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Old 2nd November 2016, 05:33 PM   #1
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Question 2n3055 mj2955 amplifier "kit"

Hello, i'm seeking for a way to apply a few of these chips i have in the scrap box, and was wondering of a nice amplifier, maybe around 100W. I will gladly sacrifice power to have better quality, but with these parts, i know there are limitations

Seen a few around the internet, but failed to get the complete project, that is:

Schematic, pcb, parts list, layout and some sort of alignment indications if necessary.

Would be appreciate some pointers to a nice proven project.

Best regards,

JC
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Old 2nd November 2016, 11:52 PM   #2
djk is offline djk
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More than one pair will be needed to get 100W, and the 60V maximum voltage will make it tough to even get 100W into 4Ω.

Perhaps you might build a bridge amp for 8Ω?
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Old 3rd November 2016, 12:10 AM   #3
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thank you for your input djk

I found this:
Audio amplifier with 2n3005

later on i found this:

400W project

pcb

I really don't want to go any way above 100W because that's a lot of noise for my ears...
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Old 3rd November 2016, 04:06 AM   #4
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100W/2N3055 seems to be an evergreen formula for amplifiers that has been around more than 40 years. A single pair of 2N3055s will produce 40W into 8R and more into 4R but that's actually plenty of noise - more than enough in most homes.

This is a favourite design that dates back to around 1980 - I know of 4 stereo builds still working too!
Attached Images
File Type: png Elektor 40W '83 schem.PNG (39.3 KB, 278 views)
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Old 3rd November 2016, 06:52 AM   #5
Boden is online now Boden  Netherlands
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Hello Ian,

You just provided the schematics of my all time favorite Elektor design. I built it almost entirely with components from my scrapbox. The whole thing did ot cost me more than a handful of (now) Euro's. The design came without a PCB, but that was quite simple making a layout that roughly followed the schematic.

One of the very few amps I built that performed flawlessly right from the start.

A very very nice design that rivalled my Crimson 608 a somewhat comparable design with the famous Quad Triples as an output stage.

Around 1981 a design with complementary triple output stages (305/2955) was published in WW by a certain gentlemen named B. Cody, if memory serves me well..
Both the Elektor and WW designs are highly recommended for building.

BTWo not let the "a 100 mHz output device is necessary for hifi" guys scare you off.

Good Luck,

Eelco
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Old 3rd November 2016, 11:06 AM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by anvilpt View Post
.................maybe around 100W. .................
Quote:
Originally Posted by djk View Post
More than one pair will be needed to get 100W, and the 60V maximum voltage will make it tough to even get 100W into 4Ω.................
Quote:
Originally Posted by Ian Finch View Post
100W/2N3055 ............. A single pair of 2N3055s will produce 40W into 8R ................
A single pair of 100W BJT output devices will get you a reliable 40W amplifier that can tolerate severe reactance speakers.
2pr gets you upto 80W and 3pair gets upto 120W
These higher power versions will be limited by the maximum supply rail voltage.
A 100Vce0 device should not be used on supply rails exceeding 49Vdc
If you want to use a 35-0-35Vac transformer then I recommend you use >120Vce0 transistors. But do check the temperature de-rated SOA at the supply rail voltage. Some are terrible when operated at half max Vce0.
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Old 3rd November 2016, 08:58 PM   #7
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Quote:
Originally Posted by Boden View Post
......You just provided the schematics of my all time favorite Elektor design....Eelco
Good to know someone else likes it too, for a design that seemed unpromising so long ago. It's actually the Crescendo design adapted to use craptanium BJT output transistors. I think though, it has much better performance and SQ than typical EF2 2N3055/MJ2955 complementary designs, which is why I suggest it in preference.

There's a larger image of the article here: Audio amplifier with 2n3005
PDF (french text) here: https://docs.google.com/file/d/0BwTS...tZSHc1b2s/edit
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Old 3rd November 2016, 09:07 PM   #8
djk is offline djk
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"A 100Vce0 device should not be used on supply rails exceeding 49Vdc"

Except the 2N3055 is only rated at 60V

http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF

I did a commercial design in 1997 using the 3055/2955 pair on 30VDC, it sounded fabulous. I bought the outputs from Allied for about $0.59 each, and used $0.08 driver transistors (MPSA06/A56), with the NE5532 for the front end.

*******************

" Yes, in 1997 DJK designed several products for the Minnesota company I was working for then.

He designed a 40 watt amplifier with a really novel circuit design that was the size of a 3.5" computer hard disc drive.

The sound quality was simply amazing ! ! ! ! !

Resolution, sound stage size, timber and dynamic punch were very noticeably superior to reference amplifiers (with Musical Concepts mods) ADCOM 555, B&K ST-202 and Parasound HCA-1500A designed by John Curl.

No, 40 watts does not play as loud as 100 or 200 watt amps.....however the dynamic contrast and resolution was superior !

To this day it is still one of the finest sound quality amplifiers that I have ever heard.

Sadly, the Minnesota company closed before DJK's design made it into mass production."
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Last edited by djk; 3rd November 2016 at 09:15 PM.
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Old 3rd November 2016, 09:26 PM   #9
selim is offline selim  Turkey
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Hi anvilpt,

If you are interested in the Elektor amplifier mentioned in your first find, I still
have quite few PCB's available.just mail me at selim_ardali at yahoo dot com
with your address and I'll send you some. This offer is open to any fellow DIY'er
in this forum.This amp is a very fine example of getting stellar sound from old
3055 / 2955 pairs. There are quite few friends in this forum building this amp
with great satisfaction. I think it is well worth a try.

Best Regards

Selim
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Old 3rd November 2016, 09:41 PM   #10
djk is offline djk
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The Elektor amplifier looks good, and I would add some emitter degeneration resistors to the diff pairs.

(an easy mod similar to the Leach amplifier design)
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