Tube amp switcher recommendation

[mirekti]

Hi all. I am ready to introduce some distortion to my living room and add a valve amp.

My spouse uses the system on a daily basis to listen to radio and what not. It would be somewhat bad she did that burning my valves so I had an idea of keeping the current amp, add the valve amp and introduce an amp switcher.

Not sure if this is valid for any amp, but I was warned the transformers in valve amps will blow up in case there’s no speakers connected to it. The problem is I only have a single pair of speakers and devices like Fosi don’t provide dummy load if powered off (that’s hazard if left around with my spouse)

Is there any passive device one would recommend I could use in this setup?
Something small and simple to do following:

Switch in a position A:
AMP1 –> Speakers
AMP2 -> Dummy load

Switch in a position B:
AMP1 –> Dummy load
AMP2 -> Speakers

 

[staticV3]

Don't overcomplicate things.

Get a tube preamp with switchable tube circuit.

Put it in upstream of your current Amp.

 

[mhardy6647]

Hi all. I am ready to introduce some distortion to my living room and add a valve amp.

My spouse uses the system on a daily basis to listen to radio and what not. It would be somewhat bad she did that burning my valves so I had an idea of keeping the current amp, add the valve amp and introduce an amp switcher.

Not sure if this is valid for any amp, but I was warned the transformers in valve amps will blow up in case there’s no speakers connected to it. The problem is I only have a single pair of speakers and devices like Fosi don’t provide dummy load if powered off (that’s hazard if left around with my spouse)

Is there any passive device one would recommend I could use in this setup?
Something small and simple to do following:

Switch in a position A:
AMP1 –> Speakers
AMP2 -> Dummy load

Switch in a position B:
AMP1 –> Dummy load
AMP2 -> Speakers

Transformer-coupled (vacuum tube) amplifiers exhibit sort of inverse behavior to direct or capacitor coupled solid state amplifiers. For a transformer coupled amplifier, a short circuit across the outputs should be harmless, but, yes, open circuited outputs can result in too-high voltage in an output transformer and thus failure in the core insulation and destruction of an output transformer. In the real world, brief open-circuit operation with no signal is often harmless with many amplifiers... but the risk of expensive damage is great enough that the "best practice" is simply: never operate a transformer coupled amplifier without a load on the output(s).

Any switch allowing the connection of the dummy load (ideally a purely resistive load of suitable power rating... just in case!) should be fine. That said, and, again just in case, I'd recommend instituting a practice such that the switch is never made with the amplifier powered on.

EDIT: In principle, I think a transformer coupled solid state amplifier might be subject to the same potential for damage, but the "B-plus" voltage on a transistor amp is usually much lower, so the risk might be much lower (I don't know). It's a fairly moot point since transformer coupled ss amps are vanishingly rare.

The modern McIntosh amplifiers that use "iron" in their output circuits employ autoformers (with electrical continuity between primary and secondary coils) and just I don't know what their behavior into no load is like. They're expensive enough that I'd suggest never operating one into an open circuit (no speaker connected), though!

 

[mirekti]

Don't overcomplicate things.

Get a tube preamp with switchable tube circuit.

Put it in upstream of your current Amp.

Could you post one as an example, please?
I am not sure what you mean with the switchable tube circuit.

 

[solderdude]

Tube power amplifiers behave very differently from SS amplifiers.
Tube amplifier besides adding harmonics and IM products generally also have a relatively high output resistance which, depending on the impedance of the speaker, might change tonality. This effect is very difficult to simulate as the output resistance also varies with frequency.

So when you want to hear 'tubes' you should buy an all tube power amplifier.
The result will differ from a tube pre versus SS pre-amp on a SS power amp as a good tube pre-amps are indistinguishable from a SS pre-amps in a level matched blind test.
Not so with certain tube power amps.

Best to only plug in the tube amp when you need it and otherwise plug the SS amp in (so inputs and outputs).

In the time the tube amp needs to warm up you can switch the cables.

 

[mhardy6647]

Could you post one as an example, please?
I am not sure what you mean with the switchable tube circuit.

Schiit had one, not sure if they still do(?).

Looks like they do -- Freya+ F

Schiit Audio: Audio Products Made in USA

www.schiit.com

EDIT: oops, I misread @solderdude's post, so I misrepresented it with a quote. Sorry!
I do agree with him, though, that there's usually a different difference between vacuum tube and ss preamps compared to that between vacuum tube and ss power amplifiers.

 

[mhardy6647]

Since it's sort of germane (if only very peripherally), and strictly FWIW...
I am using a solid state preamplifier and a vacuum tube power amplifier.
The former is fairly ASR-compliant.


(on the bottom of this short stack)

The latter... not so much.



Works for me, though.

EDIT: Note to self - dust that poor little amp before you take another photo of it, Marky!