Got Bored Today - Page 2

Tim__x · 14th June 2006, 02:10 AM

Quote:

Originally posted by DoomPixie
the pot isnt a volume pot...
when it is set towards ground it will feed signal to ground aswell.. hopefully it will never be anywhere near ground though.. as i said, i have no way to simulate it and no speaker to test it so it is very likley that i will have to change the values and change the layout a bit to get it working right.. if it will work atall...
Owen

With such a simple circuit there's no need for a sim, at least not for DC bias calculations. Please excuse me as I make up component labels as I go along

Q1+2 should saturate to around 0.6v, small enough to ignore with such a rough circuit and a 15v supply.
Rc (500ohm) determines output impedance and should be adjusted to taste.
Rc/Re(40ohm) determines gain, the higher the higher the max swing but the lower the bias pot needs to be.

Neglecting base current, with Re=0 the pot will need to be at the 8% point giving you a 740ohm input impedance. All other cases are better.

P.S. I agree with Sawreyrw, this amp, though it has the excuse of simplicity, won't sound very good.

DoomPixie · 14th June 2006, 08:32 AM

I never for a minute thought it would sound good, i was just bored and decided i'd have a look and see if i could make an amp that would "work" useing a single transistor... and yes.. i know a darlington is technically two.. but i couldnt think of anything else to do with a TIP110..lol.. I sill fancy testing it out and seeing what happens

Owen

anatech · 14th June 2006, 12:36 PM

Hi Owen,

Quote:

i know a darlington is technically two.. but i couldnt think of anything else to do with a TIP110

Regulated power supply?

-Chris

DoomPixie · 14th June 2006, 02:23 PM

good thinking.. i have about 15 TIP110's and about 20 TIP126's that came in a big bundle of transistors i bought..

DoomPixie · 14th June 2006, 02:51 PM

i just tested the amp out.. it works.. kind off... i was useing passive computer speakers as the speakers.. and the headphone out on a cd player to test it..
it was actually louder to just plug the passive speakers into the headphone socket..lol.. but thats no fun is it?
if i turn the volume up on the cd player it started to distort and i had to adjust the pot on the amp so it was biased more towards the V+ and then if i turned the volume down on the cd player i had to tur the pot back down aswell otherwise it sounded like it was latching .. suddenly it would just buzz.. other than that it was working ok..
i may well play around with it some more later.. change the 500Ohm resistor for something smaller mabey.. see what happens.. it is currently made up of 2 x 1K 1 Watt in parralell so mabey i will try adding another 1K in paralell with them and see if it makes a differance to the performance..
Owen

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14th June 2006, 08:32 AM	#12
DoomPixie diyAudio Member Join Date: Jun 2005 Location: Aberystwyth / Llanelli (wales)	I never for a minute thought it would sound good, i was just bored and decided i'd have a look and see if i could make an amp that would "work" useing a single transistor... and yes.. i know a darlington is technically two.. but i couldnt think of anything else to do with a TIP110..lol.. I sill fancy testing it out and seeing what happens Owen

14th June 2006, 02:23 PM	#14
DoomPixie diyAudio Member Join Date: Jun 2005 Location: Aberystwyth / Llanelli (wales)	good thinking.. i have about 15 TIP110's and about 20 TIP126's that came in a big bundle of transistors i bought..

14th June 2006, 02:51 PM	#15
DoomPixie diyAudio Member Join Date: Jun 2005 Location: Aberystwyth / Llanelli (wales)	i just tested the amp out.. it works.. kind off... i was useing passive computer speakers as the speakers.. and the headphone out on a cd player to test it.. it was actually louder to just plug the passive speakers into the headphone socket..lol.. but thats no fun is it? if i turn the volume up on the cd player it started to distort and i had to adjust the pot on the amp so it was biased more towards the V+ and then if i turned the volume down on the cd player i had to tur the pot back down aswell otherwise it sounded like it was latching .. suddenly it would just buzz.. other than that it was working ok.. i may well play around with it some more later.. change the 500Ohm resistor for something smaller mabey.. see what happens.. it is currently made up of 2 x 1K 1 Watt in parralell so mabey i will try adding another 1K in paralell with them and see if it makes a differance to the performance.. Owen