SMPS for tube guitar amp?

[soapfoot]

Fair points! But weight is my primary objective here.

Framing the question a bit more broadly--what is the most lightweight way to produce a good power supply for a tube guitar amp?

A linear supply with an efficient toroidal PT, maybe?

 

[ccaudle]

what is the most lightweight way to produce a good power supply for a tube guitar amp

I think it is clear that SMPS are lightest weight by far. The cost for that weight saving is much higher design and testing effort. It seems to me that the best option would be to look for one of the specialty SMPS designs made for tube amps and just check to see if it works OK. Those are not mass market products, they seem to mostly be sold from small vendors in China, so you will have to decide how comfortable you are with buying something from eBay or Alibaba and checking it out for suitability.

 

[capacitor]

As a start I would just add an extra resistor inline with the HT supply, and play around with C values in RC filtering so that peaks get through with the supply relatively intact, but sustained load starts dropping the plate supply.

Another SMPS based tube amp line comes from DV Mark. I personally have a Lil 40. It's loaned out, but when it gets back (crossing fingers there's no "if" involved ) I would be glad to see what model power supply is in use.

There's no sag capability, but it is able to lower the plate voltage via a front panel control. I'm thinking of trying an in-line resistor as @ccaudle already mentioned.

They have some custom electronics to manage the plate voltage (and it automatically biases the tubes, so there's that too) but it may use an off the shelf SMPS.

 

[ccaudle]

It occurred to me this morning that if there were commercial supplies available some place like Glass Audio would be where ads show up. I don't think Glass Audio is stand alone any longer, it was rolled in to...[google searching in the background]...audioxpress, they just have a "Glass Audio" issue every year, rather than publishing multiple Glass Audio stand alone issues per year like it used to be.
Unfortunately it seems they don't have back issues open to browse, everything is behind a paywall, so maybe that inspiration is no use if you don't have an audioxpress subscription (I do not, so cannot search for you).

 

[abbey road d enfer]

I will admit that is just an off-the-cuff guess, I have not actually looked at the dynamic output impedance of tube rectifier circuits to see how they behave under load,

Typically behaves like a resistor until it hits the current limit, where it behaves like a constant-current source. Not very easy to simulate accurately.

but my view on new designs is you don't really have to match exactly the behavior of some older piece of equipment, you just have to capture the essence of the sound with your own twist on it,

Exactly. there are some examples of amps where sag is switchable, and it turns out to be just a resistor in series with B+. It's not perfect, but with a bit of persuasion, the buyer thinks it's close enough to the real thing.