| Mark A. Gulbrandsen |
| quote: | | KSA-100 used 2 of those tunnels. |
Speaking of KSA-100...... is anyone out there interested in persuing this amp as a project? I would definately want it to be the MK-2 version. All semi's are still available excepting the VN and VP series mosfets. These however could be easily subbed by modern IR units, perhaps using the IRF9610 and 610 devices.
This would require a new board design (Al Perhaps)? I would be willing to front the $$ to make up say 100 of them so they are available.
This seems like the next logical step in creating our own Krell Klones... then perhaps on to the KSA-80 or 160.
Let me know your ideas and opinions on this(constructive only please).
Thanks!
Mark |
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| awpagan |
| quote: | Originally posted by Mark A. Gulbrandsen
Speaking of KSA-100...... is anyone out there interested in persuing this amp as a project? I would definately want it to be the MK-2 version. All semi's are still available excepting the VN and VP series mosfets. These however could be easily subbed by modern IR units, perhaps using the IRF9610 and 610 devices.
This would require a new board design (Al Perhaps)? I would be willing to front the $$ to make up say 100 of them so they are available.
This seems like the next logical step in creating our own Krell Klones... then perhaps on to the KSA-80 or 160.
Let me know your ideas and opinions on this(constructive only please).
Thanks!
Mark |
I remember the ksa50, there was something about the sound that made it.
i wasn't overly impressed with the future krells:rolleyes:
although a ksa100 with later components could be interesting:D
how much difference in the circuit is there?
do you have a schematic?
allan |
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| pinkmouse |
| quote: | Originally posted by Mark A. Gulbrandsen
This would require a new board design (Al Perhaps)? |
Though I don't need a 100W class A amp, if someone can get me an accurate schematic I would certainly be willing to give it a go as and when time allows. |
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| konst |
| all schematics and service information you could possibly ask for is at the bottom of this pagekrell service info :smash: |
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| Upupa Epops |
| ... and after one year do it again... ;) |
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| konst |
I agree with awpagan though about there having been something special about the ksa50, i wonder if it makes more sense to build a ksa100mk1 (the post 1983 edition)?
and then after that make one of the BIG monsters, just because... |
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| jacco vermeulen |
| quote: | | I wonder if it makes more sense to build a KSA100 |
Constructing a KSA50 that can deliver nearly 100 watts in Class A makes more sense than trying to do the same with a KSA100.
Bare i mind that neither the KSA50 and the KSA100 were fully biased.
The KSA100 did 160 watts in 8 Ohms, the KSA50 is a good compromise between output power and dissipation. |
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| Upupa Epops |
| More heat, please... summer will be cold.... :D |
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| konst |
| îf you compare the schematics for the ksa50 and ksa100, they are very similar, with the ksa100 having more output devices and some of the component values being changed. |
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| awpagan |
| quote: | Originally posted by Upupa Epops
More heat, please... summer will be cold.... :D |
everyone. we'll have to do it.
just to make someone happy:D
allan |
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| Mark A. Gulbrandsen |
Actually the KSAS-100 Mk-2 is very different than the KSA-50 Mk-2. The addition of cascoded pre-driver stages and multiple drivers for the output stage. Also MOSFETS thrown in as CSS .... its not at all like the KSA-50 except for the input stage. Krell sold many more KSA-100's than KSA-50's so It couldn't have been a bad amp. The KSA-80B that I owned was far more complicated than KSA-100 MK-2 and sounded excellent!
KSA-100 MK-2
Pre 1983 KSA-100
Mark |
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| konst |
| If we start now, we will probably get them up and running reliably just in time for autumn - you wont have to stock up on wood for the fireplace :grouphug: |
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| kvholio |
If my memory is correct ksa-100 was first Krell that was adequate for driving Apogees at full swing.Years ago i listened to ksa-100/caliper combo (PAM preamp, sony esd557 as transport with Meridian DA-converter i think) many times and was VERY impressed with the sound this setup produced. just dont have the $$$$ :(
I wont be building ksa-100 in near future. Too busy building ksa-50 and chasing monster ;)
With kind regards,
Klaas |
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| konst |
i think there is some confusion here about versions of the MKII, there were two MK1 versions, prior to 83 and post to 83, I am not sure but i think the MKII arrived around 88 or 89, i was selling those in Germany at time, but can't remember exact dates, sorry.
Both the MKI version were bipolar only. |
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| awpagan |
| quote: | Originally posted by kvholio
If my memory is correct ksa-100 was first Krell that was adequate for driving Apogees at full swing.Years ago i listened to ksa-100/caliper combo (PAM preamp, sony esd557 as transport with Meridian DA-converter i think) many times and was VERY impressed with the sound this setup produced. just dont have the $$$$ :(
I wont be building ksa-100 in near future. Too busy building ksa-50 and chasing monster ;)
With kind regards,
Klaas |
just put some flashing lights on the krell, and the monster will come to you:D
allan
ps thought
after the krell has cooled down.:hot: |
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| Upupa Epops |
| Remember Mark, that the best boards makes BB..... ;) |
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| googler |
| quote: | Originally posted by Mark A. Gulbrandsen
I am also able to supply you with the Pinkmouse boards minus the OP sections @ 12.00 each if you like. I have 6 that way in stock....
Mark |
Hi Mark,
Does that mean that you have a few OP sections laying around as well? I'm still looking for 2 sets (4 boards) of Pinkmouse OP boards.
~Brad |
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| Flodstroem |
Hi
My intention is to build four KSA 100 based on the KSA 50 (Als board).
But for the output devices (MJ15003/4) and for the driver devices I plan to make my own boards.
I plan to use one driver pair to each two pair output devices and it will be at least 8 pair of output devices per amp (only mono blocks) It will then be four pair of driver devices on my new driver board.
Any tip or comments how to design those board is welcomed ?
BTW, anyone bought cheap transistors from the Chine/Hong Kong ?
May be a tip though I have: MJ15003/4 priced at $0.55 each (original Motorola/ON.Semi) as an example.
Regards :cool: |
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| Mark A. Gulbrandsen |
| quote: | | Does that mean that you have a few OP sections laying around as well? I'm still looking for 2 sets (4 boards) of Pinkmouse OP boards. |
K-Amps got them all!
Flodstroem,
Since you are almost doing the entire KSA-100 MK-2 with the exception of some of the preceeding stages might I suggest that we just do an actual board for the KSA-100 MK-2 including both TO-3 and TO-247 OP boards instead. I'm not sure that the preceeding stages of the KSA-50 can supply enough drive current for 2 pairs of drivers when operating at low impedances. Take a look at the actual schematic of the 100 MK-2 and I think you will agree that Dan went to great lengths to be sure that each preceeding stage was able to make its mark. Also those obsolete VN0210N5 and VPO210N5 devices only operate at about 3 mils so good subs are Zetex ZVP3310 and ZVN3310 and they are readily available and dirt cheap. The 1N5309 current limiter diodes are still made by MicroSemi Corp and in stock at Mouser.
