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Old 2nd September 2008, 06:49 AM   #91
Salas is offline Salas  Greece
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I don't need it to deliver elevated current to the certain load. I had tested the certain setup with as high as 33uF film cap, as a coupler. The 0.68uF Mundorf delivered better subjective slam and stage on my 120k load. It sounds clearly more forceful in LF head to head with my DC coupled version of N-JFET PASS B1 buffer for instance.
It plays much better across the spectrum when biased strong. That's all. Goes without saying that the output capacitor in my schematic is just indicative for value or quality depending on load and taste.
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Old 4th September 2008, 08:53 PM   #92
Salas is offline Salas  Greece
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Quote:
Originally posted by Poindexter
Exactly so.  Even with a 100K circuit as the load, I found a 1µF output coupling cap to open up the bottom and stage beyond what I would have thought.  With a fractional µF cap on the output, we ain't gonna be delivering any big current to anything, no matter what.

On my commercial circuit, I use 2.2µF, simply because it will deliver true bottom into a 20K, or maybe even a little heavier load.

For stuff like current delivery and component values, we got to look at this stuff reasonably.


Aloha,

Poinz
Guys, you put the bug in me and I got 2.2uF Mundorf Supreme to listen to. I put the biggish caps in and listened a lot. With my amplifier load there was no missing bass that I got back quantity wise. I just got a feeling of better coherence and a bit of more relaxation. Could be the phase turning much lower and preserving a better impulse response. Non the less I can hook up the odd solid state power amp with 20k or 10k input Z now with no bass loss.
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Old 9th September 2008, 01:53 AM   #93
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Salas,

Would it be a good idea if make it a CCS plate load?
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Old 9th September 2008, 07:58 AM   #94
Salas is offline Salas  Greece
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Have done so in other preamps, I don'tlike the effect subjectively in linear enough simple circuits.
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Old 9th September 2008, 09:21 AM   #95
Zoran is offline Zoran  Serbia
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These preamps could be of very high class...
rounded plate is better sonicaly,
other tubes have the simillar are 6F6, 300B etc.
*
the tip to improve for the maximum performance IS
topology with output transformer
because the present state is shifting phase for 180deg.
that one like JANE member post before...
*
go to the maximum G2 voltage
not Vbattery...
current of 75% of max at that point.
even with 50% of Io it will be in class A.
*
OT with at least 18Hy that is app. I can calculate better value...
anyway it is not demanding so.
with secondary CT for propper ballanced option...
*
the power supply should be separate for each channel,
as well as heating transformers,
it is vital that is not from the high voltage core
and for rectifiers too...
Experiment with the rectifiers for better sonic results
it is of merrit...
*
essential for fast sound, the load line,
decresing the value, in the same time watching the distorsion,
and keep it as low as possibile,
it could be extremly low like in a solid state,
because of low level signal,
and from the same reason Lp too...
this is much lower then present values...
in some cases of that preamp concepts,
they are close ti the internal resistance of the tube
lowering the equivalent output resistance rapidly...
*
remember You are not designing a power amp
with full swing input...
*
if You make this little effort You will be amazed...
*
microphony could be the problem, like it was stated before,
but that could be solved with soft connection of subchasees,
and changing the pairs and brands of tubes...
*
if I found, I will post the sch i was worked on in the past.
*
cheers
Salas You did the good job indeed
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Old 9th September 2008, 10:12 AM   #96
Salas is offline Salas  Greece
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Quote:
Originally posted by Zoran
These preamps could be of very high class...
rounded plate is better sonicaly,
other tubes have the simillar are 6F6, 300B etc.
*
the tip to improve for the maximum performance IS
topology with output transformer
because the present state is shifting phase for 180deg.
that one like JANE member post before...
*
cheers
Salas You did the good job indeed
*Yes it is top class indeed. Have compared to many.

*I reverse at the speaker end. This one plays better than a 6C45PI with amorphous OPT of a friend. Used double mono regulators, no difference than with a common reg. Uses separate current sources for heaters, has 2 separate windings. Don't know for different heater trafo benefit as in AC heating.

*Thank you for your nice comment.
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Old 9th September 2008, 12:01 PM   #97
coresta is offline coresta  France
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Hi all ! IMHO , 6V6 is great in PP config, 6F6 far better in SE ... look at the 348/349A (6C6/42 , 6J7/6F6) Western line amp ... my next DIYproject
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Old 9th September 2008, 06:27 PM   #98
Zoran is offline Zoran  Serbia
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The comparsion of the tube preamps,
is dificult...
Because there is very few from right techical topology...
*
they could be charakterised like fashion:
over-aplifiing signal...
oposite phase devices...
easy to build and repeted wrong design...
or they are just cathode follower buffers...
*
something is always wrong,
once that is the value of pot,
second is value of Rk, Ck is constant example too...
load values, power supply, heating, ...
etc
*
while the topologyes remains the same,
tube types changing, trying to make the difference.
*
SO WHY NOT DESIGN A DEVICE FOR OTHER TO COMPARE WITH?
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Old 9th September 2008, 06:35 PM   #99
Salas is offline Salas  Greece
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''Hi all ! IMHO , 6V6 is great in PP config, 6F6 far better in SE ... look at the 348/349A (6C6/42 , 6J7/6F6) Western line amp ... my next DIYproject ''

Really good, but will require OPT. No better than 2.7k output Z in triode. And adding OPT is to make or break. Very crucial addition.
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Old 9th September 2008, 06:50 PM   #100
Salas is offline Salas  Greece
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Quote:
Originally posted by Zoran
The comparsion of the tube preamps,
is dificult...
Because there is very few from right techical topology...
*
they could be charakterised like fashion:
over-aplifiing signal...
oposite phase devices...
easy to build and repeted wrong design...
or they are just cathode follower buffers...
*
something is always wrong,
once that is the value of pot,
second is value of Rk, Ck is constant example too...
load values, power supply, heating, ...
etc
*
while the topologyes remains the same,
tube types changing, trying to make the difference.
*
SO WHY NOT DESIGN A DEVICE FOR OTHER TO COMPARE WITH?

Have had comparisons with circa $20k commercial tube preamp products that I performed service for. Considered reference by international audio press. Also about 7 diy tube line schematics including 12B4 single stage favored by many, and Allen Wright 5687 constant current & constant voltage mosfet controlled schematic. More or less I have a fair comparison idea. Its up there among top class. All else is fine tuning for taste or particular system synergy. Also to mention, that to the same conclusion ended up a friend who makes and compares whatever he sees interesting all the time. Has a full tube system. From 0.25mV to 20W, no hiss or buzz. He uses this 6V6 one for line duty in the end. If I ever feel like it, I may try OPT, or other tweaks. As it is is nice enough non the less.

Thanx for comments. Appreciated. I keep the info.
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