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Some more special small-signal tv tubes

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Hojvaelde

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Joined 2005
#1
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
 
#3
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^^
 
#6
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.
 
#7
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.
 
#10
the_manta said:
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.
Click to expand...


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?
 
#11
I used them as Pentodes with at least 10mA current. I dunno what types I used exactly. Just had a look in my cellar and there were nearly all manufacturer present. But no Ultron or Mullard branded one 😉
Maybe these are better.
 

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#13
HI Benny,

I'd be careful with that PC900. At first glance it might be interesting, due to it's large transconductance and it's tiny approach ;-). But it's a remote cutoff triode which could lead to great harmonic distortion when used as an AF amplifier. And there are no reliable data in the web, such as plate curves. So where would we start constructing the amplifier?

Best regards
 
#14
Hojvaelde said:
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
Click to expand...
I use the PCC85 ( RFT or RSD ) in my Circlotron OTL amp with very good results and in line preamp too . The EF184 I use it like CCS in a differential gain stage in another amp , with good results , Graff Amps use it for amplification . I can suggest the use of the PCC189 ( I don't try it yet but I will try it ) in a cathodyne phase spliter too by parraling the two sections , because the cathodyne has no amplification its a unity gain .
 
#15
Hello and thanks for the feedback. 😀

It is an old married couple moves to the elderly. I've got most tubes and coming packages with tubes as the family gets emptied the house.

There are some 1xx tubes for batteries.
HAM tubes, xL509/519 and PY500 tubes he has given to some HAM people.
DY87 and all similar, I have thrown out.
PL500/4/8, PL36 and other familiar tubes I save. For example, over 45 used PCL86 tubes.

There are some NOS tubes.

The last tubes is mentioned here in the thread.

Regards

Benny
 
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#18
Kay Pirinha said:
HI Benny,

I'd be careful with that PC900. At first glance it might be interesting, due to it's large transconductance and it's tiny approach ;-). But it's a remote cutoff triode which could lead to great harmonic distortion when used as an AF amplifier. And there are no reliable data in the web, such as plate curves. So where would we start constructing the amplifier?

Best regards
Click to expand...

You can find some data if you search for 6AH5 or 6HM5, which I believe is the same tube.
 
#19
Cassiel said:
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.
Click to expand...

Trioded EF184s are supposedly very good. I've got a bunch of them, but havent had time to test them yet. I've used some in guitar preamps as pentodes, and tho a little microphonic, they give a nice tone.
 
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