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In Reply to: RE: is a vacuum posted by bobbyj on April 04, 2010 at 18:07:56
"If you haven't actually used a good 45, thinking a triode wired 46 is the "same", there's where to begin. Is there a "more" linear power triode?"
Actually, as I have posted before, in my amp and my system, the 46 sounds better than any 45 I have tried. That includes some of the best vintage and modern 45s.
I don't have a technical explanation for that, but it's what I hear. Question - is linear power output the most important factor in determining what tube has the potential to sound the "best"? Thanks for your reply.
Gerry
Follow Ups:
You know what you like/prefer and ask sensible questions.
Intersting thing about CCS and the like - many folks swear by them; others claim they compromise one of the differentiating strengths of an otherwise well designed SET amp.
I guess my point is, CCS is not universally liked; in a relative world, it is no absolute technical solution.
Cheers
Raymond
“We must have concepts in order to function; they are not the problem. The problem is created when we believe they are the truth... Our suffering is rooted in a false sense of self, a self composed of concepts.” Charlotte Joko Beck
Good post. The CCS is a regulaTOR-- an active device that produces its own distortions, signatures, and time delays.For Push/Pull, the argument is: (1) should one build excellent, fast responding power supplies so that tube's performance will be exemplar without the CCS, or (2) should one destroy the power supply's sonic characteristics by installing overkill on choke and cap values, have very low hum and ripple, and then try to restore the dynamic performance of the stage in question by applying a CCS device to it to regulate current.
Of course, you now have to listen to the regulator regulating. That is not the sound of music.
For the SET enthusiast, the CCS is out, period. I know, many people use them to regulate current, but unfortunately, (and fortunately if you understand it), in a SET-- if you don't lose transparency somewhere in it, the CCS device is going to be rather---- shall we say---- obvious sonically?
SETS require lots of low-DCR power be available for every stage. Adding any active device other than the stage itself-- that is operating, simply smears the music.
The best way to regulate current in a SET stage is to have a power supply that supplies that current without a significant voltage drop.
---Dennis---
Edits: 04/06/10
No Dennis, the CCS is used as a plate load for the tube.
With a CCS as a plate load for the driver tube, the driver tube can be operated in the most linear way with the most gain.
The load line is horizontal because the CCS represents a very high impedance.
In your circuit the load line for the driver tube is determined solely by the plate resistor since it's output is direct coupled to the output tube.
(in a cap coupled circuit the grid resistor of the output tube is in parallel with the plate resistor of the driver tube making the load line for the driver tube less horizontal)
Your load line for your driver tube looks something like this.
If you had a CCS as a plate load the load line for your driver stage could looks something like this.
Dennis, can you see why a horizontal load line is better?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I wanted to say, "yes", but, I think once you've entered the category of very linear, subtle imperfections may be preferred over other subtle imperfections. Also, some may become used to a certain exaggeration (non-linearity) and when it is "improved" (made more linear) think something is "missing". Seriously. This takes careful comparisons to detect, as well as a musician's understanding of music or close.
Loading can make a very audible difference in my experience, which is why I suggested advanced versions as a possible way to "go beyond". I meant to suggest in my previous response to CCS load BOTH the driver and the output. I plan to do this myself, using a 45, and will report when finished.
And to contradict myself, I found 10's to be a very honest and clean sounding tube, though NOT technically as linear as a 45. I didn't say "sounded better", nor would I say, "sounded worse". Because I don't need any more gain than a mu 20 driving a mu 3 (60), I also plan to try a 10 (mu 8) driving another 10 (64) which should have a similar overall gain.
"Maybe" 2 x DHT's will have something that IDHT x DHT doesn't. ? We'll see.
and I have to say that I think a CCS loaded with a choke also is the best sounding...though pricey of course....
so have fun and do go all DHT or DHP or whatever...etc.
-3db
Something like a 47 perhaps? Do you have a specific circuit in mind?
TIA,
actually I apologize SomeJoe, but I cannot say hear what I am using because I find the stock is really variable...however...
I can say I have designed a 47 driving a GM 70....someday...
The 47 would of course also be excellent driving a 45...direct couple it will provide some grid current...so clipping is going to be better with the 47 DC coupled than many of the various triodes cap coupled.
The 47 is easy to work with...it doesn't oscillate...just put a .47uf PIO cap on the power supply cap driving it...regulate the screen with a Zener diode to about 25v lower than the plate, and you will be very happy...
and of course battery bias the cathode...i can't remember the voltage..
however the 2.5vAC on the cathode had some hum...I was going to build a DC supply, but went on to battery powered cathode pentodes instead..
i.e. for the 45 175V plate 150v screen and about 20ma is great...I run it straight down into the 45 grid i.e. no decoupling from the 45 plate...I can't remember for the 47, but I think this was a 12k wirewound resistor...
this will be one of the better 45's you have ever heard...
Peace,
-3db
for the 300B you will have to run the full 250v on the plate
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