Amp nerds...what wrong with this?

spark240

Got this TE combo with no speakers in it, tried with a external cab seems fine, stuck in 2 speakers known to work and get this weird high pitch noise , you can hear it as I turn up the volume, its a bit like interference, but the fact that an external cab is fine suggest its a speaker issue ?  

No input connected at this point

https://www.flickr.com/gp/149260669@N02/0G611o

ICBM

Very odd. I don't know what's causing that, or why it doesn't do it through the external cab. The only thing I can think of is that the external speakers don't have enough top-end response to hear it.

But - those speakers don't look like they're high enough rated for the amp anyway. What are they? They look like old Celestions...

mr-mac

I assume the Ohm of drivers and way they are wired up are presenting same load amp is expecting.

Danny1969

It's possible there's oscillation getting through to the power amp either from one of the opamps in the pre amp or the power amp it's self. open Snubber cap \  circuit not functioning maybe ?  and your hearing lower harmonics of that oscillation but they aren't noticeable in the external cab due to lower frequency response  

spark240

ICBM said:

Very odd. I don't know what's causing that, or why it doesn't do it through the external cab. The only thing I can think of is that the external speakers don't have enough top-end response to hear it.

But - those speakers don't look like they're high enough rated for the amp anyway. What are they? They look like old Celestions...

The speakers are Goodmans 12p Audiom Power range 

Fundamental resonance 85Hz 
Nominal power handling 50 watts
1" 3/4 voice coil
Efficiency 96dB @ 1 metre 1. 6 W

Yes probably underrated wattage, would that cause that sound?

ICBM

spark240 said:

The speakers are Goodmans 12p Audiom Power range 

Fundamental resonance 85Hz 
Nominal power handling 50 watts
1" 3/4 voice coil
Efficiency 96dB @ 1 metre 1. 6 W

Yes probably underrated wattage, would that cause that sound?

No, but you will very likely blow them. Goodmans speakers are notoriously under-rated for power handling, I wouldn't even run those with a 50W amp for *both* of them if you can avoid it. They're more like a 20-25W speaker in reality.

spark240

Mm...I have some celestion V30 16Ohm...maybe try those?

Danny1969

spark240 said:

Mm...I have some celestion V30 16Ohm...maybe try those?

I would fix the amp first otherwise you could blow some nice speakers regardless of the volume you set.