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Old 22nd December 2011, 02:17 AM   #201
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Default New 6V6 Bootstrapped CF.

It has been awhile since I have had time to do more than lurk in the forum. Came across some 6V6G's a while back and decide it was high time to sling some solder.

This is the test bed for the preamp. Still missing is the volume, a selector knobs. I am also waiting on the MJE5731 for the SSHV(1) regulator.
B+will be 330V @ 25-30mA fed by the SSHV regulator running at 60-65mA. The cathode load will be various from different styles of CCS's to a good old resistor. Right now I have CCS's galore from a previous project I was doing so they went in. The filament will either be the universal reg or LM317 setup in CCS mode.

The power supply is seperate and sports a single PT 5UG4 rectifier splitting into parallel 20H inductor and res caps of 100uF. All motor run caps. The raw filtered B+ will be 365V.
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Old 22nd December 2011, 07:58 AM   #202
Salas is online now Salas  Greece
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Quite a test construction. With double shunts and all the goodies. Keep us posted. Good luck.
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Old 24th December 2011, 01:47 AM   #203
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Default 6V6 Update

In a matter of minutes my 124b preamp was removed from the room. The 6V6 CF with raw DC feed (380V) and AC heaters biased at 25mA by far beats the 124b. Waiting on the 400V transistors and need time to design the SSHV2 circuit board. So I still have some work to do including building a dedicated measurement PC to document this thing. Until then will just be kicking back and listening.

The clarity, and depth of the soundstage is fantastic. Excuse the dust on the Opus's. Will have to clean them tomorrow. The have performed flawlessly for almost two years now. Every day.
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Old 24th December 2011, 08:59 AM   #204
Salas is online now Salas  Greece
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Told ya, it ain't bad.
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Old 24th December 2011, 03:59 PM   #205
Cassiel is offline Cassiel  Libya
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Well, a friend says he wants a great line stage. He has given me cash to play with. I bought two reds 5692's but weeks have passed and I haven't started yet.

I want something different, I have read this thread and I think I'm going for it. It troubles me the microphonics problem though. How should I build the chassis? I was planning a wooden base with a top metal plate. I can choose the thickness of the metal plate, the base will be made by some carpenter. If anyone can offer me some good tips to avoid problems I'd appreciate it.



EDIT

Quote:
Originally Posted by Salas View Post
Suspend or soft rubber decouple the tubes on a small sub chassis, it pays off.

I don't understand this.
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Last edited by Cassiel; 24th December 2011 at 04:13 PM.
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Old 24th December 2011, 05:17 PM   #206
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I'm interested too (suspend or soft rubber decouple the tubes on a small sub chassis, it pays off.) for my future #26 line preamp and Valve Itch phono, could you post a pic Salas?
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Old 24th December 2011, 05:28 PM   #207
Cassiel is offline Cassiel  Libya
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Quote:
sub chassis
Looked it up on the net but all I could find were some Matryoshka boxes. LOL.
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Old 24th December 2011, 05:40 PM   #208
RCruz is offline RCruz  Switzerland
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You can do it like in a turntable. Place the tubes on a small metal base and decouple this metal base from the undercase using rubber grommets.
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Old 24th December 2011, 05:48 PM   #209
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Default Isolation Grommets

This is what I do. For the test rig I just used a piece of pcboard. In final version will be aluminum, copper, or steel. Not sure yet.


I have no noise pick-up that is discernable. I can tap the tubes and hear a ring but not as bad as my 12b4 pre was.
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Old 24th December 2011, 05:50 PM   #210
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use rubber orings intead of the blue washers I see in the picture.
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