Reducing the heater voltage on something like a 2A3 can be bad practice. I dont really wanna drop names so i cant tell you how i know just that the guy who told me builds tubes for a living
Short answer: No.
From the TubeLab TSE web pages (Page not found | Tubelab
"The 2A3 will make about 4 watts with a 2.5 K ohm load, 3.5 watts with a 3 K ohm load and 2.5 watts with a 5 K ohm load. The distortion and damping factor improves with increasing load impedance. Most users use a 3 K ohm transformer with 2A3 tubes."
In 2A3 amps, I've typically used 3K or 3.5K OPTs, but one of the reason that I like the 300B is that there's enough power (particular with PowerDrive) to "invest" some of it in higher load impedance. I use 5K OPT with the 300B.
With your Altec set-up, I doubt that you need worry too much about power output, unless you live outdoors or in a gymnasium. If necessary, you can always tinker with the "L-pad" values on your horn.
If I were you, with that super-efficient set-up, I would be seriously considering a 45 DHT version for the top end in s bi-amp arrangement. By all means try-out your 2A3s first, but if you like those, remember that the 45s are almost always more liquid sounding than 2A3s, provided that you have speakers that they can drive (which you do).
BTW, I used to have an Altec Horn/Woofer set-up like yours; I think JE Labs influenced a lot of folks in that direction. However, I needed less "directivity" if that's a word, so have gradually moved to open-back boxes/baffles with a 12" full range and a super tweeter, crossed-over (1st order) at about 7500Hz. Positioning relative to the wall is more critical, but the sound is extremely open, airy and lifelike, no matter where you are sitting or standing.
From the TubeLab TSE web pages (Page not found | Tubelab
"The 2A3 will make about 4 watts with a 2.5 K ohm load, 3.5 watts with a 3 K ohm load and 2.5 watts with a 5 K ohm load. The distortion and damping factor improves with increasing load impedance. Most users use a 3 K ohm transformer with 2A3 tubes."
In 2A3 amps, I've typically used 3K or 3.5K OPTs, but one of the reason that I like the 300B is that there's enough power (particular with PowerDrive) to "invest" some of it in higher load impedance. I use 5K OPT with the 300B.
With your Altec set-up, I doubt that you need worry too much about power output, unless you live outdoors or in a gymnasium. If necessary, you can always tinker with the "L-pad" values on your horn.
If I were you, with that super-efficient set-up, I would be seriously considering a 45 DHT version for the top end in s bi-amp arrangement. By all means try-out your 2A3s first, but if you like those, remember that the 45s are almost always more liquid sounding than 2A3s, provided that you have speakers that they can drive (which you do).
BTW, I used to have an Altec Horn/Woofer set-up like yours; I think JE Labs influenced a lot of folks in that direction. However, I needed less "directivity" if that's a word, so have gradually moved to open-back boxes/baffles with a 12" full range and a super tweeter, crossed-over (1st order) at about 7500Hz. Positioning relative to the wall is more critical, but the sound is extremely open, airy and lifelike, no matter where you are sitting or standing.
What's "something like a 2A3"?
All DHTs? Dual plates?
And how much reduction is too much (I was talking 5-10%)?
And what's the physics behind this, that is what does "bad practice" mean?
Just curious.
Then there's THIS:
The effect of filament voltage upon vacuum tube characteristics - IEEE Journals & Magazine
Note however I'm not advocating for HALVING the filament voltage, just an interesting data point...
Good stuff here, including posts by some notable names. Note the comments about AC versus DC fils...
Heater Voltage Range, Hi or Low
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Il see if i can get the entire article. I want to know what the life test says.
Lowering the filament voltage on thoriated filaments is an old trick in the broadcast transmitter field.
The reason i cared enough to comment is that someone is gonna read that and measure at the wrong point, and run the tubes at 2.1V when wire drops are taken into account.
Lowering the filament voltage on thoriated filaments is an old trick in the broadcast transmitter field.
The reason i cared enough to comment is that someone is gonna read that and measure at the wrong point, and run the tubes at 2.1V when wire drops are taken into account.
I want to get it right before playing around. Will stick with 6.3v.
The transformer made locally performs well with 230v Primary. For the 300b builds, it took over 200 hrs for the GZ34 @5v but it did. I don't expect that to change with the 2A3 build at 6.3v.
Initially the GZ34-5v secondary wouldn't drop below 6v (at the pins) for some strange reason.
The transformer made locally performs well with 230v Primary. For the 300b builds, it took over 200 hrs for the GZ34 @5v but it did. I don't expect that to change with the 2A3 build at 6.3v.
Initially the GZ34-5v secondary wouldn't drop below 6v (at the pins) for some strange reason.
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Noted. I have actually done something similar; I use Pete Millet's Regulated Fils Supply (like a Tent PS, but with Common Mode Choke), and once set the fila voltage with no tube in the socket. [face palm]
For the record, when using regulated DC on DHT filaments, I use 10T Bourns pots and set voltage about 2-3% low, which I reckon is better than 2-3% HIGH. These 10T pots are ridiculous overkill, but they are a Tactile Treat, and give me an enjoyable, if basically useless, sense of precision (although the Millet regulator doesn't vary more than a few millivolts with the Bourns).
Tent supplies are very different, i should know because i inadvertently ended up copying the design and adding my improvements to it.
DHT heater supply design
Regulated DC filament supply
Do yo mean those? If you can live with worse efficiency a L200 is superior because you can set the current at approx 150% of what the tubes normally draw. Three terminal regs have a bit of spread in the current limiting threshold.
There is some discussion about the use of current sources, i reckon that a pure current source is bad for lifetime source: i heard that trough the grapevine.
DHT heater supply design
Regulated DC filament supply
Do yo mean those? If you can live with worse efficiency a L200 is superior because you can set the current at approx 150% of what the tubes normally draw. Three terminal regs have a bit of spread in the current limiting threshold.
There is some discussion about the use of current sources, i reckon that a pure current source is bad for lifetime source: i heard that trough the grapevine.
So, thats my rig. The TSE-300b's power the centre co-axial (Altec 604e) and the Brook 12A Monoblock's power the Altec 515 bass units at the bottom.
The air-conditioning is really close to the right channel. Was wondering if somebody could tell me if thats ok. The left channel does cool, but not as much.
Will this reduce life or performance over time ?
The TSE just runs warm.
The air-conditioning is really close to the right channel. Was wondering if somebody could tell me if thats ok. The left channel does cool, but not as much.
Will this reduce life or performance over time ?
The TSE just runs warm.
Attachments
I've encountered some microphonic preamp tubes that would prove this point rather dramatically...
I see what you mean. Its a small room and pic is distorted because there's actually very little place near that dumbell.
I've had no problems with microphonics whatsoever. I tend to use neoprene a fair bit to isolate components and its done a decent job with the vibration near the amps on top.
The AC is my biggest concern.