Tubes & Microphonics

[LL21]

Hi. Two Questions on my CJ GAT preamp:

1. Someone asked me if the GAT is "hard on tubes"...what does this mean?

The EH stock tubes became super-hissy after 800 hours...stock replacements on the way. Meanwhile, i put in Amperex 6922 US PQ White labels...better in every way. Silent...until just recently. After about 300 hours with the Amperexes, i now [occassionally] hear the teeniest, tiniest bit of "whistle" thru the R tweeter only. In general, the hiss is super, super quiet (and i have 95 db speakers)...but [sometimes not always] it has gone from effectively silent to a soft whisper now in both channels.

Can a preamp be 'hard on tubes'...and if so, is there anything one can do? Or is the 'teeny R-channel whistle' a symptom of this or something else...or just par for the course with any preamp...particularly one with a ridiculously low noise floor? i cannot get over how much super-soft detailing i can now hear thru ordinary recordings.

2. In trying to figure this out, with the unit on, i tapped each tube out of curiosity...and discovered i could loudly hear it thru each speaker. Is this normal? Should i care since i dont tap my tubes while i listen?

Other than the teeniest, tiniest bit of hiss and this occassional 'whistle', the unit is dead silent...so perhaps this 'tapping' business is a non-issue?? The tube sockets themselves are on their own floating suspension systems underneath in the unit apparently.

If i put an EAT tube damper on each tube, should this stop it? Again, should i care?...is this normal?

The EAT Tube damper apparently reduces the external surface temperature of the tube by 10%...would this help it last longer, and protect the tube against the preamp being 'hard on tubes'? i read a few posts on another site where the tube dampers "reduced hiss dramatically"...is this possible?

Thanks for any guidance!!!!!!!!!

 

[Orb]

Heya Lloyd,
the 2nd is normal for the CJ design (also applies to lower current models) and was why I asked if you could here that trait normally (not bad if only picking it up by tapping).
Another test is to clap the hand loudly in different positions to the preamp and closer/further away, again it is probable with the GAT you will hear that trait if you clap loudly close to the tubes.
If you are not picking up niggles relating to this trait with music, then I would not get hung up on the microphonics, do a search on forums and I doubt there are many who mention it.

The only one that raises my eyebrows is the hissing experience after time, although I thought this should relate more to noisy tubes passing Q/A and not be over time.
The original tubes are the stock ones from CJ and someone has not done any tube rolling even if same type-spec?
My dealer has experiences of customers doing this to their Ref5 and it not going well after time for the tube, really relies on QA-testing of the tubes sold in pairs.

One thing I can think of also with the hiss, that being related to mains; this is something I experienced myself even with an expensive but non-filtering 4-gang and the LS27 (dealer had in his box of items to help with setup).
It is possible your still having the equipment influenced by your mains, and unfortunately like me this may be from outside, so trying a quality conditioner on 30-day return may be a good idea as well *shrug*.

Hopefully those with experience on the GAT will chime in.
Edit:
Although bear in mind CJ GAT is noisier than the ARC Refs.
Cheers
Orb

 

[Orb]

Another way to get more info, I think Audiofreaks are the UK distributors of CJ so may be worth giving them a call, or contact-email Mark (you done that in the past - independent engineer) and ask if he has heard of this happening with CJ Gats.

Cheers
Orb

 

[Phelonious Ponk]

The guitar player's perspective from decades of playing through tube amps:

Someone asked me if the GAT is "hard on tubes"...what does this mean?

I can't imagine what that means. We (players) drive tubes up at the edge of failure, deep into clipping, as a matter of normal technique, and get years out of them. Hifi amps and preamps, almost regardless of design, handle tubes with kid gloves by comparison.

After about 300 hours with the Amperexes, i now [occassionally] hear the teeniest, tiniest bit of "whistle" thru the R tweeter only. In general, the hiss is super, super quiet (and i have 95 db speakers)...but [sometimes not always] it has gone from effectively silent to a soft whisper now in both channels.

Can't really help with that. Tube amps make noises. It has always been so.

In trying to figure this out, with the unit on, i tapped each tube out of curiosity...and discovered i could loudly hear it thru each speaker. Is this normal? Should i care since i dont tap my tubes while i listen?

