Guitar amplifier are often used in overheated stages that will
reduce the SOA accordingly , as an exemple i often saw 2SC2773
or equivalent used in 60W amps , theses are 150W TDP devices
and they proved reliable over decades provided they were cooled
efficently , now for higher output powers you ll have to use as
many pairs as required to stay in the 50-60W output power/pair.
Hitachi lateral fets are quite desirable devices for such usage
despite the lower output power if no additional supply is used
for the front end , in my experience theses are extremely rugged
devices that can survive much more abuse than bipolar , i guess
that they werent used due to higher costs , personaly i did use
three pairs for 64V rails and the amp is still fully rocking despite
being used even at 4R loads at full power for 20 years or so ,
theses were TO3 models , though.
It might come in handy to have so much transistor in one package, especially for class B or rail switched designs, but the usual 150-250W power output dies already take full advantage.of the TO-264 package. All in all it would have to be significantly cheaper than buying and mounting another transistor for it to be worth it, right?
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I dont know for other lfet , to this day i m only using Hitachi/renesas
but the semelab/alfet should do well assuming they re correctly
manufactured , agree that TO3 is a must for whom is concerned
by reliability , i personaly prefer theses package but unfortunately
they were purpotedly rendered obsolete for costs reduction purposes.
Danish company Gamut claim to have only one transitor to achieve 900 w into a 2 ohm load. This is of course bad marketing as there are at least two output devices. But even then there might not be the whole truth as they probably are multiple die MOS-Fets (some say intended for motor control)?
M250i Mono Power Amplifier - Gamut International
M250i Mono Power Amplifier - Gamut International
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With all this chit-chat about SOA and what chip to use or not use - has anyone given any thought to grounded-bridge topology designs ?
With such topology, you only need "half supply" across the output devices to gain the same power, because of the way the ground system is configured to the power supply.
Crown developed this in the early 70's to get around the SOA issues with transistors, to to achieve higher power outputs which are commercially viable nowadays.
Some links for your education are found here;>
http://www.crownaudio.com/media/pdf/amps/grbgpapr.pdf
http://www.hux.com.au/Soapbox Items...ervice School/Crown Service School Part 2.pdf
With such topology, you only need "half supply" across the output devices to gain the same power, because of the way the ground system is configured to the power supply.
Crown developed this in the early 70's to get around the SOA issues with transistors, to to achieve higher power outputs which are commercially viable nowadays.
Some links for your education are found here;>
http://www.crownaudio.com/media/pdf/amps/grbgpapr.pdf
http://www.hux.com.au/Soapbox Items...ervice School/Crown Service School Part 2.pdf
It's rather silly to consider blasting the outputs, especially bipolar outputs, into the rails in a guitar amp.
Consider using a Class D (or similar) dramatically over powered amp and producing your overdrive in the preamp or earlier than output circuits, and limiting the drive so that the max out is in the desired power range? Much smarter approach, imo.
_-_-
Consider using a Class D (or similar) dramatically over powered amp and producing your overdrive in the preamp or earlier than output circuits, and limiting the drive so that the max out is in the desired power range? Much smarter approach, imo.
_-_-
You'd be surprised. I built a hybrid guitar amp that mashes its output stage right into the rails when cranked up full. The prototype had 55V rails and didn't clip nearly as much, but I lowered them to 35V to reduce power dissipation and get away with a smaller PT.
It sounds fine. I've certainly never heard any complaints of heinous transistor sound at jam sessions and gigs. I just don't tell anyone it has transistors in it.
The power stage clipping in a typical guitar amp comes from running into grid current, and is pretty hard and nasty too.
I know it would not take long for my correction to appear. .Gee, I have not even got a sip of my first tea I did have to look it up and recall tuned and un-tuned class "C".
Can we make a new name,saturation/cutoff, Class "SC"
Bear, they shut me/us down on JC's thread. Why not just let it roll, it is lively, but not totally ridiculous. God all mighty $27.5K for phono pre-amp, and this should be celebrated. I think the real work is convincing someone to shell out that coin to listen to groove noise. Here I am contemplating spending $50 for a new stylus, to listen to my old records once and a while when I get in the mode.
