Banned
Joined 2002
Re: more power...
Been away from the forum for a few days and how fast it grows .
Stuart, Got the CCS boards, many thanks. It looks pretty good. Questions:
1) What would you suggest I use to cut the boards? Should I give it a groove with a box-cutter and snap it with pliers or should I use a dremel cut-off wheel? I'd rather the first because the cut-off wheel will cut too close to the wire traces.
2) With those canned toroids, what DC rails are you getting? 100vdc? at 800w into 4 ohms what do the rails sag to?
3) Still using the 565 heatsinks? I am probably going to do the same. I have a 585 and 565 that needs repairs, I will just strip out the Adcom stuff (except power switch and soft start) and use the rest for the KSA-50/500?
4) On the 100vdc rails, how much bias can the 565 heatsinks take before they hit 55C without a fan? I would guess 35-40 watts pure class-A.
5) Where have you mounted the drivers, the same heatsink?
thanks,
K-
Stuart Easson said:
Been away from the forum for a few days and how fast it grows .
Stuart, Got the CCS boards, many thanks. It looks pretty good. Questions:
1) What would you suggest I use to cut the boards? Should I give it a groove with a box-cutter and snap it with pliers or should I use a dremel cut-off wheel? I'd rather the first because the cut-off wheel will cut too close to the wire traces.
2) With those canned toroids, what DC rails are you getting? 100vdc? at 800w into 4 ohms what do the rails sag to?
3) Still using the 565 heatsinks? I am probably going to do the same. I have a 585 and 565 that needs repairs, I will just strip out the Adcom stuff (except power switch and soft start) and use the rest for the KSA-50/500?
4) On the 100vdc rails, how much bias can the 565 heatsinks take before they hit 55C without a fan? I would guess 35-40 watts pure class-A.
5) Where have you mounted the drivers, the same heatsink?
thanks,
K-
jacco vermeulen said:
Humm I was going to use a piece of string!
I guess I missed the posting about wiriing the outputs, the Positive and Negative outputs are common? They both go to the positive Speaker terminal and the Negative speaker terminal goes to ground?
For some reason I thought the Krell was a Positive/Negative drive circuit.
Regards
Anthony
Here's what John Atkinson (editor Stereophile) had to say about the KSA-50 vs. the new KSA-50S: Thought you guys might get a kick out of it.
KSA-50S vs KSA-50
The original KSA-50 has only unbalanced inputs, so for the comparisons I hooked it up with 10' lengths of unbalanced AudioTruth Lapis fitted with RCA jacks. The '50S was auditioned in balanced mode so I wouldn't have to plug and unplug RCA connections, with all the potential for blowing up speakers and amps that that entails—hey, I own the B&Ws and one of the amplifiers, okay? The balanced 'S was 3.8dB more sensitive than the unbalanced '50; again, levels were matched to well within 0.01dB at 1kHz.
Listening to the original '50, which I haven't fired up in almost six years, brought the memories flooding back. The soundstage was wicked big; the bass was wicked deep; the amp was wicked GOOD! In the "Christe Eleison," from the Mozart C-Minor Mass's "Kyrie," Barbara Hendricks soars to a glorious climax. The old Krell allowed me to hear her voice lighting up the surrounding acoustic in a delightfully unambiguous way. And in the opening of the "Kyrie," the pulse of the dotted rhythm pushed the pace along.
The new Krell was significantly better than its predecessor in one important way: that gloriously liquid quality I noted earlier made the earlier Krell sound a little "electronic" by comparison. Hendricks' voice acquired a rather phlegmy edge via the older amplifier; the '50S presented it with a significantly more natural character. The original KSA-50's high frequencies were also grainier compared with the KSA-50S, and slightly sibilant. The new amplifier had altogether a more civilized, more neutral sound, I found. But when it came to the soundstage, the Dresden walls weren't illuminated to the same extent as they had been with the old amp.
And the new amp lost something of the sense of pace. It wasn't that it couldn't boogie at all, but when it did so, it was definitely in a more mannered way. Despite the more natural, less grainy presentation of the vocal, the combination of bass guitar and kickdrum on "Tell Everybody I Know," from the killer Keb' Mo' album, for example, could officially be classified as "polite" through the '50S. Perhaps as Krell designer Dan D'Agostino and the rest of us baby boomers get older, so does the sonic character of Krell amplifiers keep pace with our shifting desires.
Conclusion
While the Krell KSA-50S's bass is not quite as awesomely kick-*** deep as the earlier KSA-50, its midrange is one of the best I have heard from a solid-state design. Its imaging and soundstaging are also both first-rate. The KSA-50S is one civilized-sounding amplifier. And perhaps that's also my only real criticism: that it has lost some of the slam, the "Wham, Bam, thank you, Dan!," that characterized the original KSA-50 (footnote 2).
