Re: Re: 3 xsistr amp
for the resistor values(or adjust resistors)the jfets vary unit to unit quite a bit
large leds have differant forward drop than small ones
paulb said:"Must select 2SK170s" - select them for what?
And how large does the green LED have to be? What happens if I put a small green LED there?
Anyway, nice little circuit.
for the resistor values(or adjust resistors)the jfets vary unit to unit quite a bit
large leds have differant forward drop than small ones
If you insist on 3055, try this link:
http://www.gmweb.btinternet.co.uk/
The old John Linsley Hood's 10W SE amp (1969) is a good solution, and proved to be a nice amp. There are a lot of discussions on it too. I still use it because I cannot find the time to build an Aleph. Definitely it's worth a try.
Regards
Asen
http://www.gmweb.btinternet.co.uk/
The old John Linsley Hood's 10W SE amp (1969) is a good solution, and proved to be a nice amp. There are a lot of discussions on it too. I still use it because I cannot find the time to build an Aleph. Definitely it's worth a try.
Regards
Asen
So you want to make something with 3055/2955s ?
http://www.diyaudio.com/forums/attachment.php?postid=37626
I used MPS A06/56 for Q5/6, made R12/14=51R, R15/16=150R, C3/4=0.01µF, D2/3=1N4148, and drove one end of R21 with an op-amp in the preamp. Only the four transistors listed above are needed. Built a couple of dozen about five years ago. They sound great for less than $2 per channel worth of semiconductors.
http://www.diyaudio.com/forums/attachment.php?postid=37626
I used MPS A06/56 for Q5/6, made R12/14=51R, R15/16=150R, C3/4=0.01µF, D2/3=1N4148, and drove one end of R21 with an op-amp in the preamp. Only the four transistors listed above are needed. Built a couple of dozen about five years ago. They sound great for less than $2 per channel worth of semiconductors.
"NICE! ....common emitter has some real attributes....
That reminds me of the "Little Tiger" (or something like that)"
Actually, the schematic in the link is an SWTPC. I just increased the voltage gain so I could run it straight off an op-amp running on +/- 12V and made a kick-butt computer sound system with it. The company that wanted this design was using the LM1875 in their current design, this blew it away.
That reminds me of the "Little Tiger" (or something like that)"
Actually, the schematic in the link is an SWTPC. I just increased the voltage gain so I could run it straight off an op-amp running on +/- 12V and made a kick-butt computer sound system with it. The company that wanted this design was using the LM1875 in their current design, this blew it away.
hitsware:
Yeah.....I meant "lateral"......lack of sleep. Or is it old age? Or both. Anyway...
Are you refering to the "GIANT" LEDs?
And yes.....all that SWTP stuff looked alike. Hard to keep them all straight after almost 30 years. But the concept of having an output stage with its own feedback loop inside of another made for stability problems.
Jocko
Yeah.....I meant "lateral"......lack of sleep. Or is it old age? Or both. Anyway...
Are you refering to the "GIANT" LEDs?
And yes.....all that SWTP stuff looked alike. Hard to keep them all straight after almost 30 years. But the concept of having an output stage with its own feedback loop inside of another made for stability problems.
Jocko
"But the concept of having an output stage with its own feedback loop inside of another made for stability problems."
Shhhh! not so loud, my 1978 McIntosh MC2120 might hear you. It runs with a voltage gain of five around the output stage. My Bryston 3B might hear you too, it runs with a voltage gain of two, just like the SWTPC.
Actually, the MC2120 will make foldback current limiting 'popping' sounds, when driven 6dB into clipping with the PowerGuard turned off and a 2 ohm load hooked to the 8 ohm tap of the output transformer.
Shhhh! not so loud, my 1978 McIntosh MC2120 might hear you. It runs with a voltage gain of five around the output stage. My Bryston 3B might hear you too, it runs with a voltage gain of two, just like the SWTPC.
Actually, the MC2120 will make foldback current limiting 'popping' sounds, when driven 6dB into clipping with the PowerGuard turned off and a 2 ohm load hooked to the 8 ohm tap of the output transformer.
Didn't say it wouldn't work......
It is probably not a good idea for someone without a lot of design experience and test equipment to try. How many of those SWTP amps came into your shop burned up? Probably several. Remember......it was billed as "indestructible".