One can also take this amp one step further and add the regulated supplies for the front end and driver stages that were in the KMA-100.
If Al is tied up with other stuff up a friend of mine that does board design at GE Medical may be able design the boards.
Of I can get at least a few others interested in this I will start a new thread for Kloning the Krell KSA-100 MK-2 and then we can proceed. Let me know if you're interested.....
Mark |
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| Stuart Easson |
...is a strange thing in an output stage...
Don't take this as meaning we shouldn't make a ksa100mk2 pcb set but...
According to most everything I've read, and so far tried, the more transistors there are in the output stage, the less current is needed from the drivers, all else being equal...ie using 3 pairs of the plastic power transistors will stress the drivers less than using 2 pairs of the to3s...
Using 5 or 6 pairs of the plastic transistors would use less current still...and since the ksa50 can drive 1 and 2 ohm loads without failing, I have to assume the ksa100 can do the same, heatsinks and power supply being the limiting factor...AndrewT has a spreadsheet that can tell you how many transistors you need for any given level of output into any particular load. Ideally the drivers need their own SOAR calculations, or you can just do as I did and go big...
I used the original board with 100v rails, mpsaX2 transistors and the CCS on the front end to keep everything alive to drive over 900w peak into 8ohms, at which point the rails had dropped to 85v or so...oh and I had 20 pairs of the to3 output transistors, ther drivers being a pair of the plastic outputs...no muss, no fuss. I don't have the means to measure distortion etc at this juncture, but assuming the PC based rightmark system can do a decent job it should be ready to go in the next couple of weekends at which point I may be able to tell whether there are other issues...
I am finally back to the point where I can work on this stuff, so I hope to be able to report something to all those that have been so patient...
Stuart |
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| Mark A. Gulbrandsen |
Stuart,
Its good to have you back here!
I am aware of your high power adaption to the 50 but there has to be a very good reason that Dan The Man did what he did in the MK-2 version of the 100.... and I suspect that it has more to do with its ability to drive very low impedances than any other factor. I remember a post about driver current way back in the thread and the lack of ability of the present driver to supply adaquate drive current to the KSA-50 OP stage.
Please compare the older pre 1983 KSA-100 versions with the MK-2 version and let me know what your take is on it and why he went the route he did... perhaps Andrrew would also chime in on this?
Mark |
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| AndrewT |
Hi,
it's a while since I last looked at the KSA Klone driver stage, so I'll sumarise from memory.
The MJE1503x pairs will take loads down to 1ohm easily.
2sa649/c669 will take loads down to 2ohm from +-40V rails.
At 1ohm loading they are being stretched to beyond MY limits but only just beyond.
If you want to go to higher voltages then the driver and output stages may (will) need to be beefed up. I would keep the drivers cooler than the outputs if designing for very low loads. CPU cooler with slow fan or copy Still4given's cool inlet over passive sink.
I suggest that if the output stage NEEDS 6pairs then the driver stage probably needs 2 pair to give the current capacity demanded by the multi outputs.
1pair MJE1503x to <5pair 2sa1943/c5200 (2ohm upwards)
2pair MJE 1503x to 6pair 2sa1943/c5200 (1ohm upwards)
1pair 2sb649/c669 to <4pair 2sa1943/c5200 (3ohm upwards)
2pair 2sb649/c669 to 4pair or 6pair 2sa1943/c5200 (1.5ohm upwards)
If you substitute higher power devices than 150W then proportion the number of devices to suit. i.e. 5pair @150W = 3pair @250W |
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| Flodstroem |
Mark:| quote: | Since you are almost doing the entire KSA-100 MK-2 with the exception of some of the preceeding stages might I suggest that we just do an actual board for the KSA-100 MK-2 including both TO-3 and TO-247 OP boards instead. I'm not sure that the preceeding stages of the KSA-50 can supply enough drive current for 2 pairs of drivers when operating at low impedances. Take a look at the actual schematic of the 100 MK-2 and I think you will agree that Dan went to great lengths to be sure that each preceeding stage was able to make its mark. Also those obsolete VN0210N5 and VPO210N5 devices only operate at about 3 mils so good subs are Zetex ZVP3310 and ZVN3310 and they are readily available and dirt cheap. The 1N5309 current limiter diodes are still made by MicroSemi Corp and in stock at Mouser.
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Yes Im with you, but I have already payed for KSA -50 boards (as you now) and also I have bought components for the KSA-50 (but, I could surely sell those at the Trading Post or in this post)
My first Krell-project will be one of (eg. four of) either the KSA 50 (100W), or the KSA 100 mk-2. I should prefer the KSA-100 mk-2 if there will be boards available.
I have the software needed to make everything for a PCB design including the Gerber generator, drill table, solder masks etc..... (one ore multi layer boards), but I havnt the component needed for to dimensioning the board etc.. and Im not a very skilled designer of Audio-boards.
But I have the experiences for to build Class-A amps (Pass) and thats good. Also I have useful ideas for the design of the driver-output boards. I have ordered Conrads heat sinks for this building project and they will be pre-toled for my output device block (+ OP boards). I could post some drawings of my ideas if need be if this is going to be a new building project.
Mark, what will be the first steps for to design this 100W mk-2 Agreement for a chematics ? or do we already have come to the next stage?
I have design a toroidal custom transformer (at Avel) for this project (for mono-blocks) and it could be used for either the KSA 50 (for 100W) or the KSA 100 mk-2 (76V CT @ 8-9 Amps 6-700VA).
I think your idea for to build this amp was an excellent innovation, especially when thinking of there is not so many building projects for a Class-A amp of 100W+ out there like this one.
Im looking forward to follow this "new" tread. Any more interested out there?
Regards :cool: |
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| pinkmouse |
| Mark, what PCB package does your friend use? I have Eagle, Osmond and Protel99SE, and if he uses one of those we could perhaps do it as a collaboration. |
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| ROVSING |
And here we go again...
I am sure that KSA100MkII would suit my PCB collection perfect:D
Any bets on the date of reply no. 1000 ? |
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| dr.strangelove3 |
Would there be an advantage if these possibly upcoming ksa-100 MK2 boards were used with the dissipation of the ksa-50?
I have most of the parts for a nice ksa-50, but the ksa-100 mk2 appeals strongly to me.
A lot of parts I have for the ksa-50 can be used for the ksa-100, what I can't use I can always sell.
But I don't want to go for a new case, and the case I have can only dissipate the heat of a ksa-50. |
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| AndrewT |
Hi,
can someone post specs for the various KSA/KMA outputs, bias & Vrail? possibly even Xpairs of devices & driver types.
