AudioNervosa

Systemic Development => Amplification and Preamplification => Tubes => Topic started by: Mike L on March 09, 2007, 04:49:23 PM

Title: Problem with specs on new tubes
Post by: Mike L on March 09, 2007, 04:49:23 PM
I received the JJ E34L tubes today for my Consonance Cyber 800 monoblocks.  These require 4 power tubes each.  When I ordered them via the phone from parts connexion I had specified the details.  When I look at them today they are matched as if I were to be installing them in different systems (matched quads instead matched octs)  4 are matched 35, 34, 35, 35 and 4 are matched 42, 43, 42, 44.  

I am totally new to tubes and don't know what Ip means or what an acceptable tolerance is etc.  Now would it be possible to use 2 of the higher valued tubes along with 2 of the lower value tubes on one monoblock and the remaining on the other, or is that totally messed up?

Another question is in regards to amp biasing.  I have no idea what that means and if it applies to push/pull amps or if this is exclusively a SET thing.

Thanks,
Mike

PS. I don't have the manuals
Title: Problem with specs on new tubes
Post by: WEEZ on March 09, 2007, 05:58:36 PM
Can you adjust bias with your amp?

I wouldn't be happy with those values, if it were me.

WEEZ
Title: Problem with specs on new tubes
Post by: Mike L on March 09, 2007, 06:29:15 PM
I don't know as I do not have the manuals.  I will email Opera Audio and ask.

Should all of those numbers be identical.  For example if I only did need 4 tubes would 42, 43, 42, 44 still be acceptable.  

They sell them as matched pairs and yet I got charged additionally for the matching.  The invoice states

 4       MP(matched pairs)             xxxx unit price          (4)xxxx price

 8 unit ordered      matching quads  xxxx unit price        (8)xxxx price (these are charges just for the matching)

Pay for matched pairs and then pay for matching quads....seems like a double charge for matching and they all don't even match.

Thanks for your input,
Mike
Title: Problem with specs on new tubes
Post by: Mike L on March 09, 2007, 07:20:42 PM
:lol:  :lol:   Here's a kicker.  I just realized one of them is an entirely different tube  JJ 7591 S.  My first time ordering from parts connexion.....not really leaving a good taste in my mouth.

Mike
Title: Problem with specs on new tubes
Post by: WEEZ on March 10, 2007, 05:18:47 AM
Mike,

First off, I would try to obtain a manual for your amps..to determine the bias proceedure and/or IF you have an adjustable bias amplifier. (if it IS adjustable; there should be bias controls near the output tubes in the form of screwdriver adjustable pots.

If the above is the case, you COULD use them as you stated (except for the one 'clinker') but I wouldn't.

Second, I'd call Parts Connexion and tell them the situation (that they screwed-up, basically) and you want to obtain a quad that matches the quad you're keeping.

It's not like you're returning rare NOS tubes, or anything. They should work with you on this.

Is there an Opera Audio dealer or distributor near you?

WEEZ
Title: Problem with specs on new tubes
Post by: Mike L on March 10, 2007, 05:52:33 AM
Thanks WEEZ.

I emailed Opera Audio last night and will ask my dealer today about it.  He has the manuals, we just forgot them the last time I was there.  For what it is worth I don't see anything like there is on the other Cyber amps, so I would guess not.

I emailed Parts Connexion last night and notified them of my situation.  Unfortunately they are strictly a Monday to Friday operation, so I wait.

Thanks again,
Mike
Title: Problem with specs on new tubes
Post by: WEEZ on March 10, 2007, 05:54:51 AM
good luck. I'm sure it will work out to your satisfaction.

WEEZ
Title: Problem with specs on new tubes
Post by: richidoo on March 10, 2007, 06:15:42 AM
I am no expert, but I know enough to injure myself.   :wink: Take it FWIW...

Ip means plate current, that is the spec that gets matched in a minimal test. You can't believe what is written on the box unless you are familiar with the company and how they test. You definitely don't want to mix different tube types together. But running one amp with 35ma quads and another with 42 is fine and would work good. They will both sound good, there might be a slight difference in tone, but I doubt you could hear it. The important thing is both monos would be running as designed. Some perfectionists may say they should all be the same, but I don't agree. Octets are for big PP tube amps that use 4 on a side per channel and all must match.

Push pull topology still has a bias adjustment, some may have 1 screw per quad, some even have one per tube. It is definitely adjustable, how easy I don't know on your amp. You connect an ammeter and adjust the current with a screw, just as WEEZ says. It should be somewhat easy unless there is some fancy beautification going on where the screw should be... haha Once set, check it a few times in first 100 hours, then one in 6 months or 500 hours whatever your instincts tell you. After break in they shouldn't change much. Always use the mfg current setting, no matter what people say about EL34 sounds best at 50ma, etc. The designer has it all on the line when he chose the bias current so that it would be safe, easy on tubes, and sound good enough sell a lot more amps by word of mouth from happy customers! Someone told me 6550s should run at 50ma. I set it there on my new (used) amp, and it sounded like crap. When I jacked them up to 75ma as manual said, it came alive.

