[Denys]

Good day everyone,

This question might sound silly, but I could not find the answer on the Web. I have an Antique Sound Lab OTL Mark III headphone amp which uses 2 6BQ5 tubes and one 12AX7 tube (this one is in the middle).

My question is... which one should I change to modify the sound of the amp? I read at several places that I should change the original tubes to improve the sound quality....But I do not know if I must changes the three of them, or just the middle one (12AX7)...

Anyone can help me?? And while you are there, any tube suggestion?

Thanks for your time...

Denys

 

[Skylab]

Both tubes will make a difference, and the stock tubes are not very good. I would change the 12AX7's first if you want/need to do it one set at a time. There are quite a few threads on this, but I would recommend the Sylvania 5751 in place of the stock 12AX7. As for the 6BQ5, the RCA grey-plate and Sylvania black-plate are both great.

 

[BushGuy]

re 6BQ5 -matched pair of Amperex EL84 (normal euro name for same tube #)
has worked best for me. Found Siemens too dry for my taste.

The absolute most important change will be dumping the damned stock 12AX7 and replacing with the 5751..........when choosing which one - you have to consider which is the best SQ influence on your EL84's (using your own ears). I had been using a raytheon/windmill, and now use Sylvania Gold w/the aforementioned Amperex . Be aware that both of the 5751 I mentioned will cost you (unless very lucky) in excess of $50 a piece these days.

 

[mow_the_hawk]

Quote:

Originally Posted by BushGuy /img/forum/go_quote.gif re 6BQ5 -matched pair of Amperex EL84 (normal euro name for same tube #) has worked best for me. Found Siemens too dry for my taste. The absolute most important change will be dumping the damned stock 12AX7 and replacing with the 5751..........when choosing which one - you have to consider which is the best SQ influence on your EL84's (using your own ears). I had been using a raytheon/windmill, and now use Sylvania Gold w/the aforementioned Amperex . Be aware that both of the 5751 I mentioned will cost you (unless very lucky) in excess of $50 a piece these days.

Yeah, I agree. The 12AX7 replacement will change the sq the most. I am now using the raytheon windmill 5751. I love it. It also depends slightly on the headphones you are using. They will determine most what you want to change about you sound. Tubes tend to have different sounds as well as quality. (ex. warm)

 

[Denys]

Thank you guys for your quick replies,

I forgot to mention I just bought the Sennheiser HD650 headphones with the Cardas cable. I now figured out that my tubes were my weakest link... This is why I asked you about the tubes...

I did not think that the headphones could also be important in the choice of tubes...

I do not mind putting $50 per tube if the result is worth it...

I read somewhere that Telefunken have decent tubes... Am I right?

Thanks again for your time... I appreciate it

Denys