Then we can see which are full ClassA (if any) and what dissipation/voltage we are talking about. |
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| acenovelty |
| This would be the board to clone? |
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| Flodstroem |
This is perfect.
acenovelty:| quote: | | This would be the board to clone? |
Yes, it looks very nice, also I liked the mountings of the input stage on same heat sink (same temp on all transistors)
But I would prefer to mount the driver stage on same heat sink as for the output devices (as where the bias device should be mounted)
I would like to post some drawings for my output boards soon so you could se what is my solution for this arrangement.
BTW, I work on the McCAD software from Vamp Inc.
Regards :cool: |
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| Mark A. Gulbrandsen |
Pinky, Thanks for creating this new thread!
Everyone,
My original desire was to ultimately build a KSA-80 but the KSA-100 Mk-2 circuit has had me greatly intreguied since the links to Mr. Macleans site was posted. kloning the KSA-80 would also involve aquireing ALOT of even harder to get parts and ALOT of device matching. The KSA-100 MK-2 version will require some matching but not to the extent that a fully balanced amp like the KSA-80 would. On the other hand a PCB design for the KSA-80 board already exists in these threads at DIY!!
Note that there also existed the KMA-100 Monoblock Krell amp that had the addition of regulated supplies for the front end and driver stages, similar to the regulated supplies done in the KSA-80. This additional supply could be a future addition to this amp and one could build a huge stereo amp or Monoblocks. I'd love to see a 6 channel version..... it would probably be the size of a refrigerator.
Al,
I know that at GE he uses Pads which is a very expensive program. I know he also has the full version of Eagle but not sure which release version. The good thing is that he is very up to date on all the industry standard design codes and such and he does alot of high voltage-high current stuff at GE. Allhe does there is PCB design. Anyway I have e-mailed Dave so we'll see if he is interested and has the time.
Getting to the Board.... Itt would be good to make it exactly as the Pinkmouse KSA-50 boards were done, just expanded a bit. Al's boards make bulding the KSA-50 VERY EASY! This would entail expanding the present driver board to accomodate the 2 extra driver devices and expanding the main board to accomodate the current source(?) MOSFETS and extra cascoded(?) predrivers. I would much prefer to see O.P. boards designed for both TO-3 and TO-247 devices done this time around and these should be done as seperate boards completely. Mk21193/94 devices are readily available in both TO-3 and TO-247P packages and are dirt cheap. This will serve to make the whole thing alot more universal and anyone wanting to purchase boards could literally go any route he desired... or could change his mind at a later date as per the O.P. device. So basically it should be the main board and driver board done together and routed to snap apart if desired. Then larger sheets of O.P. boards could be done up to just snap apart into the desired quantuty someone wanted to order. With the KSA-50 some folks didn't want the O.P. boards at all and some wanted extras...... So some board sets had to be sacrificed in order to get the extra O.P. boards. Hopefully they will sell some day.
Andrew,
I believe the rails of the KSA-100 are at +/- 48 to 50 volts. I am also pretty sure that its clip point is around 160 WRMS into 8 ohms... so the 100 watts class A might be valid as the 50 watts was in the KSA-50. Below are links to the schematics of both the main board and the output stage. Let me know why you think the driver and pre driver stages were greatly expanded upon as compared to the Post 1983 version which a link to is also below. There had to be a good reason he went to all the trouble of designing the Mk-2 version other than just plain marketing!! To me the post 1983 version IS nothing more than an expanded KSA-50! It could probably be built on the present KSA-50 board with some minor trace changes.
KSA-100 Mk-2 Main Board
KSA-100 Mk-2 Output Stage
Pre 1983 KSA-100
Every one else please jump in with your ideas and thoughts... perhaps then we can have boards on hand in about 60 days or so.
Thanks!
Mark |
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| jam |
The pre 1983 KSA-100 is almost an idental copy of the Aragon amplifiers( Krell has a hand in design) except for the bias that the unit was set at,
The Aragon had an excellent layout, with everything on one PCB that was attached to the hesstsink.............if someone has a picture,it might be a good starting point.
Jam |
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| AndrewT |
Hi,
looking at the pre83 and Mk2 versions of the KSA100, it appears that they adopted ccs (just like AL) for the LTP and simply added 2pairs of output devices giving a higher voltage version of a KSA50. As someone pointed out a while back this sometimes reduces sound quality.
With the higher driver voltage the driver becomes the limit and this could be what causes returns under warranty and possibly sound quality.
Along comes Mk2 with the return of the Zener fixed LTP source and cascode for the VAS and doubling up the driver ability. But the big change is the intermediate dual complementary LTP FET stage.
The big question:- which of these changes made 100Mk2 better than KSA50 and which made it worse.
Can I suggest that we incorporate ALL the tweeks that Dan had, that make it better, and leave traces in the board for any that cannot be shown to improve sound quality thus making these optional (the PCB space for this will be marginal) and allowing reversion to KSA50 topology where builders can experiment to find the best sound.
Looking back and comparing my driver posting, Dan has 1driver (MJE1503x) to 500W of output devices in the KSA50Mk2 and KSA100Mk2 cf. my limit of: 1driver per 750W of output device and Dan's 100pre83: 1driver per 1000W
The other difference, the driver Re has gone from 25r in KSA50 to 47r in 100pre83 to two times 75r in 100Mk2. |
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| AndrewT |
Hi,
this has been discussed before and I have deliberately NOT looked back at what was posted.
My thoughts are, the output stage is heavily biased and the running temperature depends little on the output power and much more on the ambient temperature. Once up and running and fully warmed up the output stage temperature and the consequent Vbe of the output transistors will vary very little and should not need much in the way of temperature compensation. Even when the Iq varies a little due to ambient changes with the seasons the effect on the total ClassA output will be small and consequently the effect on sound quality will be even smaller.
The driver stage is initially in ClassA and it too will depend on ambient temperature. But, the big differenece here is that the drivers are physically smaller (respond more quickly) and their temperature (Tj) depends much more on the output current. The variation in Vbe of the drivers is likely to be many times higher than the variation of the output stage Vbe (whether it is two times or ten times I cannot analyse nor measure). The Vbe multiplier if closely connected to the drivers Tj can and should compensate for the driver Vbe variation. There is little need to artificially raise the driver Tc to match the output stage heatsink temp and reduce the drivers' ability to cope with it's own loading.
I can see a possible need to optimise the driver Tc and Tj but this could only be done if it were separated from the output heatsink and then driver Re could be used to experiment with optimum level of driver Iq (controlling Tj + Tc).
If KSA100Mk2 is actually a high bias ClassAB design then a small amount of overcompensation in the driver stage will reduce output Iq as power levels rise above the ClassA level. This effect will be quite slow since the output stage has the inertia of eight Tc and a large heatsink to overcome before temperatures start to react. But at least overcompensation at high driver outputs will be in the correct direction if a little output compensation is required.
