calibrating the SRM-006tS drives me crazy

[lupoal]

Hi,
I'm asking for help because I can't understand ...
so i installed in my 006 two tung-sol 6sn7gtb tubes (American NOS)with about 250 hrs on them (so out burn-in but new), I replaced the adjustment trimmers with multiturns to have more control, I use a ceramic screwdriver, my mains voltage is 220Vac constant, I let the amp warm up for at least an hour (with signal on and volume at about 2) before calibrating, put the volume to zero and select an input with no signal (the 1, which is connected only the 3). .. tester in Vdc...first I adjust the balance or then the offset, then balance again and then offset...then I switch to the other channel

now this happens to me
- between with and without cover the read value varies sometimes even more than 2V, and it varies all the time...it swings back and forth...especially on balance
- even in constant condition, e.g., always without lid, the adjusted voltages never stand still...they constantly fluctuate back and forth...e.g., -0.8 to + 1.4...then it slows down...then it picks up again
- from one day and the next I do not find the same values again

questions:
- am I doing something wrong? should I follow a different procedure?
- what is the target value to reach for balance and offset? (I read of people adjusting to 0.25V...but in my experience it is absolutely impossible)
- what are the acceptable target values without having to continually intervene with calibration?

thank you in advance for your help 🙂

[jamesmking]

2 hours ago, lupoal said:

Hi,
I'm asking for help because I can't understand ...
so i installed in my 006 two tung-sol 6sn7gtb tubes (American NOS)with about 250 hrs on them (so out burn-in but new), I replaced the adjustment trimmers with multiturns to have more control, I use a ceramic screwdriver, my mains voltage is 220Vac constant, I let the amp warm up for at least an hour (with signal on and volume at about 2) before calibrating, put the volume to zero and select an input with no signal (the 1, which is connected only the 3). .. tester in Vdc...first I adjust the balance or then the offset, then balance again and then offset...then I switch to the other channel

now this happens to me
- between with and without cover the read value varies sometimes even more than 2V, and it varies all the time...it swings back and forth...especially on balance
- even in constant condition, e.g., always without lid, the adjusted voltages never stand still...they constantly fluctuate back and forth...e.g., -0.8 to + 1.4...then it slows down...then it picks up again
- from one day and the next I do not find the same values again

questions:
- am I doing something wrong? should I follow a different procedure?
- what is the target value to reach for balance and offset? (I read of people adjusting to 0.25V...but in my experience it is absolutely impossible)
- what are the acceptable target values without having to continually intervene with calibration?

thank you in advance for your help 🙂

Stax headphones are designed to take hundreds of volts of audio signal ,  a small offset of a few volts are absolutely not an issue.  

The offset will change with temperature. ALL amplification devices are somewhat temperature sensitive - including valves and transistors.

you can demonstrate this easily, just blow gently onto the valves and what the offset change... This is why you are getting different results with the cover on and off. So don't worry you are not going to hear any difference or cause any damage to the headphones or shorten their life... 

 

Edited November 5, 2022 by jamesmking

[Kung]

Don't worry too much about it , below 10V or even 20V is acceptable.

[lupoal]

thank you
 

what I don't understand is how the playback of the content is not affected by time-varying offsets and a balance...that is,I understand that if there is an offset, or a balance, shifted by say 2V and these are constant and I have a modulated signal around there the 2V is of little importance...but the fact that these vary continuously over time puzzles me, probably because I don't understand how the signal is sent and reproduced

anyway, it sounds... it sounds good (with ceramic cones under the amp it also sounds quite a bit better) and so I try not to think about it