Transfo coupled line out question

[Colas LeGrippa]

Hi my friends,

Since aprox 10 years ago, I play my guitar into 2 or3 cascode amplifiers linked together via multiple line out's. The idea is to take the sound coming out of the audio tranny of one amp, lower it's voltage to  a line level with appropriate resistors and a volume pot,  inject it in the input of a second amplifier and so on. I was wondering if I could use a wall wart 120/12VAC transformers for that purpose, dividing the output by 10 (instead of using resistors) and thus reaching an acceptable line level...What do yo think?

Colas

[kagliostro]

Ciao Colas

I'm not sure but I think that a wall wart transformer hasn't an adequate bandwidth

May be a line transformer ???

something like this I mean

http://store.acradiosupplyinc.com/bogent725.aspx

Franco

[jjasilli]

Depends.  E.g., per the Power Formula: 50W > 8 Ohms = 20VAC / 10 = 2VAC which may swamp the input of the next amp.  So you would still need a pot, or some circuitry, to adjust the signal voltage to line-out level.  This could render the use of a tranny superfluous.  You may also need to address the issue of impedance bridging form the output of one device to the input of the next device. 


The probable lack of tonal quality of a wall wart might be OK, or a unique effect, for a guitar amp.

[Colas LeGrippa]

test done: wall wart excellent as line out !

[Colas LeGrippa]

More overtones, a bit crunchier, I'd have to perform more tests at higher volume, compare the cheapo transfo with Jensen one (120bucks or more huhhhhh). I find that it is more easy to achieve an infinite feedback with the wall wart compare to a ressistor/volume pot.


Colas

[shooter]

it is more easy to achieve an infinite feedback

with your ganged amps can you get this at lower power?, I build low watt'rs and one of the "complaints" is you need to be too close compared to >40Watters

[Colas LeGrippa]

...I must say that I use a tube driver ( my build, 12ax7 @ 12volts dc ) between the line ou tof the first amplifier and second amplifier. Yes, infinite feedback at surprisingly low volume!Pics to come

[Colas LeGrippa]

pics

[Colas LeGrippa]

The look is not terrible but it cost me nothing, I used what I could find in my messy drawers

[Colas LeGrippa]

of course I had to hook up a dummy load on the primary ( 8R, 50W )

Thanx for info.

Colas

[92Volts]

As long as you use the dummy load so the amp sees around 8 ohms overall (for safe/normal operation), you could pass the signal through resistors or a potentiometer-- the same way volume controls work inside amps.

The transformer you're using likely decreases high frequencies and increases distortion, though this might not be bad. Distortion and limited frequency response is what 90% of people like from their guitar amps.

[Colas LeGrippa]

Sometimes distortion is very harsh and bad. In my particular case, the tone is very interesting. I will build a line out using ultra linear taps from a hifi tranny, like the Hammond 1650N that I have in stock,  achieving the right voltage  with a voltage divider and pot, to see  if the tone is better than the cheapo chinese wall wart that I used. I'll post the results.


Muchas gracias amigos !!


Colas

[Colas LeGrippa]

I have made another lineout without resistors or pot, with a Fender Champ audio transformer.
Good tone but weaker than the chinese wall wart. Here are my voltage readings when plugged in the outputs of a build of mine,  one single 6550 (SE), volume at middle.

Wall wart in 8OHM :  1.2V
Wall wart in 16OHM: 1.5V
Wall wart in 32OHM: 1.5V

Champ in 8OHM: .18V
Champ in 16OHM: .43V
Champ in 32OHM: .6 V

In fact 8,16 and 32 are 4,8 and 16. I used a HUGE OT and I had to adjust the impedance accordingly.


Colas

[Colas LeGrippa]

Hola compadres !


After many tests with 4 different lineouts, my preferred one is the resistors one. The voltage divider is a 2k2 and a 200ohm, the last resistor paralleled with a 25K pot, for fine tuning,  everything hooked up after a 8ohm dummy load. The ultimate test would be to use a voltage divider as describe above, hooked up to a 600-600 Jensen audio transformer, but I presume  that would only serve to feed long run cables.


Colas

[jjasilli]