So my suggestion is that the four drivers and Vbe multiplier be on a common heatsink that strives to keep driver Tc considerably below output Tc. |
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| awpagan |
| quote: | Originally posted by AndrewT
Hi,
looking at the pre83 and Mk2 versions of the KSA100, it appears that they adopted ccs (just like AL) for the LTP and simply added 2pairs of output devices giving a higher voltage version of a KSA50. As someone pointed out a while back this sometimes reduces sound quality.
With the higher driver voltage the driver becomes the limit and this could be what causes returns under warranty and possibly sound quality.
Along comes Mk2 with the return of the Zener fixed LTP source and cascode for the VAS and doubling up the driver ability. But the big change is the intermediate dual complementary LTP FET stage.
The big question:- which of these changes made 100Mk2 better than KSA50 and which made it worse.
Can I suggest that we incorporate ALL the tweeks that Dan had, that make it better, and leave traces in the board for any that cannot be shown to improve sound quality thus making these optional (the PCB space for this will be marginal) and allowing reversion to KSA50 topology where builders can experiment to find the best sound.
Looking back and comparing my driver posting, Dan has 1driver (MJE1503x) to 500W of output devices in the KSA50Mk2 and KSA100Mk2 cf. my limit of: 1driver per 750W of output device and Dan's 100pre83: 1driver per 1000W
The other difference, the driver Re has gone from 25r in KSA50 to 47r in 100pre83 to two times 75r in 100Mk2. |
the big question...................
Was the ksa100 better than the ksa50?
It had more power so it could drive low impedance speakers (apogee) but what about the sound?
Andrew
i agree with the possibilty of leaving things out.
everyones ears are different.
allan |
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| AndrewT |
Hi Mark,
do you have access to Krell specifications?
160W into 8r needs an output of 50v6pk. This is impossible on a dual polarity Vrail= 50Vdc and even less possible if the +-Vrail=48Vdc when fully biased.
A maximum of 120W into 8r is more likely for +-48Vdc and possibly 130W for +-50Vdc. These maximum powers would be at clipping level when distortion is likely to be quite high.
What are the bias settings for the 100pre83 and 100Mk2?
Is there a later (Mk3) release? How do the KMA numbers compare?
I (we) could do with a full set of comparative data before we second guess how the Klone should be designed. It's like selecting the timber to build a bridge but then discover we haven't measured the width of the river.
Awpagan,
a little bit of ingenuity can keep the options open, a bit like Jan's Klone with the VI limiting (use it if you feel the need) or All's piggy back add ons for the very high voltage 50Klone. |
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| pinkmouse |
| Exactly. I don't have the time to do so much development on this one, so if you guys can decide what you want in advance, and get the schematic and devices nailed down, then that makes life so much easier, and you might actually get boards this year! ;) |
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| Upupa Epops |
| Can you tell me, guys, for what do you still can a Krell's ? Personally all Krell's, which I have heard, had audible distortion... Or is main advantage, that they can drive one ohm speaker ? Are you building amp or velding machine ? BTW, one ohm speaker can design only moron.... ;) |
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| AndrewT |
Hi Upupa,
if your| quote: | | ohm speaker can design only moron |
can do this, then I'll buy ten of them.
Sorry, cheap shot you don't deserve. It's the :devilr: in me that could not desist. |
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| Mark A. Gulbrandsen |
| quote: | | Personally all Krell's, which I have heard, had audible distortion... |
Actually the open minded view that I've always taken is to say that ALL ampifiers have audible distortion of some sort. The distortion of a giiven amplifier is a certain color and it just depends on what color you like. There is no perfect amplifier:D . If we could just get Upupa Epops to contribute to the thread in a positive manner......
Andrew,
I agree with your take on the 100's power output. It couldn't be more than 120 watts. I don't have any info on the KMA100... sorry. I doubt that it had any more power output than the stero version which was basically dual mono. I have a picture of the inside of a KMA-100 which I will look for and post later today.
As for the driver and VBE sensor I agree. I just found mounting them on the main sinks alot easier. Also the JAN board had the drvices tabs reversed from each other and the VBE in another position away from the drovers making even mounting to a small common sink a tough job, especially for newbies. Keeping in mind that most of us have fan cooled our amps and mounted the drivers and VBE on the main sink temperature changes and tracking can still occur pretty rapidly but granted not as fast as the smaller tab devices can. Now convection cooling would be another matter and it would happen very slowly!
I am presently re-building my 50 with some of the original heat sink tunnel that Krell used in the production models so my drivers and VBE will be mounted the way you originally pointed out.
Everyone,
As for the PCB if we make up a MK-2 board straight over it would be easily reverse-adaptable to building any of the earlier KSA-100 circuits. Neither myself, Al, or my friend Dave have time to adapt or figure out a universal pcb to accomodate all the versions. I am only willing to foot the bill to have 100 boards made up. Its easy to envision that the Mk-2 board straight over can be very adaptable in itself just by jumpering out certain devices and changing some part values to building the earlier versions of the amp. Hopefully those that are going that route would take the time to share that in a future chart with all of us. However it should be up to each individual building the amp to figure out for him self..... Otherwise this PCB deisgn might go on for two years! So in simple terms the universal board would already exist in the from of the MK-2 board!!
As for parts the only obsolete items are VN0210N5 and VP0210N5 devices. These drvices are only drwaing 3 mils so they an be replaced with Zetex ZVP3310 and ZVN3310 as JWB did in his KMA 160 reverse engineered Krell. HE did not even bother to sink them together since they dissipate so little. So that being said all that need be changed are those devices over to the Zetex unless anyone knows of a better device (I had originally thought of IRF9610 and 610 but the Zetex's spec better). All other parts are readily available off the shelf.
Al,
So that being said how do you feel about doing the Mk-2 board straight over, perhaps adding 2 spots for extra bypass on the main board like you did for the 50 main board. Then just expand on the present KSA-50 driver board? The O.P. boards shouldn't be any big deal and could come last.
Mark |
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| jacco vermeulen |
I believe the MKI had 41Vac secondaries, which is 57 Vdc something after the bridge.
The MKI powersupply states 52Vdc at the rails, which should stand for the loaded rail voltage.
160 watts continuous at 1% distortion in 8 Ohms should be in reach of these 52Vdc rails.
The MKII is unlikely to have lower rail voltages than the MKI.
I still have the 1986 test article of the KSA100MKII, the same Loek posted some time ago.
KSA100; 160 in 8 Ohms, 280 in 4, 400 in 2.
The KSA100 was measured to have a soft clipping behavior between 145 and 160 watts in 8 Ohms.
btw: i've heard both the kSA50 and the KSA100 on proper loudspeakers.