It is normal. Tubes are microphonic. Should you care if you don't tap your tubes regularly? Maybe. You have to tap them to get them to make a "thunk" through your speakers. You only have to get them vibrating the slightest bit to make a contribution to the noise floor.

]If i put an EAT tube damper on each tube, should this stop it? [/B] Again, should i care?...is this normal?

The EAT Tube damper apparently reduces the external surface temperature of the tube by 10%...would this help it last longer, and protect the tube against the preamp being 'hard on tubes'? i read a few posts on another site where the tube dampers "reduced hiss dramatically"...is this possible?

By dampers, are you talking about the little rubber bands that go around the glass? They might reduce vibration, I doubt they'll have any impact on your whistle, or any noticeable impact on tube life.

You are right in the heart of on of the big reasons why solid state has its place. Tubes, while fabulous for instrument tone/dynamics, are too noisy and fussy for true high fidelity applications. With that said, I completely understand if you're willing to put up with their weaknesses to get their strengths. I certainly won't be playing guitar through an solid state amps, no matter how quiet and reliable they are.

Tim

 

[LL21]

Thanks to both of you. I may play around with a pair of EAT tube dampers...mainly just to see if the lower operating temperature of the tube helps at all...the unit itself is super quiet, nearly as quiet as the Gryphon which is stone silent...(the GAT is silent other than this occasional tube whistle...which is at present now gone, tho likely to come back later in the day.) The EAT tube damper actually has several fins that apparently reduce the surface temp of the tube itself...i have seen some manufacturers use brass tubes lined with silicone to do this.

And yes, i like my tubed Zanden DAC and tubed CJ GAT preamp...at this time, the system is something i am practically addicted to listening to...its crazy. I have a pair of new speaker cables from a Manufacturer who is beta-testing...he does great stuff, and i cannot even get myself to switch cables which takes 3 seconds. i'd rather just work, listen (and pop into WBF every couple of hours!) .

 

[microstrip]

Hi. Two Questions on my CJ GAT preamp:

1. Someone asked me if the GAT is "hard on tubes"...what does this mean?

In tube slang “hard on tubes” can mean that the preamplifier sound quality depends a lot on the tube quality – something that is expected with such a simple design using a tube known for excellent sound, but originally designed for RF applications and with many brands known to be microphonic, and/or that the tubes do not last for long.

The EH stock tubes became super-hissy after 800 hours...stock replacements on the way. Meanwhile, i put in Amperex 6922 US PQ White labels...better in every way. Silent...until just recently. After about 300 hours with the Amperexes, i now [occassionally] hear the teeniest, tiniest bit of "whistle" thru the R tweeter only. In general, the hiss is super, super quiet (and i have 95 db speakers)...but [sometimes not always] it has gone from effectively silent to a soft whisper now in both channels.

Can a preamp be 'hard on tubes'...and if so, is there anything one can do? Or is the 'teeny R-channel whistle' a symptom of this or something else...or just par for the course with any preamp...particularly one with a ridiculously low noise floor? i cannot get over how much super-soft detailing i can now hear thru ordinary recordings.

2. In trying to figure this out, with the unit on, i tapped each tube out of curiosity...and discovered i could loudly hear it thru each speaker. Is this normal? Should i care since i dont tap my tubes while i listen?

Tapping a tube will always generate some mechanical noise – it is normal. But a few are very microphonic and should be discarded, as usually excessive microphony is an indicator of a poor quality tube, with bad internal mechanics. Only experience will tell you what is excessive microphony. You should not tap the tubes with a hard object, such as a pencil or a screwdriver – use a small rubber hammer or make one with an erasing rubber and a pencil.

Other than the teeniest, tiniest bit of hiss and this occassional 'whistle', the unit is dead silent...so perhaps this 'tapping' business is a non-issue?? The tube sockets themselves are on their own floating suspension systems underneath in the unit apparently.

If the hiss is occasional, and does not disturb you, I would forget it. It happened several times with my ART with its 10 x 6922/ECC88 , but usually the hiss definitely vanished after a few days of playing, or for one single case the tube became too noisy and had to be replaced.

