[tomb]

Quote:

Originally Posted by jdkJake /img/forum/go_quote.gif BTW, if I understand it right, since the tubes are on the input stage and the output stage is Class A SS, the load on the amp should not affect tube bias. I could be wrong though. jk

No, you're correct. It's best to set the tube bias with the volume at zero, but it has little effect until the last 1/2-1/4 turn of travel. Even then, it's in the few tenths of a volt. There are very few instances where anyone would have the volume turned that high, however. Other than that, you can set/watch the bias while listening to music even. That makes it easy to watch the effect over a long period.

When biasing, I generally refer to tubes as mules. There's a lot of lag and overshoot when adjusting them, so be patient. Anything between 13.5 to 14.5 is probably fine. Technically, the maximum voltage swing is available at 13.5V, assuming the power supply is adjusted for 27VDC (recommended). However, the tubes will perform better at slightly higher voltages, so as long as you don't set the voltage high enough to cause clipping, you can experiment a bit with higher biases. There's no advantage to setting it lower than 13.5V, though.

None of this is very precise - it's just that as some of you noticed, going from a 12AE6 to a 12FK6 or vice-versa can change the bias all the way down to 2 or 3 volts, or as high as 27 - the same as the power supply. The tubes won't even operate at that setting.

 

[tdogzthmn]

I am enjoying my minimax more every day. I am curious what the differences between the Max and MiniMax are. Also where can I find information on how to bias the amp, I have never owned a tube amp so I am a new to tube rolling and the like.

To OP, let us know how you like the dacmagic with your Millet. I have been interested in getting one for myself.

 

[Gradofan2]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif No, you're correct. It's best to set the tube bias with the volume at zero, but it has little effect until the last 1/2-1/4 turn of travel. Even then, it's in the few tenths of a volt. There are very few instances where anyone would have the volume turned that high, however. Other than that, you can set/watch the bias while listening to music even. That makes it easy to watch the effect over a long period. When biasing, I generally refer to tubes as mules. There's a lot of lag and overshoot when adjusting them, so be patient. Anything between 13.5 to 14.5 is probably fine. Technically, the maximum voltage swing is available at 13.5V, assuming the power supply is adjusted for 27VDC (recommended). However, the tubes will perform better at slightly higher voltages, so as long as you don't set the voltage high enough to cause clipping, you can experiment a bit with higher biases. There's no advantage to setting it lower than 13.5V, though. None of this is very precise - it's just that as some of you noticed, going from a 12AE6 to a 12FK6 or vice-versa can change the bias all the way down to 2 or 3 volts, or as high as 27 - the same as the power supply. The tubes won't even operate at that setting.

Just to make sure I understand...

... you say its best to bias the tubes with the POT turned all the way counterclockwise, or clockwise - maximum attenuation, or minimim attenuation?

 

[tomb]

Quote:

Originally Posted by tdogzthmn /img/forum/go_quote.gif I am enjoying my minimax more every day. I am curious what the differences between the Max and MiniMax are. Also where can I find information on how to bias the amp, I have never owned a tube amp so I am a new to tube rolling and the like. To OP, let us know how you like the dacmagic with your Millet. I have been interested in getting one for myself.

MiniMAX Setup and Bias Settings
(Hint: click around for other stuff while you're there.)

 

[tomb]

Quote:

Originally Posted by Gradofan2 /img/forum/go_quote.gif Just to make sure I understand... ... you say its best to bias the tubes with the POT turned all the way counterclockwise, or clockwise - maximum attenuation, or minimim attenuation?

Volume is OFF - zero sound.

Note that as I posted above, though, it doesn't make a whole lot of difference - only a few tenths of a volt.

 

[xodeuce]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif No, you're correct. It's best to set the tube bias with the volume at zero, but it has little effect until the last 1/2-1/4 turn of travel. Even then, it's in the few tenths of a volt. There are very few instances where anyone would have the volume turned that high, however. Other than that, you can set/watch the bias while listening to music even. That makes it easy to watch the effect over a long period. When biasing, I generally refer to tubes as mules. There's a lot of lag and overshoot when adjusting them, so be patient. Anything between 13.5 to 14.5 is probably fine. Technically, the maximum voltage swing is available at 13.5V, assuming the power supply is adjusted for 27VDC (recommended). However, the tubes will perform better at slightly higher voltages, so as long as you don't set the voltage high enough to cause clipping, you can experiment a bit with higher biases. There's no advantage to setting it lower than 13.5V, though. None of this is very precise - it's just that as some of you noticed, going from a 12AE6 to a 12FK6 or vice-versa can change the bias all the way down to 2 or 3 volts, or as high as 27 - the same as the power supply. The tubes won't even operate at that setting.

Good analogy with the mules. I found when I was biasing that I'd make an adjustment that had an immediate 0.30v incremental change Then I would leave the meter connected for another 10 minutes or so to see if it drifted, and sure enough it would creep up another 0.15 or so. It was really frustrating at first.

Finally I found that if I would make a small adjustment, and even if it didn't have an immediate effect on voltage I left the meter connected and let it sit for 10 minutes, and sure enough I could get smaller incremental adjustments that way.

As far as MiniMax vs Max, here's something I've stolen from one of Tomb's posts in another thread:
Quote:

Originally Posted by tomb /img/forum/go_quote.gif The regulated power supply circuit on the MiniMAX was much improved over the regular MAX. That resulted in more detail, tighter bass, etc. Whether the difference is striking vs. incremental depends on your listening experience with the Millett Hybrid. I would say that the MiniMAX is as good as a Millett Hybrid with Diamond BJT buffers can be, period - it's that refined. The new V1.2 MAX board incorporates the same power supply as the MiniMAX, but it's not quite available, yet. Glass Jar Audio should have kits when it is, though. The biggest difference between the two amps is that the regular MAX can be built with a Diamond-MOSFET-buffer. As far as we know, a Diamond-MOSFET-buffer is unique in DIY and commercial amps (guess I'll find out after saying that ).

Quote:

Originally Posted by tdogzthmn /img/forum/go_quote.gif I am enjoying my minimax more every day. I am curious what the differences between the Max and MiniMax are. Also where can I find information on how to bias the amp, I have never owned a tube amp so I am a new to tube rolling and the like. To OP, let us know how you like the dacmagic with your Millet. I have been interested in getting one for myself.

I'll certainly keep y'all posted. I'm waiting on the DacMagic to come in. Apparently the distributer that the local stereo shop buys from is out of stock and won't have any until the end of the month. I'm hoping to have it by the first full week of July at the latest.