New Express Build Questions??? I have added a Voltage Chart

[hot_tube_tone]

OK I have completed an Express clone, and I have a few questions about the characteristics of this amp. I get a full on high gain tone with the volume at 9 o'clock and all of the tone controls at 12 o'clock. Is this too be expected? The amp seems to reach wide open at 12 o'clock on the volume control and anything above that doesn't seem to change the tone. Is this to be expected? I also think that I might have some voltage problems also, because I have 2 Tung-Sol Reissue 6v6GT tubes in it and with the amp powered on one side of each tube glows red. If I play a power cord the red goes away, but once I let it idle the red comes back. Is this to be expected? I have checked the B+ voltages with the updated Kelly schematic and they are in range. I would like to know if someone has a voltage chart of expected voltages for each pin of the tubes. I know that it wouldn't be exact voltages, because of wall voltage differences. But I would like to see if there are some ball park voltages.

Thanks in advance and I wouldn't have made it this far without everyones help!!!

[Allynmey]

Hi HTT, what are you biasing that amp at? I use the KF method of adjusting the BIAS until there is -30VDC on the grids. Never had a problem with it.

Allynmey

[hot_tube_tone]

As for the Bias I did the same thing, but I was wondering what the other pins voltages should be.

I used Nik's layout, from CeriaTone. I think that it is close I would just like to have some voltages to check it by.

Also should it go into distortion so quick on the Volume control?

[UR12]

Try bumping your bias down to -33v.

[Normster]

Check you volume pot and make sure it's log taper. Mine begins breaking up about 10 o'clock and gets pretty saturated by 2 o'clock. I don't know about the -30V thing with 6V6s. I added 1 Ohm bias check resistors and set my 6V6's to 22mA.

[hot_tube_tone]

Try bumping your bias down to -33v.

I have tried the bias all of the way down to -38v and I get the same results.

Check you volume pot and make sure it's log taper. Mine begins breaking up about 10 o'clock and gets pretty saturated by 2 o'clock. I don't know about the -30V thing with 6V6s. I added 1 Ohm bias check resistors and set my 6V6's to 22mA.

I checked the pot and it is an Alpha 1MA pot. My amp doesn't respond anything like that, it goes from no volume to breaking up in the first quarter turn. That is why I am wondering if I have some high voltages. Any other ideas of something to check?

Please let me know if these voltages look right:

[rhinson]

forget about the idea of neg. voltage in terms of setting your bias--ken could say this because he was using nos mullards and siemens--el34's today will almost never bias properly at -30v--it's way too hot for them---you need to know how much current the tubes are drawing realative to what plate voltage you have. if you haven't installed the 1 ohm resistors on the power tube cathodes do so and measure the voltage there---this will be equal to the current draw of each tube (because of ohms law). i would not set the 6v6's over 20-25ma. this circuit will give you very little cleans with 6v6's in there, period. but you need to check the current draw----you may have a faulty pair that redplates regardless. rh

[hot_tube_tone]

What do I need to do if my bias pot will not allow me to get the 6v6's in range? I have the EL34's running at 43.9 ma @ -30 volts, so that is way to hot for 6v6's right?

[bueller]

To lower the bias supply. If your pulling the voltage from one the transformer H.V. legs and using a 220k resistor, drop it to 180k. Or you can increase the bias pot from 25k to 50k, or increase the 47k to ground by 5K or so. Any of these will incease the negative voltage available. I like to use seperate bias pots for each tube. 25k pots will just barely have enough range for 6V6s and EL-34s.