, LT1028, LME49990 at the input. Current noise is too high on these for quietest performance with MM.
  Reply With Quote
Old 19th October 2014, 03:10 AM   #9
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
G'day all, most interesting!
More tweaking and purely on the basis of 'sonics' and I ended up putting an LM4562 in the first (bass EQ) stage and an OPA2134 in the second (block gain) stage of my DIY ESP P06, and the combination sounds amazing with a dramatic sense of detail and 'attack', and musicality! Perhaps the 'apparent' noise is slightly higher with this combination, but it 'sounds' superb.

I know that some of the learned amongst us on the internet elsewhere continue to tell us that op amp 'sound' is a myth, and in all honesty I might have been in that camp as well at one time, but no longer! My ears like what they hear with this combination for whatever reason. Regards, Felix.
  Reply With Quote
Old 19th October 2014, 04:07 AM   #10
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by loepke72 View Post
Lowest noise (-114dB absolute) went to the NE5534, with the OPA1614 only 1dB worse at -113dB. The LME49710 showed a noise level of -104dB, and the LME49990 was worst of all with a level at 1kHz of -105dB, but rising to a peak of -100dB between 5-10kHz.
You understand that this is about a hundred times lower than the intrinsic noise of the phono cartridge, thus totally insignificant?
__________________
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

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
Anyone built the phono pre from LM4562/LME49720 datasheet? Tolu Analog Line Level 27 23rd September 2014 03:52 PM
LM4562 Phono Pre Amp Circuit Board eldarvanyar Parts 2 3rd April 2013 03:40 PM
Hum hunting - LM4562 Phono stage JesseG Solid State 11 1st January 2013 02:22 PM
DIY phono to replace roksan phono stage seroxatmad Analog Line Level 6 14th December 2008 06:46 PM
Should I replace Scott 222C phono stage with Claret phono stage? Bing Yang Analogue Source 0 22nd August 2005 07:41 AM


New To Site? Need Help?

All times are GMT. The time now is 09:59 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