To regulate or not to regulate

[duderduderini]

Hi Again
I have been experimenting with a few phono stages and I tried same circuit with regulated psu using 6080, At7 and a 5651 and then a lcrcrc non regulated... i 'll be blowed if the non regulated version to me sounded more musical( yes I know its an airy fairy term) which begs the question is it worth regulating?
Given my findings I am not so sure I will bother to regulate future endeavours
Nick

[kevinkr]

Pretty much the reverse of my experience, are you sure that your current regulator design could not be improved?

Can you share your topology? Based on your description it is probably not all that different than what I do.

The primary advantages to regulation in my mind is the low and relatively consistent source impedance that is possible across the audio range, very low noise levels, and one variable (varying supply voltage) removed from the operating point equation.

In most applications except the highest current ones I use 6550, EL34, 6BQ5 as pentode connected followers for their high internal impedance and low output impedance. (I have used the 6080 and 6336 and generally find them inferior except at very high currents.) I use 5651 or zeners for references, and 12AX7 or 12AT7 as error amplifiers. A cascode 12AT7 or 12AX7A based error amplifier can provide quite a lot of gain. (The 12AT7/6201 may be preferred for cascode operation.)

My error amplifiers have the reference in the cathode circuit, and here zener diodes shunted by caps provide more in band gain than the 5651 due to the difference in dynamic impedance - however the zener reference is more prone to drift.

I tend to use a good film cap on the output of all tube based regulators, typically something on the order of 10uF - 22uF..

I have noticed that unregulated supplies feeding phono stages can result in some rather interesting subsonic behavior in that the variation in ac line voltage over some period of time actually looks like vlf noise on the output. (10Hz and below)

[duderduderini]

http://eshop.diyclub.biz/article_info.php?articles_id=3
Hi
That will get you to the site which describes the mods and circuit.
i did notice a lot more speaker movement when hearing it and by shielding the last tube in the line stage that stopped.
Perhaps my implementation in this instance is overkill. ie using a circuit capable of providing 100mA when it only really needs 20 tops.
Would you be able to share ytour topology. I would like to use 12at7's and the 5651 (i have a "few" of them)
Thanks
Nick

[kevinkr]

Hey duderduderini,
Send me an email and I will send you a schematic. (Link through my site if you can't get it through diyaudio.)

I'd be curious to see what you are doing if you have something you want to share.