Bob Pease on the New LM4562

[Tolu]

Hi

after more listening and comparisons with Lightspeed preamp and KR Audio P150 (with input and output buffers only with OPA2134) I remarked with a friend a very remarkable lack of deep bass with the LME49710. The details and sound stage is great but the bass is too weak. That is a fact.

So, I am now looking for some adequate circuits for preamps with a different opamp setup for the different buffer stages.

I will try the LM4562 as input buffer together with OPA 2134, OPA 2227 and OPA2228 and vice versa to get a good compromise between details and bass.

Has anyone some ideas or experiences?

Regards

Tolu

 

[stef1777]

I still have the same advice.

LM4562 is VERY good for input, buffer circuit but not for DAC output or in general for output circuit.

OPA2134 is still a reference. Work fine will many type of circuit and no surprise with sound signature.

;-)

 

[jackinnj]

Wait until you taste the LME49713 -- the current feedback opamp tailored for audio.

 

[Tolu]

Did you tasted it already? It's only SOIC, no DIP and no Dual. But the datasheet makes it very desireable.

 

[jackinnj]

I just received some samples -- I guess the first thing to try is the line amplifier and have a bake-off with the LME49710 (single).

 

[Tolu]

Please keep us informed about your results of the bakery contest. 😉

 

[maxlorenz]

Dear Jackinnj,
Do big companies send "second selection" (below standard) units as "sample"???

One sample LM4562 used as input buffer (active XO) exploded with no apparent reason on the third day of use. One LME49740 began to make "popcorn" noise and I had to change it...
Was it only bad luck?

Thanks,
M

 

[Magnetar]

Hi

after more listening and comparisons with Lightspeed preamp and KR Audio P150 (with input and output buffers only with OPA2134) I remarked with a friend a very remarkable lack of deep bass with the LME49710. The details and sound stage is great but the bass is too weak. That is a fact.

So, I am now looking for some adequate circuits for preamps with a different opamp setup for the different buffer stages.

I will try the LM4562 as input buffer together with OPA 2134, OPA 2227 and OPA2228 and vice versa to get a good compromise between details and bass.

Has anyone some ideas or experiences?

Regards

Tolu

I just think the 4562 has better resolved bass and isn't as fat. If you build a system with the 2134 and switch to the 4562 it will have less thud hence thinner bass. If the system is then optimized for the 4562 it will have better bass detail and less coloration.

 

[Tolu]

I just think the 4562 has better resolved bass and isn't as fat. If you build a system with the 2134 and switch to the 4562 it will have less thud hence thinner bass. If the system is then optimized for the 4562 it will have better bass detail and less coloration.

Yes, but this thud must be hearable when it is on the CD. The OPA 2134 does a little too much bass. It is a very warm OPamp or a velvet blanket for the ears. I like both. I almost think that you can't have the mix of both. A full basement and clear highs.

I just ordered the LM4562 to test as input buffer and OPA 2134 as output buffer. Perhaps a benefit.

Do you have a circuit of a nice preamp with the LM4562?

Otherwise I think the opamp per se is so dominant for sound quality that the surrounding parts (Rs, Cs ..) will influence the sound very little. They are just necessary for correct technical function (no distortion, no oscillating, no explosions).

Hoping to find the best compromise one day...

 

[SimontY]

The thuds are very audible through my preamp using LM4562, no less than when using 2134. The bass is just a lot less distorted and overblown. I find it's closer to no op-amp sound of the two.

Simon

 

[Tolu]

The thuds are very audible through my preamp using LM4562, no less than when using 2134. The bass is just a lot less distorted and overblown. I find it's closer to no op-amp sound of the two.

Simon

Could you please post your circuit?

 

[SimontY]

Could you please post your circuit?

It's just the Rod Elliott project 88 circuit, using his board. It's upgraded with a large toroid and S Power regulators . Decoupling caps are Cerafine, nothing close to the chips.

http://sound.westhost.com/project88.htm

I'm not convinced this circuit is one to look to for inspiration, but it does a job.

I do have an excellent CD player, and without this perhaps the sound would be lacking in some areas. The CDP has a discrete output stage and before this using LM4562 the sound could be a bit "cold".

Simon

 

[Tolu]

Hi Simon

did you test a setup with different opamps for the two stages?

The original setup has two OPA2134. What gain have the two stages?

 

[SimontY]

Thomas,

I'm not sure of the gain

For a while I enjoyed one 2134 and one 4562 as this gave a more euphonic or warm character. As other things in my system improved I found it sounded best with both sockets filled with 4562. Changing them noticably increases detail, reduces treble grain and bass congestion. I feel like I've had to make certain parts choices elsewhere to accommodate these op-amps.

I've also tried OPA2132 (no different to 2134), LM6172 (like 4562 but with added coarseness) and a couple of others I can't remember. I did like OPA627bp in my CD player, but it is surpassed in detail and clarity by LM4562, again! This op-amp also has the closest sonic character (or lack thereof) to the class A single ended FET output stage I replaced it with, only the op-amp doesn't manage to sound quite like music.

Ultimately I'd like to have no op-amp ICs in the signal path. I heard a couple of other preamps vs mine and mine was the weakest. I think they were called "Lightspeed passive" and "Heretic". Everyone present (this was at the UK meet) was impressed by the 4562, however.

Simon

 

[Ryssen]

I used LM4562 on my soundcard (Emu1212m) and LM4562 + buf in my headphone amp,thought it sounded nice,clear highs and tight bass etc.Then I tried AD8672 in the headamp, and to my surprize it was better...more relistic cymbals bassguitar,room voices,and more.
Will later try AD8672 on soundcard to..
If you have the chance try it!(AD8672)

 

[SimontY]

Ooh, I'll look out for that one! Thanks.

 

[gaetan8888]

Hello

Looking at the data sheet graphs of the LM4562, the THD+N vs output voltage show a very big raise of distortions at low level output and it should be higher in a dynamic situation, this is a sign of high crossover distortions.

Any though about that ?

I can not access the Bob Pease article on the LM4562, does he say anything about that high crossover distortions of the LM4562 in his article ?

Anyone try class bias on the LM4562 ?

Thank

Bye

Gaetan

 

[DSP_Geek]

Hello

Looking at the data sheet graphs of the LM4562, the THD+N vs output voltage show a very big raise of distortions at low level output and it should be higher in a dynamic situation, this is a sign of high crossover distortions.

Any though about that ?

That curve is consistent with 1 microvolt input noise. Do you have the input conditions for the test?

 

[jan.didden]

That curve is consistent with 1 microvolt input noise. Do you have the input conditions for the test?

Indeed. 1uV noise at 10mV input signal is 80dB S/N ratio, which translates into -80dB THD. Exactly what the data sheet says. Nothing to do with xover distortion.

Jan Didden

 

[gaetan8888]

Hello

Yes, a part of that low level thd+n are the noise floor, but with a typical input noise of 2.7 nv at 1 khz the raise of thd+n whould not start at 5 volt but at a lower output voltage less than 5 volt ?

Thank

Bye

Gaetan