The KSA100MKII may have been better on Apogee's, i've never understood the charm of those metal washboards. |
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| awpagan |
| quote: | Originally posted by jacco vermeulen
btw: i've heard both the kSA50 and the KSA100 on proper loudspeakers.
The KSA100MKII may have been better on Apogee's, i've never understood the charm of those metal washboards. |
or very big cheese graters:D
"family size"
or morgue table
allan |
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| Flodstroem |
Mark:| quote: | | As for the PCB if we make up a MK-2 board straight over it would be easily reverse-adaptable to building any of the earlier KSA-100 circuits. Neither myself, Al, or my friend Dave have time to adapt or figure out a universal pcb to accomodate all the versions. I am only willing to foot the bill to have 100 boards made up. Its easy to envision that the Mk-2 board straight over can be very adaptable in itself just by jumpering out certain devices and changing some part values to building the earlier versions of the amp. Hopefully those that are going that route would take the time to share that in a future chart with all of us. However it should be up to each individual building the amp to figure out for him self..... Otherwise this PCB deisgn might go on for two years! So in simple terms the universal board would already exist in the from of the MK-2 board!! |
:up: Yes, to me it sounds like a good idea to make a MK-2 board with only minor changes due to the component substitutions and output board connections etc. Then the boards could be made in a relative decent time period and also to an acceptable fair price, dont you think?
Im in for 6 boards of the KSA100 MK-2.
Regards :cool: |
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| Mark A. Gulbrandsen |
It seems the logical way to go to me Flodstroem. The Mk-2 board is certainly able to please all others merely by jumpering out components and changing other parts values.
Mark |
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| Upupa Epops |
Andrew, if exist something like recomendation about impedance of speaker and somebody wittingly ignore it, how do you can term it ? :xeye:
Mark : Some more, some less....Krell markedly... ;) |
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| Mark A. Gulbrandsen |
Here are a couple of photos of the inside of the KMA-100. It appears that the power supply regulator and the main board aare stacked together on one side and the power supply also looks a tad larger.
Mark |
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| Mark A. Gulbrandsen |
| Another vuew of the power supply regulator board and main caps. |
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| Flodstroem |
Hi Mark
Any idea for what reason Krell used a power supply regulator ?
Was its purpose to rise the efficiency of the output stage
(this could be done by having a 5-10V higher rails on the input/driver stage)
Or was the purpose to lowering power supply ripple noise/buzzing?
Maybe both.
A long time ago I built a Pass 40W Class-A and implemented a solution similar like the Krells (I think but Im not sure about that). I think I used a regulator for ± 7-8 volt higher/lower than for the power devices who was darlingtons).
The benefit for doing it for me was lowering power supply noise AND a rise in power output capability, thus rising the efficiency of the amp (also: rising the total audio quality )
Wandering if this implementation should be located together on the amps driver board ?
It could be done though its not a high power circuit. Or is it impractical?
(benefit: you only need to make one board, not two. drawback: a more complex board/circuit)
What do you think?
Regards :cool: |
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| BillWW |
| quote: | Originally posted by Mark A. Gulbrandsen
So that being said all that need be changed are those devices over to the Zetex unless anyone knows of a better device (I had originally thought of IRF9610 and 610 but the Zetex's spec better).
Mark |
I have been experimenting with jfets on my Aleph 3 and found those are much more musical than the zvp3310a.
I am using the j176 jfet and do not know its complimentary version, but there are a whole range of mA versions for more or less driver power. It seems to be more spacious and much more extended in the highs with less distortion.
I have compared the j176 to the zvp3310a and found the zvp3310a is still very nice sounding, but not quite as sweet.
Since, we are designing a new board, I think this would be a good time to check on jfets. They do make a great big improvement on my Aleph 3.
Mark, when your ready, I could bring my Aleph 3 over to let you compare the zvp3310a in your mini Aleph vs the j176 in my Aleph 3, so you can decide what you like.
Regards, Bill |
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| dung0981 |
I am in for 4 set MKII
Thanks |
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| AndrewT |
Hi Mark,
do you still have that KMA? to take measurements and read off the psu data (+-80mF?) |
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| Upupa Epops |
| Sweet is sugar, honey, wine... What is sweet sound ? Is here technical forum or club of cooks ? :xeye: :D |
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| konst |
| i think we should stick as close to the original desing as possible, including using devices that are as close to the original as are avalalble, otherwise this would not be a Krell clone. |
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| pinkmouse |
Some things might be easy, others more complicated. What are the pinouts of the JFets and ZTX. Do the JFets need extra support components, or will they drop straight in?
You guys need to come up with answers, not more questions! :) |
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| pinkmouse |
| quote: | Originally posted by Upupa Epops
Is here technical forum or club of cooks ? :xeye: :D |
Pavel, I just keep flipping the burgers and shaking the fries. I know my place! :) |
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| Upupa Epops |
| Me too, Al...I was cooking at AM... ;) |
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| Mark A. Gulbrandsen |
| quote: | | i think we should stick as close to the original desing as possible, including using devices that are as close to the original as are avalalble, otherwise this would not be a Krell clone. |
Couldn't agree more but it needs to be the Mk-2 board. It would be easily backwards compatable with those desiring to be backwards in wanting to build the older versions. These older versions can be easily built on the existing KSA-50 boards we already have. Also just jumpering out some of the un-needed parts on the KSA-100 MK-2 board would also allow the same.
Flodstroem, Andrew,
Take a look at Mr Macleans site and look at the actual KSA-80 manuals and also at JWB's thread. I believe that the KSA-80 used a similar supply. Take a look at JWB's thread and schematic starting in Post 12 of the KSA-80 regulated supply. It is probably very similar to the KMA-100's. Note that the power supply WAS part of the KSA-80 main board and its a relatively simple supply.
Andrew......
Unfortunately I let go of the KSA-80B about 6 years ago. I wish I had kept the thing. The manual states that the rails in the KSA-80 were +/= 75 volts and the bias was 325mv across the 1 ohm emitter resistors. On all versions of the KSA-100 the bias was set for 575mv across those 1 ohmers. Hopefully this will help you out......
Al, The fries are getting overdone:xeye:! Here is the Zetex ZVP3310A and the ZVN3310 And the 1N5309 Current regulator Zener
JWB did not thermally couple his together in his KMA-160 rebuild, they are quite small in size so it is probably not really necessary since they will change temp from the ambient quite rapidly. Other than these parts I think you are already familiar with everything else used.
Mark |
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| Mark A. Gulbrandsen |
Here is a link to data on the old Supertex MOSFETS that were used but are now obsolete. Krell used the TO-220 versions of these devices.
