Amplifier suggestion for college project

Greetings everyone,


I have been searching around for a medium power (b/w 30 and 50 W for 8 ohms), amplifier (or pre-amplifier + power amplifier), with a *fet output stage (if possible, using the IRF series), and also using "easy to find" components (although "easy" is pretty relative; btw, i'm from Brazil :)) to build as a college project.

Elliott's project #101 (http://sound.westhost.com/project101.htm) seems to be perfect, but component values are not listed :(... as this is a school project, i can't just buy the psb (unfortunately :p)

I have already found some schematics, but none seem to satisfy all (or at least most of the requirements above). I'd prefer a pcb-ready project, but this is not really a requirement...

Any special suggestions???
 

taj

diyAudio Member
2005-02-23 8:49 pm
Contact Elliot

You never know. Why not send an email to Rod Elliot to see if you can just purchase access to his private area where the assembly instructions are? Just because you cannot use the PCB doesn't necessarily mean you cannot build his circuit.

I don't know what Rod policy is in the regard, but it certainly doesn't hurt to ask. His PCB prices are dirt cheap, given the quality of his designs, so purchasing a PCB and not using it, might also be an option for you.

..TAJ
 

djk

R.I.P
2001-02-04 4:23 am
USA
I wouldn't even give you a grade for building a design that wasn't your own.

The ESP design is for Lateral MOS only.

The IRF type FETs are very difficult to run in class AB without bias problems.

Why don't you take a look at the PASS Citation 12 Mosfet?
 

paulb

Member
2001-06-01 4:53 pm
Calgary
djk said:
I wouldn't even give you a grade for building a design that wasn't your own.

Good thing you're not a teacher.
djk said:
The ESP design is for Lateral MOS only.

The IRF type FETs are very difficult to run in class AB without bias problems.

Why don't you take a look at the PASS Citation 12 Mosfet?
A link might be helpful.
http://www.passdiy.com/pdf/citation.pdf
 
djk said:
I wouldn't even give you a grade for building a design that wasn't your own.

The ESP design is for Lateral MOS only.

The IRF type FETs are very difficult to run in class AB without bias problems.

Why don't you take a look at the PASS Citation 12 Mosfet?

Actually, we are not supposed to design our own amplifier, as we don't have a good background on audio; this is not an end of course project; teacher's recomendations are: find a good, ready to use, design on the internet and build it
 
Thanks for all the suggestions and comments... I really liked the Citation 12 (actually, the Mosfet 12, at figure 8).

I've read the file, but couldn't find a power rating for the amplifier... Something like 70W @ 4 Ohms?? What's the effect of decreasing the DC supply voltage (the suggested 42V is a little too high for me; would 30-35 be a good value? i'd be happy with an output power ~50W). Also, are the IRF130, MPSL51, MPSL01 easy to find? or are they obsolete by now? If so, any clues on replacements?

Thanks
 

djk

R.I.P
2001-02-04 4:23 am
USA
"Good thing you're not a teacher."

Ames, Iowa 50011, (515) 294-4111. Published by: University Relations, [email protected]. Copyright © 1995-2004, Iowa State University of Science and Technology. All rights reserved.
Non-Discrimination Statement and Information Disclosures

John Kleitsch
A retirement reception for John Kleitsch, associate professor of electrical and computer engineering, will be held from 1:15 to 2:15 p.m. Wednesday, Aug. 18, in the Hughes auditorium, Reiman Gardens. A short program will begin around 1:30 p.m. Kleitsch has been with the department for 21 years after working for 25 years in industry.

"Actually, we are not supposed to design our own amplifier, as we don't have a good background on audio; this is not an end of course project; teacher's recomendations are: find a good, ready to use, design on the internet and build it"

If those are the requirements its OK. My father wouldn't let his students get off that easy. How much can you learn by duplicating?

"Hum, that's weird... I've tried to simulate this circuit in pspice, and it doesn't seem to work: no matter how is the input signal (i simulated using a sine wave), the output is constant @ -6V"

Gee, did you set the bias?

The bootstrap current source won't work properly if there is no current flowing in the output stage.

"I've read the file, but couldn't find a power rating for the amplifier... Something like 70W @ 4 Ohms?? What's the effect of decreasing the DC supply voltage (the suggested 42V is a little too high for me; would 30-35 be a good value? i'd be happy with an output power ~50W). Also, are the IRF130, MPSL51, MPSL01 easy to find? or are they obsolete by now? If so, any clues on replacements?"

MPSA06/A56 and IRFP240/250 would work fine on ±35V or so.

Power out on ±42V is about 50W at 8 ohms, ±35V would probably do 50W at 4 ohms.
 
djk said:


If those are the requirements its OK. My father wouldn't let his students get off that easy. How much can you learn by duplicating?


how much can you learn? quite a bit. im still very new to all this stuff, and ive built a few things and never designed anything. and at this point in my learning, i wouldnt have it any other way. chances are, you wont get it 100% right the first time and you will need to troubleshoot. ive learned a lot just from troubleshooting and re-working things, etc...

plus, you dont know the level of education we are talking about. you cant ask high school students to design their own amplifier from scratch (well, you can, but i dont know how worthwhile it would be).

i think its great. i wish i had something like that when i was in school. at the very least, you learn how to use a soldering iron, grounding schemes, wiring, isolating your power supply from main circuit, etc. there is still plenty to learn with a borrowed circuit.
 
Whatabout something like this : 60 W/8, 100 W/4, full power 1 Hz- 300 kHz, SR 100 V/microsec, SNR over 120 dB, THD 0.002 %, IMD bellow 0.002 %, IRF 540/9540
 

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djk said:
"Good thing you're not a teacher."

Ames, Iowa 50011, (515) 294-4111. Published by: University Relations, [email protected]. Copyright © 1995-2004, Iowa State University of Science and Technology. All rights reserved.
Non-Discrimination Statement and Information Disclosures

John Kleitsch
A retirement reception for John Kleitsch, associate professor of electrical and computer engineering, will be held from 1:15 to 2:15 p.m. Wednesday, Aug. 18, in the Hughes auditorium, Reiman Gardens. A short program will begin around 1:30 p.m. Kleitsch has been with the department for 21 years after working for 25 years in industry.

"Actually, we are not supposed to design our own amplifier, as we don't have a good background on audio; this is not an end of course project; teacher's recomendations are: find a good, ready to use, design on the internet and build it"

If those are the requirements its OK. My father wouldn't let his students get off that easy. How much can you learn by duplicating?

.

D,

now we know what the J and K stand for..


;)
 

djk

R.I.P
2001-02-04 4:23 am
USA
"you cant ask high school students to design "

Obvious that you did not read the whole thread.

"btw, i'm from Brazil ) to build as a college project"

The Pass A40 article walks you completely through the design, plus discusses frequency compensation too.

zlast:

The Leach is excellent, but it may be a bit hard to find some of the parts locally in Brazil. The suitable N-ch fets are generally cheap and easy to find, as are the MPSA06/A56 parts.