while on the subject of output devices, what about MJ15024/25? they seem to be able to dissapate as much as MJ15003/4's can.
by the way, i've never heard a Krell in my life. would you guys say this amp subjectively sounds 'warm' ?because i've heard a Bryston 3B ST and it sounded a little sterile, so i'm shooting for the opposite.
by the way, i've never heard a Krell in my life. would you guys say this amp subjectively sounds 'warm' ?because i've heard a Bryston 3B ST and it sounded a little sterile, so i'm shooting for the opposite.
You could certainly try them, but they are quite fast IIRC, so you might want to check for oscillations with a scope.
As for the sound, they just sound like Krells! Not really helpful, I know, but it's the truth!
As for the sound, they just sound like Krells! Not really helpful, I know, but it's the truth!
I have a question that some may find annoying and elementary. If you feel that way, feel free to tell me to go pound sand and buy a book. It's OK, I'm going to buy the book anyway🙂 The question is mostly for Stuart, but is general enough as well.
The ksa50 runs on ~40v rails. Stuart kicked it up experimentally to ~105 and developed a ccs(??) for the diff. ? I have dug thru the thread and can't find it, or at least any detail about it.
Is it possible to ramp the power up on this topology by simply giving the front end board it's +-40v with a small supply and running the driver and output on a (much) higher voltage, larger supply? Maybe I'm thinking wrong and the drivers should be at +-40 v as well, with the outputs at a higher voltage? Maybe I have no idea what I'm talking about and none are even a possibility (probably the latter🙂 ).
OK, should I get Self or Slone first?😉
D'uh.
Thanks,
Marc
The ksa50 runs on ~40v rails. Stuart kicked it up experimentally to ~105 and developed a ccs(??) for the diff. ? I have dug thru the thread and can't find it, or at least any detail about it.
Is it possible to ramp the power up on this topology by simply giving the front end board it's +-40v with a small supply and running the driver and output on a (much) higher voltage, larger supply? Maybe I'm thinking wrong and the drivers should be at +-40 v as well, with the outputs at a higher voltage? Maybe I have no idea what I'm talking about and none are even a possibility (probably the latter🙂 ).
OK, should I get Self or Slone first?😉
D'uh.
Thanks,
Marc
The Vas stage/transistor delivers all of the voltage amplification, therefore it needs as much voltage as the driver/output stage or more.
Everything that comes in front of the Vas stage gives current gain and can do with lower voltages on the rails.
Everything that comes in front of the Vas stage gives current gain and can do with lower voltages on the rails.
Thanks,
So, If I understand you correctly......
It would be possible to, in the case of the pinkmouse boards, give the input board +-40v. Then give the driver board and output boards say +-100v? All assuming the devices etc. can handle the voltage?
Is the driver board in this case the vas?
So, If I understand you correctly......
It would be possible to, in the case of the pinkmouse boards, give the input board +-40v. Then give the driver board and output boards say +-100v? All assuming the devices etc. can handle the voltage?
Is the driver board in this case the vas?
Hi Mp,
no, the front end is the voltage amplifier.
The output voltage is produced by the front end.
The output current is enabled by the output stages, pre-driver, driver and output devices.
You need the same voltage on the feed to the LTP and the VAS and the predriver and the driver and the output device.
The semiconductor that runs out of necessary voltage when trying to develop maximum output will cause clipping of the signal.
There is an exception, the tail of the long tail pair differential amp can be fed from a much lower voltage . However this amp has a pair of complementary LTPs and the top end of each pair needs the high voltage supply. So nothing to gain here in this case.
no, the front end is the voltage amplifier.
The output voltage is produced by the front end.
The output current is enabled by the output stages, pre-driver, driver and output devices.
You need the same voltage on the feed to the LTP and the VAS and the predriver and the driver and the output device.
The semiconductor that runs out of necessary voltage when trying to develop maximum output will cause clipping of the signal.