The KSA-50S is undoubtedly a contender, but its sonic character makes it essential for you to audition it in the context of your own system. Recommended—but news we've just received from Krell could make this moot. Apparently the KSA-50S might be discontinued in September, due to lack of demand: Krell customers appear to be more prepared to spend the big bucks for the bigger amplifiers. Given the '50S's sweet sound and massive power delivery, I feel that this is a pity
KSA-50S vs KSA-50
The original KSA-50 has only unbalanced inputs, so for the comparisons I hooked it up with 10' lengths of unbalanced AudioTruth Lapis fitted with RCA jacks. The '50S was auditioned in balanced mode so I wouldn't have to plug and unplug RCA connections, with all the potential for blowing up speakers and amps that that entails—hey, I own the B&Ws and one of the amplifiers, okay? The balanced 'S was 3.8dB more sensitive than the unbalanced '50; again, levels were matched to well within 0.01dB at 1kHz.
Listening to the original '50, which I haven't fired up in almost six years, brought the memories flooding back. The soundstage was wicked big; the bass was wicked deep; the amp was wicked GOOD! In the "Christe Eleison," from the Mozart C-Minor Mass's "Kyrie," Barbara Hendricks soars to a glorious climax. The old Krell allowed me to hear her voice lighting up the surrounding acoustic in a delightfully unambiguous way. And in the opening of the "Kyrie," the pulse of the dotted rhythm pushed the pace along.
The new Krell was significantly better than its predecessor in one important way: that gloriously liquid quality I noted earlier made the earlier Krell sound a little "electronic" by comparison. Hendricks' voice acquired a rather phlegmy edge via the older amplifier; the '50S presented it with a significantly more natural character. The original KSA-50's high frequencies were also grainier compared with the KSA-50S, and slightly sibilant. The new amplifier had altogether a more civilized, more neutral sound, I found. But when it came to the soundstage, the Dresden walls weren't illuminated to the same extent as they had been with the old amp.
And the new amp lost something of the sense of pace. It wasn't that it couldn't boogie at all, but when it did so, it was definitely in a more mannered way. Despite the more natural, less grainy presentation of the vocal, the combination of bass guitar and kickdrum on "Tell Everybody I Know," from the killer Keb' Mo' album, for example, could officially be classified as "polite" through the '50S. Perhaps as Krell designer Dan D'Agostino and the rest of us baby boomers get older, so does the sonic character of Krell amplifiers keep pace with our shifting desires.
Conclusion
While the Krell KSA-50S's bass is not quite as awesomely kick-*** deep as the earlier KSA-50, its midrange is one of the best I have heard from a solid-state design. Its imaging and soundstaging are also both first-rate. The KSA-50S is one civilized-sounding amplifier. And perhaps that's also my only real criticism: that it has lost some of the slam, the "Wham, Bam, thank you, Dan!," that characterized the original KSA-50 (footnote 2).
The KSA-50S is undoubtedly a contender, but its sonic character makes it essential for you to audition it in the context of your own system. Recommended—but news we've just received from Krell could make this moot. Apparently the KSA-50S might be discontinued in September, due to lack of demand: Krell customers appear to be more prepared to spend the big bucks for the bigger amplifiers. Given the '50S's sweet sound and massive power delivery, I feel that this is a pity
jacco vermeulen said:
......yeah....I ran a 3-in-1 shielded cable for that purpose. Its actually a pretty high quality copper with teflon insulation. I guess I could sub this for some teflon/silver (which I have) but damn! This board just has too many wires between the driver and outputs. (ooops...not a complaint not a complaint)
K-amps said:
Thanks K, it's really interesting to read that old report from JA.
Once again I think the selection to clone KSA 50 is the correct one. With all the care we are doing these amps plus the more recent JBT's I'm sure we will get the best part of both amps.
Patiently waiting to hear these amps roar on my space.
With your meter on diode check range you will not get any reading beteen the collector(metal case) and the emitter. You will get 400 to 700 ohms typical between the base and collector(metal case) in one direction only. You will get that same reading or very close between emitter(pin) and base(pin) in one direction only.
Do the check and then report back and let us know which is which...... I know the pinout, but you do the test and so on and post.......
Thanks!
Mark
Do the check and then report back and let us know which is which...... I know the pinout, but you do the test and so on and post.......
Thanks!
Mark
k-amps
I'm still experimenting with cutting, so far, a mini-hacksaw used slowly and carefully to cut through half way, then snap over a straight edge...
GFA565 heatsinks seem good for 55w each, no fan. Assisted, I'm still not sure what the maximum dissipation would be, I added a 120mm fan and things are much cooler, just no real measurements yet, but ~1A total idle is not a problem. With the second xfrmr, I'm shooting for ~2A, think of it as a KSA50 with a little more class B headroom...
