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Starved my 26 filaments & damn....

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Posted on January 18, 2008 at 20:25:56
JANDG
Audiophile

Posts: 1584
Location: Washington State
Joined: February 27, 2004
 Took my dual output labs supply I use for the 26 filaments supply & after reading Steve B.paper on this I decided to do it. While have Nora J. playing at a semi-low volume I slowly reduced current & voltage & watching the 26 filaments, I immediatley noticed a sweetness happening with the music & retention of all of what 26 does well. actually evrything across the boeard seems better. I did this slowly 1 channel at a time & then back to 1.05a & then back to 80ma. Its only been a few hrs, but I really feel the starved filamnets are far superiour to them ran to spec..what the heck..? I have read Steve B. take on this. Anyone else run there the DHT pre in a starved filament mode & notice the seemingly vast improvement to a allready nice DHT.?

 

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What I think is happening, posted on January 18, 2008 at 21:25:26
Mark Kelly
Manufacturer

Posts: 7175
Location: Willy, VIC
Joined: February 28, 2002
 I read SB's stuff a while ago and I think it's interesting but I have a completely different explanation for why the effect occurs.

I think it's the interaction of two effects, one of which is easily modelled, the other not.

The easy part is the reduction in the filament voltage drop emission correction factor (see p 189 of Spangenberg "Vacuum Tubes" 1948).

The other is a change in the higher order derivatives of the tube constants which in turn alters the balance between harmonics. I haven't done the modelling necessary to confirm this but what I think is happening is that you are decreasing the curvature of the plate current derived characteristics so you are sliding closer to the point at which third harmonic due to plate current curvature and that due to variation of mu with grid voltage balance each other out. This is the effect responsible for the WE Harmonic Equaliser and the sonic effects attributed to WEHE seem similar to those you are describing.

Mark Kelly

 

Yes,, posted on January 19, 2008 at 04:22:21
Nickel Core
Audiophile

Posts: 870
Joined: February 11, 2005
 Hi,

I the integrated amp I'm currently building, the filament voltages of the three last stages (all DHT) are adjustable for exactly the reasons you metioned. I even managed to come up with a design that allow me to fine adjust AC voltages without using variacs.

Regards,
NC

 

RE: Yes,, posted on January 20, 2008 at 08:59:36
JANDG
Audiophile

Posts: 1584
Location: Washington State
Joined: February 27, 2004
 After 2 days of this Filament starving I have concluded this a beutifull thing. All my source material responds to this in a wonderfull & extremelly holographic way, w/ a sence of detail & sweeteness that was not present in this magnatude.I don't waste much time on things that are very subtle anymore. But I would say this is not one of those gig's. I also can swing my soundstage anyway I want with a few Ma one way or another for seemily perfect channel balance, I can literaly swing a singer to dead center with 1 0r 2ma differance in channel's. I didn't have perfect stage before,but I do now..I am running 80ma on the 26's.I should also say that I can't hear a comrimise or trade of, as is lack of defanition, bass, extention,etc. I would also swear micro-dynamics & just percieved dynamics in general are much better. Fun stuff...

 

Starving E & I on Fils Can Sound Great !!!, posted on January 20, 2008 at 14:11:20
Interstage Tranny
Audiophile

Posts: 3063
Location: Eastern
Joined: October 4, 2006
 Even though the scientific types will scold us how we are starving the filaments and abusing our tubes, they must not have tried the trick !
I starve output tubes, as well. Yes, I am a filament starving addict. There, I admit it ! Actually, it all started while warming up some ancient 2A3 amps with my Variac. Listening, while only at 80 Volts AC in, was jaw dropping. That was over 20 years ago ! Many experiments followed.

Through the years, I have built many amps, including running 6A3s at 5V fil., subbing for 300Bs. Oh My, what a treat that became. I quickly realized that within their power rating, the 6A3, at 5V, was more natural sounding than the expensive WE300B. What a pleasant surprise, that was, freeing my 300Bs for extra cash ! I also tried the 7.5V tubes, like 210, VT52, 250 at 6V challenging the 6A3 naturalness of sound. Well, friends, I must tell you that any of the 7.5V triodes work fine at 6.3V, or even at 6V, as long as you are using good testing tubes.

So, while these starved tubes might have less years' life than "proper" filament voltages, they sure sound fantastic ! Another great example of this is easily verified in many vintage tube preamps, which supply 10.5-11 VDC to their 12AX7s. Their designers knew of the virtues, we can be sure. The classic amp, the Acrosound 2020, one of the sweetest, albeit hot running amp, used starved voltage on the front end tubes, purposely, to increase linearity, according to their lit. The sonic merits make this practice very worthy, as you have found with your 26 tubes...ENJOY!

 

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