I have been seeing quantities of the A42 and A92 transistors on Ebay!
I am looking for the W42 and W92 versions however.
What is the difference between the A & the W versions????
Zero
I am looking for the W42 and W92 versions however.
What is the difference between the A & the W versions????
Zero
Zero Cool
Frankly I don't know 😉
However I'm sure somebody "out there" can tell us 😀
Normally I use the MPSA's for almost all my project as they are cheap, realiable and I like the sound they produce 🙂
Frankly I don't know 😉
However I'm sure somebody "out there" can tell us 😀
Normally I use the MPSA's for almost all my project as they are cheap, realiable and I like the sound they produce 🙂
Jan, Pc = colector dissipation. 15032 / 33, which have Pc = 50 W are not on this position optimal, 42 / 92 are better 😉 .
Just a comment or two.
The lack of V-I limiter is what makes Krell a Krell. As is, the 'clone' would not be able to do what Krells become famous for - drive insane loads (Apogee Scintilla and like) without compression.
I've never seen an output coil in any of the Krell amps - I doubt it is needed.
All Krell amps from that vintage I've seen had input low pass at around 350kHz or so, hence C101 should be calculated as such.
Despite ridicule from some, KSA50 will whip the pants off most of todays amps with ease, and sound MUCH bigger than its 50W rating suggests.
The lack of V-I limiter is what makes Krell a Krell. As is, the 'clone' would not be able to do what Krells become famous for - drive insane loads (Apogee Scintilla and like) without compression.
I've never seen an output coil in any of the Krell amps - I doubt it is needed.
All Krell amps from that vintage I've seen had input low pass at around 350kHz or so, hence C101 should be calculated as such.
Despite ridicule from some, KSA50 will whip the pants off most of todays amps with ease, and sound MUCH bigger than its 50W rating suggests.
What's a V-I limiter?
Another Krell from 1989 has a low-pass at 250kHz on the input.
Edit: I found the answer at http://sound.westhost.com/vi.htm
Edit: Also the KMA-160 does have diodes to prevent the signal from swinging outside the rail voltage, but no active V-I protection that I can see.
Another Krell from 1989 has a low-pass at 250kHz on the input.
Edit: I found the answer at http://sound.westhost.com/vi.htm
Edit: Also the KMA-160 does have diodes to prevent the signal from swinging outside the rail voltage, but no active V-I protection that I can see.
Elso Kwak said:
Hi Bratislav, Don't overlook the transformer(s).......
Any specs on that?
Yup, FeO3Kr2 (Ferro-Kryptonite) core with 0.00001% regulation 😀
BIG and HEAVY comes to mind ...
Pavel:
Thanks for correcting me 😉
I must learn not to read and write when I'm tired 🙁
Bratislav (and others):
The V-I limiter was put in as an additional options for those who would like some kind of protection.
Don't like it ??? Don't use it 😉
The output coil are shown in the schematic for those who will build this amp with new high freq. transistors....
I'm not sure how it will respond to modern components, so better be safe than sorry 😉
And again: Don't like it ??? Don't use it 😉
Please keep the comments comming😀
Thanks for correcting me 😉
I must learn not to read and write when I'm tired 🙁
Bratislav (and others):
The V-I limiter was put in as an additional options for those who would like some kind of protection.
Don't like it ??? Don't use it 😉
The output coil are shown in the schematic for those who will build this amp with new high freq. transistors....
I'm not sure how it will respond to modern components, so better be safe than sorry 😉
And again: Don't like it ??? Don't use it 😉
Please keep the comments comming😀
Re: Transformer Specs
The quality of transformers in Krell amps I've seen (heard) varied quite a bit. Some were dead quiet, some had quite a buzz.
All were generously specified (more than enough VA to run at rated power even at low impedances). As far as regulation and flux density I woudln't have a clue, I only had one specimen to look up closely(ish), and at 3KW it was reasonably good as far as sagging (<2% I think), but then most big trafos are.
I don't think they were special devices, despite impressive logos on them 🙂
Elso Kwak said:
The quality of transformers in Krell amps I've seen (heard) varied quite a bit. Some were dead quiet, some had quite a buzz.