I am going to try and get all the pieces together tomorrow, I'll let you know soon thereafter...
Stuart
I'm still experimenting with cutting, so far, a mini-hacksaw used slowly and carefully to cut through half way, then snap over a straight edge...
GFA565 heatsinks seem good for 55w each, no fan. Assisted, I'm still not sure what the maximum dissipation would be, I added a 120mm fan and things are much cooler, just no real measurements yet, but ~1A total idle is not a problem. With the second xfrmr, I'm shooting for ~2A, think of it as a KSA50 with a little more class B headroom...
I am going to try and get all the pieces together tomorrow, I'll let you know soon thereafter...
Stuart
drivers...
k-amps,
The drivers, in this case a pair of to247 21193/4, are mounted on the 'main' heatsink, I have q111 clamped to this heatsink as well. There is a secondary heatsink that holds the last 6 pairs of outputs, which will be part of the same windtunnel, which ever ends up hottest will be the cold air end of the tunnel...
I used my variac to set the rails at 105 unloaded, they dropped to approx 80-85 at 800w RMS into 4ohm resistive. I didn't measure the mains voltage at this point, but I'm guessing it was suffering, as was the variac...I was feeling nervous about my 100v power supply caps...
So now I'm making a cable to run from the dryer plug, I can get 240v at 30a, should be more than adequate for prototyping purposes...
More later
Stuart
k-amps,
The drivers, in this case a pair of to247 21193/4, are mounted on the 'main' heatsink, I have q111 clamped to this heatsink as well. There is a secondary heatsink that holds the last 6 pairs of outputs, which will be part of the same windtunnel, which ever ends up hottest will be the cold air end of the tunnel...
I used my variac to set the rails at 105 unloaded, they dropped to approx 80-85 at 800w RMS into 4ohm resistive. I didn't measure the mains voltage at this point, but I'm guessing it was suffering, as was the variac...I was feeling nervous about my 100v power supply caps...
So now I'm making a cable to run from the dryer plug, I can get 240v at 30a, should be more than adequate for prototyping purposes...
More later
Stuart
Banned
Joined 2002
now, now, sticks and stones...
Don't get all excited, I need a higher voltage, lower impedance power source for prototyping. By using 240V, the current to the amp is halved, and the 30A feed means all the cable runs from the point of entry are heavy and will drop fewer volts as the amp demands grow...do I think I'll ever need all that 240V/30A, not likely, but it makes for a much better supply for the 2kW I want to use...
Many, apparently more pedestrian amps, can already overload a normal US outlet. The adcom GFA565 monoblocks I used to own could each use all of a normal domestic circuit. If we look at the krell models, a KSA50 is close to the limit as it approaches it's maximum class B output (>800va), a KSA100 is going to shut off the breaker if it is ever truly taxed...and without custom wiring no-one can use a KSA200 to more than a small fraction of it's potential...
Once the protoype is complete I'll probably sell it, or turn it into a (big) family of KSA50's...
You'd only have to look at my collection of components and equipment to realise I'm nuts, but hey, it's for fun...once I get a family, (my fiancee says soon), it will probably all go away.
Stuart
Don't get all excited, I need a higher voltage, lower impedance power source for prototyping. By using 240V, the current to the amp is halved, and the 30A feed means all the cable runs from the point of entry are heavy and will drop fewer volts as the amp demands grow...do I think I'll ever need all that 240V/30A, not likely, but it makes for a much better supply for the 2kW I want to use...
Many, apparently more pedestrian amps, can already overload a normal US outlet. The adcom GFA565 monoblocks I used to own could each use all of a normal domestic circuit. If we look at the krell models, a KSA50 is close to the limit as it approaches it's maximum class B output (>800va), a KSA100 is going to shut off the breaker if it is ever truly taxed...and without custom wiring no-one can use a KSA200 to more than a small fraction of it's potential...
Once the protoype is complete I'll probably sell it, or turn it into a (big) family of KSA50's...
You'd only have to look at my collection of components and equipment to realise I'm nuts, but hey, it's for fun...once I get a family, (my fiancee says soon), it will probably all go away.
Stuart
Banned
Joined 2002
Re: weird...
Saying your nuts is like saying wow your brave : O ) my dad did that same thing ran a new ( snake ) cable when i was a kid i remember it he ran a huge snake cable from the breaker box to the sound system it was nuts.. The post i was talking about sounds like your going to town and want to start welding : O ) WOAHH!!
Stuart Easson said:
Saying your nuts is like saying wow your brave : O ) my dad did that same thing ran a new ( snake ) cable when i was a kid i remember it he ran a huge snake cable from the breaker box to the sound system it was nuts.. The post i was talking about sounds like your going to town and want to start welding : O ) WOAHH!!