Not only SE but single valve too

[andrew ivimey]

With three different spud (one valve) amps I have noticed something that has only now become apparent. There may be only one watt to play with and even though one of the three I have built was not 'so very good actually', the real joy and hugely significant positive point in favour of just one valve is that it reproduces music with enormous and wonderful dynamic range. Before distortion settles in, one valve is superb.

Dynamic range is only one aspect of music reproduction sure, but IMHO that you just don't get anything like this with push pull amps and very few SE amps either, even when some of both camps can be marvellous amplifiers.

My present spud isn't right yet, infact messing with the PSU caps has made the overall balance wrong, but the sound is so beguiling, as loud as I could wish with Fostex206, and wholly worth spending a lot more time tweaking - possibly even spending more money but that was NOT the point of the exercise.

Are there any more spud lovers out there, or am I alone?

[Brian C.]

Hi Andrew.
No you are not alone. For several years I used my "The Great El Spuddo!" 6S45 amps and now use a single 801A (with Lundahl amorph-core 1:8 step-up).
Great dynamic, unadulterated sound.

El Spuddo! lives on in a friend's system and on Bas Horneman's website.

Brian.

[andrew ivimey]

So El Spudd is on Bas' site? I couldn't remember where I first saw it. A nice choked valved PSU and ultrapath. I could do ultrapath easily, so will before I try to get back to a decent version of 'civilisation', as I haven't finished with EL84s - oh no!

And, Brian, I have thought of using stepup/ input transformers, indeed a I have a pair so really should be worth it, but blimey! when.

[Brian C.]

Hi Andrew. I DO use the step-ups immediately after VCTs (the amp is "stereo integrated") to ensure a very low capacitance feed.
My next project will not have this convenience (monobloc with separate pre) so I shall probably be making a two-tuber this time, replacing the step-up with a valve stage.
Tho' one never knows, the step-up might still work the magic.

Hmm, wonder if the step-up secondary has enough Hs to serve as grid choke....

Brian.

[andrew ivimey]

All right then, spoken throught gritted teeth, I have a chassis of sorts and have decided to get to the bottom of SS Vs valve rectification. The little
6DN7 spud is worth it. Up to 500volts HT, valve rectification and a very sweet spud amp. Let's see how it goes....

I still have Cheepnissmk7 for comparison, but this one isn't going to be cheap; James transformers, Obligato caps, prob. put blackgates in where BGs could help, and then I shall see ...

I envy you chaps in the north who can get together and compare and contrast.

Here I am stuck in the middle of England and no one to play with, so I have to build ever more amplifiers, draggsville!

[G.Axiom]

Andrew,

Count me in as wanna-be
I still have those E55L:s and irons lyin around , just awaiting a quiet weekend...
That is that circuit (far our of my scope) made by one of my friend , pentode-connected spud, with output iron includin separate secondaries for current feedback for 2.nd grid...
I'll report as soon as I got them up an running.

"the real joy and hugely significant positive point in favour of just one valve is that it reproduces music with enormous and wonderful dynamic range."
Ah, that made me wet... I am planning to use them as mid amps in +100db-sensitive active system