Many bass amps are exactly like that with a switchable horn..in that case you use the horn to save the driver whilst playing slap bass. The bass driver does not like the sharp transients and you'll cook the voicecoil.
Is this a new amp? If so, back to dealer.
If you get a pop turning standby on and off it suggests the rectifier and power tubes are working. If turning the volume knob up does not result in any hum/increase plus it's both channels it indicates the phase inverter tube may be dead.
I had a 70 watt Pro Reverb which sounded and weighed like a Twin Reverb - pulling the boost created a slight volume hike and a transistor-y trebly unpleasant sound lacking mids and bass. After I tried it once, I never did it again. I never played with the tone controls as I didn't ever conceive...
If the heaters are far away from the audio bits why not. Old Fenders like Champs have one leg of the Noval heaters through the chassis, the other was a straight wire. The two I had were dead silent. Ditto Tweed amps.
Part of the Topboost magic is the cut control. You can run the Topboost treble very high and use the cut control to add a nice compression. It's wired backwards to a standard tone control -
as you turn it up more it cuts more treble.
Topboost channels have plenty of bass. You can get farty...
Because the crossover effectively stops the low impedance speaker being 'seen' at above cutoff frequency and vice versa.
Although there's no inductor knocking the highs out of the low, speaker impedance varies enormously by frequency - at high frequency the low woofer is basically out of the...
Wow weird one Wally. I think like Jon says there's going to be some sort of weird cross connection. Unless it's some sort of arc happening - that's possible with a broken socket with some sort of conductive glue I'd guess.
Do you have a proper grounding plate or scheme? The originals have a brass plate under the pots soldered by braid to the chassis. Do you have a ground on the pot backs?
Could be as simple as a ground issue on the pots.
Hence consider your amp to be like a small environment with radiating components. All your transformers and coils put out EMF radiation.
Even resistors put out a sizzle
And if lead dress is such an important factor, why are PCB amps looked down on? You have perfect (if the designer knows what...
To get a negative bias voltage is no biggy.
On a Princeton they just use one leg of the HV sec and use a big 2 watt resistor to pull it down from 100s of volts to 40ish then into a backwards diode. Couple of ripple caps to smooth it.
You're right - I was thinking of the 12L6s I had in the wardrobe find 74 Pro Reverb I had recently.
The Oxfords which I presume were 12T6s in my 70 watt Pro from 20-25 years back were not terrible but to my memory I wouldn't have sought them out however. Very bright but that may have been the amp
Any era T6s do not sound good with anything more than mild overdrive. They fuzz out badly. They can sound nice clean or with amp breakup but do not handle anything stronger than Tubescreamer drive. They sound sweet for moderate tones, or the 74s I had did in a transition Pro Reverb.