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Old 22nd December 2004, 05:49 PM   #1
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Default tubes 5965A and 5814A

Hi,
I have a question.
I bought a used preamp conrad Johnson PV-5 and I found in it 2 tubes 5814A instead of the 5965A, and 6 ECC83 instead of two 12AX7 and four 5751. I know that ECC83 are compatible with 12AX7 and 5751 tubes required,
but the 2 tubes 5814A are electrically full compatible with 5965A or can damage the preamp?
The preamp seems to work well, but I am sceptical on this configuration.

Thanks to everyone can answer me and HAppy Christmas.

FAbio.
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Old 22nd December 2004, 06:35 PM   #2
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Depends on the circuit. They behave differently, but it may or may not trash it. 5814 is a 12AU7/ECC81 equivalent.

Tim
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Old 22nd December 2004, 07:21 PM   #3
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Thanks for answer!
I know 8514, equivalent to 12AU7/ECC82
But I don't have idea if it can replace 5965A in PV-5.
The preamp seems to work, but I am afraid of damage that can appear.

this is schematic of PV-5: http://www.triodeel.com/cjpv5p1.gif
and this is part list: http://www.triodeel.com/cjpv5p2.gif

thanks again to anyone who can help me.
Now there are Christmas holidays, so I have to wait 20-30 days to have correct tubes from importer. So I have to decide if I can use saftly this preamp with 8514(waiting for correct tubes), or I have to renounce to listen to my music just in this period that I have more time to enjoy my records without the anxiety of work.
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Old 22nd December 2004, 08:39 PM   #4
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Hrm, rather odd design. Interesting way to provide time delay too, RC constant plus UJT plus SCR to latch a relay. Also double regulated supply?

It appears to be reasonably solid, if it still sounds good, without distortion (especially at high output volume), it should be okay.

One thing, since it seems to use active compensation, the frequency response will be a bit flatter (along with somewhat lower overall gain) with lower gain tubes like 12AU7.

Tim
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Old 23rd December 2004, 12:45 AM   #5
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Hi,

Quote:
but the 2 tubes 5814A are electrically full compatible with 5965A or can damage the preamp?
The 5965 is the analogue computer version of the 12AU7/ECC82 etc.

I'm surprised C.J. designed with that tube but either way the 5814A and close equivalents should all work fine provided they're put where they belong.

The 5751 is very similar to the 12AX7A, it has slightly lower gain and is often prefered over the 12AX7 and equivalents as the first tube in a phono stage.(V1 through V4 in the case of the PV5)

The RIAA correction is of the NFB type so it's best to stick with what CJ designed it for unless you want to deviate from the RIAA standard.

Cheers,
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Old 23rd December 2004, 08:52 AM   #6
316a is offline 316a  England
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Quote:
Originally posted by fdegrove
Hi,



The 5965 is the analogue computer version of the 12AU7/ECC82 etc.


Hello ,
Don't you mean the 5963 ? 5965 is more like a 12AT7 than a 12AU7

cheers

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Old 23rd December 2004, 10:07 AM   #7
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Took me a moment to see what was going on in the phono stage, then I realised that it's a dressed up version of the RCA design, just add cathode followers. That being the case, it hasn't got an awful lot of gain, so it will be important to make sure that the valves deliver the design gain, otherwise, as Frank said, RIAA is likely to be incorrect.

As to damage from using slightly incorrect valves, it's a pre-amplifier and has anode load resistors - they will protect against almost anything. Nothing unusual was done in the heater circuit so I wouldn't expect anything to go wrong. Enjoy your Christmas music through it.
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Old 23rd December 2004, 10:41 AM   #8
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Default Re: tubes 5965A and 5814A

Konnichiwa,

Quote:
Originally posted by TheGatesOfFate
but the 2 tubes 5814A are electrically full compatible with 5965A or can damage the preamp?
There are differences, but as the 5695's are in the cathode follower positions the substitution of what amounts to ECC82/12AU7 is fine. It will (obviously) change the sound from the 5965, but in terms of voltages and currents all will be in the green, no danger of damage.

You can get 5965's easily & cheaply, they are actually closer to an ECC81/12AT7 than to a ECC82/12AU7 and yes, an ECC81 can alos be fitted without danger to the preamp.

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Old 23rd December 2004, 03:26 PM   #9
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Hi,

Quote:
Don't you mean the 5963 ? 5965 is more like a 12AT7 than a 12AU7
Oh dear...yes, I did have the 5963 in mind when writing.

As for its use as a CF, well sure, there's a bunch of valves out there that will "work" fine as a replacement.

The audible differences will all be subtle enough to drive anyone up the wall so I'd suggest to stick with the "original"....
After all, the guys at CJ are supposedly the ones that actually design through extensive listening tests before commiting their stuff to the marketplace so by the same logic, if you buy their product I assume you also trust their ears.

Merry X-Mass to all,
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Old 23rd December 2004, 07:43 PM   #10
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Ok,
thank you all for reply!
So I can enjoy my preamp before having the tubes of default.
I undestand that I can also try ECC81 instead of 5814A.
I will try them too.
Have a wonderful Christmas!

P.s. Conrad Johnson say that in therms of sound, 5751 is better than ECC83. you can find on their FAQ: http://www.conradjohnson.com/It_just...ght/index.html

Also you can read from CJ that PV-5 was a fine design because of "famous "CJD" polystyrene capacitors were used throughout the signal path".
Opening the preamp I noticed that no electrolitics was used in this preamp. Only polypropylene and "CJD". And also Low noise mil-spec resistors.
It was a great and glad surprise for me to see the preamp opened!
http://www.conradjohnson.com/It_just...-products.html
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