help understanding amplifier schematic

[audioguru]

looks like they used online translator... probably they got borred doing it by themselves (?)

They no speaky zee English.

 

[Nigel Goodwin]

@Nigel i was hopping it will be useful both for listening to music decent enough and as a small guitar amp... (i don't mind the output power at all...)

A guitar amp, and an amp for listening to music are completely different things, people like to use valve amps for guitar for the poor quality, it's what they want.

If I get time tonight I'll have a look for an old book I have, which show how to build decent quality valve amps - but they aren't really suitable for guitar.

Why not just build a better quality transistor or IC amp?.

 

[whiz115]

If I get time tonight I'll have a look for an old book I have, which show how to build decent quality valve amps - but they aren't really suitable for guitar.

Why not just build a better quality transistor or IC amp?.

nigel i have many chip amps, a tube amp is something different and more interesting if i manage to finish it.

well... i don't know... if you want check your books... thanks!
i was equaly interested using it for guitar and for listening music...but
i understand it's not possible.

 

[Nigel Goodwin]

nigel i have many chip amps, a tube amp is something different and more interesting if i manage to finish it.

well... i don't know... if you want check your books... thanks!
i was equaly interested using it for guitar and for listening music...but
i understand it's not possible.

It's certainly possible, but it won't be optimum for both.

Here's a circuit for the Mullard 3-3, it's from 1955

 

[Nigel Goodwin]

Here's another design, this one uses two triodes instead fo the pentode preamp.

Both circuits are from a book published in 1958 - I bought it at a secondhand book shop a good few years ago now.

 

[whiz115]

can i replace the tubes with the ones i have?

atleast for the first design, looks possible to me...

 

[audioguru]

The tubes amplifier schematics posted by Nigel have negative feedeback for improved sound. Then the transfoemer must be very high quality and have a low phase shift.

 

[whiz115]

audioguru can you tell me what makes an output transformer good?
i only know that the winding must be tight and not crossing the windings...

if you tell me everything i need to know i might have the chance to get
some good output transformers because they aren't ready yet.

 

[crutschow]

Here's another design, this one uses two triodes instead fo the pentode preamp.

Looks like one dual triode for input gain and tone control, and a tetrode output.

 

[audioguru]

I have never made an audio output transformer for an old tubes amplifier so I don't know what the manufacturer does to make it wide-band with a low phase shift.

 

[crutschow]

Google "audio transformer design" for many references.

 

[whiz115]

about the power supply are there any suggestions?

i'm going to do full wave rectification with 1N4007 a couple of
capacitors 150uF/400V and 220nF/400V maybe an inductor and i think i need a load resistor because the transformer outputs 220VAC...

about the heater the transformer outputs 6.3V/3A and i think i'll leave it as is and if the hum is high we will see...

 

[Nigel Goodwin]

about the heater the transformer outputs 6.3V/3A and i think i'll leave it as is and if the hum is high we will see...

Run the heater wiring as twisted pair, and route it away from any sensitive points (like the inputs).

 

[whiz115]

ok... but only the heaters? i was thinking to do it for every cable...
what about the other thing, do you think i need load?

 

[Nigel Goodwin]

ok... but only the heaters? i was thinking to do it for every cable...

Only the heaters cables feed AC.

what about the other thing, do you think i need load?

You should NEVER run a valve amp without a load.

 

[whiz115]

Only the heaters cables feed AC.



You should NEVER run a valve amp without a load.

what about the input? i thought every cable inside there can catch noise...

when i'm saying "load" i mean a resistor in parallel after the rectification to dissipate some power...
the power supply is 220VAC/250mA



probably you mean that i must always have my speakers connected right?! if yes what's going to happen if i forget it? can i blow off the tubes or only the output transformers?

 

[whiz115]

Nigel other than the schematics you send me i also found this one...
is there anything interesting? looks very similar to mine is it better?

**broken link removed**

 

[audioguru]

The Tube Power Amplifier EL84 was used in cheap AM radios in 1952. When I was a kid I remember the radio that was nice and warm but it sounded like hell.

 

[Nigel Goodwin]

what about the input? i thought every cable inside there can catch noise...

No, only sensitive parts - the input would normally be a screened cable.

when i'm saying "load" i mean a resistor in parallel after the rectification to dissipate some power...
the power supply is 220VAC/250mA

Not normally required.

probably you mean that i must always have my speakers connected right?! if yes what's going to happen if i forget it? can i blow off the tubes or only the output transformers?

It's the transformer mainly, although it can kill the output valve.

 

[Nigel Goodwin]

Nigel other than the schematics you send me i also found this one...
is there anything interesting? looks very similar to mine is it better?

**broken link removed**

It's another guitar type amp, with no feedback - notice it even has a line output.