I replaced R4 with a Hammond 193J and added a Solen 100uf, 400V capacitor to my TSE tonight.
I found it very difficult to get reasonable bias current after doing this. I measured the resistance of the 193J and found it to be under spec (at about 74 ohm). To bring my B+ back down (it's at about 327V now), I added a 50 ohm 10 watt wirewound resistor in series with the choke. Bias is set to about 71ma, driver supply is set to 175v.
The amp seems to have more gain now (I guess from the higher B+?) - this could be good, since I'd like to try my 86db speakers with it.
The hum I had is completely gone now. I can hear a very faint hum if I hold my ear up to my full range driver (95db) - but it disappears in about 6in of distance. This is great!
I notice, though, that the mids seem ever so slightly harsher and less defined than they were before the change. I feel as if the amp were smoother and warmer before the change.
Is this my imagination? Or, are changes of this nature capable of producing this result?
Should I have just dealt with the higher voltage using just the 193J without the additional resistor?
Thanks in advance for any help!
Peter
I found it very difficult to get reasonable bias current after doing this. I measured the resistance of the 193J and found it to be under spec (at about 74 ohm). To bring my B+ back down (it's at about 327V now), I added a 50 ohm 10 watt wirewound resistor in series with the choke. Bias is set to about 71ma, driver supply is set to 175v.
The amp seems to have more gain now (I guess from the higher B+?) - this could be good, since I'd like to try my 86db speakers with it.
The hum I had is completely gone now. I can hear a very faint hum if I hold my ear up to my full range driver (95db) - but it disappears in about 6in of distance. This is great!
I notice, though, that the mids seem ever so slightly harsher and less defined than they were before the change. I feel as if the amp were smoother and warmer before the change.
Is this my imagination? Or, are changes of this nature capable of producing this result?
Should I have just dealt with the higher voltage using just the 193J without the additional resistor?
Thanks in advance for any help!
Peter
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