Phono stage stepup with opamps?

[tommytube]

I would like to try to build some sort of stepup amp to amplify my phono cartridge going into an MM phono stage. Essentially do an opamp stepup stage.....if possible. My cartridge is a Denon 103R with .28mV output. I would assume someone has explored this already but I haven't found info. Is it possible to do this lowlevel cartridge output justice? Thanks for any info you can provide.

Tom

[preiter]

Look here

http://sound.westhost.com/project06.htm

Lots of good stuff on that site.

[ken.berg]

a better solution to a head amp might be the single fet as shown in

The Analogue Addicts Phono Preamplifier 2006 Edition

[phn]

You will have no problem using step-up transformers with your DL-103. The Altec 4722 should do. It's common and relatively cheap. I believe it has a ratio of 1:18. Step-up transformers go hand-in-hand with the DL-103 and Ortofon SPU.

You might have to parallel a 10k resistor to match the load.

[ThorstenL]

Konnichiwa,

Originally posted by tommytube
I would like to try to build some sort of stepup amp to amplify my phono cartridge going into an MM phono stage.

Few Op-Amp's are quiet enough. Those that are are very expensive, hard to get and in order to not make their low noise worse need very low resistance feedback network which heavily load the outputs making the sound worse.

An affordable transformer that works well enough with a 103 is the Amplimo TM3.

Others have mentioned the "single gemstone headamp", which originiating the japano-french envoironment of Kaneta, l'Audiophile and co is seriously good. Here a version redrawn as stand alone pure headamp....



This is as build this time, you can increase the values of all PSU capacitors as large as the space you have and you can get them, mains transformer needs to be off-board, current consumption is around 30mA.

You could also try just a set of 10 Rechargable NIMH Cells, if you get the 2100mAH AA cells you should get 11 days constant non stop play from a single full charge. In that case the batteries replace the PSU from the 7812 onwards.

Sayonara

[phn]

Doh! Just ignore my first reply.

Kuei Yang Wang, sweet design. I'm not into fets, but I could learn to like this.

[ThorstenL]

Konnichiwa,

Originally posted by phn
Kuei Yang Wang, sweet design. I'm not into fets, but I could learn to like this.

Thanks for the flowers.

Variations of this theme where my MC Stepups for a long time. I only found one MC Stepup transformer I really liked before the custom designed (and ultra expensive) S&B TX-103, an ancient grampian console Amp pull (quite similar to the Altecs you mention, but mo bigga an betta).

Given that the 2SK170 from Shuro costs 58 Euro Cents and the rest of the parts even at high quality cost very little it is a worthwhile little device for stepup.

Sayonara

[Holger Barske]

Very nice. How much gain does it?

[ThorstenL]

Konnichiwa Stereo San,

Originally posted by HBarske
Very nice. How much gain does it?

This version does 20db pretty much on the dot.

If you give 4V/kOhm more supply voltage the gain scales lineary with the drain load. You can think of the J-Fet as a trasconductance cell with (due to the 68R source resistor) around 10mV/V transconductance....

So if you up the pre-regulator to a 7818 and the main regulator to a 7815 you can increase the Drain load from 1K to 1K8 and get around 25db stepup.

The next round up would be 7824 (and more AC) & 7818 as regulators and 2K7 Drain load for nearly 30cb stepup.

Ein remains all the time around 2nV|/Hz due to the added circuit resistances.

BTB, in my case this is part of a complete Phonostage, which is pretty traditional, but non the worse, sonically, for it:

http://www.diyaudio.com/forums/showt...394#post942394

Sayonara

PS, I noticed the OPA1632 via your website. I'll be cooking something with it soon....

[tommytube]

Thanks Kuei, that looks perfect. I think I'll try to prototype one and check it out.