VP0210N5
VNO210N5
Mark
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| pinkmouse |
| It's tempting to adapt the input stage of the KMA, just so we have a balanced option. |
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| konst |
| Mark I agree totally. |
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| Flodstroem |
pinkmouse:| quote: | | t's tempting to adapt the input stage of the KMA, just so we have a balanced option. |
konst:| quote: | | Mark I agree totally. |
Al and konst: an excellent suggestion . I also agree to this option for the KSA 100 mk-2, though my plan was to implement a balanced circuit input board for my planned KSA 50/100W building project.
Regards :cool: |
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| Mark A. Gulbrandsen |
| quote: | | It's tempting to adapt the input stage of the KMA, just so we have a balanced option. |
Al,
Actually neither the KSA-100 nor the KMA 100 had a balanced input stage at all but they did somehow eliminate ALL capacitors from the signal path probably including the caps in the feedback path. The write up at Krell History about the KMA-100 says.......
"KMA-100 and KMA-200 mono amplifiers introduce DC coupling from input to output, eliminating capacitors from the signal path. They also contain fully regulated power supplies for the front-end voltage gain stages and sophisticated protection circuitry for the output amplifiers. These innovations, coupled with massive power supplies, enable Krell amplifiers to drive any speakers."
The KSA-80 not only had a balanced input but was fully balanced differential from input to output.
" With the KSA-80 and KSA-200 amplifiers, Krell introduced fully balanced amplifier design, which maintains balanced operation from input to output."
I believe the KSA-80 would be pretty difficult to build and it would require alot of device matching......although the gerbers for a board design does already exist here .
Adapting the balanced part alone from the KSA-80 would be very difficult, adapting a balanced inoput to the KSA-100 MK-2 might be possible but is not true to the original. Anyway I doubt that many of us would be using a balanced input were it to be added....
Really, we should keep to the original design anyway if this is really going to be a klone just with the exceptions of adding more bypass caps as you did for the KSA-50... that can never hurt to have!
Mark |
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| jacco vermeulen |
| Do a fully biased KMA160 with vents. :clown: |
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| AndrewT |
Hi,
the KMA160 shows 3pair repeated as the output stage.
Is it repeated twice making 6pair or is it quads making 12pair for each channel? The pics seem to show 6BJTs on each sink and 4 sinks in total coming to just 6pair per channel.
In Krell's KSA80 & 200, KMA 160 & 400 manual it shows 325mV bias for all models. This equates to 0.975A per 3pair.
So what is the Iq? 1.95A or 3.9A? 1.9A gives ClassA =60W, 3.9A gives ClassA=240W
Is the KSA100mk2 a 4 pair output stage? Re=1r0? Bias voltage =325mV? or 575mV? Iq=1.3A or 2.3A? This gives 27W or 84W of ClassA.
Are we getting closer to some design numbers? |
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| Mark A. Gulbrandsen |
The KSA-100 MK-2 is a 4 pair O.P. stage. The KSA-80 is 6 pair per channel. The LMA 160 is 12 pairs that are driven from one main board. JWB's KMA 160 thread was all about building extra main boards to convert his KMA 160 monoblocks into KSA-80 stereo amps. Both share the same chassis, same power supply, same heat sinks.
Mark |
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| jacco vermeulen |
| To make it more complicated, the KSA-80B was a KSA-100 overhere. Confusing ? Of course not. |
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| Upupa Epops |
| Try to think economically, guys... and make this model like washdryer.... your wives will bless you.... ;) |
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| darkfenriz |
| Class A washdryer ? |
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| Mark A. Gulbrandsen |
| quote: | | To make it more complicated, the KSA-80B was a KSA-100 overhere. Confusing ? Of course not. |
Probably a mixup with the language barrier. All of the Krell's that I have seen for sale in Europe are exactly the same as over here in the states excepting the 220 volt primary.
| quote: | | Class A washdryer ? |
My Dryer runs on natural gas:hot:... how do we make a Krell to do that?
Mark |
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| Upupa Epops |
| Relationship between " power to speaker " vs producing heat is by normal listening levels app. 1:100, so why not... :D |
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| Flodstroem |
| quote: | Adapting the balanced part alone from the KSA-80 would be very difficult, adapting a balanced inoput to the KSA-100 MK-2 might be possible but is not true to the original. Anyway I doubt that many of us would be using a balanced input were it to be added....
Really, we should keep to the original design anyway if this is really going to be a klone just with the exceptions of adding more bypass caps as you did for the KSA-50... that can never hurt to have! |
Original is fine for me.
Now, if a decision will go for a KSA 100 mk-2 original, then it is not a big issue regarding designing of the front/driver board but what about the power supply?
In the schematic there is no information about what was the rail voltage for the front end /driver board except for those 39V zener diodes. Was Vcc/Vee ± 52V, 70V or 87V ? Was the front/driver board fed by the same rail as for the OP devices?
Does it exist a schematics for the power supply or was it same as for the KSA-80? Or have I missed something?
What transformer could be used for the KSA 100, mk-2, a custom or a standard? Just mention this because the original Krell main transformers for the KSA 80 etc..., could hardly be substituted with standard industrial types or could they?
Do we need to start a GB for a main transformer (I can do it).
Regards :cool: |
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| jacco vermeulen |
| quote: | Originally posted by Mark A. Gulbrandsen
My Dryer runs on natural gas |
Construct a James "dandy" Bongiorno amp. |
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| Mark A. Gulbrandsen |
Foldtrroem,
If this does end up going another way to something completely different both you and I can also still do the original MK-2 version although you and I would just split the proto run of baords as I doubt a production run would be worth it. I just got an e-mail from Dave and he is willing to do it. He says its a tiny project compared to what he's used to. I just have to get a list of component parts and types and get that to him along with the schematic. He will use "Pads" to do the files so we may have to post a viewer to be able to look at it.
As for the Xformer I would think that Plitron must have something that would work but I have not checked. A G.B. on that might be worthwhile for all interested in building it. Another possible might be Victoria Magnetics if they are still around. They were VERY reasonable to have custom trannys made. They stock an 8 amp transformer for the larger Dr. Leach amp... I wonder what the secondary voltage is on that tranny?
Mark |
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| Mark A. Gulbrandsen |
Jacco,
Is this Gas Amp what you were thinking of????? |
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| Mark A. Gulbrandsen |
Please see this post in the KSA-50 thread that pertains to both the KSA-100 Mk-2 and KSA-50 amps!
Mark |
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| Flodstroem |
Did ask them about possibilities (Custom design, steel can, shielding etc...). Ill post their answer in here later.
Mark:| quote: | If this does end up going another way to something completely different both you and I can also still do the original MK-2 version although you and I would just split the proto run of baords as I doubt a production run would be worth it. I just got an e-mail from Dave and he is willing to do it. He says its a tiny project compared to what he's used to. I just have to get a list of component parts and types and get that to him along with the schematic. He will use "Pads" to do the files so we may have to post a viewer to be able to look at it.
|
Absolutely Mark. I also agree to your suggestion regarding a proto run of boards.
