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Old 21st April 2010, 12:00 PM  
SY is offline SY  United States
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Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
Default 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...

Last edited by Variac; 2nd April 2011 at 12:17 AM.
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13th March 2017
6L6's Avatar
6L6
diyAudio Moderator
Herman,

He's designed it, "The Equal Opportunity"

Published in Linear Audio in two parts - 1) https://linearaudio.net/article-detail/2170 2) https://linearaudio.net/article-detail/2206

And here's the diyAudio thread - "Equal Opportunity" MM Pre

I'm building one, slowly. You have to get the articles from Jan. There might be a set or two of PCB still floating around.
13th March 2017
noviygera
diyAudio Member
6L6, thank you!
13th March 2017
Freecrowder
diyAudio Member
Are boards for purchase available from someone on this project? Is it one board or multiple boards? Thanks in advance.
13th March 2017
cogeniac
diyAudio Member
I am building the EO preamp as well. I decided to do my own boards because of the physical layout I wanted. So, I have the signal components and the CCS's on two identical boards with the tube sockets on the opposite side from the components (so the tubes can protrude through holes in the chassis), and I have the power regulator circuits on a separate board that is mounted a couple of inches away in a vertical setup so the big regulators all have convection cooling. The chassis top and vertical section is done with mirror finish stainless, so the tubes will be nicely showcased. The rest of the "chassis" is varnished teak, and there is a perforated cover to protect the supply while allowing for convection cooling. It is about 90% done.

I started by collecting parts for the HMN preamp, and then, like noviygera, realized I wanted to do an MM design. So, the power transformer I had was wrong (too high a secondary and no separate tap for the negative supply. I built it up anyway thinking that Sy's statement "the higher the better" in terms of regulator overhead would save me, but then I realized that later in his article he pointed out that at 16 mA, the overhead can't be too high before the heat dissipation in the regs becomes too high. Edcor does make one that works, but it is a special order. Not too expensive, but 6 week lead time!!! This modified raw supply should produce about 165 volt B+ rail, and an 18 volt B- rail.

I'll post pics of the build in a few days.
Scott
13th March 2017
lehmanhill's Avatar
lehmanhill
diyAudio Member
Herman,

SY is on a vacation from diyAudio. While not speaking for him, what SY did do was design an MM phono preamp. There are two articles in Linear Audio volumes 7 and 8 for the Equal Opportunity MM Phono Preamp. There is also a thread here in diyAudio started by jackinnj.

I found it very interesting to read both the "Majesty's Noise" and the "Equal Opportunity" because he clearly explains his design philosophy and the differences in approach between the MC and MM.

It takes some looking, but I found I could buy just the articles from Linear Audio on their website.

By the way, I'm one of the guys that built the EqOpp preamp and love it.

Jac
13th March 2017
cogeniac
diyAudio Member
Here are my boards for the EO preamp. I'll start a new thread on this so we don't drift this one.

As noted, I put the tube sockets on the top of the boards, and put the components on the bottom. This allows me to have the tube sockets poke through holes I cut in the stainless top plate of the chassis, and allow room for the somewhat large components. The tubes will thus show, while the boards won't.

Once I test this, I'll post the board artwork so that anyone can get the boards fabbed. They were pretty expensive in small quantity (about $60 each), but they are very nice quality. I did the layout in Eagle. Signal boards on the right, regulator on the left..





Scott
13th March 2017
lehmanhill's Avatar
lehmanhill
diyAudio Member
Scott,

Nice design. I get what you are trying to do. The advantage of the way that SY designed it is that he can use the input boards for other projects.

Jac
26th March 2017
frankwilker
diyAudio Member
Hi,
could somebody take a look to my design? Are there correction needed? Or have someone an idea for improvements?
The board is 240x140mm cause it has to fit an empty cabinet in my Hovland HP100. I bought the Hovland used, without Phono Amp.
The design is not symmetrical. So its possible to put the GND of both Channel together if needed. Is this okay?
i would use Glimmer-capacitors for the 32nf-capacitor. The board can be fitted with Wima, Mundorf or Hovland capacitors.
The connection for the tube filament will be soldered directly at the sockets.
Thanks for your help.



26th March 2017
jackinnj's Avatar
jackinnj
diyAudio Member
New boards awaiting testing:
31st March 2017
mrdave45
diyAudio Member
Ive ordered my new turntable and cartridge. Ive gone for a gyrodec se with a benz micro wood SL.
This is quite a bit hotter than the cartridge in the article.
its a 12ohm resistance and outputs 0.4mV at 3.54cm/s which i believe translates to about 0.56mV at 5cm/s

Im under the impression that His masters noise give about 68db of gain based on 0.2mV input producing 0.5V output.

I think i want about 59db with this cartridge to get to 0.5V output. Im sure a bit more gain would also be ok.

I dont think this would overload anything in the circuit as it seems theres plenty of headroom but it may well be a tad hot on the output, about 1.4V. I dont think my impasse input tx would mind this but im then going to end up attenuating it quite a lot on the volume control. This seems daft.

The sowter 1480 (replacement for the 8055) can either be used as 1:5 or 1:10
1:10 gives 20db gain
1:5 about 14db.
This would give me most of the reduction in gain to essentially match the 0.2mV example in the article ensuring no overloading anywhere.

It seems that if i can get more clean gain from the input tx that would be preferable and just add less gain later. The D3a would still be seeing fairly low voltages.

Can this be done by altering the 1k plate resistor R12?

Suggestions? even if going for a totally different phono stage.

Regards

D.

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