hi friends,
@Sergiu / @Damon1983 / @AndrewT ,
can anybody please help me decide the secondary voltage of the transformer. i would need 24VDC for the 30W amp board [this is from Jims Audio off ebay].
can i just consider 1.44 factor after rectifier to decide the voltage or are there any other parameters to be taken into account? [that gives around 17V secondary Voltage].
also i see that both Damon and Sergiu have used capacitors of voltage rating of 35VDC. is that safe for this kind of voltage or should i consider higher voltage ratings?
@Sergiu / @Damon1983 / @AndrewT ,
can anybody please help me decide the secondary voltage of the transformer. i would need 24VDC for the 30W amp board [this is from Jims Audio off ebay].
can i just consider 1.44 factor after rectifier to decide the voltage or are there any other parameters to be taken into account? [that gives around 17V secondary Voltage].
also i see that both Damon and Sergiu have used capacitors of voltage rating of 35VDC. is that safe for this kind of voltage or should i consider higher voltage ratings?
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I think you're right, if calculating by idle transformer's voltage. I using small transformer 2*15VAC*7,5A (2*16,32VAC idle) +-20VDC after diodes bridge.
gaborbela what did you use for small signal transistors? Also did you have to change any resistor values from the original schematic?
I am thinking of using KSA992/KSC1845, BD139/140 and MJ15024/25, would it work?
BD139+140 (and doesn't matter - ST, Fairchild, NXP, Philips or ON SEMI) don't use in Hiraga's AMPs, because infinitely increases bias. Better to find NEC 2sc1845+2sa992 or Hitachi 2sc1775+2sa872. In output best variants: ON Semi MJL3281+MJL1302 or MJ15024G+MJL15025G (MJ15024G+MJ15025G like me more).
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Those NEC & Hitachi parts are difficult to find and I would not trust to buy them from ebay, I believe KSA992/KSC1845 equivalent to those.
Why would BD139/140 increase the bias? Is it the HFE or some other parameter that causes that? They seem to have about the same HFE with say MJE15031/32 if not less...
Why would BD139/140 increase the bias? Is it the HFE or some other parameter that causes that? They seem to have about the same HFE with say MJE15031/32 if not less...
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Better to ask BD139+140.
I don't using BD series and Fairchild BJT at all.I don't buying parts on ebay/ali and etc.
MJE15034G+MJE15035G good variant for 30W version of 1985.
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For drivers I tested several orig Toshiba, BD and other semis. Even I had the orig NEC (I think I still have some left over used ones somewhere)
The mentioned ON Semi is the best choice with that power transistors - and other several I tested.
I spent countless hours with testing and a lot of $$$ on semis..
I do not say you can not find something may be as good or better but you will have to go true some research and tests..
I did had all the original NEC and Hitachi semis to the Hiraga Class A including the power transistors, to me the ON semi performed way better sound wise. Better and dipper bass with more control and cleaner midrange
The mentioned ON Semi is the best choice with that power transistors - and other several I tested.
I spent countless hours with testing and a lot of $$$ on semis..
I do not say you can not find something may be as good or better but you will have to go true some research and tests..
I did had all the original NEC and Hitachi semis to the Hiraga Class A including the power transistors, to me the ON semi performed way better sound wise. Better and dipper bass with more control and cleaner midrange
Is there an english translation of the article in post 795? http://www.diyaudio.com/forums/solid-state/193-hiraga-20w-class-80.html#post4246265
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Somehow it would feel just 'wrong' to translate it (even though I don't speak French). I think I would want to work from it as-is, taking the time and trouble to understand it, with dictionary in hand, working directly from the Masters blue print. I can't explain why.
I have started with the conclusion (with a dictionary and Google translate), but I can see what you mean. I regret I didn't pay more attention in my french lessons....
Hello,
Finally in back home from a long journey trip for my job..
Here are some of my thoughts when i made my variant of this amp:
"For drivers i tested the following pairs:
a)2sa1837/c4793
b)2sa1220a/c2690a
c)2sa1930/sc5171
And found the followings:
a) the best pair, with a very precise sound, very good soundstage, pleasant mids, very good imaging, low,punchy bass and tight, extended hights and beautifull overall sound;
b) too fast pair because of the hight FT, flat soundstage (didnt have presence), tight bass but abit soft, the hights where not impressing and the mids where at the same level as the bass and hights so nothing impressing here.
The sound was focused but was hard to distinguish the instruments and effects and because these trannies where too fast it was hard and exausting to listen to the amp. It wasnt pleasant at all.
c) same as the b) variant;
Conclusion: altought all the above pairs where better aprox in all aspects compared to the original drivers used, Cob an FT, it seems that this amp doesnt love drivers with FT faster than 90-100 Mhz altought the CoB is better than the original ones....
I used as output pair 2sa1943/2sc5200 Toshiba NOS for tests.
The source: ipod 5.5 classic@80gb@Wolfson DAC chip moded to Rockbox for FLAC format support.
Speakers: modified Tento closed enclosures rated at 40w sinus and 8 ohms from an Kashtan mag.
The music (in Flac format):
* luminary-amsterdam (smith and pledged remix); -- depht of field, vocals, effects;
*julio iglesias-crazy;-- vocal and for the big trompet (dont know the name in english);
* katie melua- nine million bicicle;--guitar, flaut, violin, vocals;
* sting-fragile;--- mandoline, dinamics, vocals, depht of field;
*dave brubeck-take five; dinamics, rithm, timbre;
*mantovani and his orchestra- limelight and moulin rouge;-- soundstage and precision;
*above and beyond--full concert film live from Porchester Hall (not FLAC; it is dirrectly from youtube@1080p); sound stage, sound stage and vocals;
I made the listening tests for 3 days from 8AM to 24:00PM continous listening to the same mellodies over and over again.... I think that after i'll finish the tests i will not want hear again those mellodies..
So my friend i think that MJ15034 and his complement and the 2sa1837/c4793 and other good pairs with COB lower than 40pF and FT lower than 100mhz is best for this amp."
If i remember clear this was exhausting... For a precise difference between the batches of different transistors you have to listen to the amp allot (same mellody, over and over and over again...) and choose what you like best.
Cheers
Sergiu
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