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Old 12th June 2013, 09:23 PM   #311
Bigun is offline Bigun  Canada
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Gabor,

One thing that interests me is the apparent variability of sound with choice of the output devices. You mention a few times a couple of years back already, that this is critical for the right sound and you were very keen to find the parts you had used once before. But more recently I see people are getting very nice sound with other parts - or am I mistaken ? The VSSA is essentially your schematic, but with lateral FETs and people also report very good sound.

For example, I have 7-pairs of Sanken Darlington output devices (recovered from a Pioneer home theatre amplifier only 3 years old), I also have those nice Toshiba 5200/1943 type devices. Neither are the same as the device you recommend. Does this mean that if I were to build another symmetrical amp I should not use what I have but seek out the devices you recommend in order to get good sound ? This is not a criticism and I am not trying to make an argument, it is genuine interest to understand (and perhaps I just have to build to find out !)
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Old 12th June 2013, 10:54 PM   #312
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Originally Posted by Bigun View Post
Gabor,

One thing that interests me is the apparent variability of sound with choice of the output devices. You mention a few times a couple of years back already, that this is critical for the right sound and you were very keen to find the parts you had used once before. But more recently I see people are getting very nice sound with other parts - or am I mistaken ? The VSSA is essentially your schematic, but with lateral FETs and people also report very good sound.

For example, I have 7-pairs of Sanken Darlington output devices (recovered from a Pioneer home theatre amplifier only 3 years old), I also have those nice Toshiba 5200/1943 type devices. Neither are the same as the device you recommend. Does this mean that if I were to build another symmetrical amp I should not use what I have but seek out the devices you recommend in order to get good sound ? This is not a criticism and I am not trying to make an argument, it is genuine interest to understand (and perhaps I just have to build to find out !)
Hello
Several good and interesting questions .
Lets go and check the facts.
These Darlington device is a built up package
A power transistor, a driver, two resister and a diode
You can find the circuit of these darlington package on the web.
So we can not replace a darlington with a common BJT. You need that driver etc.
It is possible to use your Toshiba transistors?
Yes but you must get the rest (and the right) of the components to otherwise in these circuit you will be unable to drive those power transistor!
To do that you must seat done do some calculation how to ad up the 2 transistor to get the right result, speed, capacitance, resistance etc
With out that you end up like someone would drop you at middle of the night deep in the forest.
Again it is possible to build up the darlington package? The answer yes.
With the right parts you can achieve much better device like these cheap darlington transistors.
Now I can not comment on your Sanken Darlington since I never tested or use them in these or any other circuit.
I wish I know about more, or to have some experience with them.
All I know those old darlington from Philips, Texas instrument etc no longer in production.
But there is a German amplifier close to $10 000 still use those Philips BDV transistors.
Where they get I don't know, probably direct from Philips after market.
Now let talk about mosfet
You can drive both vertical and lateral mosfet with a simple pair JFet like 2SK170BL/2SJ74BL etc.
For example Pass F5 or ProFet both amplifier driven by a pair JFet.
You can use mosfet in these circuit with the right modification and you can achieve great sound.
How you stated there are several similar great sounding amp built using power mosfet
I do have the mosfet version circuit available and posted, not tested yet but I do not see why can't work or sound properly or great.
Now many people opinion the mosfet has softer sound specially comes out at low frequency.
Not necessary bad think, but I do built many BJT and mosfet amps to and yes you can hear most of the time the difference.
Before someone would think I'm against mosfet devices I have to say that is totally wrong.
I do like good sound, cant be mosfet, BJT even tube to.
When I seat done to listen music I want to forget devices used in the amplifier, amplifier, speaker cables, speakers etc.
I think many of us want that and think the same way.
Feel free to test your device you have at your hand, just mind the mentioned facts.
You do not need to use the recommended devices to achieve good sound only reason I stick with them because I do know them, I did tested and know the result, have some experience with those.
Do I think the given parts in the circuit are the best for these amp?
The answer is simple NO, and YES we can improve further the amp sound wise, stability etc.
I would be more than happy to get some good report back or if someone adopt these circuit to recently available top quality devices like Sanken darlington and achieve great or phenomenal result.