There is an exception, the tail of the long tail pair differential amp can be fed from a much lower voltage . However this amp has a pair of complementary LTPs and the top end of each pair needs the high voltage supply. So nothing to gain here in this case.
mpmarino said:
For some amplifier circuits voltage for the stages before the Vas can be lower. For instance: one that spreads the voltage gain by having an opamp chip in the front of the circuit that runs on ~15 volts. The general rule is that the full rail voltage is needed for the Vas and everything behind it.
For the KSA50 it's like Andrew says, the Vas devices need the full voltage swing on their base. So, the rail voltages of each stage needs to be at least at the level of the one for the output stage.
Guys,
l you need do is take a peek at the KSA-80 schematic on Lloyd Mclean's site to see what stage is powered by what supply.....Krell did much refinement in these later models with several seperate power supplies.
Mark
l you need do is take a peek at the KSA-80 schematic on Lloyd Mclean's site to see what stage is powered by what supply.....Krell did much refinement in these later models with several seperate power supplies.
Mark
Even better, take a look at the KSA100 MKII schematic on McLean's homepage.
The LTP of the KSA100 runs on 39 volts because of voltage drop through zener diodes, like the Leach design. You can run both designs with separate lower voltage PS's for those stages.
The LTP of the KSA100 runs on 39 volts because of voltage drop through zener diodes, like the Leach design. You can run both designs with separate lower voltage PS's for those stages.
Stuart, (or anyone else that can do the maths 😉 ), You may remember the "Low Bias" Krell, I built a month or so ago, which I'll be getting back in a couple of weeks. I ended up with 55V rails, (didn't bother with the ccs, just tweaked the tail resistors a little), and 5 pairs of MJ15003/4 cans per side. I would like to use it to drive my AV15, with 2x2ohm VCs. How near, or far over, the safety margin would I be? Or even a simple way of calculating for myself would do!
Thanks
Thanks
depends...
...are the voicecoils are in series or parallel? are you bridging amps? How 'big' is your power supply, can you expect it to collapse under heavy load? i.e. 55v at idle falling to 45v at full output is a much 'safer' situation.
5 pairs of mj5003/4 have plenty of current capacity (75A peak) for even a 2 ohm load. The aggregate power handling (>2500w) of the 10 transistors is pretty big, most "pro" amps wouldn't use this much output stage with 55v rails.
The average temp of the output transistors makes a huge difference to the margin, if they are cool to the touch at idle, I'd guess you are in good shape, I don't have the bensen spreadsheet here to run the numbers, but since you are defining and directly connecting the speakers there is less concern for highly reactive loads...
When I get home I'll dust off the spreadsheet and see what it says, someone else may have it handy and chime in before then.
Stuart
...are the voicecoils are in series or parallel? are you bridging amps? How 'big' is your power supply, can you expect it to collapse under heavy load? i.e. 55v at idle falling to 45v at full output is a much 'safer' situation.
5 pairs of mj5003/4 have plenty of current capacity (75A peak) for even a 2 ohm load. The aggregate power handling (>2500w) of the 10 transistors is pretty big, most "pro" amps wouldn't use this much output stage with 55v rails.
The average temp of the output transistors makes a huge difference to the margin, if they are cool to the touch at idle, I'd guess you are in good shape, I don't have the bensen spreadsheet here to run the numbers, but since you are defining and directly connecting the speakers there is less concern for highly reactive loads...
When I get home I'll dust off the spreadsheet and see what it says, someone else may have it handy and chime in before then.
Stuart
The driver has two 250W RMS 2ohm voice coils. I could series them up, and just use one channel, but it seems a bit of a waste really, so I was hoping to use one channel per VC. The traffos are s/h, I don't have the specs, but I would guess they are around 300VA each, and when I get it back, I can see how stable they are under load. I'll post a pic of the amp when it was under construction when I get home from work in an hour or so.
Just as an aside, this thing is unlikely to ever run at full load for an extended duration, I live in a terraced house and my usually tolerant neighbours would kill me!
