Hi Terry,
This amp is so darn good that I might just put my 50 in the closet for now. I just added another 58K mfd to the power supply and that also made a noticable improvement... mianly in the bottom end slam department.
To begin with I'm only up to 200mv bias due to the smallish size of my heat sinks and the wimpy power x-former I'm using so the amp will get even better with the 1.5 kva toroid and a fan on each sink so I can get the bias to normal levels Actually I think you could put this board into a KSA-50 and just leave one driver device out. Adjust the zeners in the front end accordingly or better yet power the front end from a seperately regulated +/- 50 volt siupply, this board allows for that.
The first thing you will notice is the lack of congestion that this amp has over the 50. In my room the speakers have literally left the room and there is just a huge sound stage that makes pinpointing any instrument or vocalist incredible easy. You could also expand your KSA-50 into a 100 provided you have enough space for another pair of outputs per channel. I prefer the TO-3's as they allow for an extra 50 watts of disipation over the plastic devices but I guess you could use either type. I am using MJ21193/94 pairs. Mine are pulls from rebuilding QSC 1400 power amps and I have alot of them stashed. This entire amp was built from surplus parts except some of the semi's and the PCB.
Mark
This amp is so darn good that I might just put my 50 in the closet for now. I just added another 58K mfd to the power supply and that also made a noticable improvement... mianly in the bottom end slam department.
To begin with I'm only up to 200mv bias due to the smallish size of my heat sinks and the wimpy power x-former I'm using so the amp will get even better with the 1.5 kva toroid and a fan on each sink so I can get the bias to normal levels Actually I think you could put this board into a KSA-50 and just leave one driver device out. Adjust the zeners in the front end accordingly or better yet power the front end from a seperately regulated +/- 50 volt siupply, this board allows for that.
The first thing you will notice is the lack of congestion that this amp has over the 50. In my room the speakers have literally left the room and there is just a huge sound stage that makes pinpointing any instrument or vocalist incredible easy. You could also expand your KSA-50 into a 100 provided you have enough space for another pair of outputs per channel. I prefer the TO-3's as they allow for an extra 50 watts of disipation over the plastic devices but I guess you could use either type. I am using MJ21193/94 pairs. Mine are pulls from rebuilding QSC 1400 power amps and I have alot of them stashed. This entire amp was built from surplus parts except some of the semi's and the PCB.
Mark
Mark- when you are still in testing,you can mebbe try this:
replace R15 and R19 with 200K,R16 at 8K25, C2+C3 combo with 10Uf film cap.....and try to hear difference....
mebbe I'm missing here something,as usual
replace R15 and R19 with 200K,R16 at 8K25, C2+C3 combo with 10Uf film cap.....and try to hear difference....
mebbe I'm missing here something,as usual
It hasn't does yet and is still a nice easy way to build a 1st time class a power amp. Still plenty of boards left. I;m still not clear that it IS actually the KSA-50 MK-2 version as I woild think there would have been the same MOSFETS in there.... I have a picture of a 50 MK-2 board someplace I;ll try to find it... very different that what we built.
Choky,
What are you thinking might happen with these changes?
Mark
Mark A. Gulbrandsen said:
Hi Mark,
I hope you find the time and curiosity to build a regulated power supply for the driver circuits and report the results. I posted an example regulator schematic that differs from the KMA80 in the single PCB KSA100 thread, and your experiments may rekindle interest in a KMA100 simgle PCB design
Well the first thing I would think of is higher noise, and dubious improvement due to the elimination of the electrolytic. IMO not worth it, and for any feedback-based amplifier you'll seldom see a 200k resistor in the feedback path.
As to the KMA-on-KSA PCB, it certainly is a good idea but size may be a limiting factor. For a full-out attempt the regulator(s) will take up as much space as the amp itself, especially if separate ones for the front-end and drivers are used. The drop-in replacement of the original boards will certainly not be possible anymore. The basic zener-follower regulator as shown in the KSA technical manual is much smaller, but not the ideal choice.
All in all it will be possible for a single-PCB solution, but I think that due to all the different requirements and space it will be better to use separate regulator boards. The large amount of on-board capacitance on the KSA boards makes it possible for longer cables from the regulator boards, and added resistance or inductance will even be a good thing. The simplicity of the regulators doesn't necessarily warrant a dedicated PCB though, especially the follower circuit.
As to the KMA-on-KSA PCB, it certainly is a good idea but size may be a limiting factor. For a full-out attempt the regulator(s) will take up as much space as the amp itself, especially if separate ones for the front-end and drivers are used. The drop-in replacement of the original boards will certainly not be possible anymore. The basic zener-follower regulator as shown in the KSA technical manual is much smaller, but not the ideal choice.
All in all it will be possible for a single-PCB solution, but I think that due to all the different requirements and space it will be better to use separate regulator boards. The large amount of on-board capacitance on the KSA boards makes it possible for longer cables from the regulator boards, and added resistance or inductance will even be a good thing. The simplicity of the regulators doesn't necessarily warrant a dedicated PCB though, especially the follower circuit.
Mark A. Gulbrandsen said:
A question I asked several times in the other thread and never got an answer to.
PWatts said:
even if I saw more than few amps with 150-180 K in feedback leg (and I mean on bip based diff stage ,not jfet or mosfet) ......mebbe is 100K and 4K1 and 10UF more appropriate........in that case- 3db corner will be under 4Hz
I'm sure that difference will be audible.
who knows?
mebbe even without 10UF,just dc coupled,with one eye on the scope 😉
Probably not in my lifetime, ZM.
What we need is to entice BillW to bring that commercial Krell amp out again, the one that set Mark's solder salivary glands going a few months ago.
And perhaps we could get Mark to fire up those huge Pass Aleph 1.2 monoblocks. It is getting cold out here in the Rockies, and we could use some heat...or something to blow out those wimpy Dynaudios.
😎
It's Halloween here in Utah, and the kiddies are ringing my doorbell for the treats. I give them the candy, but they ignore my advice: Don't record on 8-track or cassette. Don't leave any vinyl records in the back window of your parent's cars...Be sure to leave all amp projects with lethal voltages open ended with nothing covering them, to ensure maximum heat transfer and death to small pets and children.
What we need is to entice BillW to bring that commercial Krell amp out again, the one that set Mark's solder salivary glands going a few months ago.
And perhaps we could get Mark to fire up those huge Pass Aleph 1.2 monoblocks. It is getting cold out here in the Rockies, and we could use some heat...or something to blow out those wimpy Dynaudios.
😎
It's Halloween here in Utah, and the kiddies are ringing my doorbell for the treats. I give them the candy, but they ignore my advice: Don't record on 8-track or cassette. Don't leave any vinyl records in the back window of your parent's cars...Be sure to leave all amp projects with lethal voltages open ended with nothing covering them, to ensure maximum heat transfer and death to small pets and children.
Break from school.
Well, I am taking an online exam after this posting, but thought you would like to hear when the best time would be to meet.
I should be out of school for one day before Thanks Giving holiday. I could bring the real Krell KST-100 for comparison, although you already know that amp will be more scratchy sounding, but probably more power due to the beefed up stock Krell transformer.
If the KSA-100 is using the Avel transformer and that one is the same as my KST-100, I think that is a noisy transformer compared to my other transformers laying around.
Maybe, the toroid is being run harder than I use for my Alephs and that is why it hums more?
If that day won't work, I should be out some time in December. I am not sure when my finals are, but guessing in the worst case scenario no later than December 12th or so.
If you really want to pop your Dynadios, Todd could hook up his 850 RMS watt Adcom mono blocks to your speakers? He blew his Lowther PM6C's from those amps a couple of years ago. 🙁
Bill
Mark A. Gulbrandsen said:
Well, I am taking an online exam after this posting, but thought you would like to hear when the best time would be to meet.
I should be out of school for one day before Thanks Giving holiday. I could bring the real Krell KST-100 for comparison, although you already know that amp will be more scratchy sounding, but probably more power due to the beefed up stock Krell transformer.
If the KSA-100 is using the Avel transformer and that one is the same as my KST-100, I think that is a noisy transformer compared to my other transformers laying around.
Maybe, the toroid is being run harder than I use for my Alephs and that is why it hums more?
If that day won't work, I should be out some time in December. I am not sure when my finals are, but guessing in the worst case scenario no later than December 12th or so.
If you really want to pop your Dynadios, Todd could hook up his 850 RMS watt Adcom mono blocks to your speakers? He blew his Lowther PM6C's from those amps a couple of years ago. 🙁
Bill
And three square blocks worth of his neighbors windows! Sometime just before gobble gobble day should be ok. I've been a traveling fool lately!
I remember posting that photo and asking the same question and getting ignored too. I would bet our KSA-50 is a mid generation KSA...
PWatts,
What do you think about leaving one driver out and using this same board as a KSA-50 or to sub it in place of a MK-1 board? I would think that it ought to work just fine.....
Mark
Amp comparison
I hate all of you! 😀 You’ve got me thinking of building the KSA100 amps and I have yet to complete the KSA50. But before I go into this “little” venture - Mark are you sure that this amp sounds better? Perhaps limiting the output to 50watts would be a fairer comparison, as big amps usually sound better??
Regards
Harry
I hate all of you! 😀 You’ve got me thinking of building the KSA100 amps and I have yet to complete the KSA50. But before I go into this “little” venture - Mark are you sure that this amp sounds better? Perhaps limiting the output to 50watts would be a fairer comparison, as big amps usually sound better??
Regards
Harry
ALOT better! Here is a review I found a little while ago. Strangely it says some of the same very things I said about it earlier today. Is good to know my ears are in tune!
You might also consider being the first one to use this board in your KSA-50.....
Mark
_____________________
Summary:
My friend just upgraded to a KSA-200, so he gave me his KSA-100 Mark II to sell on eBay for him. But he offered me a good price if I'd buy it myself.
I was not expecting this amp to be such an improvement over my Aragon 4004 MkII, but I can't deny it after hours of comparing the two back to back. In fact, I was biased against hearing a difference because I wanted to hang on to my Aragon. The 4004 is well known and respected; it's very neutral but detailed and with good bass response. The Krell is huge, heavy, generates a lot of heat, and won't fit on my stereo cabinet. Those of you with some experience know that personal bias can make a big difference in what our ears perceive. Also, the Aragon is rated at 200W per channel into 8 Ohms, while the Krell is only rated at 100W at that impedance. So I was fully expecting the 4004 to at least keep up. Despite these biases against the Krell, it easily won in my back to back testing.
Well, first of all the KSA-100's power rating is apparently extremely conservative, because music was actually a tad louder at the same volume setting than with the Aragon. My speakers are Sonus Faber Concertos, noted for being difficult to drive and needing a beefy amp.
So what was the obvious improvement in the sound? Mainly threefold:
1. A clearer and more detailed upper midrange and high end. With the Krell, I nearly got goosebumps listening to tracks with fine vocals; it felt like the singer was in the room. With the Aragon, the music sounded like the recording it was.
2. A much wider and deeper soundstage. Instruments in the right channel sounded like they were coming from somewhere *beyond* the right speaker. Percussion often sounded like it was coming from behind the speakers somewhere, just where you'd expect the drum kit to be. With the Aragon, the sound was boxier and more confined, especially at higher volumes.
3. Greatly improved imaging. Closing my eyes, it was difficult to locate the speakers whereas before it was pretty clear. Instead of the soundstage being comprised of separate point sources as before, it's now continuous and the channels meld in the middle.
Another minor improvement is that the upper bass seems tighter, more controlled. This area still needs improvement and I think the only solution for this is to get full range speakers (the Concertos are small), but the KSA-100 did improve matters. I was able to hear the upper bass line more clearly in my rock music, whereas before it just muddled in with the subwoofer. Because of this, I was able to lower the crossover frequency of my sub to about 60 Hz (but up the gain a bit).
Overall, the sound is much warmer and livelier than with the 4004. After getting the 4004 I'd spent months enjoying my music collection several times a week. Guess what, it's time to do it again, the music sounds that much better. I suspect that this amp is finally letting my CD player (with tubed output stage) sing with the warmth it's known for.
Ok, so the amp is large and heavy. It's nearly two feet deep and well over a foot wide, and weighs around 100 lbs. It contains two internal fans to dissipate the enormous amount of heat it generates; the fans are completely inaudible to me unless I put my ear very close to the grille (and risk getting burnt!). As with all large Krell amps, there's a pair of handles on either side for easy transport with two people.
I love hearing the two loud clicks as the protection circuitry completes its self-check. This is a true Class A dual mono amp, with a huge transformer for each rail.
Well, I'm sold and am keeping it, putting the 4004 up for sale. Unfortunately this means that I'll need to get new furniture to put it on.
Btw, before bringing the amp home we also auditioned it for a few hours directly against my friend's KSA-200. The KSA-200 has better bass response and a more detailed top end, but isn't as warm in the midrange. This is most evident with male vocals, which through the KSA-200 sound a good deal quieter relative to the instruments. A startling difference, actually. The KSA-200 may be better suited for classical music. The KSA-100 seems to be better suited to rock and mainstream music.
For $900-$1200 used, this amp is an incredible bargain IMO. Due to its rugged construction, it's just as good used as new. The only issue to think about is aging of the capacitors. At some point they may need replacement. Everything else in the amp will last for decades to come.
My other equipment:
Ah! Njoe Tjoeb 4000 CD player
Aragon Soundstage preamp
Sonus Faber Concerto speakers
ACI Titan subwoofer
Strengths:
Warm midrange, apparently unlike later Krells from what I've heard.
Very clear and detailed high end.
Enormous power reserves, will drive anything.
A steal on the used market.
Weaknesses:
Sound wise, nothing I can think of.
Size and weight.
Low wife acceptance factor.
High power usage due to Class A operation, runs hot.
Similar Products Used:
Aragon 4004 Mk II
You might also consider being the first one to use this board in your KSA-50.....
Mark
_____________________
Summary:
My friend just upgraded to a KSA-200, so he gave me his KSA-100 Mark II to sell on eBay for him. But he offered me a good price if I'd buy it myself.
I was not expecting this amp to be such an improvement over my Aragon 4004 MkII, but I can't deny it after hours of comparing the two back to back. In fact, I was biased against hearing a difference because I wanted to hang on to my Aragon. The 4004 is well known and respected; it's very neutral but detailed and with good bass response. The Krell is huge, heavy, generates a lot of heat, and won't fit on my stereo cabinet. Those of you with some experience know that personal bias can make a big difference in what our ears perceive. Also, the Aragon is rated at 200W per channel into 8 Ohms, while the Krell is only rated at 100W at that impedance. So I was fully expecting the 4004 to at least keep up. Despite these biases against the Krell, it easily won in my back to back testing.
Well, first of all the KSA-100's power rating is apparently extremely conservative, because music was actually a tad louder at the same volume setting than with the Aragon. My speakers are Sonus Faber Concertos, noted for being difficult to drive and needing a beefy amp.
So what was the obvious improvement in the sound? Mainly threefold:
1. A clearer and more detailed upper midrange and high end. With the Krell, I nearly got goosebumps listening to tracks with fine vocals; it felt like the singer was in the room. With the Aragon, the music sounded like the recording it was.
2. A much wider and deeper soundstage. Instruments in the right channel sounded like they were coming from somewhere *beyond* the right speaker. Percussion often sounded like it was coming from behind the speakers somewhere, just where you'd expect the drum kit to be. With the Aragon, the sound was boxier and more confined, especially at higher volumes.
3. Greatly improved imaging. Closing my eyes, it was difficult to locate the speakers whereas before it was pretty clear. Instead of the soundstage being comprised of separate point sources as before, it's now continuous and the channels meld in the middle.
Another minor improvement is that the upper bass seems tighter, more controlled. This area still needs improvement and I think the only solution for this is to get full range speakers (the Concertos are small), but the KSA-100 did improve matters. I was able to hear the upper bass line more clearly in my rock music, whereas before it just muddled in with the subwoofer. Because of this, I was able to lower the crossover frequency of my sub to about 60 Hz (but up the gain a bit).
Overall, the sound is much warmer and livelier than with the 4004. After getting the 4004 I'd spent months enjoying my music collection several times a week. Guess what, it's time to do it again, the music sounds that much better. I suspect that this amp is finally letting my CD player (with tubed output stage) sing with the warmth it's known for.
Ok, so the amp is large and heavy. It's nearly two feet deep and well over a foot wide, and weighs around 100 lbs. It contains two internal fans to dissipate the enormous amount of heat it generates; the fans are completely inaudible to me unless I put my ear very close to the grille (and risk getting burnt!). As with all large Krell amps, there's a pair of handles on either side for easy transport with two people.
I love hearing the two loud clicks as the protection circuitry completes its self-check. This is a true Class A dual mono amp, with a huge transformer for each rail.
Well, I'm sold and am keeping it, putting the 4004 up for sale. Unfortunately this means that I'll need to get new furniture to put it on.
Btw, before bringing the amp home we also auditioned it for a few hours directly against my friend's KSA-200. The KSA-200 has better bass response and a more detailed top end, but isn't as warm in the midrange. This is most evident with male vocals, which through the KSA-200 sound a good deal quieter relative to the instruments. A startling difference, actually. The KSA-200 may be better suited for classical music. The KSA-100 seems to be better suited to rock and mainstream music.
For $900-$1200 used, this amp is an incredible bargain IMO. Due to its rugged construction, it's just as good used as new. The only issue to think about is aging of the capacitors. At some point they may need replacement. Everything else in the amp will last for decades to come.
My other equipment:
Ah! Njoe Tjoeb 4000 CD player
Aragon Soundstage preamp
Sonus Faber Concerto speakers
ACI Titan subwoofer
Strengths:
Warm midrange, apparently unlike later Krells from what I've heard.
Very clear and detailed high end.
Enormous power reserves, will drive anything.
A steal on the used market.
Weaknesses:
Sound wise, nothing I can think of.
Size and weight.
Low wife acceptance factor.
High power usage due to Class A operation, runs hot.
Similar Products Used:
Aragon 4004 Mk II
KSA-50 vs KSA-100
I hope you will have both the ksa-50 and 100 to compare so others can support this review or deny it. 😉
Bill
I am done with my test!!!
Mark A. Gulbrandsen said:
I hope you will have both the ksa-50 and 100 to compare so others can support this review or deny it. 😉
Bill
I am done with my test!!!
Just using one driver for the KSA50 shouldn't be a problem, which would make it an easy upgrade. I would however prefer just to double the output devices - most people use TO-3P's on a very large heatsink so adding more transistors should be very easy. In that case you can wire it up as a KSA100 and then later when the upgrade itch starts just jack up the PSU and turn the fan on harder ;-)