All Tube Stereo power amplifier

[Dusk]

Hi
I would want to build a all-tube stereo power amplifier 50watts per-side. the problem is how can i use only one channel and have the other channel switched off....is there a circuit that will do this......i have been told that you can't have a tube amplifier on with no load on the output......i only have one speaker cab now.
please help....THANKS DUSK

 

[lineup]

1.
I would want to build a all-tube stereo power amplifier 50watts per-side.

2.
the problem is
how can i use only one channel and have the other channel switched off
....is there a circuit that will do this......

3.
i have been told that you can't have a tube amplifier on with no load on the output
......i only have one speaker cab now.

1.
I say you could try to build an easier project.
- all tubes
- two channel, stereo power
- 50 RMS Watt per channel ( into what? 4 or 8 Ohms )
.... this is TOO MUCH, even for most any very experienced tube builders
But is not impossible, almost nothing is.

2.
You should not be needing circuit for this.
A simple On/Off switch would do nice.

3.
Maybe there is some situation / some amplifier, where you need to have load connected all the time.
Load may be used as a part of the circuit.
But amplifiers shouldnt be built that way.
In in 95% they are, and you can connect / disconnect load
and circuit will work nice in both situations.

Now, before connect / disconnect we should always
turn amplifier Power Off.
But this is another thing.




TO3 Active PowerResistor pictures!

😎 lineup 😎 the clever man
... got circuits you dont have, you cant figure out
and some poor never ever will get to know ...


.

 

[Dusk]

All Tube Stereo Power Amplifier

Hi LINEUP
Iam sorry i should have mention that both 50watt channel will be fed from the same power supply as well as sharing the same heater supply. So you mean that all i need is a switch to turn off one channel's power while iam using the other? It seem so simple....iam no amp GURU.......JUST A GUITAR PLAYER....DUSK
the amplifiers will feed 4and8 ohm speaker load.

 

[Bare]

hendrix land? yer in Coquitlam BC ?

 

[Klimon]

Hi Dusk,

It seems to be the consensus that most tube amps don't mind when they are powered up without a load; the decware zen for one gets it's output trafo's burned down in this situation -- I never found an explanation why some amps always need a load and some don't.

A simple solution - if you want to be safe - is to use a 4/6/8 ohms power resistor, mounted on a heatsink or metal strip to increase power dissipation. Just install a switch between the speaker output and the dummy load.

edit: if you're running both channels from one power supply you can't disconnect one signal channel; the voltages on the other channel will rise dramatically and probably exceed the components max. specs and destroy a few components.

Best,

Simon

 

[Dusk]

50watt tube stereo power amplifier

Hi Klimon
This sound like what i am looking for ......many thanks for the info
...DUSK
oh, Bare......not quite.....peace.....DUSK.....crosstown traffic......ha,ha....i can see you had your fun...................yea.

 

[rdf]

Hi Dusk,
It seems to be the consensus that most tube amps don't mind when they are powered up without a load; the decware zen for one gets it's output trafo's burned down in this situation -- I never found an explanation why some amps always need a load and some don't.
Simon

Hi Simon. Does the Zen fry without an iput signal? Sounds like oscillation to me if so. There's a good thread on the consequences of running a tube amp without a load somewhere on this site. Essentially, as I understand it, without a secondary load the voltage across the OPT primary skyrockets and can exceed the wire's insulation breakdown.

 

[lineup]

...as I understand it, without a secondary load the voltage across the OPT primary skyrockets
and can exceed the wire's insulation breakdown.

yes,
the load on a secondary winding or the absence of load
will effect the impedance on primary winding

the suggested 'dummy load', 4 / 8 Ohm, conntrolled by a 2-way switch
is a suitable and good solution
if amplifier will need this

99% of solid state transistor output amplifier, will not need this.
A major difference between Valve amps with OPT, output transformer,
and transistor based power amps with 'normal' transformerless output.


lineup - prefer OTL, tube amps without output trafo - but here we are talking only preamps

 

[lndm]

Re: Re: All Tube Stereo power amplifier

1.
I say you could try to build an easier project.
- all tubes
- two channel, stereo power
- 50 RMS Watt per channel ( into what? 4 or 8 Ohms )
.... this is TOO MUCH, even for most any very experienced tube builders

The first serious all valve power amplifier I built was just that. Go for it I say, if you feel you want to 🙂


I often switch amps on the bench without a load. I know in theory I shouldn't. I was taught that this was only a problem when a signal was present, and it only affects some amps. There are always oscillations though, sometimes. I haven't had a problem with it.

Though an 8 ohm dummy load would be ideal, I would use something a little higher if there was signal present, to save energy and ease up on the power supply.

Of course, if the inactive channel has its input shorted, you can use a moderately powered 8 ohm resistor as it won't have anything significant to dissipate.

 

[lineup]

1.
I say you could try to build an easier project.
- all tubes
- two channel, stereo power
- 50 RMS Watt per channel ( into what? 4 or 8 Ohms )
.... this is TOO MUCH, even for most any very experienced tube builders
But is not impossible, almost nothing is.

one line was missing, for a correct quotation
🙂
of lineup

 

[lndm]

one line was missing, for a correct quotation
🙂
of lineup [/B]

OK, but even still 🙂

 

[Klimon]

Hi Simon. Does the Zen fry without an iput signal?

No, without a load