120W amplifier

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_world_

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Joined 2007
#1
I started this project 10 years ago (the first one on the top of the page):

Ñõåìè íà íèñêî÷åñòîòíè óñèëâàòåëè 120W, 200W. Åêâàëàéçåð. Í×Ó, êîéòî ñå çàõðàíâà îò àêóìóëàòîðè 12V/24V. Äðóãè ïîäîáíè ñõåìè è óñòðîéñòâà.

I am curious now is there anybody who made this circuit before. And if not can you provide me with some information is there are any mistakes in the design?
I already made the PCBs and the amplifier was working only for tests measurements. Still I didn`t test it completed with good boxes.
How is this schematic looking into your eyes? Is it worth it to be finished?
Regards
 
#3
The driver transístors can be BD139/140, MJE340/350, MJE15032/MJE15033 or MJE15030/MJE15031, the rest of the transistors in the frontend can be 2N3904/3906, 2N5551/2N5401 or similar depending on the rail voltages.

The output transistors i recommend MJL4281A and MJL4302A as they have a nice big fat SOA and can take alot of abuse.

The original circuit uses darlington outputs which is why there are no drivers drawn out.

I illustrate that here: http://i.imgur.com/AjAWI.png
 
#8
_world_ said:
I started this project 10 years ago (the first one on the top of the page):

Ñõåìè íà íèñêî÷åñòîòíè óñèëâàòåëè 120W, 200W. Åêâàëàéçåð. Í×Ó, êîéòî ñå çàõðàíâà îò àêóìóëàòîðè 12V/24V. Äðóãè ïîäîáíè ñõåìè è óñòðîéñòâà.

I am curious now is there anybody who made this circuit before. And if not can you provide me with some information is there are any mistakes in the design?
I already made the PCBs and the amplifier was working only for tests measurements. Still I didn`t test it completed with good boxes.
How is this schematic looking into your eyes? Is it worth it to be finished?
Regards
Click to expand...
The audio amplifer diagram is much like that of PSS Audio audio amplifiers. The biggest practical disadvantage of the that audio amplifier diagram is very hard to find darlington transistors with identical hFE. On the other hand, in the 21st century, does not justify implementation an audio amplifier with bootstrap capacitor. However, in certain situations, under hobbies, such audio diagram can be made, but not spectacular results.
 
#15
_world_ said:
What`s the pros and cons about changing the original darlington BDX 66B/67B with MJL4302A?

Thanks allot for the advises given 🙂
Click to expand...

Pros are being able to find the devices and being able to better match Hfe, also the Vbe multiplier will not be a Darlington. Temp coefficient is different.
Cons are more parts since you will have to add an extra current gain stage.

It may be a little advanced for you but Dr Hawksford devised a way to 'linearize' the Hfe of Darlington output transistors. The paper can be found easily by searching HEC. (Hawksford Error Correction)
 
#16
Tekko said:
.....the rest of the transistors in the frontend can be 2N3904/3906, 2N5551/2N5401 or similar depending on the rail voltages.....
Click to expand...
You might have pointed out that the rail voltages in the OP schematic are 40V (more than a bit higher than your 18V rails). With the exception that T1,2 should be B and not A grade, there's nothing wrong with the original parts either but don't try 2N3904/6 in this front end.

I suggest keeping the supply voltage as shown and don't use a large transformer or there may be trouble with parts ratings. There are some subtle features to old designs that many are unaware of as they super-size power supplies, caps and wiring. It's not a good idea when parts are run at their max. Vceo and can't withstand much current unless the rails sag. Be warned.

For the quality of sound output, you can use whatever large, modern plastic TO264 audio power output transistors you can find. At these rail voltages, that includes 2SC5200/A1943, Fairchild or ST micro equivalents, On Semi MJL21193/4 and also quite a number of various voltage rating and case style types in the MJL3281/1302 fqmily, including those suggested. Just use a decent heatsink of ~1 degC/Watt per channel, the appropriate insulator washer and bush and it should be fine - better than the original darlington version.
 
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#19
HEI TEKKO .. willing to help but always running too fast ...

word :
each and every amplifier made with different semis will have his own sonic signature good or bad one have to listen to decide if good or not

obviously simple things tend to sound always better

then again beginner or not, wise thing to is to work on a more updated circuit , keep away from any circuit that work with darlingtons , and of course choose a circuit that has proper support in the forum

your project is seriously outdated

kind regards
sakis
 
#20
True dat. It is outdated but is a solid base to get started on, adding a CCS for the IPS and perhaps a current mirror, then replace the bootstrap circuit with a CCS and drop THD from 0.1% to maybe 0.01%.

And make a OPS with discrete drivers and output transistors to replace them shoddy darlingtons.
 
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