Headphones with the Stereomour

[Guy Boisvert]

I need advice.  After building the Crack, I am anxious to start a new kit. I'm leaning towards the Stereomour with 2A3 valves. The big question: will I be able to use my Sennheiser 650 headphones with it.  Some say there may be a hum because the Stereomour has AC heated filaments instead of DC. Others indicate that there may be little or no hum depending on the headphones and/or the tubes.  I have been canvassing the web on this: there are suggestions such as placing resistors when hooking up the headset etc etc. I even wondered if I could not add a DC power supply to heat them filaments ?

I would appreciate anyone's experience with this and any suggestions to solve the problem, indeed if a problem does exist.

Many thanks in advance to one and all.

[Paul Birkeland]

The Paramounts will work very well with the HD-650, but I would have my doubts about the Steremour.

I'd suggest the SEX amp if you're looking to build another headphone amp. 

[Guy Boisvert]

Thanks Paul.....I just would like to have something with 2A3 valves.....for speakers and heaphones if possible.....the monoblocks are an option I suppose. Still, I wish someone would come up and say that they worked out a way to marry headphones with the Stereomour.

[Paul Joppa]

We have an experiment planned but not yet tried, to see if a simple DC heater supply can work with the Stereomour. Haven't seen much interest yet, and there's a lot of stuff in the pipeline already, but I thought I should mention it.  :^)

[Guy Boisvert]

Is it a feasible thing [for a novice like me] to build/add a DC heater The reason that I'm favouring the Stereomour over the S.E.X. is for the ability to use 2A3 valves. I appreciate all the feedback.

[Paul Joppa]

Guys - it may be that simple, or it may be that you can't get enough voltage, or it may be that it works but the hum isn't reduced enough for headphones, or there may be some problem I haven't foreseen - I just won't know until we try it.

[iamnothim]

Hi,
I'm a noob.  I signed up because I'm looking at Bottlehead "stuff" for my LCD2's.  A friend suggested the forum to see if the Stereomour could be adapted for cans. Pretty much for the same reasons as Paul.

Anyway I'd thought I'd share rectifying a 6.3V AC heater trans to DC.
I'm attempting to re-invent a BK 606 valve tester.

I followed these instructions.
http://www.electronics-tutorials.ws/diode/diode_6.html
I'm a novice and it worked.
Rectron BR31 full wave bridge rectifier  $0.50
6800

[grufti]

The setup on your bench doesn't strike me a being very "nooby". It looks rather nicely done!

[iamnothim]

have you ever heard of "more money than brains"?

[iamnothim]

Kits?
I can build kits.

Tell you how it works?
Right.

[Paul Joppa]

"E88CC style" is not sufficiently specific - the 6DJ8 variants cannot handle enough plate voltage, though the 6922 types can. However, all of these tubes really want more current to operate properly, and with enough current they are likely to exceed their dissipation limitation.

To get the hum down for headphone use, you must rectify the 2.5v filament power (one for each tube). Doing this is more difficult due to the high current, and voltage losses in the diodes. There are other ramifications, but this is a post, not a dissertation!

[iamnothim]

Cool Paul.

Not asking for a dissertation.  Just curious and want morsel so I can go out and read a bit.
What kind of plate voltage we talk'n about?
Dissipation limit.  Have to ask.... Is that the grid collecting cathode coating and becoming an emitter?
(You don't have to answer)

Heck,  I didn't even look at what valves the Stereomour has.
I did look at the Crack and saw 12AU7'  so I went to compare a bit.

I just picked one of my 9-pin Lyr compatible variants out of the air. 

I only know these because I am a collector and like to read spec sheets.
The 7L / 6922 / E88CC has a 6.3V 300 mA heater.  THey typical Plate voltage is 90V / 15 mA.
The VR / 7398 / E188CC differs slightly with 6.3V / 335 mA heater and typical Plate voltage of 100V / 15 mA
The 6DJ8 / ECC88 has a 6.3V 360 mA heater with typical Plate voltage of 90V / 15 mA

I'm only reciting spec sheets.  I'm just learning this stuff.

Many thanks !

[Grainger49]

The Stereomour uses a 12AT7.  One side is for each channel, the first stage/driver for the 2A3 output tube. 

You might be able to use a pair of transformers to supply the voltage and current that you need for the heaters.  But... Bottlehead is very careful about their transformers.  They are shielded so that they don't induce hum.  A cheaper transformer might add hum to the audio circuit.  Then again, it might not.

[iamnothim]

Thanks.

Just poking my nose around at this point.
Great stuff to know.

That said,
I'm smitten by these kits 

[Paul Joppa]

The Stereomour driver runs 200v at about 4mA. On the spec sheet, look for maximum plate voltage - must be 200v or grater - and under typical operation, look at the ratio of plate voltage to current - that will let you get into the ballpark for the current needed at 200v; it's in the 15-20mA range I think. Then calculate the dissipated power (volts times current) - 3-4 watts, and the maximum is 1.5.

Actually, any time "typical operation" is far different from the maximum condition, there is probably a reason and you want to be cautious about pushing it....