An actual hifi question

HiFi
1

A friend has asked if he can bring his Tripath amp so he can hear it driving my Tannoys.

I’ve been warned to never power up a valve amp without speakers connected or bad things can happen apparently.

My Luxman valve integrated has Pre-amp Out and Main In rca sockets on the back. There’s also a switch on the front panel to separate the preamp section from the power amp section. (Edit: There’s also a knob to select speaker set A or B or turn off the speaker output.)

I’m thinking it would be 100% safe to use the Luxman in separated pre-amp mode (speaker output knob set to off) into the Tripath with my Tannoys connected to the Tripath i.e. no speakers attached to the Luxman but I don’t want to make any potentially disastrous assumptions hence the question.

Thanks in advance for your expertise.

2

That arrangement should be fine. What valve amps generally don’t like is amplifying a signal with no load (speakers or resistors) attached. But if you can take a ‘pre-out’ to the tri-path and have the valve power amp stage disconnected there should be no issues.

3 Likes
3

Thanks Guy, that’s reassuring. Just to clarify: by using the pre-amp outs together with the “Separate” switch, the power amp section receives no input signal and therefore does not try and operate, meaning it is totally safe to not have any load attached to the amp. Is that correct?

4

Yes. It’s when the output stage gets a signal and tries to amplify that voltage with nothing loading it down, that’s when problems occur as the voltages swinging around in the primary of the transformer get quite large when there’s no load on the secondary (speaker) side.

1 Like
5

That’s crystal clear. Thanks very much Guy. I’m very grateful to you.

6

I’m with Guy on this one (on pretty much every one, come to think of it …).

The only thing I would mention is that if the no-input power amp is prone to loud switch-off clicks (i.e. mains power switch-off) then there is a very remote possibility that one of those could generate a voltage spike at an unloaded output. The safest fix is to plug a couple of spare speakers into the power amp. Pretty much anything would do. In fact valve amps tend to be safer with the output terminals shorted together than with them left unconnected. This is the exact opposite of solid-state amps of course. Some SS amps are protected against output shorts but plenty aren’t and the consequences of an output short can be catastrophic (a great deal of blown silicon).

2 Likes