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| General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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10th Jul 2017, 11:38 am
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#1 |
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Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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ECC83 to ECC82 or ECC81 at VU meter
Hey Guys,
Can I replace an ECC83 tube which is controlling the VU meter in my tube amp with an ECC82 or ECC81? If it is possible, which one is the best or will not give me correct VU metering at all... Thanks! 
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10th Jul 2017, 12:10 pm
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#2 |
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Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: ECC83 to ECC82 or ECC81 at VU meter
The dc characteristics of each of those double triode types are different, so I doubt whether any direct substitution would work.
Can you not just use a new production 12AX7 like: http://uk.rs-online.com/web/c/semico...archTerm=12ax7 It doesn't cost any arms or legs and presumably it's not in the audio path so even if you're an audio fanatic it shouldn't cause any sleeplessness 
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10th Jul 2017, 12:15 pm
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#3 |
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Hexode
Join Date: Nov 2016
Location: Budapest, Hungary
Posts: 386
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Re: ECC83 to ECC82 or ECC81 at VU meter
 Too right...too right..very true. Just had a few spares of ecc81 and ecc82, and wondered if I can use them otherwise just sits in my drawer....thats all.. thanks for reply tho.. |
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10th Jul 2017, 2:35 pm
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#4 |
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Octode
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,873
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Re: ECC83 to ECC82 or ECC81 at VU meter
The pin-outs are the same - time for an experiment using known signals at various levels.
Leon. |
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10th Jul 2017, 3:19 pm
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#5 |
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Rest in Peace
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
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Re: ECC83 to ECC82 or ECC81 at VU meter
All of them will 'work'; only the correct one will give anything like the correct meter response.
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10th Jul 2017, 3:52 pm
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#6 |
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Octode
Join Date: Apr 2005
Location: Peterborough, Cambridgeshire, UK.
Posts: 1,898
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Re: ECC83 to ECC82 or ECC81 at VU meter
I tried testing ECC81/2/3 s in an amp chassis just so as I knew if they worked at all. the only difference I noticed was that the gain went down slightly. ECC83s producing the most ECC81s the least. There wasn't much in the differences. and the results could be distorted by the condition/emission of the valves.
Rich.
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10th Jul 2017, 7:22 pm
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#7 |
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Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: ECC83 to ECC82 or ECC81 at VU meter
That is more or less what I would expect. The mu values are 100 for the ECC83, 60-70 for the ECC81 and 17-20 for the ECC82. Oddly enough, the ECC82 is the low-mu valve, so the numbers don't follow a sequence as far as mu is concerned. You might not see a huge difference in performance between the ECC83 and an ECC81 substituting for it.
For those that aren't familiar with the term mu (Greek, but I can't do that with the fonts available), it is the "amplification factor" of a valve, i.e. the change in the anode voltage divided by the change in grid voltage that produced it. Colin. |
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10th Jul 2017, 7:55 pm
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#8 |
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Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: ECC83 to ECC82 or ECC81 at VU meter
Amplification factor, not to be confused with voltage gain....
Lawrence. Last edited by ms660; 10th Jul 2017 at 8:00 pm. |
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10th Jul 2017, 9:45 pm
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#9 |
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Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: ECC83 to ECC82 or ECC81 at VU meter
gmRa. In the real world, Ra is always shunted by the actual anode load resistor and the input resistance of the following stage.
You could get pretty close to it with a constant current anode load and a multimegohm next stage input R.
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
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