Greetings G
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Old 12th June 2013, 11:08 PM   #313
Bigun is offline Bigun  Canada
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I am more interested in BJT than MOSFET. I have not used any MOSFET in my DIY amplifiers so I'm more comfortable using BJT. I think it's better to make use of the tools you are familiar with unless you have the time and resources to get familiar with many different kinds. The laterals look like the ideal output for this topology though - because of their favourable temperature coefficient at sensible bias current. However, I do have some Sanken Darlington devices and it would be silly not to find a good use - so I may have to try this. Thank you for your thoughts on this.
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Old 13th June 2013, 04:09 AM   #314
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Bigun: I will be testing the circuit with a 2SC/2SA discrete Darlington. I can strap on the driver externally. But this needs to wait for a couple of days till I have fully tested the current module . Need to check a few things.

Gaborbella: Are you sure my heat sink is too small ? It isn't a flat plate . It's a finned heat sink which is now painted matt black. The size of the heat sink is about 100x100mm and 45 mm deep. There are 14 fins each 45 mm long. I'll post another picture later as the original didn't show the fins which are facing down.
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Last edited by ashok; 13th June 2013 at 04:13 AM.
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Old 13th June 2013, 04:58 AM   #315
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Here is a pic with the heat sink fins. Note the oversize heatsink on the driver transistors ! Just added it to see if it affected the bias drift. With the sink on the driver the drivers hardly get warm
Attached Images
File Type: jpg G-20Yamp.jpg (82.6 KB, 196 views)
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Old 13th June 2013, 08:35 AM   #316
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Yes in these profile your heatsink bigger than I taught.
Still be careful the 40V rail voltage a bit close to the max on one pair TIP transistor.
The driver does not need heatsink.
Please replace the input transistors and the BD139 to.
I advise to get read of that cap multiplier stuff and use a CRC capacitor bank.
If you have time, energy etc please test my PC board, that was carefully designed , tested and tested again until I get the best performance as possible.
Also those caps especially the Samwah very bad for audio..
I do have very negative experience with.
I know you just built these amp and just test it now but soon you will realise what I'm talking when you start swap some of those devices.

What type of Sanken darlington you guys has?

I do have some ON semi rugged TO3 case darlington, I have to test them.
You know N Pass A40 also use darlington power transistors..
All do that amp was designed decades a go we can still get information for transistor replacement at Mr. Pass website.
That is a Class A amplifier and different design but sound very good.
Mark Finnish built that amp long time a go, after built a Aleph5, Aleph4, and SOZ.
He wrote there is something in the sound of the A40 what he miss when he listening the Aleps or SOZ.
The reason I wrote done these darlington can sound great if everything properly matched and set up well.
I saw A40 built with TIP142/147 to..

Now I tried to use the TIP darlington in the Eliot Cap multiplier circuit. There the result was disaster, horrible.
So I replaced with ON semi transistors (built up Darlington) it got better but still far from good.
I do had a old JVC receiver with 2SA1095 and complementary and the driver 2SA968 with complementary.
I knew that was matched up in that amplifier so I used those transistors.
The result was excellent!
I didn't tested that set transistor in these amplifier because I have only one pair.
But from that I know the darlington device can be built to get great result.
I did tried and tested some ON semi transistor built up darlington but with a very bad result.
I spoke with a engineer and he told me if I build a darlington from regular BJT I must calculate the transistors Fz, speed, capacitance etc to get good performance.
So I gave up my research. Way back I didn't had Internet so that made my life more difficult.
At my last test even with the mentioned cheap darlington with these drivers ans JFet on the input I got excellent performance.
I'm satisfied with the sound of the amp now again.
That not mean I'm not open to do more test but I got tired over the years. Also now I'm satisfied and happy with the sound.
Only reason I do search for more rugged output device that would make the amp more stable, a piece of mind.
Again I do built some great amps like Symasym, Profet, Aleph30, Aleph X, Hiraga Class A, M Hiraga, some tube amp, P Daniel chip amp so on.
The little amp beat those so much even a so called non Audiophile guy could hear the difference.
An older, experienced gentleman came to my home for some listening seance and testing.
At firs he could not believed that amp drive the speakers the way like that.
The amp was just built on a PC of plywood..
He put his hand on the speaker cable and followed until the speaker from the amp and back..
To him still was unbelievable.
Not one or two guy ask me to build the amp to them and they pay good money for.
So if the amp is beaten by an amplifier from the shelf that mean to me there is a lot of improvement available..
That not mean the amp is unbeatable, just it hold his place even against the big guns to.

