Topologies using darlingtons.

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Dear Friends,


in the Sanken's web site I found this statement:" Darlington transistors do not require drive transistors".
I wonder why darlingtons are not much more common as they could be used in simpler circuits.
I mean 1 darlington can replace 1 drive bjt + 1 output bjt.
Am I missing something ?
And also high current darlingtons are available.
Any link to very simple topologies using darlingtons?

Thank you very much indeed.

Kind regards,

beppe61
 
beppe61 said:
Dear Friends,
in the Sanken's web site I found this statement:" Darlington transistors do not require drive transistors".
I wonder why darlingtons are not much more common as they could be used in simpler circuits.
I mean 1 darlington can replace 1 drive bjt + 1 output bjt.
...
beppe61

Sure is possible very easy make of a strong power amplifier
covering well beyond 40 kHz with good sound quality.
Using powerful darlingtons, that can take a lot of heat!

This thread about the LAB10 Amplifier is only one fine example!
http://www.diyaudio.com/forums/showthread.php?s=&threadid=71292

:cool: :smash:
 
richie00boy said:
A very good point.
One issue is that they tend to be slower, and that reverse biasing the base to switch off quicker/cleaner is not possible.
Also there is no control over the main transistors base-emitter resistor.

Dear Sir,
thank you so much for your extremely kind and valuable reply.
First of all I must confess my almost complete ignorance in electronics.
Anyway this statement makes me think about the possibility to build a minimalist audio power amp with just 5-6 active devices.
It should be very interesting.
By the way, I noticed that darlington were more used in the past (I know of amps using them in the '80s).
I particular like one from the UK firm Albarry audio.
Just one pair of output darlingtons. Very very good sound indeed.
If only I could find the service manual ...

Thank you very much again.
Kind regards,

beppe61
 
Re: Re: Topologies using darlingtons.

lineup said:

Sure is possible very easy make of a strong power amplifier
covering well beyond 40 kHz with good sound quality.
Using powerful darlingtons, that can take a lot of heat!
This thread about the LAB10 Amplifier is only one fine example!
http://www.diyaudio.com/forums/showthread.php?s=&threadid=71292
:cool: :smash:

Dear Sir,

thank you very much for the very interesting information.
To be honest I do not like the op-amp based preamp too much.
Any all discrete option for a let's say 60 W/8 ohm power amp?
It could sound great indeed, if minimalism is the way of course.

Thank you very much indeed.
Kind regards,

beppe61
 
Dear Sir,

thank you so much again for your kind reply.
Let me explain my point of view hereafter.

>
richie00boy said:
It depends what you mean by minimalism.

I mean minimum number of active devices used in the best operational conditions. But I am not an expert at all.
I just like the idea on principle.

> ... but the same actual number of devices is there whether you use darlingtons or discrete drivers and outputs.

Well, so I was very wrong.
I wanted to reduce the number of active devices.
For instance, if I am not wrong again, at Sanken I understand they build power bjts that are multiple bjts in the same package (multiemitter or something like that).
I like this as well, of course always on principle.

> Darlintons can sound good and measure good.

This is my personal experience as well.

> It's just that absolute ultimate performance is more readily available from discrete.
I am not looking for the "absolute ultimate performance" .
I am looking for a exceptional simple but nice sounding circuit.
I heard for instance some single mosfet class A power amp, but I did not like completely the lower frequencies, not powerful enough.

Thank you very much indeed.
Kind regards,

beppe61
 
It is not possible to have a good external control of the quiescent current of class B output stages when darlingtons are used as power devices. Sanken seems now to provide darlington with internal bias diodes for a good thermal compensation : a thirty years old demand of amplifiers engineers.

~~~~~~ Forr

§§§
 
forr said:
It is not possible to have a good external control of the quiescent current of class B output stages when darlingtons are used as power devices.
Sanken seems now to provide darlington with internal bias diodes for a good thermal compensation : a thirty years old demand of amplifiers engineers.
~~~~~~ Forr
§§§

Thank you very much Sir.
This could be one of the reason why darlingtons based audio power amps are not so common.
Nevertheless I have heard an old UK design one sounding very nice indeed.

Thank you very much again.
Kind regards,

beppe61
 
Another example of a power amp using darlingtons is the swedish Sentec PA9, which is world famous in all of Sweden. :)

Although probably not in the state-of-the-art league, it is considered by many as a very good power amp, and is the reference amp of the swedish autiotechnical society. The design is probably about 15 years old.
 
