No pun intended, just a good opportunity to adress that most folks point their eyes and ears to the large notorious, but are unaware of the numerically less impressive.
I've got lots and lots of Tosh A1301/C3180, mom and dad of the A1942/C5199, in my experience often more favorable than the higher digit step ones when a tour de force is not the main objective.
Even more so with the Sanken A1216/C2922 competitors, the baby A1215 and C2921 are the real performance monsters (application depending), had to scavenge the globe for bulk numbers of those.
Hi Marc,
When I drew the schematic, many years ago, I didn't have the Eagle 2SA1837/2SC4793 components, so I just used the BD139/BD140 components.
I have 2 of the amps using 2SA1837/2SC4793 drivers while the other has BD139/BD140. The amp using BD139/BD140 as drivers also has a BD139 for the VAS. In garage testing, the amps using BD139/BD140 drivers and VAS doesn't sound as good but I don't know if it is because of the drivers and/or the VAS.
VAS Transistors
regards
Hi sng001,
I just got caught with this. The free shipping only applies if you buy from Mouser Australia.
regards
Ok. I passed some time this week-end to redrawn your schematic and the pcb. The gaol was to mount driver and OPT direct on on heatink (without alu L bracket), to mount TO220 driver, to be able to mount big poly caps at input and to have no part on solder side. Sure mine is bigger as yours but that's no matter for me but it's largely inspired from your work. I drawn a Sanken MT200 OPT version
Marc
Hello Greg
It is because of the VAS.
The BD139 are too slow and have to much capacitance (the COB) to do a very good VAS transistor, you can use it for driver but not for a VAS.
For the VAS it's better to use a transistor with at least a Ft of 120 mhz with a cob lower than 10 pF.
For the VAS, I would suggest one of those transistors: 2SC1819, 2SC3423, 2SC3503, KSC3503
And it is better to use the lowest value possible for the lag compensation capacitor C5 in the VAS, it need some experiment so you get best sound, if you have a scope you check the amp stability with a 10KHz square wave using a real speaker load and wen you have the right value of that cap, the amp will be stable.
Did you match the two LTP input transistors ?
Matching those transistors for HFE and VBE give better sonic result.
Bye
Gaetan
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Hello Greg
I did try to edit to ad another comment but it was to late.
So I would also say that C5 in the Vas are very important, Too big value and the amp sounds slow and leaden. Too low and it sound tizzy, bright and fatigueing. And it's better to use a silver mica capacitor.
But it's better a value of C5 a bit to high than too low, a tizzy sound are more difficult to listen than a sound a bit slow.
Bye
Gaetan
I did try to edit to ad another comment but it was to late.
So I would also say that C5 in the Vas are very important, Too big value and the amp sounds slow and leaden. Too low and it sound tizzy, bright and fatigueing. And it's better to use a silver mica capacitor.
But it's better a value of C5 a bit to high than too low, a tizzy sound are more difficult to listen than a sound a bit slow.
Bye
Gaetan
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I used the BD139 for the VAS (I don't think the AKSA original VAS devices are easy to find anymore?) with good results (TGM amplifier) but as remarked above, the choice of compensation capacitor is key. I tried several values and there was definitely a sweet spot in the middle where the music had the most 'magic'.
I used the 2SA1837/2SC4793 drivers, which I like on account of their larger package size making for easy mounting onto the main heatsink.
I used the 2SA1837/2SC4793 drivers, which I like on account of their larger package size making for easy mounting onto the main heatsink.
Thanks Gaetan for the info.
I am using KSC3503 for VAS on 2 of the amps, I think I have 98 left.
The 2N5401 are matched for hfe and DC offset is close to zero.
The 68pF cap is silver mica and I started off at that value because of the original schematic. I have a few others to try.
Idefixes,
It's a good idea making your own PCB, you get exactly what you want then.
regards
I am using KSC3503 for VAS on 2 of the amps, I think I have 98 left.
The 2N5401 are matched for hfe and DC offset is close to zero.
The 68pF cap is silver mica and I started off at that value because of the original schematic. I have a few others to try.
Idefixes,
It's a good idea making your own PCB, you get exactly what you want then.
regards
Mouser site is pretty smart: I entered Mouser Electronics - Electronic Component Distributor and I got redirected to au.mouser.com & Australian flag appears on the top right corner.
Cost of components for a stereo amp can easily exceed A$100 and I just bought extra transistors for matching & parts bin & got free shipping. They have a big range of capacitors & resistors but you have to take extra time to research.
Have fun.
Idefixes,
It's a good idea making your own PCB, you get exactly what you want then.
regards
Greg mine is not really mine as it's an arrangement of yours in few point to match with my needs.
Marc
I just found out from a guy at work who buys isopropyl alcahol illegally from an arts supply store. They ignore this silly law and sell it anyway in 500ml containers
I just use methylated spirits, which of course is ethyl alcohol denatured with methyl alcohol and a touch of pyridine. It's just as effective, quite inexpensive, but when it dries it leaves a white frosty residue. You can then wipe this off with a stiff dunny brush - a precision instrument n'est pas - and it then has a lovely shiny, slightly grainy clean look to it.
Hugh
Hugh
Thanks Hugh, Meths is far too valuable, makes a very refreshing drink
But i will try it and see how I go next time Im soldering. I have always used isopropyl, but Im out at the moment.
Is this amp really have a secret? and also stopped because of efficiency?
Here are many kit amp sold but OCL150W is still best seller. OCL is Old with positive FB (bootstrap) that risen box effect.
Link for better efficiency may help:
http://www.diyaudio.com/forums/soli...opology-where-diy-projects-2.html#post2223627
Here are many kit amp sold but OCL150W is still best seller. OCL is Old with positive FB (bootstrap) that risen box effect.
Link for better efficiency may help:
http://www.diyaudio.com/forums/soli...opology-where-diy-projects-2.html#post2223627
That's Bigun, he says magic.
May I guess the secret has similar with OCL150W, it become best seller kit amp in my country since I was a little child until this day, because of secret or unknown.
OCL150W is a modified version of old black and white television (I couldn't clearly remember, may be JVC). It is simple schematic, but changing feedback DC blocking elco may change the sound. If it replaced with higher grade electrolyt cap, the sound is getting worse, may this cap has minor handling for spk displacement. And also some other strange modification effect.
Biggest effect is in box design, it is caused by that bootsrap.
Greg placing zobel like that.
May I guess the secret has similar with OCL150W, it become best seller kit amp in my country since I was a little child until this day, because of secret or unknown.
OCL150W is a modified version of old black and white television (I couldn't clearly remember, may be JVC). It is simple schematic, but changing feedback DC blocking elco may change the sound. If it replaced with higher grade electrolyt cap, the sound is getting worse, may this cap has minor handling for spk displacement. And also some other strange modification effect.
Biggest effect is in box design, it is caused by that bootsrap.
Greg placing zobel like that.
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Is this what you meant ontoaba: http://www.eleccircuit.com/wp-conte...amplifier-hifi-ocl-150w-rms-by-transistor.jpg
positive feedback: Aksa pleased people who listened to it
positive feedback: Aksa pleased people who listened to it
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