His Master's Noise: A Thoroughly Modern Tube Phono Preamp - Page 7

21st April 2010, 12:00 PM
SY On Hiatus Join Date: Oct 2002 Location: Chicagoland	His Master's Noise: A Thoroughly Modern Tube Phono Preamp After more than 25 years of faithful service, it seemed that it might be time to redo my phono system. After all, I like to think that I've picked up a few tricks in the intervening years... The old system consisted of a VPI HW17-II, a Linn Ittok LVII tonearm, and a Troika cartridge. The Troika was... Click here to read the entire article Last edited by Variac; 2nd April 2011 at 12:17 AM.

24th October 2010

jackinnj

diyAudio Member

SY -- where did you park the shield lead from the Sowter 8055's.

Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?

24th October 2010

On Hiatus

On the first stage input ground.

edit: Scratch that, bad memory. On actually looking at it, it's returned to the chassis solder tag at the DIN input.

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

24th October 2010

volleynbike

diyAudio Member

Here's a simple little improvement that i've had wonderful results with. Splice in a simple diode (1N4007 or similar) in between the screen grid of the pentode and the Plate with the cathode of the diode pointing toward the screen grid.

Easy to remove if you don't like it. But every pentode amplifier stage i've tried it in shows a marked improvement (extended range, lower dynamic compression, etc.) Admittedly i haven't tried it in such a low level stage as 1st phono, but worth a try...

I've been looking for new mc phono circuit to try, and i think this may be it! Nice job =)

27th October 2010

jackinnj

diyAudio Member

Here's a comparison of the HMN to my Linn LK-1 which has a dedicated MC input:

Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?

27th October 2010

Pano

diyAudio Moderator

The HMN certainly looks a lot cleaner.

27th October 2010

jackinnj

diyAudio Member

I will have some boards made as a Group Buy -- I'll absorb the cost of the first set of prototypes -- but I have to figure out all the mistakes I made on the first set. Price will be the manufacturing plus shipping to the US. I think it's going to work out to be something like $7.20 per board. The board will have provisioned the amplifier, hv supply, set of regulators (4x) and heater supplies.

Mistakes I made on my prototypes included spacing some of the mosfets a bit close, failing to include take off points for the heaters, building in only one set of HV regulators (SY recommends 2), using a 2A bridge rectifer for the heaters instead of 5A (seems to work fine, however). I'll provision it for various types of caps (Wima, Vishay, etc.) and make it a bit easier to tweak the R and C values for the RIAA equalization.

Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?

1st November 2010

studeb

diyAudio Member

Interested in boards.
Any feedback from the NJASDIYM?

2nd November 2010

jackinnj

diyAudio Member

Yes, I am going to have some boards made -- it requires a bit of tweaking the original since SY specified 2 regulators -- one per channel. I am not going assume that folks will use transformers with wires rather than PCB pins.

I would think we'll have the boards in about 2 weeks.

I think I will have plenty of power supply boards since folks ask for these all the time, regardless of what they happen to be building!

Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?

2nd November 2010

On Hiatus

I haven't tried this with a single regulator, but if the pass device is well heatsinked, it should also work- the PSR of the circuit is really high and the current draw is exceptionally constant. Not to discourage you from laying it out as originally designed...

"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."

12th November 2010

Slobo

diyAudio Member

I'm also interested in boards.