EC Aficionado (was: The Studio Jr.)

Apart from rectifiers, another thing that can account for voltage drop and the amp not sounding at its best is AC mains Voltage variation. In my country, 10-15% of mains variation is legally permissible and it can affect the plate voltage and tube operating points significantly in unregulated power supplies like these.Mains voltage tends to vary from 250VAC in winters to 205VAC in summers and the plate voltage varies accordingly.When the voltages are low, I have noticed reduction of bass slam and some leanness in my diy amps.

One possible solution that I have been considering is to use a isolation transformer with multiple secondaries around 10VAC apart, selectable by a switch and a panel voltmeter. This way one can keep the input mains voltage constant.

 

Good catch, although in developed world this really shouldn't be problem.
My countryside place (Eastern EU) used to have old soviet era substation that likely had all the connections badly corroded. I used to have voltage variation from 200V to 260V depending on phase loading. My EC2A3 or other tube gear that I used there sounded worse at times the voltage was low.
A temporary fix was an autotransformer based voltage regulator gadget that had automatic relay switched taps. I think the taps were around 7..10 V apart.

 

There is also the topology of the amps to consider. The more wooliy OTL sound vs the tighter transformer coupled sound, which could also be affecting the difference outside the impedance.

 

OTL capacitor coupled output is forming roughly a 1. order high pass filter with load;
in case of low impedance headphones it likely happens in audible range and it ruins phase around the cutoff point.
This and the tubes used for OTL with low plate resistance is the key technical attributes to the sound.

Transformer output is usually less affected by load, unless it's tiny.
SET trafos are all with airgaps (that also means large core), it helps to lessen problems in bass.

 

You'd be surprised, the family farmhouse I grew up in in Illinois still has wild power variations today.

 

Important update:

I am delighted to report that I fixed my AF. Marv suggested there was something funny going on, maybe with the tubes I was using.

I swapped out all the tubes; no dice. Then on a whim I tried removing the socket saver I'd had in the driver position, and...



I am rescinding all my prior impressions. This sounds completely different and way better. I need a bit of time to get my head round it, but it is clear that the things I didn't like have gone away and the things I did like got better. Now I can hear what the fuss is about.

Thanks y'all for your civility in dealing with what were accurate impressions of a dodgy socket saver (one of the Tubemonger ones btw). Though as a sort of epiphenomenal froth we did end up with some useful ideas and discussion about the AF. More to follow...

 

its tilting though how some small stuff can cause such huge issues

glad your issue is fixed!

 

I'm sort of convinced - especially after @gixxerwimp 's MCTH got nuked by one - that all socket savers should be opened and inspected before use.

Anyway cool! Now you don't have to sell/modify/cap roll an expensive amp

 

I'd still be interested to hear Garn's impression if he changed the cap.

 

Well sure but there's a big difference between "this is great, let's see if I can make it better" and "this kind of sucks, let's see if I can fix it"

 

For sure. I've only heard the Af in modded form and would be curious to see what Garns thinks of the impact of different caps, if he does decide to change them out.

 

Hey everyone, 30% off your .4632% improvement:
https://www.partsconnexion.com/DUELUND-79270.html

 

Sorry for the off topic question: it's Duelund or Dueland?

At first I thought it was Duelund (Steen Duelund), but I keep reading "Dueland" everywhere, even in "mainstream" magazine reviews...which is the correct name?

 

Duelund......

 

Ahh thanks, that's what I thought at first but I've read the "Dueland" typo so many times that became confused.

 

your measurement drop is 5db more than what I measured.
Not sure if it is any variancce at play.

Socket "adapter" killed an amp of mine.
caused PSU transformer heater winding to burn.
I would be wary of any type socket but I still use them (gold pin).