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Old 10th December 2012, 02:31 PM   #21
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@Shoog: What is the preferred manufacturer for the 5687?

Regs, Dirk
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Old 10th December 2012, 03:54 PM   #22
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I have no particular preference - I use what I could get.

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Old 10th December 2012, 04:19 PM   #23
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Default so try these???

2 x JAN 5687 WB Raytheon Röhren / Tube - Neu/New Made in USA | eBay

Dirk
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Old 10th December 2012, 06:13 PM   #24
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Looks fine.

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Old 11th December 2012, 07:48 AM   #25
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Mine are "National" brand.

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Old 12th December 2012, 01:20 PM   #26
vtr is offline vtr  Switzerland
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Default no fets

i had some years ago the rtp with fet on top and bottom of the slcf-its way below the all tube version, and the fets can fail for example cahnging cables etc.






Quote:
Originally Posted by HVfanatic View Post
And to continue: You also have experience using fets for the slcf:

My idea is, using a cascoded bjt current source, and a mosfet for the upper part. Should I use 6h30 for the cathode follower (best current?)

I really don't understand, why a valve for the upper follower is a benefit...

Did you try with fet and valve in comparison??? Or did you try the fet for current source and upper follower, an then switch over to 6922 valve arrangement?

I highly appreciate your opinion, because I thing, you gained valuable experience...

Regs, Dirk
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Old 13th December 2012, 12:43 PM   #27
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Thanks for the info. So I will not try to substitute tubes with fets...
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Old 16th June 2013, 04:55 PM   #28
6L6 is offline 6L6  United States
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Does anybody know the gain of the linestage?

Also how many volts can it swing without clipping? (I'm interested in trying it as gain for Pass F4...)
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Old 21st November 2014, 11:04 PM   #29
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Quote:
Originally Posted by Shoog View Post
Given a bias point of -2.7V @ 0.006A (2.7/0.006) gives a cathode resistor of 450R.

You could use the 5687 as the Constant Current souce - but in my opinion it would be better to use each triode for each channel of the front end. Then use a single ECC88 for the bottom and middle of the SLCF, with the top been taken by another ECC88 with one triode for each channel.

The is absolutely no sonic benefit to keeping the two channels in different valve bottles as there will be no noticable cross talk.

Shoog
Hi Shoog, I'm also interested to build the FVP5a with Salas SSHV Regs. I've often heard about the problems of using 6922 in the common cathode stage. So I think I will also use the 5687. You suggested to use the bottom and middle triode of the SLCF in one ECC88! Will there not be a problem with the max. Ukf because the heating of the middle triode should be elevated? Best regards, Falk
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Old 22nd November 2014, 09:50 AM   #30
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New FVP-6 with 12AT7's, by Joe Rasmussen from Custom Analogue.
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