[Bones13]

week, month, year... it all blends together after awhile.  Known issue for this device.  Consensus is that it is a worthwhile wait.
 
I am anticipating arrival "soon", but there is no reason to get irritated at this point in the game.
 

 

[TheAttorney]

  Well I don't have a tube tester and anyway I'd have thought the simplest step would be to test the headphone output socket, as that point is the culmination of the entire amp. Assuming that's a good first test, what is it I should be measuring to show if the amp is performing correctly or not? Above the usual balance/offset of course.

No takers? So how about this:
With amp fully warmed up (i.e. balance and offset measuring near 0V), the measurement at the bias pin is 337V. That's against earth or any of the other pins. Does that look right?
 
Annoyingly, my dba meter seems to be playing up, so I can't get a reliable reading of maximum loudness at the headphones.

 

[Jones Bob]

The pin is not the place to measure bias.

If the bias supply is similar to my KGST, it would have a 4.7Meg Ohm series resistor to limit current to the pin. Most inexpensive VOMs have an input impedance too low (draws current, bias voltage drops) to accurately measure the bias voltage after this resistor. You need to measure bias at the PS PCB before the resistor to get a true reading.

 

[georgep]

I would not recommend opening up your bhse to test bias before the resistor. Beside, the value given at the pin tends to be pretty consistent across similar amplifiers. If I recall kgsshv was in the 380v range as is my diy-t2.

It doesn't seem like there are any issues with attorney's amp, but most likely issues with the other fellow's setup .... I would stop sticking in probes and just stick in the stax cable and listen to your tunes.

 

[Jones Bob]

If you are using the same meter, no wonder the relative measurements were below 580VDC and similar. That's problem with measuring bias at the pin. It is not the voltage the diaphrams are seeing.

I do agree with georgep that if Attorney's amp is working, don't dick with it.

 

[Golfnutz]

  No takers? So how about this:
With amp fully warmed up (i.e. balance and offset measuring near 0V), the measurement at the bias pin is 337V. That's against earth or any of the other pins. Does that look right?
 
Annoyingly, my dba meter seems to be playing up, so I can't get a reliable reading of maximum loudness at the headphones.

Last suggestion...
 
I know you don't have a tube tester, but I think you should try and find someone who does and get those tubes tested.
 
If you read comments on the internet about the life span of a tube, one of the first signs of tubes starting to go is having to turn the volume up (beyond what you would normally use).
 
It could be that the volume you listen to isn't so bad, but as you start to crank it, they just can't handle that much current anymore.

 

[TheAttorney]

Don't worry, I have no intention of opening up the amp and sticking probes into dangerous places )
 
If the measurement at the bias pin of the headphone socket is no "quick win" indicator of amp health, then I'll forget about it.
 
BTW, my digital multimeter is indeed a cheap one. The spec claims 10Mohm internal resistance on voltage readings.
 
Edit: Golfnutz, yes I'll try the tube tester option when the occassion arises, but I'm not in a rush for that.

 

[kevin gilmore]

for about the 10th time you cannot correctly measure the bias
voltage at the headphone connector with a dvm with a 10M
input impedance.

go and find a 50 year old vtvm
or a keithley

 

[alcyst]

  It means it will be a week after the week before it's ready.

Nice. It is a relativistic rather than absolute quantity. Had been wondering if he worked off US standard or metric,

 

[Jones Bob]

Nice. It is a relativistic rather than absolute quantity. Had been wondering if he worked off US standard or metric,

More Einsteinian than Newtonian.

 

[wink]

More Heisenberg than Einsteinian, Newtonian or Schrodingerian.
 
Of that, you can be certain........

 

[icebear]

... after all it is Wilsonian

.

 

[wink]

Idealism is a great perspective.
 
Realism is what were stuck with unless you like delusionism.
 
 

 

[icebear]

Put in a good measure of optimism, some day it will be completed.
Good things take a little longer ....

.

 

[krakadilgena]

What the screw are you nerds talking about??