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-   -   A 100-150 watt power amp using TIP41-142-147 transistors, how about (http://www.diyaudio.com/forums/solid-state/100618-100-150-watt-power-amp-using-tip41-142-147-transistors-how-about.html)

gaetan8888 24th April 2007 07:00 AM

A 100-150 watt power amp using TIP41-142-147 transistors, how about
 
Hello

What do you think off that 100-150 watt power amp ?

I found it, some times ago, on the Net.

Where, in that 100-150 watt power amp schematic, would you place a bias adjustment, to adjust it ?

And where would you place, in that same schematic, an dc offset adjustment ?

http://img240.imageshack.us/img240/8...150wampam3.jpg


Thank you very much

Gaetan

sixtek 24th April 2007 10:29 AM

Hi,

There are already many topic related to this design.

It's hard to believe that this amp can working fine, because it has many design fault.

My comments:

1., 1 pair TIP142/147's SOA (safe operating area, check datasheet) isn't enough for that rails and output power. I would use 2 pairs, with +/-40V idle rails for 100W-RMS on 4Ohm.

2., Boucherout-cell (serial RC - Zobel) missing on the output. 6,8Ohm-2W and 220nF foil cap in serial would be just perfect

3., something supply decoupling needed. 47uF ELKO with paralel 100nF foil would be OK.

4., where is Cdom? A Miller cap between VAS transistors C and B is needed. try 47pF

5., TIP41 is too slow for VAS function.

6., I would use a Vbe multiplier for bias assigment instead of the two silicon diodes.

7., change 10uF bootstrap cap to 47uF

8., gain is 40dB!!! that's too much... use 1K instead of the 220r feedback resistor.

9., change 10uF input cap to 2.2uF

10., change input resistor from 27k to 22k...

And there are more comments... But these were the most important...

Cheers,

east electronics 24th April 2007 10:45 AM

it s not working
 
2 Attachment(s)
except all these very correct things that sixtec told you this is not working .....

i spend a year working with that playing here and there i managed to get 175w off it


but its extremelly unstable

there is a picture of my version using far more advanced transistors from on semi mj 11015-16 but still ...at high rail voltage like 50+50 volts is trully unstable

plus the originall working at low voltage may be 40+40 volts is not stable at all as is

destroyer X 24th April 2007 11:09 AM

I have made it, and was dismounted as i did not have apreciated the sonics.
 
But i could fix the unstability problems.

Was dismounted as i do usually, to have parts to check other circuits..only 8 amplifiers had my respect and are assembled.

I have tried more than 4000 units.... they were in almost 36 groups of different schematics, with different circuitry.

Install a 18 picofarads capacitor in parallel with 22K resistance, the one at the feedback line....one side will go to the output line.

Install 470 to 680 picofarads capacitors into the output darlingtons, from colector to base.

Install a 47 picofarads capacitor into the TIP41, from base to colector.

It will work fine.....as i did that and worked for days without problems...the audio quality was the problem.

Suggested modifications were sent to Mr. Sakis...i have a copy of the mail sent to him.... he forgot that mail, or did not have received it.

regards,

Carlos

quasi 24th April 2007 01:52 PM

Just in case you didn't get the general consensus ....
 
Hi Gaetan

A good amplifier will include one or more of the following attributes;

- A stable constant current fed input stage.
- Well thought out gain stages (2nd and 3rd stages)
- Well thought out component choices for low noise, speed, reliability etc.
- A degree of symmetry so that the positive going signal is treated in a similar manner to the negative going signal.
- A clear and logically drawn schematic
- A clear and logically defined physical layout

This amplifier does not display any of these. I have seen this schematic around the internet for a long time now. Why anyone would bother to build it is beyond me. It would be cheap to make of course, but that saving will be lost very quickly when it fails and takes out more than you bargained for.

Have a look around DIY Audio, there are some excellent designs here that are not that much more complex but will perform to a good even excellent standard.

Cheers & Good Luck
Quasi

gaetan8888 24th April 2007 04:05 PM

Hi

Thank everybody for those answer, this amp are quite bad, I will not lost parts and times on that amp.

Gaetan

gaetan8888 24th April 2007 04:10 PM

Re: I have made it, and was dismounted as i did not have apreciated the sonics.
 
Quote:

Originally posted by destroyer X
But i could fix the unstability problems.

Was dismounted as i do usually, to have parts to check other circuits..only 8 amplifiers had my respect and are assembled.

I have tried more than 4000 units.... they were in almost 36 groups of different schematics, with different circuitry.

...
regards,

Carlos


Hi

You say that only 8 amplifiers had you respect and are assembled.

Please, can you tell me what are those amp where I can find those plans ?

Thank you

Gaetan

gaetan8888 24th April 2007 04:27 PM

Re: Just in case you didn't get the general consensus ....
 
Quote:

Originally posted by quasi
Hi Gaetan

...
Have a look around DIY Audio, there are some excellent designs here that are not that much more complex but will perform to a good even excellent standard.

Cheers & Good Luck
Quasi


Hi

Is there a files section here in DIY audio where to find all of those excellent designs ?

If not, how about creating a files section with the best amp, preamp, and other best design. Because searching all messages here in DIY audio, without knowing which one have those best design, can be veryyyy long.


Thank

Gaetan

gaetan8888 24th April 2007 04:41 PM

Hi

I should say a bit about me.

I'm not good in circuit design and analysing, I did somes amps and preamps kit, a 7294 amp and a lm3886 amp and some preamps. Those one chip amp are good but do have a bit lack of clarity in mid high and a lack of front-back space between voices and musical instruments.

I did compared them with a Sima and a Radford amps and a Dynaudio and a Spendor loudspeakers (there's friend systems).

Btw, I'm french speaking, so excuse my english.

Gaetan

sixtek 24th April 2007 06:45 PM

OFFtopic

Sakis, please be patient, I will answer!

ONtopic


gaetan8888,

I have a design called ST151. That's a relative simple, short-circuit protected universal (sub, pa, hifi, guitar, etc....) audio power amplifier with easly-available and cheap parts, running with +/-40V and produces 100W-RMS. Stable and sounds good. I have full documentation (schematic, PCB, etc...)
Please tell me if you are interested.

Maybe I'm going to open a new thread for ST151?


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