[mikeg]

I need guidance regarding a question involving bias setting of my ASL AQ-1005DT power amp. This is an 8 watts per channel 300B based single ended power amplifier.

According to a technical rep. for Antique Sound Lab. (ASL), the bias setting of this amp. should be set to 720mv. But, I have not been able to increase the bias setting to this level with the tubea that I have used. When using Valve Art 300B tubes, the max. bias setting that I can achieve is 695mv. When using Electro Harmonix 300B tubes, the max setting that I can achieve is 645mv; while with TJ meshplate 300B tubes, the max. setting is 505mv. According the tech. rep., all these settings are OK, and only a small loss of output power occurs at lower bias settings (e.g., 5 watt output instead of 8 watt). But, since I only use this amp. to drive headphones, and since I have volume to spare, the tech. person feels that there is no loss in sound quality.

My questions are as follows:

1) is there any loss in sound quality obtained fromTJ meshplate 300B tubes, when operated at a bias of 505mv, rather than at the 720mv which is the setting specified for this amp.?

2) What tube specs can I use in order to predict which 300B tubes are the most appropriate for use with this amp?

3) Is it necessary to achieve a bias setting of 720mv in order for tubes to be appropriate for use in this amp.?

4) Are WE300B tubes likely to work well in this amp.?

5) Are EAT-300B tubes likely to work well in this amp?

 

[Swampwalker]

I do not think that specs will enable you to make that prediction. However, you could probably get a pretty good answer to the technical portion of your question over at AudioAsylum or Audiogon. you should be aware that the very high cost of WE 300bs may make that portion of the ? irrelevant unless you have 0.5K$ for a used pair.

 

[mikeg]

Quote:

Originally Posted by Swampwalker I do not think that specs will enable you to make that prediction. However, you could probably get a pretty good answer to the technical portion of your question over at AudioAsylum or Audiogon. you should be aware that the very high cost of WE 300bs may make that portion of the ? irrelevant unless you have 0.5K$ for a used pair.

Thanks for your response. I'll pass the question to AudioAsylum or Audiogon if I can't get help on Head-Fi. As for cost of the WE and EAT tubes, I realize how expensive they are. But, I'd like my amp. section to be optimal for the R10 that I've ordered.

 

[braillediver]

Look for member Joe Lau (I think). And PM him?

He's the guy. I think ASL is his company or some similar major relationship like that. He seems very helpful.


Mitch

 

[mikeg]

Quote:

Originally Posted by braillediver Look for member Joe Lau (I think). And PM him? He's the guy. I think ASL is his company or some similar major relationship like that. He seems very helpful. Mitch

Thanks Mitch. I'll do so.