If there is only one bias adjustment per quad, you want the tubes to be closely matched so they will all operate at correct current. If the amp has multiple adjustment screws, you can use different Ip tubes, you just gotta check that manual for instructions. Those quads you got, if correct, are an awesome match (except for the wrong tube....) Using mismatched Ip tubes on opposite sides of push-pull will result in crossover distortion which you will easily be able to hear, so keep the quads together per amp.

Since you are a new tuber (CONGRATS!!!! You wil love it) here are some tips I learned the hard way.
If you shut if off for changing wires or a quick tweak make sure you let er cool down before you turn it back on, not doing so can cause arc in rectifiers which will shorten their life. Rolling rectifiers had a good effect on my Cary. I got some 60s vintage RCAs.

If something goes wrong, or starts to act funny, just shut it off first, think about it later.  Check your fuses before you bring it for service. You can usually fix a tube amp yourself. Keep some spare fuses on hand, and a spare set of tubes is handy too, even if they are just crappy spares to get you through waiting for shipping on replacements. Supposedly tubes don't like fingerprints so handle with a rag or gloves. Lift them out of the sockets by the base if you can. Pushing them in from the top is OK. You will find that power conditioners have a different effect on tubes than on solid state, the ones I have tried sound bad. Plug the amps straight into the wall before you final judgement on their sound quality. If you mfg says it's OK, and you like very clear powerful sound instead of sweet syrup try a set of Svet Winged C 6550s. That did it for me. Lastly, don't listen to those tube rollers who say "try this tube, it is so awesome" haha
Rich
Title: Problem with specs on new tubes
Post by: Mike L on March 10, 2007, 06:35:36 AM
A lot of great information there Rich.  Thanks.

The Ip then has nothing to do with gain?  My fear was that I would have one channel that had more gain than the other.

WEEZ thanks as well.

Mike
Title: Problem with specs on new tubes
Post by: richidoo on March 11, 2007, 05:51:34 PM
I am not positive about the influence of Ip on gain. My guess is that adjusting the bias to an equal current on each amp will negate the effect of the varying plate current in different quads. Since this is so important to stereo music, the owners manual should spec matched quads or matched octet.

On Tuesday I will ask a friend who knows tubes reeeel good.
Rich
Title: Problem with specs on new tubes
Post by: Mike L on March 11, 2007, 06:58:51 PM
Thanks for your help Rich.

Mike
Title: Problem with specs on new tubes
Post by: Mike L on March 12, 2007, 03:25:08 AM
Apparently my amps are self biasing.  Is that a good thing or bad thing.  Simple is usually good for me  :)

Thanks,
Mike
Title: Problem with specs on new tubes
Post by: richidoo on March 12, 2007, 07:06:49 AM
Self biasing circuit maintains the bias of the tubes over their lifespan, gradually increasing bias to match the tubes' internal deterioration so the bias setting is always maintained at the right level. It is a simple feedback circuit. The only drawback I have ever heard was just marketing BS, that the boards for such a circuit don't like tube heat, and may fail.
Audio Research, VTL and even Prima Luna have auto bias and they don't have those problems so it comes back to good design.
Title: Problem with specs on new tubes
Post by: WEEZ on March 12, 2007, 08:20:34 AM
As Rich says, there are mixed schools of thought on whether self/auto bias vs. fixed/manual bias is the best. I've had both types in the past, and maybe...and I emphasize maybe, the self bias amps are a little 'creamier' sounding..but then again, maybe not. :lol: There are excellent amps of both types.

The auto/self bias amp that I had was the infamous Quicksilver Mini-Mite 25 watt mono's. Mr. Sanders always recommended 'matched' tubes for them. I took that advice regardless of the amp I had at the time.  :?

I would talk to Opera and get 'their' advice. My guess is, that they will recommend matched tubes.

WEEZ
Title: Problem with specs on new tubes
Post by: richidoo on March 14, 2007, 02:51:30 PM
Quote from: "richidoo"
On Tuesday I will ask a friend who knows tubes reeeel good. - Rich

Quoting myself now, hmmm. That can't be good.  Anyway, Mike, I got an answer back from my friend about your bias vs. gain question. His response:

bias DONOT affect stage gain, either voltage or current. it sets the working stage for the output tubes, that's all. topology sets the gain, voltage or current, normally with penthode connected amps, (plate output).   i always recommend replace full set of tubes in both channels of quad, that way the bias mount is more uniform (+/- 2/3 ma), and the demand of power from each tube is more even, on tubes is alittle less critical than SS, but still better that way.
-Alex (theanalogstore.com)

Hope this helps
Rich
Title: Problem with specs on new tubes
Post by: Mike L on March 14, 2007, 05:17:04 PM
Thanks Rich...I guess no worries then  :)

Mike