Anyway....back to the LED issue......the green ones I have used for years are closer to 1.8 V. Never tried those huge ones.
Followers can oscillate, and quite easily, if loaded by capacitively.
It is probably not a good idea for someone without a lot of design experience and test equipment to try. How many of those SWTP amps came into your shop burned up? Probably several. Remember......it was billed as "indestructible".
Anyway....back to the LED issue......the green ones I have used for years are closer to 1.8 V. Never tried those huge ones.
Followers can oscillate, and quite easily, if loaded by capacitively.
Re: Didn't say it wouldn't work......
Not the huge.....More like medium....These may be rated 1.8 but measure 1.65
At the risk of sounding dumb....What's SWTP stand for?
We (Quintessence) built a 150W/C amp with a u709(biased class A) front end and bipolar (gain of 10) output stage. They were stable once they were running, but prone to self destruct at turn on........Really sounded nice though.....Something about the output off the collectors......Maybe the tranconductionness or ?
Jocko Homo said:
Not the huge.....More like medium....These may be rated 1.8 but measure 1.65
At the risk of sounding dumb....What's SWTP stand for?
We (Quintessence) built a 150W/C amp with a u709(biased class A) front end and bipolar (gain of 10) output stage. They were stable once they were running, but prone to self destruct at turn on........Really sounded nice though.....Something about the output off the collectors......Maybe the tranconductionness or ?
At what current are you measuring the voltage?
SWTP stood for Southwest Technical Products. They made a series of amps, in kit form, in the early 70s. Along with color organs and other chessey stuff from that era. They were located in San Antonio. It was headed up by a guy named Danile Meyer, who helped move solid-state amp designs into the modern era.
Not familiar with the amps you refer to, but was the output stage a stand-alone type (a la Threshold Stasis), or was there overall feedback that included the op-amp?
I've built lots of the stand-alone types, and they responded well to ferrite beads (of the right mix) feeding the base of the outputs.
Jocko
SWTP stood for Southwest Technical Products. They made a series of amps, in kit form, in the early 70s. Along with color organs and other chessey stuff from that era. They were located in San Antonio. It was headed up by a guy named Danile Meyer, who helped move solid-state amp designs into the modern era.
Not familiar with the amps you refer to, but was the output stage a stand-alone type (a la Threshold Stasis), or was there overall feedback that included the op-amp?
I've built lots of the stand-alone types, and they responded well to ferrite beads (of the right mix) feeding the base of the outputs.
Jocko
simplest amplifier
The question how to build the simplest possible amplifier using transistors intrigues me. I will report here my recent findings. My design criteria were:
* output power no real issue, around 1-5 Watts RMS is okay.
* input impedance above 33kOhm, sensitivity of around 1 Volts RMS or higher.
* two gain stages max.
* no fets or mosfets.
* class-A
* single-ended
* no global feed back
I came to this set after visiting Rudi Stor's website (just search at google by typing in his name, do not know the site name now). Here was the AR-3 head phone amp designed for simplicity and 8 ohms load. I built this amp for fun and it sounds very very good with whatever phones you like. I have several tube headamps for comparison (musical fidelity, Morgan Jones, Futterman). Actually, this is the first transistor amp that really intrigued me. The amp delivers around 50 mW RMS @ 8 Ohm. Just for fun I hooked up my Klipsch speakers: not bad at all.
Why not beef this amp using only 3 transistors (of which 2 2N3055's) to a few watts? I used around 1,25 Amps of idle current and an emittor resistor of 8,2 Ohms (50 Watts, becomes very hot of course) and a voltage of around 20-25 V DC.
The output power now is around 3/4 Watts RMS. This is the best transistor amp I ever heard in my house. It betters the Hiraga and the John Linsley Hood, my references in simple class A transistor amps. Actually it rivals the best tube amps.
Now I started the quest for even more power. The power is limited in the design by the input stage that can not give enough swing. I changed some resistor values to get more swing and ended with around 3 Watts RMS (but a lower input impedance). The magical sound was gone however. I fiddled around using several other input transistors that can deal with more current. I did not succeed in getting the sound as good as I wanted it.
