Welcome to my DIY audio forum.

Per-Anders Sjöström

Main Menu

Recent posts

Phono RIAA amplifiers / QSXM2 Input Transistor Biasing
Last post by MattB94 - October 05, 2023, 02:51:41 AM
Hi Per-Anders (and to anyone here who can answer this question),

First, just want to say thank you for all your good work designing all these things and making them available to us DIYers. On to the question...

I am planning on building a QSXM2 phono preamp, and I hope to optimize it for my Sumiko Blue Point No.3 MC cartridge. It has a fairly low output impedance, 28 ohms. I hope to bias the input transistors of the QSXM2 (so, T5-T12 and T17-T24) to 1mA, at least. Do I need to change anything? Presumably, I would alter the value of R16-R23 to something other than 15kohms. Should I change these resistors? Or something else?

Thank you for your help with this!
Power supplies / Re: Placement of regulator and...
Last post by Branko - June 18, 2023, 07:56:06 PM
Power supplies / Placement of regulator and tra...
Last post by Branko - April 03, 2023, 03:56:39 PM

I am in the process of building a streamer, a dac and a phono pre.
As I would like to have the enclosures as small as possible I would like to put some parts a little away.
Here is the question: could I put the transformers and or the super-regulators in separate enclosures away from the other items (some feet)?
How long could the dc line be and what cable to use?
If in separate enclosure would it be better to use normal transformer or toroidal type. Normal type would be also cheaper.

Best regards
Phono RIAA amplifiers / Re: QSX03 A new RIAA amp with ...
Last post by goldkenn - March 04, 2023, 09:05:31 AM
20230 =P
Power supplies / Re: SSR01 malfunctioning
Last post by kunlun121 - December 29, 2022, 11:22:38 AM
I found something that looks odd. There were some more SSR01 boards lying around. It looks like the others have the AD825 rotated 180 degrees. It looks like this one is up side down. I e-mailed you a pic, dunno how to upload it into this thread. Does it look right to you?

Power supplies / Re: SSR01 malfunctioning
Last post by kunlun121 - December 29, 2022, 10:50:13 AM
They are there.
Power supplies / Re: SSR01 malfunctioning
Last post by peranders - December 29, 2022, 07:12:46 AM
Tin drops on J1 and J2?
Power supplies / SSR01 malfunctioning
Last post by kunlun121 - December 28, 2022, 08:34:16 PM
Hi. I'd much appreciate some help on the 13V SSR01 I'm trying to build. I can't get it to work.

I am feeding it rectified / smoothed DC @ 21-22V, so well above the target output of 13V. The output of the SSR01 is not quite stable at around 18.2V. It looks like it's not going into regulation.

The build is using the LM431 as voltage ref. It has the AD825 that you soldered on the board. I used the 12V SSR01 version as I found it in the documentation. The only change to the BOM / schematic is adding 15K @ R17 to get 13V output.

Just now I have meticulously double checked each component against the schematic and the BOM. Everything is right where it should be.

I tried 13V (or 13.2V to be precise) in a different configuration: I removed R17 and changed R8 (1k) out for 1k2. Same thing: still not quite stable at around 18.5V.

What could I be missing? Are other changes to the schematic needed when adding R17 @ 15K?

Thanks for looking into this.
Phono RIAA amplifiers / Re: QSXM2 - My realisation
Last post by slimak - June 26, 2022, 04:29:44 PM
Phono RIAA amplifiers / QSXM2 - My realisation
Last post by slimak - June 19, 2022, 08:30:05 PM
QSXM2 from Slovakia :-)
Very nice sound.