Greetings G
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Old 13th June 2013, 09:38 AM   #317
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.....Yes in these profile your heatsink bigger than I taught.
Still be careful the 40V rail voltage a bit close to the max on one pair TIP transistor.......

The supply sags on playing loud. My scope unfortunately has a problem with the switches so the display is not accurate vertically. So I can't confirm what the real clip level is.Will have to fix this or buy another scope. Will try to fix the dead scopes first. Maybe just spray Doxit-D5 on the switch contacts first!

........The driver does not need heatsink...........

Most likely. But it does get slightly warm. Will remove it and see what happens to the bias drift.

.......Please replace the input transistors and the BD139 to.........

Yes I will search for the BC560C. It has to be here because I bought both pnp and npn at the same time.

......I advise to get read of that cap multiplier stuff and use a CRC capacitor bank..........

The cap multiplier does improve the PSRR especially at the LF end. But I did plan to remove it and make a comparison.

.......If you have time, energy etc please test my PC board, that was carefully designed , tested and tested again until I get the best performance as possible........

Let me see. Time is in short supply right now !

........Also those caps especially the Samwah very bad for audio........

Well the amp still sounds very nice even with it. Maybe better with Nichicon or Panasonic or others. Will check this out.

.......At my last test even with the mentioned cheap darlington with these drivers ans JFet on the input I got excellent performance.........

I will try out the input FET's ( 2SK246/J103) I also have the 2SK170 but not sure about the complement 2SJ74.
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Old 13th June 2013, 07:36 PM   #318
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............Please replace the input transistors and the BD139 to.........

I will try out the input FET's ( 2SK246/J103) I also have the 2SK170 but not sure about the complement 2SJ74.
It would be good to test the drivers with out heatsink and with heatsink I mean to make some measurement.
I never did it.
I touched any time only it get slightly warm. In case the heatsink help to make the amp more stable please use it and let me know.
Thank you.
Be careful with the 2SK246/J103 those are not the same like the 2SJ74BL/2SK170BL.
If you do not have please stick with BC550C/560C.
The biggest difference between the JFet and BJT warmer sound to the favour of the JFet, there are some other differences but if you don't have.........
Those are hard to get and expensive today and only BL type the direct replacement for the BJT.
Yes I understand your amp sound good even with the Samwah caps to but I know how bad they are for audio. I did tested in the Symasym and after few sound track I trow them away... They are that bad!!!!
Panasonic FC great bad but in the bass area a bit weak.
Nichicon Gold or MUSE (the black) not expensive and great value for the money.
BD140 you need on the heatsink, also it influence the bias set up. I'm amazed the amp works properly with the BD139 to.
I understand hard to swap components because your PC board design (mounted on the heatsink).
That is why I don't like that type of PC board specially until the amp thoroughly not tested done to the last components.
I do had a friend who always designed our PC board that way with software.
I do hate that, when I want to test something always has to be removed from the heatsink..
It take lot of time, most of the time I'd rather left the amp how it was.
But you can mount my PC board the same way like yours to because small compact size..
All that I asked from you please take it as a advise only!!
Only one think motivated I know the amp, I tested thoroughly over 20 years, I used a lot of parts it does sound good with most of them but with the rightly matched components it is incredible good.
OK please enjoy your amp and when you find out new thinks, improvement etc please share it with us.
Thank you
Greetings G
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Old 14th June 2013, 02:16 AM   #319
Bigun is offline Bigun  Canada
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There are two threads that I am following with interest at the moment - this one, and the one on P3A upgrades. I wonder if anybody has both amps that they could compare them since they are both radically different topologies that such a comparison would be quite interesting !
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Old 14th June 2013, 02:44 AM   #320
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Yes that comparison would be interesting. However both output devices should be similar types , either LatFET or Bipolar.

G: The BD139 or BD140 will work well in the same place provided the variable resistor is located in the base emitter section. Otherwise I don't see any difference apart from polarity issues. It's only a voltage multiplier.
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