Re: What's your favourite voltage regs?

Don Pearce wrote:


I was thinking of the best way of doing the FR test, I could do a sweep. But maybe it would be better to just use a 400hZ square wave, I think that might be interesting.

Any thoughts?


Not so easy to interpret since a great deal depends on the quality of
the wave, and of course a good few low octaves are missing. A nice
slow sweep 20 to 20k would be better. I have to say, though, that I
can't think of a mechanism by which the heater bias method might
change the FR.

What exactly is it you are measuring? Is it a single DHT stage or a
whole power amplifier implemented with a DHT in it?

d


Fair enough, I can do both, the square from the Farnell sig gen I use seems to ok enough looking on a scope, I would have thought it was less important as we can still compare the two cases.

Its just some bits I put together for the test. 6sn7, 1k cathode, 40k anode, cathode bipassed by 220uf. 1uf coupling cap, 220k grid resistor on 2a3. 750R on 2a3 cathode, bipassed by another 220uf cap, 3K:8R 50H transformer into 8R resistive load. Both stages powered by 350v from bench supply. 6sn7 AC heated, 2a3 heated by a current source made from three pin voltage reg, a sense resistor and a pot. Switched to voltage mode by shunting a 33000uf cap across it. Cathode resistor on 2a3 taken from -ve leg of supply.

In my subjective comparisons of the different heating methods, the difference has been in the higher frequency ranges. I won't try to describe what I hear.

TBH, my view on this, is I am interested if we can measure something that I am sure that I can hear, not to determine if I can possible hear something, your view may differ, but thats not important to what we are looking at anyway.

--
Nick
.

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