SAE2100L, LINE AMP PCB, 17-0437, did anyone ....?

[kumpa56]

Hello and Happy New Year! Anything started when a horrible noise came out of my loudspeakers when playing Randori, a CD by Nik Baertsch via the preamp SAE 2100L, AUX1 input, I actually thought it was the power amp, so I connected the CD player straight to the power amp, same CD track ,,, no noise. Back to the preamp, same CD track, noise again. Well, to be short, the preamp looked faulty, In the AUX area. This meant a lot of disassembling, to reach the Line Amp pcb. Of course, Line Amp 17-0437 schematics were unfindable. I decided to reverse engineer the pcb in order to understand a little more. Now I have a schematic. The ICs are NE5534. Surprise! The compensation capacitors are connected between pins 1 and 5 instead of between pins 5 and 8. QUESTIONS: can anyone imagine why. please? Can anyone foresee what could happen? Were NE5534 the original ICs? I'm scratching my empty head, wondering and resultlessly... Thanks in advance, should anyone be willing to remark. Kind regards. Alberto

 

[BSST]

Hi Alberto,

According to the data sheet linked below, pages 3 and 9 indicate the comp cap is connected between pins 5 and 8--- as you would prefer.

I see the part is EOL, last time buys, etc. I feel I'm losing an old friend. Sigh.

Steve

https://www.ti.com/lit/ds/symlink/n...l=https%3A%2F%2Fwww.ti.com%2Fproduct%2FNE5534

 

[kumpa56]

Hello Steve. Thanks for this immediate remark. I’ve been working with 5534s for years now and I humbly say that I know them a bit. I’m actually wondering if they were the original component for 2100, because I’d be amazed to realize that the 1-5 “compensation” could be a pcb mistake and no one ever detected it. 5534 is internally compensated for gain equal - and greater than 3. Difficult to say if this condition is applicable to the topology of 2100 Line Amp. If yes, the “compensation” cap could also be removed. If not, in my opinion (not my “preference”, dear Steve) it should be placed between pins 5 and 8. According also to manufacturer’s specs you kindly highlighted.
So, again, sorry … was it a designer’s choice? Was it a multiple choice op amp? Was it an innovative solution? Is it a pcb mistake, as it looks like? Was a bulletin ever issued by SAE? I doubt I can get answers. I’ll keep with a reasonable solution, say pins 5-8 cap. Cheers and thanks again. Alberto

 

[Mark Tillotson]

The schematics on hifiengine only show 5534A's in the phono preamp, with comp caps correctly on pins 5&8. Other parts use 4136/4558's

 

[kumpa56]

Yes, Sir. Phono preamp compensation caps are correctly placed (or not soldered at all). Both on the schematics AND on the pcb. Many Thanks and Cheers. Alberto

 

[kumpa56]

Well, I please submit my reverse-engineered schematic for Line Amp board, SAE 2100L. Of course schematic could not be perfect. Pick it AS IT IS. If mistakes occurred and detected, please report here. Have fun!