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View Full Version : No speakers connected to solid state amp - any risk of harming the amp?

HeartfeltDawn
12-05-2009, 03:53 PM
If I turned a totally solid state amp on with no speakers connected, would there be any potential for damaging the amp this way?
bluesdoc
12-05-2009, 04:14 PM
No...
HeartfeltDawn
12-05-2009, 04:59 PM
Good. I was 99.9% sure but it's good to have things confirmed. Thank you!
cap'n'crunch
12-05-2009, 05:43 PM
They actually sound better that way.....

J/king.

Actually there's a lot of good sounding SS amps out there.
HeartfeltDawn
12-05-2009, 05:49 PM
They actually sound better that way.....

J/king.

Actually there's a lot of good sounding SS amps out there.


I'm hoping to score a JC-120 head in the next few days. It's just the ticket for early Smiths jangle.
cap'n'crunch
12-05-2009, 05:54 PM
I'm hoping to score a JC-120 head in the next few days. It's just the ticket for early Smiths jangle.

I had one of those. The 2 x 12 combo version. Sweet amp but, It was all I could do to move that thing around. I hate getting old.
circusinthesky
12-05-2009, 05:57 PM
Good. I was 99.9% sure but it's good to have things confirmed. Thank you!

Bluesdoc's opinion is worth .1%?
EADGBE
12-05-2009, 08:18 PM
That's one of the benefits of a solid state amp.
claytonbigsby
12-05-2009, 11:53 PM
I'm hoping to score a JC-120 head in the next few days. It's just the ticket for early Smiths jangle.
i'm just pleased there are some johnny marr fans out there. he was a monster back in the day. don't hear his name tossed around much anymore
rockon1
12-06-2009, 07:03 AM
There are I believe exceptions to no load being OK for SS but I doubt you will run across them in the SS guitar amp world. Bob
Jef Bardsley
12-06-2009, 08:46 AM
There are I believe exceptions to no load being OK for SS but I doubt you will run across them in the SS guitar amp world. Bob
An old McIntosh would be one - they had output transformers.
ekp
12-06-2009, 09:24 AM
If I turned a totally solid state amp on with no speakers connected, would there be any potential for damaging the amp this way?

This question is a bit more complex than a simple yes or no. In general solid state amps do not use an output transformer. Without an output transformer, the answer is no. However, the old PRS Harmonic Generator amp did have an output transfomer. But what saves it, are flyback catch diodes in the output FET's.

Tube amps generally do not use catch diodes in parallel with the output tubes, but some do. I have seen a series connection of three 1N4007's from ground to plate of output tubes with the cathode towards the plate.

Electronically, what happens is this. When playing dirty, the transformer flysback when the tubes cutoff. This flyback can produce very large voltages. Eventually, the insulation breaks down and the power supply is shorted to ground through the output transformer winding. Bad news for the output transformer. However, when the transformer flys back and the tube just cutting off has a very large plate voltage (say much greater than 1,000 volts) the plate of the other tube has a negative voltage. The diodes catch this flyback, or at least most of it. This substantially limits the flyback to double the power supply voltage except for the flyback of the substantially smaller leakage inductance between the two halves of the transformer primary.

And then some companies use shorting jacks to short out the output stage when the load is not connected. This technique works fine for tube ams because the tubes can withstand short term overloads far better than transistors -- with the notable exception of the PRS Harmonic Generaotr which could drive full power into a dead short and eventually turn itself off.

Have a great day, Eric