[kevin gilmore]

The complete lack of any discussions of tube designs here coupled
with a bunch of trys at various geometries has finally led me to this
rather interesting design. No caps in the signal path.

http://gilmore.chem.northwestern.edu/ayu1.jpg

And i want to see what people think.

Biggest problem is that 6lf6's are hard to find and the center
stage eats more power than even the output stage. I've tried
a few other tubes, but can't find anything suitable for the
center tube that's small.

Sounds rather interesting. Hard to describe. Not the lowest in distortion
levels. (about .1%)

 

[drewd]

Would an EL509 work in place of the 6LF6? I'm just shooting from the hip...

-Drew

 

[pabbi1]

Nevermind... March Madness has crept into June.

 

[steinchen]

no madness, the voltages are significantly lower than the voltages of the march monster. 150 Volts is a voltage I dare to handle, 600V aren't

 

[kevin gilmore]

something smaller without an anode cap is what i'm looking for.
especially without the anode cap. el360's also work and are
a bit smaller, but latest production tubes are crap and the anode
caps come off way too easy.

 

[DaKi][er]

2.36MB pic?

Learn to format pic's appropriately, especially for the poor 56k'ers

50kb is much more reasonable?

 

[nikongod]

Quote:

Originally Posted by steinchen no madness, the voltages are significantly lower than the voltages of the march monster. 150 Volts is a voltage I dare to handle, 600V aren't

i think its 300V... its ceneter tapped, 150 above and below, 300V rail-rail.

anyways, i think the big problem will come in getting the 2 output tubes matched well enough.

 

[NOTHINGness]

Quote:

Originally Posted by DaKi][er 2.36MB pic? Learn to format pic's appropriately, especially for the poor 56k'ers[/IMG]

It could be worse. Look back at the Dynahi thread where he was using his 14mp digicam.

 

[nikongod]

Quote:

Originally Posted by NOTHINGness Quote: Originally Posted by DaKi][er 2.36MB pic? Learn to format pic's appropriately, especially for the poor 56k'ers 50kb is much more reasonable? It could be worse. Look back at the Dynahi thread where he was using his 14mp digicam.

or we could be talking about resizing pictars in a thread about an amp...

is the feedback there to reduce dc offset, or lower gain? im somewhat lost.

 

[kevin gilmore]

quote
is the feedback there to reduce dc offset, or lower gain? im somewhat lost.


Both.
Open loop gain about 30db.
Closed loop gain 10db (which is still a little high)

The feedback pretty much takes care of just about any output tube
variations. You could use a 6as7 section for the top and the other
section for the bottom and then parallel as many tubes as you like for
lower output impedance.

Or replace them with 6c33's which is what i'm going to do this weekend.
If i'm going to use 25 watts in the driver stage, i might as well use 60
in the output stage.

Note regarding resolution. 14mp is no big deal anymore.
I'm borrowing one of these for something special i'm doing this weekend
http://www.dpreview.com/news/0312/03...jifilmback.asp
Its a little over 40mp and raw files are 132 megabytes each.
6gb compact flash disappears in only 60 pictures.
Camera + back + tethered stuff + lens >$35k
I don't ever see myself actually owning one of these.

 

[eric343]

40mp is upsampled due to the CCD layout... it's actually more like 20mp. Which begs the question, why not go with a 22mp (true) resolution back, which are plenty available.

Quote:

Originally Posted by kevin gilmore Note regarding resolution. 14mp is no big deal anymore. I'm borrowing one of these for something special i'm doing this weekend http://www.dpreview.com/news/0312/03...jifilmback.asp Its a little over 40mp and raw files are 132 megabytes each. 6gb compact flash disappears in only 60 pictures. Camera + back + tethered stuff + lens >$35k I don't ever see myself actually owning one of these.

 

[rickcr42]

I like the idea of a pentode stage driving the triode output and is pretty much where my SE 300B amp is headed.Parallel triodes or even the present Mu stage seems like a step back from the simple pentode.
Using a power tube,the pentode,gives you enough muscle and low impedance to drive just about any output stage but that puppy Kevin selected is not cheap !
Ask Counterpoint SA4 owners what they think of this tube

Have you built and listened to this design keving or is this still on paper ?

If just in the theoretical stage I am windering if maybe the front end (gain and driver stage) could maybe be fiddled with to use a 6BM8 combination tube (triode and pentode in a single package)to reduce layout size and save major $$$$.Thinking out loud here man.

Pretty cool topology trhough all things considered and this IS DIY so cost really is not an issue if that is the only path

also nice to see something new around here.Been getting a bit boring lately

 

[rickcr42]

http://www.altavistaaudio.com/6lf6.pdf

http://www.drtube.com/datasheets/6bm8sv96.pdf

The output power from the 6GM8 is "only" 1.8 watts but should be up to the output stage driving duty.If no then there is always the 11BM8 at 8 watts.

Still thinking out loud and trying to get a discussion going

http://www.nj7p.org/Tube1.php?tube=11bm8

16A8 ?

http://www.nj7p.org/Tube1.php?tube=16A8

 

[rickcr42]

Quote:

Both. Open loop gain about 30db. Closed loop gain 10db (which is still a little high)

Yeah 30 would be unusable without major attrenuation before the stage and if a volume control used instead of fixed attenuation it would be "hair trigger" and on the edge at all times.Nothing more aggravating than a "twitchy" volume control in real use.
X10 ten usable but still may require pre volum control attenuation in most systems to bang it down to 5dB or mnaybe the ideal 6dB.

The 12AX7 is a great high gain tube but limited in low level line applications without tossing off some gain.Some beleive this creates a higher dynamic range for the stage overall while others beleive it just causes problems bu adding undue noise to the stage.Kinda the square peg round hole thing

 

[erix]

Quote:

Originally Posted by rickcr42 If just in the theoretical stage I am windering if maybe the front end (gain and driver stage) could maybe be fiddled with to use a 6BM8 combination tube (triode and pentode in a single package)to reduce layout size and save major $$$$.Thinking out loud here man.

The 6BM8 has been used by Eric Barbour (ex-Svetlana) in his headphone amp cum lunchbox, the TM-4 (now discontinued..).

I wonder if he'd share the schem since he isn't making them anymore..

ok,
erix