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Old 3rd January 2012, 07:52 PM   #1
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Default Some more special small-signal tv tubes

Hey

I have received some TV tube, which I have sorted.
Most I have discarded or placed into stock.
There are some who teases me a little.

Here they are left over:
EF91 ( 6AM6 ) sharp cut-off but audio?
6AK5/6AK5W some audio.
EC86 (6CM4) Is almost sure of audio properties
PC86 (4CM4) See above
PC88 (6DL4) Maybe
PCC189 (7ES8) No
PCC88 (7DJ8) Hm..
PCC85 (9AQ8) I think this is OK
EF184 (6EJ7) Should be OK

Anyone know them before I start TubeCAD?

Regards

Benny
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Old 3rd January 2012, 08:23 PM   #2
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At college in 1966/7 I built a single valve radio and after that a single valve audio amplifier both using the EF91. Sounded good.
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Old 3rd January 2012, 08:44 PM   #3
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According to MJ books (and some simulations / breadboarded test circuits I did) EF184 makes a very good tube for a pentode CCS.

Greetings,
Andreas

PS. If you plan to get rid of the 184's, I would give them a new home^^
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Old 3rd January 2012, 09:11 PM   #4
Cassiel is offline Cassiel  Libya
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Quote:
Anyone know them before I start TubeCAD?
TubeCad doesn't work with pentodes.

I know the ef184 which is OK for guitar amps and current sources and if you design with care it could also be good for hifi. I'd use the 6AK5 and that's it.
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Old 3rd January 2012, 09:23 PM   #5
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I have a working EF184 model for LTSpice, if needed.

Greetings,
Andreas
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Old 4th January 2012, 12:17 AM   #6
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Benny,

Even the PCC189/7ES8 has some audio applications. The variable μ has little impact in cathode follower service. Also, use in the 1st gain block of a phono preamp can work out, as the plate current variations are quite small. The thing NOT to do is plug an 'ES8 into a 'DJ8 "hole" and expect all to be well.
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Old 4th January 2012, 12:36 AM   #7
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Used all of them in temporary designs.
Except the xCC189 since that is variable-µ valve. But even that can be operated in the more or less linear region. Just have a look at the curves and you see if you can use them.
Biggest problem is microphony since most of these tubes were used in tuners where low frequency interference wasn't a problem. So you need huge batch to sort the good ones out. I have far over a hundred EF80 and nearly all have such a strong microphonic effect, that every step in the room is a problem. Even <> EF800 do that.
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Old 4th January 2012, 07:51 AM   #8
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EF91 (Z77) was used in some EMI professional tape machines.
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Old 4th January 2012, 09:50 AM   #9
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PCC88 is the same as 6DJ8/6922 with a different (0.3A, ~7.2V) heater...
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Old 4th January 2012, 11:33 AM   #10
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Quote:
Originally Posted by the_manta View Post
Used all of them in temporary designs.
Except the xCC189 since that is variable-µ valve. But even that can be operated in the more or less linear region. Just have a look at the curves and you see if you can use them.
Biggest problem is microphony since most of these tubes were used in tuners where low frequency interference wasn't a problem. So you need huge batch to sort the good ones out. I have far over a hundred EF80 and nearly all have such a strong microphonic effect, that every step in the room is a problem. Even <> EF800 do that.

I have never noticed that with 3 brands of EF80 (Mullard, 2 kinds of Ultron). Maybe because I use them in high current regions? Maybe cause I use them as triodes?
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