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Old 13th November 2007, 11:13 PM   #71
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I was thinking of something more elaborate than only an Oring over the bases. Thought of a piece of thin marine plywood or PCB to mount both bases plus circuit and hang this board with 4 Orings from the main topboard or other hangers inside the box, Origs will hang a 45º towards the center of the subboard to limit movement, this way we may have more compliance for the suspension. Only connections to this board would be B+ Grd, input and output pairs. Maybe not the best option, we might find a better solution, but how does this sound to you? Other ideas?
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Old 13th November 2007, 11:20 PM   #72
Salas is online now Salas  Greece
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Excellent approach. Do it by all means. Post pics and review here whenever ready. Best of luck!
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Old 13th November 2007, 11:27 PM   #73
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Thanks for the encouragement Salas and of course will report my impressions when built.
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Old 18th May 2008, 10:09 PM   #74
Salas is online now Salas  Greece
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Default Maida addition & 12B4 comparison


This is an update on the 6V6 line preamp.

Two things are new:

1. A Mosfet Maida regulator was added in the 6V6 preamp.

2. A comparison was performed against a 12B4 preamp. The 12B4 has Mosfet Maida too.


Results:

1. The Maida works well. Benefits 3D, bass slam, transparency, drops background noise. Thankfully it does not change the 6V6 line stage's tone. Tone remains as when with the passive PSU. The valve rectifiers feeding the Maida, are still audible for sound signature if rolled. Only less drastically so than with a passive PSU.
All in all the Mosfet Maida presents a worthwhile positive add on.

2. There is no comparison. The 6V6 beats the 12B4 stage easily. The 12B4 line stage sounds gray and shy compared to the 6V6 line stage. Musical information from bass to highest treble, is just so much more and it breaths when using the 6V6. Also dynamics are clearly better. I did not expect such an easy victory. I did the comparison with a DIYer friend present. He is the maker of the 12B4.
He draw the above conclusions only too fast. I was listening and not speaking for much longer. I draw the same conclusions.
He will modify towards 6V6 immediately he said.

*The 12B4 line stage is shown in the attached picture. RCA NOS 12B4s, Mundorf Silver Oil Supreme coupling, ditto for cathode bypass parallel on Silmics, great hook up coax.
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File Type: jpg 12b4-maida.jpg (76.9 KB, 2117 views)
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Old 18th May 2008, 10:43 PM   #75
Zen Mod is offline Zen Mod  Serbia
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did you tried shunt reg with these two preamps?
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Old 18th May 2008, 10:53 PM   #76
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Quote:
Originally posted by Zen Mod
did you tried shunt reg with these two preamps?
Not yet. I hope it will give even more music if I will. Please suggest your best preference shunt reg schematic for 330V B+

The two preamps are equivalent in concept with the particular 12B4 application having some more aces by using better hook up wire, Silver Oils over cathode lytics, separated PSU box, and a stepped attenuator.
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Old 19th May 2008, 07:48 PM   #77
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Hi salas,

Really elegant build - both preamps.

Have you tried a 100uF cathode bypass value for the 6V6?

BTW, with the ‘umbillical’ you use in your 12b4 preamp, is the connection to the psu removable or is it ‘captive’?

Thank you,
fred
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Old 19th May 2008, 08:03 PM   #78
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Default Toobz Day

It was high time for a 6V6 tube comparison.

Two people, 6 tube pairs.

SPL constant, notes taken. Standard music. Standard listening positions.

Disclaimer: The following listening impressions are subjective, based on performances exclusive for the line stage described in this thread.

Tubes:

1. MOV / OSRAM 6V6G Coke bottle:
Melodic mid tone (euphonic coloration), soft bass, open but not harsh highs. A 'cozy' sound, not particularly clean. Microphonic enough.

2. Visseaux 6V6G Coke bottle:
Still melodic enough but noticeably cleaner than the MOV, good balance across the spectrum, firm but not big enough bass. Good microphonics for an ST bottle.

3. Sylvania 6V6GT VT107A:
Nice mid balance, close to neutral. Good bass. Soft, not open enough HF. Good microphonics.

4. Philips Miniwatt 6V6GT:
Great balance. Only a hint of mid tone romance. Clean and open but never harsh. Very good bass and microphonics.

5. electro-harmonix 6V6GT:
Open, clean, lean enough balance, deep bass not enough. Some hardness in the presence range. Not bad, catchy sound. Excellent microphonics.

6. Tungsol reissue 6V6GT:
Spot on neutrality. Proportionate sound, excellent analysis. No highlights, no harshness. Excellent microphonics.

Conclusions:

No bad 6V6 in the above list. Two stand outs: For NOS is the Miniwatt, for new is the Tungsol. The Miniwatt adds just a bit of euphonic expression in vocals and other midtones, posing as correct , clean and big, but alluring too. But the Tungsol reissue is the monitor tube. It has all the stuff needed and makes no statements.

Regards to all tubephiles

Salas.
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Old 19th May 2008, 08:08 PM   #79
Salas is online now Salas  Greece
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Quote:
Originally posted by fred76
Hi salas,

Really elegant build - both preamps.

Have you tried a 100uF cathode bypass value for the 6V6?

BTW, with the ‘umbillical’ you use in your 12b4 preamp, is the connection to the psu removable or is it ‘captive’?

Thank you,
fred

Thank you.

- Not lower than 220 uF. Haven't tried 100 uF.

- It is removable. One box houses the tube rectifier, pi CLC, fillament supply. Main linestage box houses the Mosfet Maida regulator too.
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Old 20th May 2008, 04:57 AM   #80
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'It has all the stuff needed and makes no statements.'

My experience exactly.  I have a very small, wimpy power amp that uses 6V6s, and in my travels with my much more widely listend clientele, the Sovtek Tung-Sol is the mutha for ya.  It adds less, subtracts less, interprets less, than any other.

The gray-paint RCA and Bendix Red Bank (it had another designation; 7408, maybe) sounded just as good (the Bendix perhaps just a little more tonally dense), but both had a lot more cathode-coupled (and unequally, so it would appear on the output) HUMM!

I hate hum.

The Tung-Sol does suffer from crooked bottles, though.  Not too good, if your tubes are on display.  I use those quads for my breadboards.

Aloha,

Poinz
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