Mark, have you ever seen a schematics for the mk-2´s power supply ? If not available then we had to measure some amps some where, or is there another possibility ?
Regards :cool: |
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| pinkmouse |
| Oh well, sacked again! Better fire up the griddle. :) |
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| gerhard |
| quote: | Originally posted by Flodstroem
What transformer could be used for the KSA 100, mk-2, a custom or a standard? Just mention this because the original Krell main transformers for the KSA 80 etc..., could hardly be substituted with standard industrial types or could they?
|
Why not, if the voltage & current ratings are right?
Quality-wise, standard industry transformers probably won't be inferior to that thing that sits in my Krell KST 100 and that annoys me with its loud hum.
Does anybody out there have circuit diagrams etc of the KST 100 ? I bought that used Krell because I really don't have the time to start yet another project. I'm already working on a PreAmp plus some RF / phase noise stuff and a day has only 28 hours... But it looks like the Krell is going onto the operation table RSN.
regards, Gerhard |
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| Mark A. Gulbrandsen |
| quote: | | Does anybody out there have circuit diagrams etc of the KST 100 ? |
Gerhard,
Throw out the KST-100 guts, it was never a very good amp but it is a great classic chassis! really, you've got the chassis and heat sinks to build your KSA-50 in! That should shorten your construction time to two days or less:) .
Everyone,
As far as a balanced input version I feel that is up to the individual to do that him/her self. Only a very few will be building this amp anyway and even fewer will want to make it balanced and then actually use it that way. Like Stuart Easson did up the current source for the front end of the KSA-50 you could also do up a balanced input board that could be piggybacked to it for a balanced input option. Having owned complete balanced systems in past years(Krell included) I can tell you how greatly unimportant balanced is in a home system. If you really want balanced then we need to do the KSA-80/KMA-160, but I feel that is a year down the road for us as a project. It will be quite dofficult and the j-fets needed will be somewhat difficult to obtain.
Lets make this a many sided project with those wanting options doing the design work themselves and posting it in the thread.... then we can do a small piggyback board for it. But above all lets at least keep the main board as clean as in the original or should I say lets keep it a klone and not branch out into outer space where the original board never went. Someone else could also do the power supply for the main board and I feel that looking at the KSA-80 regulated power supply diagram is a good starting point. Power supplies don't get much simpler than that! Perhaps it could be made even better.
Al,
You've hardly been griddled..... er... ah.... sacked. I only sack potatoes and you're peachy keen! Dave only agreed to do the main board. What would be nice would be if you also did one and we combined the best of the two together. Keep in mind that Dave knows all the standard PCB criteria for high voltage/high current boards, component spacing, copper clearance, etc. We also will still need the driver and output board files done as well. He did not agree to do those too. It couldn't possibly take you more than an hour to modify the existing KSA-50 driver board files for two extra driver devices...... Dave could use them to work backwards with that board in his mind so the terminals, rail connection points, etc match up the forst time around. The KSA-50 output board file is also easily modified for the 100. A TO-3 board would have to come from scratch. Since you say you're very busy I was only considering that the main board was more than your time allotment could tackle??? Its probably a couple hour job for Dave. But if you wanna tackle the whole thing its fine with me also. I am just attempting to get this going in as short of time as possible to keep this thread going and I am still willing to foot the bill to make up 100 board sets. Perhaps I could ship you half the boards in return for you doing the files and you could do overseas sales of them and I would take care of this part of the globe. That way we both might break even. Presently the KSA-50 board sales I'm running about $600 US negative with most of the second batch still sitting here, but thats ok too. I didn't expect them to disappear overnight like the forst batch did, neither will the run of 100 KSA-100 boards disappear very fast.
Mark |
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| Luke |
Has anyone compared this to the KSA50 we just built? I like the idea but not sure its a much better performer. People here seem to think the KSA50 was the better krell. Also, I never understood why the drivers were on a separate board in Als version of the KSA50. Isn't it easier to have the front end and drivers on one board?
Im not knocking, just trying to decide if I get boards for this project, I really want my Aleph-X to be next, but I have too little time these days and too long a wish list:)
seeya ab |
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| Flodstroem |
| quote: | Why not, if the voltage & current ratings are right?
Quality-wise, standard industry transformers probably won't be inferior to that thing that sits in my Krell KST 100 and that annoys me with its loud hum. |
Take a look at my last post, the link will tell you why I suggested a custom transformer though it could be very difficult to find a transformer like the ones used in Krell originals (all the output voltage, shielding, potted in a can, low noise etc..etc). The issue of a custom is relevant if the power supply will be similar as to the KSA 80/160/200..................otherwise you are probably right.
Regards :cool: |
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| AndrewT |
Hi,
is anyone else having trouble downloading the PDF in post 80?
Is my school viewer too old? |
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| pinkmouse |
| It comes out as completely blank on my Mac with the latest Safari and pdf plugin. Is that your problem as well? |
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| pinkmouse |
Mark, no problem, I was only joking! :)
A TO3 output board should be no problem, as will be upgrading the driver board. What format should the files be so Dave can read them? Can he take Protel/Eagle files, or will he need to import Gerbers? |
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| gerhard |
| quote: | Originally posted by AndrewT
Hi,
is anyone else having trouble downloading the PDF in post 80?
|
works here. Firefox 1.5.0.2, Acrobat 6.0
and no, I won't kill the KST100. Ignoring the mechanical hum, it's completely ok. Sounds good, controls the speakers oooh so tightly etc. If necessary, I'll have someone wind me a new transformer or overhaul the old. Should be no problem here in Berlin.
Buying a working Krell and killing it for parts is not cost effective and shows some hybris. Glueing pre-existing kits together is boring, as far as I'm concerned.
I'm not interested in soldering per se but more in design, simulation and learning new tricks. A few years ago, I built an amp for applications in geophysics that could spit out +- 650V, 1A, w/o bridging, no time limit, open, short and funny loads allowed. Sooner or later I'll redo it for audio with bipolars, without having to stack lots of p-channels to make them safely withstand 2 KV.
regards, Gerhard |
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| konst |
| quote: | | few years ago, I built an amp for applications in geophysics that could spit out +- 650V, 1A, w/o bridging, no time limit, open, short and funny loads allowed. Sooner or later I'll redo it for audio with bipolars, without having to stack lots of p-channels to make them safely withstand 2 KV |
Now this i have to see, have you got a schematic, perhaps we can do a little sideline from the krell :smash: :smash: :smash: |
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| Flodstroem |
| quote: | | Now this i have to see, have you got a schematic, perhaps we can do a little sideline from the krell |
Yeah! ±650v thats something, realy. 459.6Vrms thru 8 ohm yield a power output like 26406W. Hmmmmmm, had to change my speakers, but then it was the d... 1Amp, -we must get rid of that!