Christer said:
Another example of a power amp using darlingtons is the swedish Sentec PA9, which is world famous in all of Sweden. :)
Although probably not in the state-of-the-art league, it is considered by many as a very good power amp, and is the reference amp of the swedish autiotechnical society. The design is probably about 15 years old.

Dear Mr. Christer,

thank you very much indeed for the kind and very valuable reply.
Any idea about even a basic circuit of the PA9?
Thank you very much indeed.

Kind regards,

beppe61
 
Sorry, I have no schematic for the PA9. I tried to google for it, but I didn't find any. I friend of mine has a pair of PA9 (they're monoblocks), but he currently lives on Iceland, so I don't have access to them for reverse engineering. Maybe if I ask him to take of photos of the PCB, it could be possible to reverse engineer? I did that with photos of the corresponding preamp SCA1. It is hard to do from photos, though, and usually impossible to se exactly what compnents there are.
 
Christer said:
Sorry, I have no schematic for the PA9. I tried to google for it, but I didn't find any. I friend of mine ...]

Dear Mr. Christer,

please do not worry about that.
Anyway as this amp is regarded to be very good sounding, it would be interesting to find out the general schematic.
I mean, the part number and the number of output devices are employed, the total number of active devices, its performances driving difficult loads, etc.
I googled as well and find some reviews in Swedish

http://www.faktiskt.se/modules.php?name=News&file=article&sid=141

and some nice pictures of the PA9 monoblock and its mate, the SC9 preamp.
If only your friend had a service manual at hand ....

Anyway, thank you very much again.
Kind regards,

beppe61
 
beppe61 said:
I googled as well and find some reviews in Swedish

http://www.faktiskt.se/modules.php?name=News&file=article&sid=141

and some nice pictures of the PA9 monoblock and its mate, the SC9 preamp.
If only your friend had a service manual at hand ....

[/B]

Strange, that one looks quite different from the ones my friend has, but I think there were two version of the PA9, but they didn't change the name, so probably it is the same basic design.

If I remember correctly, the ones my friend has are only 50 W, into 8 Ohms, but with good current capacity. I think there is only one pair of output devices, but I can't remember which types they are. It is nothing exotic, though, just some standard, easily available darlingtons.

You are right, of course, that the corresponding pre is SC9. My friend had the somewhat older SCA1, which I think had no corresponding power amp. The SCA1 is an interesting design, but hardly anything worth cloning.
 
Dear Mr. Christer,

thank you very much again for your appreciated reply.
Let me reply between the lines.

>
Originally posted by Christer
Strange, that one looks quite different from the ones my friend has, but I think there were two version of the PA9, but they didn't change the name, so probably it is the same basic design.
If I remember correctly, the ones my friend has are only 50 W, into 8 Ohms, but with good current capacity.
I think there is only one pair of output devices, but I can't remember which types they are.
It is nothing exotic, though, just some standard, easily available darlingtons.

In my humble experience simple design can sound very very good indeed (transparent and with great imaging abilities).
I like the idea of a single pair of output devices/channel because it frees from the need of matching devices.
Of course this makes the choice of the devices a little critical (and also the choice of the speakers that should be easy to drive, differently from my present Dynaudio).
I am pretty sure that the PA9 are really great sounding units.

> You are right, of course, that the corresponding pre is SC9.
My friend had the somewhat older SCA1, which I think had no corresponding power amp.
The SCA1 is an interesting design, but hardly anything worth cloning.

If you ever obtain any more information on the circuit of the PA9 please feel free to e-mail me directly.

Thank you very much indeed.
Kind regards,

beppe61
 
hi beppe61,
I also thought of a simple amplifier as you describe. The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet.
 

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consort_ee_um said:
hi beppe61, I also thought of a simple amplifier as you describe.
The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet.

Thank you very much Sir, for the very interesting schema.
Actually I am looking for an amp able to deliver at least 50-60 W/8 ohm and to drive adequately also demanding loads.
In my humble experience a very nice example is the Albarry M408.
Just a single pair of darlingtons at the output and a very very musical sound.
That would be a very interesting schema to study.
The best power amp I have experienced in my set-up so far.

Thank you very much again.
Kind regards,

beppe61
 
consort_ee_um said:
hi beppe61,
I also thought of a simple amplifier as you describe. The problem of thermal compensation I solved by using schottky diodes which have a lower forward voltage but almost the same temperature drift as the darlingtons
So in this circuit the Bat54S doule schottkys would have to be attached to the heatsink. I have modelled it in Spice but not built it yet.
Very similar to the Alexander amp. See mine and the original AN211 or AN211 with better text
 
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