After more than one month of listening, soldering, experimenting, I finished the result with one of the first trials, leaving me with around a 1 Watt of power.
If only this design could be brought to about 5 Watts of output ... Who wants to take over the fiddling from me, I think this is it given the design criteria...?
Rudy
The question how to build the simplest possible amplifier using transistors intrigues me. I will report here my recent findings. My design criteria were:
* output power no real issue, around 1-5 Watts RMS is okay.
* input impedance above 33kOhm, sensitivity of around 1 Volts RMS or higher.
* two gain stages max.
* no fets or mosfets.
* class-A
* single-ended
* no global feed back
I came to this set after visiting Rudi Stor's website (just search at google by typing in his name, do not know the site name now). Here was the AR-3 head phone amp designed for simplicity and 8 ohms load. I built this amp for fun and it sounds very very good with whatever phones you like. I have several tube headamps for comparison (musical fidelity, Morgan Jones, Futterman). Actually, this is the first transistor amp that really intrigued me. The amp delivers around 50 mW RMS @ 8 Ohm. Just for fun I hooked up my Klipsch speakers: not bad at all.
Why not beef this amp using only 3 transistors (of which 2 2N3055's) to a few watts? I used around 1,25 Amps of idle current and an emittor resistor of 8,2 Ohms (50 Watts, becomes very hot of course) and a voltage of around 20-25 V DC.
The output power now is around 3/4 Watts RMS. This is the best transistor amp I ever heard in my house. It betters the Hiraga and the John Linsley Hood, my references in simple class A transistor amps. Actually it rivals the best tube amps.
Now I started the quest for even more power. The power is limited in the design by the input stage that can not give enough swing. I changed some resistor values to get more swing and ended with around 3 Watts RMS (but a lower input impedance). The magical sound was gone however. I fiddled around using several other input transistors that can deal with more current. I did not succeed in getting the sound as good as I wanted it.
After more than one month of listening, soldering, experimenting, I finished the result with one of the first trials, leaving me with around a 1 Watt of power.
If only this design could be brought to about 5 Watts of output ... Who wants to take over the fiddling from me, I think this is it given the design criteria...?
Rudy
plastic tiger 2955/3055 and ne540
what might be simple enough would be "what i thing": was called the placic tiger amp from swtpc it was a signetice ne540 ic and mje 2955 and mje3055 ( plastic) transistors. no reason why the metal or other eqiovalents cannot be used.
it was not high power but was certainly low parts cound and simple.
I don't know if signetics and the ne540 still exist.
with 3 (only) active devices per channel what could be easier to build.
maybe a smarter idea would be to use an amp module and let the transistors regulate the power supply!
what might be simple enough would be "what i thing": was called the placic tiger amp from swtpc it was a signetice ne540 ic and mje 2955 and mje3055 ( plastic) transistors. no reason why the metal or other eqiovalents cannot be used.
it was not high power but was certainly low parts cound and simple.
I don't know if signetics and the ne540 still exist.
with 3 (only) active devices per channel what could be easier to build.
maybe a smarter idea would be to use an amp module and let the transistors regulate the power supply!
What about a simple 4 transistor amp???
Here's one I designed for you. 24V single supply, with a decent heatsink, shouldn't dissipate too much power, if you want different, just change the 22K resistors to higher values for higher voltages. You can also adjust the bias with the 5K POT.
Circuit should have a gain of around 20, with 10K input impedance.
Drivers feedback through the 470 ohm resistors, and they are connected to the emitters of the outputs instead of to each other for thermal feedback from the output and 0.5 ohm resistors.
Uses large feedback cap because of the low 22 ohm feedback resistors.
If you really wanna get creative, try bootstrapping it.
Here's one I designed for you. 24V single supply, with a decent heatsink, shouldn't dissipate too much power, if you want different, just change the 22K resistors to higher values for higher voltages. You can also adjust the bias with the 5K POT.
Circuit should have a gain of around 20, with 10K input impedance.
Drivers feedback through the 470 ohm resistors, and they are connected to the emitters of the outputs instead of to each other for thermal feedback from the output and 0.5 ohm resistors.
Uses large feedback cap because of the low 22 ohm feedback resistors.
If you really wanna get creative, try bootstrapping it.
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