Regards :cool: |
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| konst |
heheh Imagine the spark into a 0ohm "Funny Load"
:D |
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| AndrewT |
Hi,
could it cope with the 0r5 load that Krell say they can do?
now 650V divided by 0.5 ..... hey, that's a big number! >420kW :hot: |
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| Mark A. Gulbrandsen |
| quote: | | Also, I never understood why the drivers were on a separate board in Als version of the KSA50. |
Its been covered before.
1. The JAN board had the tabs of the two drivers reversed form each other.... not a user friendly way to mount them and difficult for newbies to deal with.
2. Most also did not like the addition of current limiting..... Krell never used any.
3. 1/2 watt Vishay resistors just barely fit between the holes.
4. No bypass options.
With Al's board design you have the option to leave the driver board attached, or break it off and mount it in the main sink. what ever is your pleasure........
Al,
Dave does have Eagle but I don't know what version. He uses PADS for all his design work though so a gerber translator will be necessary.
Gerhard...
I've heard the KST-100 before. The KSA-50 is far better.
Mark |
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| Upupa Epops |
| One of basic test at UL, VDE, etc. is test of shorting output of amp.... Have Dan d'Agostino some exemption clause ? :D |
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| kvholio |
Since we're talking ridicilous numbers anyway...
How about using 6 x 100kw/12.7 Vac transformers in series to get +/50Vdc...at my job we use them to kick out 10Vac (600Hz) and roughly 3500 AMPS. They weigh about 200lbs. each and need watercooling.Also "a few" extra OP-devices would be needed and some nice C's after rectifying(with what ?????).
But it would drive a 0.002 ohms load without problems.
FYI: we use them for welding thin metal sheet (0.16 mm) at "walking speed" (65 meters/min).If you approach welding-circuit at 2 feet with magnet in hand it'll vibrate at 600hz :D
http://www.soudronic.com/metal/114-...dy_welders.html
Since i get my "amps-kick" at work i just need music at home
Klaas |
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| gerhard |
| quote: | Originally posted by AndrewT
Hi,
could it cope with the 0r5 load that Krell say they can do?
now 650V divided by 0.5 ..... hey, that's a big number! >420kW :hot: |
It can cope with 0r5 for output voltages that don't require more than 1A :cool:
Thats not very loud. I burnt a lot of FETs until the current limiting worked and until the amplifier did not oscillate at the onset of limiting. Having isolated differential scope probes is important and developing the habit of having one hand in the pocket helps to survive.
They used the amp to pump current into the soil, measured potentials every few meters and then could oracle what was down there 20 meter deep.Rubber boots are essential, worms don't like it. I wonder why nobody has died.
Konst, I won't publish the circuit of this HV amp. The audio version is a different story but will not happen before autumn. It's quite Self-ish, so many people here will miss the euphonic distortions :-) It will not current limit but instead remove both rail voltages with transistor switches. These might double as capacitance multipliers to improve PSRR, I have not yet made up my mind.
regards, Gerhard |
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| konst |
| Hallo Gerhard, verstehe Ich volkommen, freue mich schon auf die audio version :D |
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| Flodstroem |
Here is a link to my suggestion (have tested it in practice) for to mount To-3 devices to a flat surface of a heat sink. Because of the mounting solution it is very easy job to design a PCB for whole power/output stage (one board for all components including copper strips for the rails)
Could be useful if this is the way to design a power device board (a sort of a surf mount board)
http://www.diyaudio.com/forums/atta...tamp=1146061771
in the thread:
http://www.diyaudio.com/forums/show...&threadid=78412
Regards :cool: |
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| K-amps |
| quote: | Originally posted by AndrewT
Hi Mark,
do you have access to Krell specifications?
160W into 8r needs an output of 50v6pk. This is impossible on a dual polarity Vrail= 50Vdc and even less possible if the +-Vrail=48Vdc when fully biased.
A maximum of 120W into 8r is more likely for +-48Vdc and possibly 130W for +-50Vdc. These maximum powers would be at clipping level when distortion is likely to be quite high.
What are the bias settings for the 100pre83 and 100Mk2?
Is there a later (Mk3) release? How do the KMA numbers compare?
I (we) could do with a full set of comparative data before we second guess how the Klone should be designed. It's like selecting the timber to build a bridge but then discover we haven't measured the width of the river.
Awpagan,
a little bit of ingenuity can keep the options open, a bit like Jan's Klone with the VI limiting (use it if you feel the need) or All's piggy back add ons for the very high voltage 50Klone. |
Just saw this thread... I am not getting emails again!!!
I owned the KSA-100mk.II. Thought it sounded a little dark and limited HF extension. Had tight bass/ midbass. personally I think the KAV-250a (which I still have) sounds much better... but thats my opinion...
I measured the loaded rails on the KSA-100 mk.II
with 118v mains, the DC rails were +/- 53.5vdc. 690mv across the 1 ohm emitter resistors meant it was biased to 122 watts pure class-A into 8 ohms. |
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| AndrewT |
Hi Kamps,
thanks for your info.
It confirms that your Mk2 was almost fully biased (about 80 to 90%) into ClassA for an 8ohm load.
Much different from the mk1.
It also confirms the dissipation of the 4pair output stage @295W, more than double the KSA50mk2 |
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| K-amps |
| quote: | Originally posted by AndrewT
Hi Kamps,
thanks for your info.
It confirms that your Mk2 was almost fully biased (about 80 to 90%) into ClassA for an 8ohm load.
Much different from the mk1.
It also confirms the dissipation of the 4pair output stage @295W, more than double the KSA50mk2 |
Why 80-90%, Isn't it 122%? |
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| AndrewT |
Hi Kamps,
not quite, your measured Vrail supports the contention of Mark that the peak output of the 100Mk2 is nearer 160W (50.6Vpk) into 8r.
0.69V bias gives Iq=2.76A.
Peak voltage in ClassA will be just below 2*2.76*8= 44.16Vpk.
I would expect the KSA100mk2 to manage quite a bit than 44.1Vpk into 8r.
ps what is the rated input voltage for the rated (specification) output voltage? |
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| Stuart Easson |
Hi All,
Not been keeping up so I'm going to jump in here with a potentially ill informed comment....
The peak voltage required to get 100w RMS (200w peak) (class A or B) into 8 ohms is 40v...so the peak current is 5A, so the idle current needs to be a minimum of half that, ie 2.5A...now if I read the comments thus far the contention is that 2.76a bias is not a 'real' ie 100%, 100w Class A amp, I think it is...assuming you have a resistive load, and the fact that Krell used 2.76A gives a 10% margin for slightly weird loads.
The extra voltage and extra current are gravy, Krell promised 100w RMS Class A into 8ohms.
Please point out the flaws in the reasoning....
Stuart |
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