ultrasimple mm/mc riaa preamp

[Mad_K]

Have anyone tried this?

(I'm going to

http://www.users.nac.net/markowitzgd/phonopre.html

[halojoy]

The Analog Addicts Phono Preamp
By Thorsten Loesch

It is also called "El Cheapo" (low price)

Hope noone will hang me, if I provide a schematic.
I have changed the size a bit, to fit DiyAudio.com.

Best is to read the whole article, that Thorsten Loesch have written.
See Link in post above!

/halo

[Mad_K]

BB OPA 637 is not 'cheapo in my book...

(But the design is 'cheapo in comparison to other Loesch riaa designs)

[Optical]

Originally posted by Mad_K
Have anyone tried this?

(I'm going to

http://www.users.nac.net/markowitzgd/phonopre.html

i'll be keen to hear what you think of it when its done!
Ive been meaning to build all of these simple phono circuits and do a comparison of each to mark the differences for future reference..

[lohk]

Have you ever ordered an OPA627/637 ?

Must be one of the most expensive opamps available...

Klaus

[lohk]

and please ask Kuei Yang Wang about that design

[ThorstenL]

Hi,

and please ask Kuei Yang Wang about that design

Speak of the Evil one....

Not much to say about this thing really. I started fafelling about with Selfs "Precision Preamp" Phonocircuit. It sounded BAD. So I messed about a lot and tried many things.

Doing this circuit with lead acid battery power, OPA637A and a 10k Pot (later an unusual active linestage with a FET Buffered LM6181 and Volume control with a 1k Shunt Pot and a 150 Ohm output resistor) sounded rather decent for solid state. Acrylic case BTW, mixture of hardwiring and PCB.

Still, I like valves and transformers better. Butafter you put don the long green for a pair of S&B TX-103 MC Steups and the same amount for the LCR RIAA EQ Module and shelled out the green for a PSU using 8pcs 10H chokes and 6pcs 120uF Film Capacitors you appreciate just how good this little job is for the money, how simple to build.

And the price of a pair of OPA637 plus a pair of 2SK147 and four 12V/2.1AH Lead acid batteries is not THAT outrageous. Hell, my current RIAA Stage clocks in at near £ 1,000 in materials uses near unobtanium NOS Valves and it is NOT ten times better than the little ugly duckling solid state stepchild. In wood, netal and all it looks a lot better though.

Sayonara

[Mad_K]

Originally posted by lohk
Have you ever ordered an OPA627/637 ?

Must be one of the most expensive opamps available...

Klaus

I have them in a little box, along with some other goodies TI was kind enough to send me

And, yes I have yet to see an opamp with a higher price...

[Mad_K]

As I've changed the circuit somewhat I'm not allowed to say it's Thorsten's, but I think it is close enough.
Changes:
1. Only MM stage.
2. Not rechargeable batteries.
3. None of the specified components (brands) are used, except for the OPA637BP.
3. Supply filtering changed: Elna RJH 1000uF + 100nF Rifa MMK.
4. RIAA caps are WIMA FKP2, 2,5% but matched to exact value.
5. Outputcaps are Elna RJH 330uf (arranged as descibed) bypassed with 0,47uF SCR.

So, here comes the pics; board:

[Mad_K]

Hardwired my usual way. You can see that it was put together with a little haste. I know this is not the best way to build a circuit like this (PCB with ground-plane and p2p combo should be best), but it's my way..

backside: