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Old 11th September 2012, 01:39 AM   #1
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Default 2010 lemon year for EH 6922 tubes

so I bought 8 EH 6922 gold for my tube pre. sounded great till about a month ago when I started to get tube hiss. replaced the tubes to determine the source and the hiss followed the tubes. did some google searchs and found that EH 6922's manufactured in 2010 are prone to tube hiss after only a few hundred hours. 160 bucks out the window. So if your in the market for 6922's and are thinking EH, double check the production date.
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Old 11th September 2012, 10:47 AM   #2
palmas is offline palmas  Portugal
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Got some toillet noises from some other than 2010 6922.
Even from JAN 6922.
I'm moving into sussian counterparts to avoid odd noise problems
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Old 11th September 2012, 10:51 AM   #3
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speakerfritz: does your pre use a SRPP or another kind of totem pole stage?

edit: or a cathode follower?
If it does, check the heater to cathode voltage...

Last edited by Vincent77; 11th September 2012 at 11:01 AM.
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Old 11th September 2012, 10:16 PM   #4
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I'm using in my circuit a EH6922 in a mu-follower configuration. It is probably from the end of 2010. More than 200 hours of use until now and no signs of hiss at all.
When I designed the circuit I attended the maximum cathode to heater voltage stated in the datasheet of the ECC88/6DJ8 and elevated the heater voltage in order to not exceed it, although the E88CC and 6922 have supposedly higher rating.
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Old 12th September 2012, 01:09 AM   #5
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Quote:
I'm moving into sussian counterparts to avoid odd noise problems
is that a direct replacement with no re-wire. the tube preamp is a sonic frontier SFl/2. It's a two piece model...pre section in unit one....power supply section in unit two.
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Last edited by speakerfritz; 12th September 2012 at 01:13 AM.
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Old 12th September 2012, 02:41 PM   #6
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I suggest using 6N23P which is reportedly what EH based it's 6922 off of. No re-wire, pinout is the same.

edit: you could also try 6N1P, but that needs twice the heater current.

Pinout in all three is the same.

Last edited by mace1337; 12th September 2012 at 02:45 PM.
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Old 12th September 2012, 03:39 PM   #7
palmas is offline palmas  Portugal
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Quote:
Originally Posted by speakerfritz View Post
is that a direct replacement with no re-wire. the tube preamp is a sonic frontier SFl/2. It's a two piece model...pre section in unit one....power supply section in unit two.
You have one of those? I do also, and have always problem with noisy 6922.
Do you have the schematics?
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Old 12th September 2012, 04:49 PM   #8
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Quote:
Originally Posted by palmas View Post
You have one of those? I do also, and have always problem with noisy 6922.
Do you have the schematics?
All a bit hasty;
I suspect this TV front tube is oscillating in the upper VHF band and it will do, given half a chance, caused by minor gm changes or circuit layout and cathode follower config is particulary prone. I use damping resistors 100-470R and ferrite beads in both grid and cathode and must be soldered right on the pins. The anode in such config also needs decoupling right on the solder pin.
A clue is verify the DC conditions when it's running peacefully; and compare the DC figures when it is noisy. If the figures vary with the finger manipulated around the tube glass, it's a sure sign it's oscillating and way above most oscillosopes.
Beware of the decoy; the probe actually making it oscillate too!
Solving RF oscillations in bog standard audio circuits is a nasty surprise. In fact one of my first debugs around 1954. Some datasheets mention this tube can be used for audio stages; but it's home was a tuner front end..

There is alot of merit for beginners to work audio tube stages with the dedicated ECC83/SN series of lower ft tubes designed for such work, avoiding the oscillations and birdy noises.

If course you lot may actually have a ropy lot of tubes....so be it.

richy
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Old 12th September 2012, 09:19 PM   #9
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Quote:
Originally Posted by palmas View Post
You have one of those? I do also, and have always problem with noisy 6922.
Do you have the schematics?
no schematics...my position is based on internet research identifying 2010 EH as having a hissing sound after a few hundred hours. No qualifications or conditions were identified. So, in my mind....time to change to a new brand of tubes. Maybe I'll try some PSVANE 6922's. Sounds like the russian tubes could be suspect. And USA NOS is a crap shoot...very few provable NOS stock out there.......seems like if a tube test pass as good...its a NOS tube....becuase it test like a new tube.
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Old 11th January 2013, 08:06 AM   #10
nitrate is offline nitrate  United Kingdom
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Default Good tubes

I just had to step in here and say i've been using Electro-Harmonix EH6922 tubes in my hybrid amp for over 5 years now with no signs of any problems whatsoever. I think a lot of it boils down to how well designed the application is. Remember that these tubes are very quick and given half a chance will oscillate well into the VHF/UHF region. The use of grid stoppers and correct biasing is essential here. When used correctly you will find these tubes some of the sweetest quietest tubes available today. My tuubes are employed as the preamp and driver stage of my own design hybrid. They have been in use for over 6000 hours now ( all my Audio and television/radio go through this amp ) and still sound as good as the day i built the amp. They are emplyed in both Constant current and active elements of dual stage preamp and cathode follower buffer to the power finals. 3 tubes per channel, and i can tell you they perform brilliently.

Just my thoughts on these little jems,
Leigh
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