Stereomour with DC heating

[Follow the white rabbit]

Hi, I am being chased by higher hum...maybe 100Hz(germany).
Anyone fiddling around with DC for the heaters on for instance 45 tubes?
With a friend I built up a small test with some devices for regulated 2.5V and the hum was history. At least on one tube. We only tested the right side...
But I heard that the sound from the right speaker was not so loud as the left AC side...???
And the heater wire from the right tube didnt glow as strong as the left tube...
Some ideas? What about sound?

 

[Grainger49]

Alice,

I know that DC will give lower hum levels.  But I wonder why you are having a problem.  It could be that your speakers are very sensitive.  That reveals the low (1-2mV) hum of the Stereomour. 

If that is the case then go for DC heaters.  The Paramounts use an inductor (Bottlehead designed) to smooth the DC for the heaters.  It is very quiet on 104dBW speakers.

 

[Follow the white rabbit]

Hi, yes I do have over 100dB/W speakers. This is part of the problem... so, I will go on the DC path.
Thanks for your reply, grainger...

 

[Follow the white rabbit]

I will take a more modern approach to DC...I will post soon...

 

[Follow the white rabbit]

Hi Folks, we found that the power tubes(45s) built up the audible hum I had... so we did it!
AND now all is dead quite ...hahaha...exept for the music, now, creeping very spooky out of the silent background without unwanted noise!
We used two LT1085 - 7.5A, 5A, 3A Low Dropout Positive Adjustable Regulators

 

[Grainger49]

That is the first time I have seen a volume knob on a power transformer.....

Beautiful work.  Do I understand that you triple regulated the heater power supply?  Nice move! 

 

[Follow the white rabbit]

The Volume Knob is just a silencer! hahaha
The transformer top covering rang with a high tone after taking away the original heater wireing for the 45 tubes... !!! 

Sorry for the confusion! There is no triple regulation! hahaha
We used a separate power transformer with two 6 V secondaries (3A
each), and for each filament supply a Schottky rectifier bridge, a
10000u capacitor and an LT1085 regulator providing 2.5V. For good
measure, we added a soft-start circuit.  Interestingly enough, the (EI
core) power transformer had to be widely separated from the plate
chokes and output transformers (speakers: way beyond 100 dB) to avoid direct
coupling (which was quite audible even with about 5 inches of
separation).

 

[howardnair]

if one were to put lead-coated copper shields between or around a transformer/transformers  would this do anything to alleviate any coupling from one to the other?

 

[Follow the white rabbit]

I once put a small transformer and some bridge rectifiers in tin cans... did a great job defensing unwanted noise...
But lead coated copper shields?...donoh... try and error...

 

[2wo]

Why don't you put a resistor across the unused filament winding, add a bit of load...John

 

[Paul Joppa]

To prevent magnetic hum coupling (the most likely source) you must use magnetic material, preferably with a high permeability. Soft iron pipe has been used by amateurs (better than steel) - at least it's think! - but nickel alloys such as permalloy, molyperm", mumetal, etc. are the reference standard.

 

[Follow the white rabbit]

Finally I realized that a second switch for the first heating of the cathode filament would be a good idea...
http://koti.mbnet.fi/siliconf/JukkaTolonen/ga/amptimer/amptimer.html

Happy listening!  ;D

 

[Grainger49]

Alice,

Great!  This will baby your tubes.

BTW, those are awfully cool looking, which are they?

 

[Follow the white rabbit]

Sophia Electric 45 mesh plate. I just thought I should give them a try...
In comparement to some 45's from Rogers I can say that the Sophias have a little more width in soundstage...sometimes I feel the musicians are stretched to an unnatural width...
The Rogers tubes have a little more natural inward fokasing.
Both sound very rich! I like the pings the tubes make warming up in the first 3-4sec. ting...ping...ting... ;D
Their plant is in Virginia I think...
http://www.sophiaelectric.com/
Maybe someone has interest? http://www.shinelimited.co.nz/work/the-becks-edison-bottle

 

[galyons]

Sophia Electric 45 mesh plate...
Their plant is in Virginia I think...
http://www.sophiaelectric.com/

Sophia is another "label" for Chinese tubes and equipment. Sohpia is located in Virginia. They likely don't make anything.  The tubes are made  by TJ Full Music. The Chinese plant makes them, quite well, I might add!  That being said, I have a pair and like them very much.

My favorite 45's are a pair of 1937 vintage RCA Radiotrons  They just have a wonderful sound.  The Sophia's get everyday use, as they are replaceable. My OS 45's get played on occasions when I am dedicated to listening.

It is wonderful that new stock 45's are being produced, especially at high quality levels!

Cheers,
Geary

 

[Grainger49]

Hmmm, I remember that TJ Full Music was one of the favorite 2A3s on the old forum.  Not a bad recommendation.  I have looked at Sophia a few times.  After a few more weeks working and a conversion for my Paramours I just might get a pair. 

I knew that the shape was familiar and interesting.

 

[2wo]

have an older pair of the TJ mesh 45's with the white base.

The internal structure looks the same...John