Bias Board

[FlaCharlie]

That is a real problem. I have to adjust my amp every three or four years. What a nuisance! LOL.

As I recall, @Legrace was having serious issues with tube failures in his VTA amps. I don't remember if the exact cause was ever determined. Perhaps it was a design flaw or issues with certain parts, but I do remember that he reported losing numerous $$ output tubes and VTA was unable to solve the problem.

So, at least in his case, these boards did alleviate a real problem. I'm guessing that he would have been quite happy adjusting bias pots manually every 3 or 4 years if the amps weren't eating tubes.

 

[TriodeLuvr]

As I recall, @Legrace was having serious issues with tube failures in his VTA amps. I don't remember if the exact cause was ever determined. Perhaps it was a design flaw or issues with certain parts, but I do remember that he reported losing numerous $$ output tubes and VTA was unable to solve the problem.

So, at least in his case, these boards did alleviate a real problem. I'm guessing that he would have been quite happy adjusting bias pots manually every 3 or 4 years if the amps weren't eating tubes.

There could be many reasons for those failures, and many reasons why simply doing something different regarding bias improved the situation. That doesn't mean a circuit like this will be advantageous in a new build, or that it will magically increase tube life as claimed in this thread. No fixed bias amplifier that's correctly designed should require this. The OP asked if anyone had comments on this product, and that is my opinion.

Jack

 

[Lavane]

As I recall, @Legrace was having serious issues with tube failures in his VTA amps. I don't remember if the exact cause was ever determined. Perhaps it was a design flaw or issues with certain parts, but I do remember that he reported losing numerous $$ output tubes and VTA was unable to solve the problem.

So, at least in his case, these boards did alleviate a real problem. I'm guessing that he would have been quite happy adjusting bias pots manually every 3 or 4 years if the amps weren't eating tubes.

If I remember right, those boards used in the VTA amps were either implemented wrong, or used an earlier version with problems. I haven't seen any posts anywhere about the new boards failing. Erhard has been using them without issue for some time now.
I'm not against the idea itself, its just all those SMD parts and other sand bits that bother me a bit.

 

[Stavee]

You essentially have two monoblocks. Except they are on a common chassis. 2 boards is required. If you use one board, which power supply will you power it off of? The boards can be adjusted to exactly the same and they will not change.

It makes sense. In their directions they tell you to use a volt meter to set the voltage, and since maintaining that constant voltage is the whole purpose of the unit I don't really see why one might drift away from the other. Just stinks to spend almost twice as much

 

[Stavee]

Certainly if you're planning on tube rectfication that's a good way to go. IMO the 4 tube board is preferable to maintain identical bias across all 4 tubes.

I got lucky and my dad handed down to me a differential volt meter. So I can probably get the two units pretty close to exact. He is an electrical engineer, but has no experience in the audio amp realm. We are both having a good time learning

 

[TriodeLuvr]

He is an electrical engineer, but has no experience in the audio amp realm.

Just curious, what's his specialty?

Jack

 

[Stavee]

Just curious, what's his specialty?

Jack

He designed power systems for mobile pipeline. But those B******* forced him into a severance deal that cheated him out of what his retirement would have been. He finished out his working years at a battery power systems company

 

[TriodeLuvr]

He designed power systems for mobile pipeline. But those B******* forced him into a severance deal that cheated him out of what his retirement would have been. He finished out his working years at a battery power systems company

Sorry to hear that. I went through something similar many years ago. I eventually settled into an industry that paid less, but the work was still satisfying. Sometimes you have to play the cards you're dealt, even when the dealer cheats.

Jack