I finally bought my first Hybrid SACD, Pink FLoyd, Dark Side 30th anniversary edition. Where elsse Amazon. I want to compare SACD against my old EMI LP & CD.
I thought those Semelab bjt parts are cheap, so worth a try, run them hard for a long while to see how well they hold up. Run them in clipping for an extended period of time and get the die up their. I contact their sales for some information = brick wall.
Rick
Can we make a new name,saturation/cutoff, Class "SC"
Bear, they shut me/us down on JC's thread. Why not just let it roll, it is lively, but not totally ridiculous. God all mighty $27.5K for phono pre-amp, and this should be celebrated. I think the real work is convincing someone to shell out that coin to listen to groove noise. Here I am contemplating spending $50 for a new stylus, to listen to my old records once and a while when I get in the mode.
I finally bought my first Hybrid SACD, Pink FLoyd, Dark Side 30th anniversary edition. Where elsse Amazon. I want to compare SACD against my old EMI LP & CD.
I thought those Semelab bjt parts are cheap, so worth a try, run them hard for a long while to see how well they hold up. Run them in clipping for an extended period of time and get the die up their. I contact their sales for some information = brick wall.
Rick
Put some deep orange LED's on the pcb, so when they look in they think they see a heater filament
I guess there is a fine line to a tube front end driving a bjt o/p. I think that if you adjust tube bias you could control what is clipping first the tube front-end or the bjt o/p. Sorta a cheap effects unit?
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Sure, but they can't tell because of the distortion stomp boxes you are running in front of the amp??
Class SC?? South Carolina operating conditions? So you want massive crossover distortion AND flat topping with nasty odd harmonics too? Whooo...
Ok, this is just silly. Have at it as you wish.
Oh, I always use and like amber LEDs...
I used them to illuminate the heatsinks of my SE Mosfet "It Thinks It's A Trode" amps! That was in the 90s... ancient times.
_-_-
Class SC?? South Carolina operating conditions? So you want massive crossover distortion AND flat topping with nasty odd harmonics too? Whooo...
Ok, this is just silly. Have at it as you wish.
Oh, I always use and like amber LEDs...
I used them to illuminate the heatsinks of my SE Mosfet "It Thinks It's A Trode" amps! That was in the 90s... ancient times.
_-_-
I don't run a distortion pedal, I use a clean boost to overdrive those BJTs more.
I used the MJL3281/1302 audio BJTs, which are pretty fast, and a circuit with no global feedback. This means it doesn't "hang up" in saturation for more than a microsecond or two.
I used the MJL3281/1302 audio BJTs, which are pretty fast, and a circuit with no global feedback. This means it doesn't "hang up" in saturation for more than a microsecond or two.
Yup. Most push-pull guitar amps will spontaneously bias themselves colder when they run into grid current. It is a form of blocking distortion that leads to crossover distortion. You pretty much described a cranked Marshall.
blocking usually forces the tubes to turn ON too much... the coupling caps "hang" with a less or non negative bias value...
Wondering how massive clipping is without any global feetback... hmmmm... maybe it is mo' bettah than I expect?
@rsavas, this is OT, but a quick comment - CDs brought lowered noise floor and increased dynamic range, which while still very flawed, obviated some of the problems that do exist with tape and LP. Interestingly enough LP has done a jut-jitsu type move and the upped maximum performance (read: data extraction) improved substantially over what it had been. That comment on my now old website is a historical observation, not a statement to be interpreted as being absolute or representative of current technology.
Wondering how massive clipping is without any global feetback... hmmmm... maybe it is mo' bettah than I expect?
@rsavas, this is OT, but a quick comment - CDs brought lowered noise floor and increased dynamic range, which while still very flawed, obviated some of the problems that do exist with tape and LP. Interestingly enough LP has done a jut-jitsu type move and the upped maximum performance (read: data extraction) improved substantially over what it had been. That comment on my now old website is a historical observation, not a statement to be interpreted as being absolute or representative of current technology.
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