If i put an EAT tube damper on each tube, should this stop it? Again, should i care?...is this normal?
The EAT Tube damper apparently reduces the external surface temperature of the tube by 10%...would this help it last longer, and protect the tube against the preamp being 'hard on tubes'? i read a few posts on another site where the tube dampers "reduced hiss dramatically"...is this possible?

The use of the EAT damper will modify the mechanical resonance of the tube. Only you can know if you like its effect or not. CJ used red rubber rings in the ART – I would ask them for their advice.

 

[microstrip]

(...)

You are right in the heart of on of the big reasons why solid state has its place. Tubes, while fabulous for instrument tone/dynamics, are too noisy and fussy for true high fidelity applications. With that said, I completely understand if you're willing to put up with their weaknesses to get their strengths. (...)

Tim

Tim,
Just to say I disagree with your provocative comment. I consider that my tube based system is a "true high fidelity application".

 

[MylesBAstor]

the guitar player's perspective from decades of playing through tube amps:




You are right in the heart of on of the big reasons why solid state has its place. Tubes, while fabulous for instrument tone/dynamics, are too noisy and fussy for true high fidelity applications. With that said, i completely understand if you're willing to put up with their weaknesses to get their strengths. I certainly won't be playing guitar through an solid state amps, no matter how quiet and reliable they are.

Tim

rotflmaox10

 

[flez007]

Lloyd, I have heard that term as well, and it relates to some designs where valves are pushed to near-extreme bias threshold, hence its life could be less than normal biased designed valves.

Now, what the &$&&$) were you doing "tapping" your preamp valves to test your system!!! ... Curiosity killed the cat! ...

 

[LL21]

OK! OK! i wont do that anymore...to be fair, i used a wooden ruler and tapped the rubber tube damper...but still, i wont do it anymore. sorry! thanks for the fair warning.

The tube hiss is gone at the moment...so leave it for now, and see what happens. Certainly no emergency.

As for EAT Tube dampers, i may try, but am not convinced the hiss is going to be solved by it...hence not something i will jump on doing immediately. Will just wait and enjoy music in the meantime.

As for Microstrips comments about tubes and Myles answer...RIGHT ON!!!!...i like my tubes...

 

[microstrip]

OK! OK! i wont do that anymore...to be fair, i used a wooden ruler and tapped the rubber tube damper...but still, i wont do it anymore. sorry! thanks for the fair warning. (...)

No, you should do it to select tubes and train yourself. I learn this trick from an old RCA tube book and it was also referred in old Naval engineering manuals. George Kay once sold a tube tester that allowed us to carry these tests.

But please do not do it with your expensive setup. Use the less expensive preamplifier using the 6922 and system you can find to carry these tests.

 

[LL21]

Hi...i first learned about microphonics from my Zanden DAC and watching a former BBC engineer tap quietly on the tube and listening to it thump thru the speakers. i did tap the tube damper and not the tube itself. In any event, your point is well taken...dont experiment on car mechanics with the Bentley...work on the 25 year-old Deux Cheval first...

Or better yet (in my case)...be educated...but perhaps dont try to be a mechanic...either live with quieter tubes from a reliable source or get tube dampers and call it a day...

...i got my Amperexes from Brent Jessee and i will say of all the tubes i have ever bought from him...close to 14 at this point...they have all been great. This little hiss thing i suspect is either the nature of tubes in a super-low-noise-floor preamp (which i've never had to this level before)...or just a very, very minor fluke. time will tell...

 

[Phelonious Ponk]

Just to say I disagree with your provocative comment. I consider that my tube based system is a "true high fidelity application".

Indeed, some tube gear is quiet enough and distortion free enough to be high fidelity. Pardon my overstatement.

Tim

 

[MylesBAstor]

No, you should do it to select tubes and train yourself. I learn this trick from an old RCA tube book and it was also referred in old Naval engineering manuals. George Kay once sold a tube tester that allowed us to carry these tests.

But please do not do it with your expensive setup. Use the less expensive preamplifier using the 6922 and system you can find to carry these tests.

