soldano SLO

[bullpeters]

hey i know its not Hi Fi but it applies. The Soldano SLO has elevated parallel heaters. they are not close enough to cancel each other. It is a very high gain amplifier. it is also very quiet. So what gives?? google a picture, buss wire heaters.
i have googled this and there is a bunch of nonsense, so i come to the source: engineers please reply
i am building a low gain hi fi amp, why cant i use the same heater wiring that a hi gain, low noise guitar amp uses. it looks fantastic.
mick

 

[JonSnell Electronic]

As long as the heater wiring is twisted if AC, no problem as far as can see.

 

[bullpeters]

i worded that badly. the amplifier uses straight buss bar for the heater conections, they are Not twisted and altho they are parralell they are to far apart to suppress ripple. one straight run down the line of 9 pins and one straight line thru the 4, 5 pins. on a very high gain amplifier. basically everything they tell you not to, and it works just fine

 

[gingertube]

The elevated straight bus bars is also how Tektronix wired the heaters in their oscilloscope amplifier modules which were certainly designed for low noise.
Separation from signal wiring is the key.

Cheers,
Ian

 

[Enzo]

You didn't link a schematic. Are they running on straight AC, as opposed to DC heater supply? Did they take care to cross these heater bus lines at right angles with any signal wires?

If you are looking for absolutes, you won't find them. Ther are any number of ways to build quiet circuits. "Rules" about heater wiring are rules of thumb, not laws of nature. The rules talk about tendencies in a circuit, not guarantees.

 

[gingertube]

AC Heaters but some of them sitting on DC voltages to manage heater cathode max ratings. There are 4 or 5 heater circuits in the typical Textronix Oscilloscope.
Got one at home 1/2 pulled apart (and all tubes ratted fro other things), will try to get a picture.
Cheers,
Ian

 

[JMFahey]

google a picture,

You are asking, so you should provide schematic and pictures.

 

[gingertube]

Picture of Tektronix Heaters. Bus wires below, signal wiring on top, this is a high voltage regulator section but was the clearest place to photograph with the phone camera.
Cheers,
Ian

 

[AquaTarkus]

The SLO 100 is superb example of a hand-wired amp. You can find plenty of got shots online. And it has a totally insane amount of gain in the preamp, yet is quiet as far as hum goes. The Allman Brothers used to play through these ampd BTW.

The heater wiring is indeed parallel buss bars, carrying elevated AC. Apparently, they are close enough together to cancel their radiated magnetic fields at a reasonable distance away.

So here's the deal. A lot of people get too deep into theoretical details, including how exactly any twisting should be done, etc. This amplifier is living proof, that we sometimes overthink this stuff. I've also built experimental amps that just used zip cord for the heater wiring, without any kind of hum issues.




Sent from my phone. Please excuse any typpos.