Biasing a tube amp

[speakerman1]

I'm about to do it so I will take pics. NEVER TURN ON A TUBE AMP WITHOUT A LOAD IE SPEAKERS.
Well the manual calls for o.4vdc. Will see what it is The tubes are warming up now.
Always use an insulated adjustment tool. If not you might find out how much voltage is there. LOL You should do this once a week while burning in the tubes. Then once a moth after the burn in. By doing this you increase the life of your tubes. Plus it sounds better.
All were low or close but 1 was high. The pot is very touchy so it doesn't take much to adjust it.
Here are the pics.

Larry[attachment=9:1bdr60s6]bias 001.JPG[/attachment:1bdr60s6][attachment=8:1bdr60s6]bias 002.JPG[/attachment:1bdr60s6][attachment=7:1bdr60s6]bias 003.JPG[/attachment:1bdr60s6][attachment=6:1bdr60s6]bias 004.JPG[/attachment:1bdr60s6][attachment=5:1bdr60s6]bias 005.JPG[/attachment:1bdr60s6][attachment=4:1bdr60s6]bias 006.JPG[/attachment:1bdr60s6][attachment=3:1bdr60s6]bias 007.JPG[/attachment:1bdr60s6][attachment=2:1bdr60s6]bias 008.JPG[/attachment:1bdr60s6][attachment=1:1bdr60s6]bias 009.JPG[/attachment:1bdr60s6][attachment=0:1bdr60s6]bias 010.JPG[/attachment:1bdr60s6]

Larry

 

[orange]

So if you bias too high it will sort of develop a Sheen, I see. Unwanted behavior and burnout.

Thank you for teaching us about this, Larry.

 

[speakerman1]

I'm still learning on tubes. I know some not a bunch though. Rex probably knows more. With 4 tubes being over 100.00 you try to keep them going as long as you can. I may try some other tubes in this amp soon. Some amps are self biasing so you don't have to do this.

Larry

 

[Web Police]

I just biased my tube amp tonight. the first time after about 1oo hours of use. I wouldda done it sooner but the damn dealer I bought the thing from didn't include the insulated wrench. I made a 2mm insulated allen wrench and ran the thing for a hour or so to warm up then adjusted the bias voltage to .35 mvolts. The four tubes were actually all still within specs but most were closer to .40 mvolts. Well they ranged from .36 to .41 so I guess it needed the adjustment. I am running it for another hour then I will recheck and re adjust if necessary.

 

[speakerman1]

LOL That dealer only had one left and it would have cost you big time. LOL

Larry

 

[Web Police]

The dealer I bought it from had superb customer service. You don't find that type of service nowadays. I am happy with the amp but may be looking for some tubes sometime in the future to try some tube rolling.

 

[speakerman1]

The tubes I rolled did make a better amp. It sounded good with the Chinese tubes in it; but putting these others in sounds so much better. When I got mine 2 power tubes were broken. So I went with Mullards right off the bat. Now the other tubes are switched out it sounds like a whole different amp. It can be costly rolling tubes though. And I'm a cheapskate. LOL

Larry

 

[stuwee]

The tubes I rolled did make a better amp. It sounded good with the Chinese tubes in it; but putting these others in sounds so much better. When I got mine 2 power tubes were broken. So I went with Mullards right off the bat. Now the other tubes are switched out it sounds like a whole different amp. It can be costly rolling tubes though. And I'm a cheapskate. LOL

Larry

So, your amp has a circuitry that responds to diff tubes? I always wondered about that. That makes gear fun and expensive

btw, I put Sovtex's in the Pilot amp, much better than the Sylvania's and (?)'s that were in there before, I've heard that the 232 likes the really expensive Telefunkin's Golden Dragon's / Lions whatever the heck they're called. I can't afford $300 a tube I love the tube sound, that's why I have the Marantz as a pre-amp, that magic sweetness, synergy Larry, your favorite word, hehe! love ya bro!

 

[speakerman1]

They tell me the Chinese have gotten better at making tubes. I think on the Phillips box I read 1968 was the manu. date. And they were mil spec. Why start at the high price tubes. How if your amp likes the cheaper tubes and you get the same sound. Some people are even doing Cryo on their tubes and charging a lot more for them.

Larry

 

[Web Police]

I agree start with the cheaper tubes and if your not satisfied upgrade. I like the way my amp sounds with the cheap chinese tubes, but I wouldn't mind getting some replacements before the ones I have die. I am in no rush and will have to do some research to find the right ones for me.

I just re-biased the tubes in my amp and increased the bias voltage slightly. It seems to have helped the low end in the music spectrum.

 

[speakerman1]

I have a tube tester. Was going sell it to Steve; but I have to many things with tubes. I think that amp might have had 5 hours on it. I never used it after I dropped it. LOL

Larry

 

[Web Police]

Yep so now it probably has 105 hours on it. I am sure the tubes will probably last for several more years. I do have a set of backup Chinese EL-34B tubes you sent me too.

 

[speakerman1]

I think I read that power tubes will last about 5000 hours I think. The other tubes are as long as 10,000 hours. Yes those EL-34s were my replacements for the broken ones. I couldn't wait so I got the Mullards. LOL

Larry

 

[Web Police]

I have been eying upgraded Chinese tubes. They are still affordable and hopefully will sound a lil sweeter, although I am happy with the amp as is.

 

[speakerman1]

Let me know before you buy any tubes. I can get them wholesale and matched pretty cheap. I think a set of Mullards is 70.00 my cost.

Larry

 

[Elite-ist]

Hi all,

I just bought my first old generation tube amplifier from the local mini flea market. It's a Heathkit AA-32 built around the mid 60's. When I bought it for $20, I had the store owner, momentarily, turn it on for 30 seconds to see if the tubes would light up. They all did. Would I have damaged anything in doing so? I read this thread, and Larry warns against powering up a tube amplifier without a load on it.

Nando.

 

[speakerman1]

Not for 30 seconds I guess. Have you played it yet? I have forgotten I had the speakers unhooked and turned on the amp before. I remembered real quick though.

Larry

 

[Elite-ist]

Not for 30 seconds I guess. Have you played it yet? I have forgotten I had the speakers unhooked and turned on the amp before. I remembered real quick though.

Larry

Hi Larry,

I haven't tested the Heathkit AA-32, yet. I'll post pictures of it, along with the retro British speakers I picked up about a month ago, within the week.

Nando.

 

[speakerman1]

What do you mean about the Brit speakers? Who made them? I really like my Epos. Some people don't like the Brit. sound. I really like mine. I have to get my sound room cleaned up. I haven't listened to my Creek in awhile.

Larry

 

[Elite-ist]

What do you mean about the Brit speakers? Who made them? I really like my Epos. Some people don't like the Brit. sound. I really like mine. I have to get my sound room cleaned up. I haven't listened to my Creek in awhile.

Larry

Hi Larry,

These speakers date back to the mid 60's. They are 2-way, 15 ohm impedance, and have low power handling. But, I think they offered leading-edge innovative design for that period. I think the AA-32 will be a proper amplifier to drive them. They are Leak Sandwich speakers.

Nando.