All were generously specified (more than enough VA to run at rated power even at low impedances). As far as regulation and flux density I woudln't have a clue, I only had one specimen to look up closely(ish), and at 3KW it was reasonably good as far as sagging (<2% I think), but then most big trafos are.
I don't think they were special devices, despite impressive logos on them 🙂
Krell KSA50 PCB
Hi
Is there any chance that we can do a group order once all the designwork is done as it will most likely solve those hard-to-get parts problem.
Personally I am very keen to build this amp.
Jozua
Hi
Is there any chance that we can do a group order once all the designwork is done as it will most likely solve those hard-to-get parts problem.
Personally I am very keen to build this amp.
Jozua
... what makes Krell a Krell.
Physical limits or specification of devices are the same for every manufacturers. In this type of amp, which have probably +/- 50 V rails, two output devices with 15 A colector current each and standard SOAR you cannot " go " with load impedance too low, I mean only to cca 2 Ohms. Apogee boxes, which have impedance ( as I know ) around 1 - 2 Ohms, are for this type of amp dangerous, independent on claims of amp's manufacturer.
Physical limits or specification of devices are the same for every manufacturers. In this type of amp, which have probably +/- 50 V rails, two output devices with 15 A colector current each and standard SOAR you cannot " go " with load impedance too low, I mean only to cca 2 Ohms. Apogee boxes, which have impedance ( as I know ) around 1 - 2 Ohms, are for this type of amp dangerous, independent on claims of amp's manufacturer.
Re: ... what makes Krell a Krell.
Well, even going by theory, 400W peak only requires 20A (10A per device). Pushing it into dangerous waters, definitely, with 20A devices, but real life music only requires these kind of peaks less than 10% of the time. At those power levels the speakers, rooms and owner's eardrums will be giving up probably lot quicker than output transistors.
But more importantly these are not claims, Krells actually WORKED with Apogees - that is how legend was born.
Besides, other Krells used lot more ouput devices than two pairs.
My version of KSA100 for example has 16 20A devices per channel. I don't really think I'd need any V-I limiters even with 1 ohm loads !
(my version == the version I've made as DIY, of course!)
Upupa Epops said:
Well, even going by theory, 400W peak only requires 20A (10A per device). Pushing it into dangerous waters, definitely, with 20A devices, but real life music only requires these kind of peaks less than 10% of the time. At those power levels the speakers, rooms and owner's eardrums will be giving up probably lot quicker than output transistors.
But more importantly these are not claims, Krells actually WORKED with Apogees - that is how legend was born.
Besides, other Krells used lot more ouput devices than two pairs.
My version of KSA100 for example has 16 20A devices per channel. I don't really think I'd need any V-I limiters even with 1 ohm loads !
(my version == the version I've made as DIY, of course!)
Attachments
While discussing different Krell opinions and models etc., maybe we for a short moment could return to the KSA-50 Clone project 😉
Please comment the schematic I have posted, so I can get started with the PCB-layout
Please comment the schematic I have posted, so I can get started with the PCB-layout
Any "last minute" changes before I start making the PCB layout ??? 😉
Which size do you prefer ???
Single or double side ???
Other mods ????
😉
Which size do you prefer ???
Single or double side ???
Other mods ????
😉
Jan, it must be simply, one sided, cheap and with multipled output stage ( n - times two transistors ) for easy driving 0.1 Ohm load, 'cos still exist idiots, which make boxes with this impedance 😀 .
ACD said:
Make some room for a switch for a quick change of bias ("winter" and "summer" setting). Every summer when Melbourne temepratures hit 40+ C I wind the bias down and that is a lengthy (and risky) job.
Updated schematic
I have just uploaded an updated schematic:
www.delta-audio.com/temp_acd/Krell-Clone_KSA-50_1-2.pdf
I have also started the PCB-layout, so if you got any ideas or mods, please write a.s.a.p. 😉
I have just uploaded an updated schematic:
www.delta-audio.com/temp_acd/Krell-Clone_KSA-50_1-2.pdf
I have also started the PCB-layout, so if you got any ideas or mods, please write a.s.a.p. 😉
Jan, C 109 is there for improvement dynamic property of VAS, not for limitacion of oscilation, so you can get it directly on PCB 😉 .