Yes I have one of George's small signal tube testers. Very nice and useful piece. It's very easy to hear microphonics-either thru headphones or the built in "speaker." What I hear, at least for 6DJ8 and 12AX7 tube types is two types of ringing: one that is induced by tapping and one that tapping produces a cascade/shower of ringing (like a box spring ringing ). Many EI 12AX7s, have one microphonic and one good triode

 

[Orb]

OK! OK! i wont do that anymore...to be fair, i used a wooden ruler and tapped the rubber tube damper...but still, i wont do it anymore. sorry! thanks for the fair warning.

The tube hiss is gone at the moment...so leave it for now, and see what happens. Certainly no emergency.

As for EAT Tube dampers, i may try, but am not convinced the hiss is going to be solved by it...hence not something i will jump on doing immediately. Will just wait and enjoy music in the meantime.

As for Microstrips comments about tubes and Myles answer...RIGHT ON!!!!...i like my tubes...

Just for kicks the GAT is also meant to suffer from this even if you do a loud handclap (came out in the Hifinews review, but did not affect the subjective listening).

BTW just to be my broken record going back months now in all your other threads about sound quirks....
Get a quality mains conditioner on a 30-day trial
That way can test for free.
Still think some of your problems all come back to some kind of mains issue, possibly a combination of noise/DC offset.

Cheers
Orb

 

[LL21]

Hi...i have to admit, an EAT tube damper would definitely solve that. i've tried it on my Zanden and it works perfectly...you can tap the casing of the unit hard now and utter silence.

As for the conditioner...i actually do use a Transparent Audio Reference Power Conditioner through everything (except the Sub which is too far away and the Antileon which goes straight into the wall and has its own internal conditoning). I also put a Nordost QX4 between the wall and the Transparent Ref power conditioner, and i did find a benefit by using both. Far lower noise floor, far greater delineation of notes and instrument detailing, and the QX4 does something astounding in terms of making musical patterns (contrapuntal themes, etc) far more easy to understand...not sure how it does this, but it does. You suddenly realize how many instruments are actually playing off one another in ensemble pieces...weird.

But to your point, i agree conditioning done well works. Thanks as always Orb.

I took the R tube out of the socket as per Brent Jessee of Brent Jessee Tubes, tapped it on the table lightly (on the pins not the glass!)...and reinserted it. whistle gone for now!!!!!

 

[fas42]

I also put a Nordost QX4 between the wall and the Transparent Ref power conditioner, and i did find a benefit by using both. Far lower noise floor, far greater delineation of notes and instrument detailing, and the QX4 does something astounding in terms of making musical patterns (contrapuntal themes, etc) far more easy to understand...not sure how it does this, but it does. You suddenly realize how many instruments are actually playing off one another in ensemble pieces...weird.

This is exactly the sort of benefit achieved by the "right" type of tweaking: the Qx4, whatever it is and does, has helped reduce that background distortion your ear/brain has to try and find its way through otherwise, and you're actually hearing the true nature, the actual quality of the recording ...

Frank

 

[LL21]

Pretty much agree, Frank, even though i fully admit the "technology" behind the QX4 is at the outer edge of my understanding and sounds more like science fiction. Quantum resonance is what they call it...supposedly something that first got used when massive banks of computers first started being stored in close proximity...and the QR was apparently used to sort out video and audio feed that was getting messed up or something. i dunno...it works. that's all i care. i took one listen with Roy Gregory and (he predicted 5 minutes), i said it was definitively better after 5 seconds. Then i took it home and put it in and out of my system 3x after careful listening to make sure i actually was prepared to buy the darn thing.

Sure enough, my new speakers (which i was having trouble dialing in)...suddenly snapped into place exactly where i wanted them, musically, tonally, something. And i am not looking back. I have no desire to replace any of my components...but i strongly suspect the digital will be replaced someday, maybe the pre...but the QX4 just does what it does well, and i wouldn't be surprised since there are no downsides, if i just automatically keep it in my system for good.

 

[Orb]

Lloyd I didnt think you had a mains conditioner.
Ah well, looks like I need to stop my broken record now

Thanks
Orb

 

[LL21]

You're always a source of wisdom, Orb. Thanks.