OP amp replacement for TLO71

Hello everyone,

Recently I have replaced the NE5532 with the BB OPA2604 and the LM741 with the AD711 in my cd player. The player uses a pair of 12ax7 tubes as buffer.

There is one more pair of TLO71 (right behind the 12ax7s) which I intend to replace with either the BB OPA604 or the BB OPA627. I am not too technical and would like to chose one as a direct drop in "plug and play" kind of mod. Which op amp will be mine best bet?

I read that the 627s draw too much current and may pose a problem.?

Thanks for any inputs.
 
lm741 is a generic op-amp, not even a audio-use op amp that means the cd maker was really X 100 trying to cut cost. tl071 is a single op-amp that means you can try the standard ne5534 to ad825. Of course for really good improvement try the ad825. The op-amp is a jfet style opamp. Really good. Try chaning along the lines of a fet opamp. ad 825 if the price is right for you go for it
 

BrianL

Member
Paid Member
2002-03-29 5:19 am
USA
Oops, missed the TL071 business.

But it's ALMOST as poor a component as
the 741. Wouldn't use it in anything
that I have to listen to. The
AD711 would be an OK replacement though
as others noted there are many possibilities
in single op-amps.

Still, this all begs my previous question:
Why would anyone mix the likes of LM741,
TL071 and a 12AX7 TUBE and call it an
audiophile component?!!

Would you enlighten us (no pun intended)
as to what the make/model is of this
player?
 

mlloyd1

Member
Paid Member
2001-02-25 7:10 pm
Northern Iliinois
Re: Are they serious?

I saw a REAL product schematic recently (I wish I could remember what product, it obviously didn't impress me :) ) that used a LM741 as a DC servo.
I agree about lack of credibility; good suggestion - time for a shopping trip.
With the SACD wave starting, shouldn't the great red book only players start appearing at fire sales now? I've got my eyes on some old tanks that I can drop a new DAC board in.

mlloyd1

BrianL said:
Not wanting to sound surly, but what sort of CD
player uses a 741 followed by a tube?

This one is beyond any sort of credibility.

Maybe you should unload it and buy something
competently designed.
:)
 
BrianL said:
Oops, missed the TL071 business.
Would you enlighten us (no pun intended)
as to what the make/model is of this
player?

Thanks for your inputs Brian.

The cdp I have is the nOrh CD-1 which is the OEM of CAL and I was told that it is idential to the CAL Sigma.

Honestly, the player sounds much better as compared to the Marantz CD17 MKII which I owned previously.

I have tried tube rolling and like the Yugo Ei 12ax7 best. I have also swap the stock diodes(1000v/1amp) to the Harris (600v/4amp). There are 15 of them in the player. The diode mod has removed a pillow from my speaker. The improvements were very well worth the 15$ I have spend.

The BB 2604 and AD711 have brought much better seperation hence more clarity in finer detail like back ground vocals are now much clearer.

I have the BB627 and 604 on hand and shall try them out this week. I have also order some AD OP275 which I intend to swap with the 2604.

I am trying to add the internal pic of the player here. Hope it works.

[IMGDEAD]http://www.norh.com/products/cd1/cdplayerinside1.jpg[/IMGDEAD]
 

BrianL

Member
Paid Member
2002-03-29 5:19 am
USA
Interesting. Thanks for the picture. But I still don't
understand the tube thing. I could understand
a passive I/V (i.e., a resistor) if a current output DAC,
followed by tube stage(s) if you were inclined to tubes,
or just tube line-level stages if a voltage output DAC,
but why would you run the audio signal through what
appears to be three spaciously laid out (not a good thing
in itself) op-amps (and poor ones at that) per channel,
and then just run it through a tube output just for good
measure?

There's a major cognitive disconnect here and I don't think
I'm the one disconnected.

My advice would be to get rid of the tube and lash some
sort of output buffer to the last op-amp stage. Of course,
the normal tweaks should be done to the analog. I think
you'd have a much better chance of having a decent sounding
player if you just did the solid state part correctly.

Really what do they teach these designers in school
these days, assuming any of the guys that do this.
sort of thing even go to school...
 
This is my first ever post - seems a shame to do it in reply to a 2 year old thread, but here goes...

There is no signal going through the 741. It must be a servo or bias stage for the tubes. Using a 4k7 resistor into my Grado headphones (now that's safe in a tube circuit) there is signal out of the DAC, more on the 5532s, nothing on the LM741s, and I was too chicken to try the TL071s or prod around the tubes. I assume (but didn't measure) the voltages are reasonably low. The output provides a surprising amount of drive current for a 12AX7.

BTW if anybody has a circuit or knows any more mods (this page was a handy find) I'd be interested, as I'm thinking of modding one of these players. It does actually sound pretty good as it is.