[Daveze]

Beefy nailed it: an Opus is about one [Opus price] more expensive than two y1's...

I think the real option is to try my DAC-301 in balanced mode, then look into a Twisted Pear design...Buffalo32 would be nice if I could just keep track on the availability.

 

[Beefy]

Quote:

Originally Posted by Daveze /img/forum/go_quote.gif Buffalo32 would be nice if I could just keep track on the availability.

I am subscribed to their news announcements

 

[linuxworks]

more color photos

 

[Caribou679]

WoW! Looks grand!! Well done!!

How does the "Tube Bias" connections works?

regards

 

[linuxworks]

the short answer: find the total voltage in your unit (27v normally) and divide in half, then set the bias to that midpoint (13.5v in my case). measure from center post (ground) to left and then center post to right.

I think you have to check this ever so often, based on the tube aging (?) and also when you CHANGE or swap-out tubes. (is that correct?)

 

[tomb]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif the short answer: find the total voltage in your unit (27v normally) and divide in half, then set the bias to that midpoint (13.5v in my case). measure from center post (ground) to left and then center post to right. I think you have to check this ever so often, based on the tube aging (?) and also when you CHANGE or swap-out tubes. (is that correct?)

Ice Creammmm!!

That LED is cool.

You're right, though - those tube sockets are sitting high in the saddle.

What you'll find is that the Millett tubes will take a couple of hours to settle. So even with broken in tubes, it might be best to set the bias for 14V or so. That way, they'll probably hit 13.5 after a couple of hours and stay there the rest of the day. This is highly variable, though, and seems to be more prevalent for 12AE6's than 12FK6's. 12FK6's will tend to settle out very quickly and stay there. I think it has to do with how much amplification the plate is putting out - the more there is, the more it has a chance to move around a bit.

Yes, you should always check the bias when you change tubes - even if they're tubes of the same type.

 

[linuxworks]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif You're right, though - those tube sockets are sitting high in the saddle.

well, if your socket falls off the saddle, you need to tell it to get right back on it again or it will be afraid for life.

 

[linuxworks]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Ice Creammmm!! That LED is cool.

'cherry garcia', anyone?

 

[patton713MW]

Another MiniMAX lives!!

 

[tomb]

Quote:

Originally Posted by patton713MW /img/forum/go_quote.gif Another MiniMAX lives!!

Way to go, Andrew! Glad to hear it worked out well for you, but knowing the care you were taking, I didn't doubt the result.

I hope Mouser gave you your money back for that walwart.

 

[patton713MW]

I'm about to hit them up for it. Question: What volume do I bias the tubes at? I had them dialed in, then went to check them a bit later, and was surprised to see that they changed a lot at a different volume setting.

EDIT - Interestingly, the left tube varies much more than the right:
Bias Voltage, from Min volume to Max volume:

w/ 12AE6 tubes
Left: 13.27V - 14.92V
Right: 13.43V - 14.17V

EDIT2 - Even more interesting, the bias voltage doesn't change at all with the 12FM6.

 

[tomb]

Quote:

Originally Posted by patton713MW /img/forum/go_quote.gif I'm about to hit them up for it. Question: What volume do I bias the tubes at? I had them dialed in, then went to check them a bit later, and was surprised to see that they changed a lot at a different volume setting. EDIT - Interestingly, the left tube varies much more than the right: Bias Voltage, from Min volume to Max volume: w/ 12AE6 tubes Left: 13.27V - 14.92V Right: 13.43V - 14.17V EDIT2 - Even more interesting, the bias voltage doesn't change at all with the 12FM6.

Yes, you'll see some strange readings if you attempt to bias at anything other than Volume Knob = 0.

The 12AE6 has such high gain that it will overdrive the buffer at maximum volume under no load - one tube may go almost to zero while the other tube goes to 27V. It's not a condition where the amp is expected to operate - at all. The other tubes will have a lesser effect as you've noticed.

Keep in mind that your bias will tend to drift for the first few hours or so - and much more on new tubes than ones that have been well-broken-in. Because of the high gain of the 12AE6, it's always going to be finicky with bias - very mule-like - whereas the 12FK6's are often set once and they stay.

 

[patton713MW]

Thanks, that's really helpful information! I just called up Mouser, and they are going to refund me for the wallwart, and I don't have to send them the bad one. Cool!

This amp sounds like happy!

 

[patton713MW]

Live pictures!

Originally, I went with orange tube LEDs, and a blue LED1. However, after casing it up, I decided that I didn't really like the orange tubes. Maybe if the case were black; the orange glass of the tube just didn't jive with the silver case. Luckily, I socketed the tube LEDs, so I just wiggled them out, and dropped in some blues. Then I wired up 3 orange LEDs in series for LED1, and I think it looks great. I definitely stole the idea from rds, so thanks for the inspiration! I really like how he used the 3 LEDs to even out the lighting around the case. I decided to wire them in series vs parallel, but otherwise I used his same idea.

Here it is with the blue tubes and orange case lighting. One thing that I love about the blue tubes is that it allows you to see the orange glow of the tube heater. With the orange LEDs, you can't even tell that there is a heater. The orange heater glow looks great with the blue tube glow.

 

[tomb]

Great work! Great pics, too!

Yeah, I put amber tube lights in my prototype MiniMAX and I don't like them. I'll change them some day.