Just as an aside, this thing is unlikely to ever run at full load for an extended duration, I live in a terraced house and my usually tolerant neighbours would kill me!
Mark, when you see this, i would really like to buy a pair of PCBs - i haven't been able to successfully email you in the past. please let me know. otherwise, does anyone have a spare pair of boards laying around?
BikeHorn:
I think Mark is out hiking in the desert today. He should get back to you late tonight, mountain time. He was helping me plan out my 12b4 linestage yesterday...his own system is looking and sounding very good. I had a short in my Grounded Grid preamp, and had to use my old Sherwood receiver as preamp duty into my Krell. I can't tell you how much I appreciated that ugly little Grid when I put it back into my system.
Mate the Krell with a good preamp, and you won't be sorry!!!
Lyndon
(Who wanted to post a Samuel Jackson photo on the Cables-Good or Bad? thread, but knew the mods wouldn't let us use the right language..."Cables!!! We got **** cables on this *** plane!!!")
😀
I think Mark is out hiking in the desert today. He should get back to you late tonight, mountain time. He was helping me plan out my 12b4 linestage yesterday...his own system is looking and sounding very good. I had a short in my Grounded Grid preamp, and had to use my old Sherwood receiver as preamp duty into my Krell. I can't tell you how much I appreciated that ugly little Grid when I put it back into my system.
Mate the Krell with a good preamp, and you won't be sorry!!!
Lyndon
(Who wanted to post a Samuel Jackson photo on the Cables-Good or Bad? thread, but knew the mods wouldn't let us use the right language..."Cables!!! We got **** cables on this *** plane!!!")
😀
thanks Lyndy, i'm sure mark's just busy...DIY audio is just a hobby and most people have a real life(i assume? heh).
on the subject of preamps, i've been looking around for a little while, and i think i'm going to go with Rod Elliot's P88 and P06 phono stage. inexpensive, lots of support for a not-so-experienced DIYer, easily available PCBs and pretty simple design. actually i was also interested in a single JFET design by carlosfm, on decibel dungeon(http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonepre2.html) but i'd have to make the PCBs myself and it uses a 47 volt single supply...i wanted to put the phono stage in the same chassis and i don't know of any that use a supply voltage anywhere near that so i tossed that idea, though i'd still like to build it one day.
on the subject of preamps, i've been looking around for a little while, and i think i'm going to go with Rod Elliot's P88 and P06 phono stage. inexpensive, lots of support for a not-so-experienced DIYer, easily available PCBs and pretty simple design. actually i was also interested in a single JFET design by carlosfm, on decibel dungeon(http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonepre2.html) but i'd have to make the PCBs myself and it uses a 47 volt single supply...i wanted to put the phono stage in the same chassis and i don't know of any that use a supply voltage anywhere near that so i tossed that idea, though i'd still like to build it one day.
Hi,
I have a quick question: does anyone know what the KSA-50's input impedance is? Or how I can go about to measure it?
The reason I ask is because I have to add a DC-blocking cap on the input, but don't know what value to use.
Thanks.
Paul
I have a quick question: does anyone know what the KSA-50's input impedance is? Or how I can go about to measure it?
The reason I ask is because I have to add a DC-blocking cap on the input, but don't know what value to use.
Thanks.
Paul
JoeyDD said:
Here is how I remember how to do this from 10 years ago.
Connect a known series resistor, say 10 ohms, the lower the better to the input and apply a known voltage, say 1 volt (don't connect a speaker when you are doing this).
Measure the voltage across your resistor. Compute input current "I in" from V = IR.
Now measure the voltage to ground across the input on the other side of the resistor. You now have "V in"
Compute R input = Vin/Iin
Have I got this right?
input impedance...
Hi,
With a DC blocking cap the DC resistance to ground will be enormous, theoretically infinite...measuring might not be useful.
Based on the 1k input resistor and the 22k resistor to ground, for audio frequencies I think you're going to find it's ~23k.
The input transistors have pretty high gain driving a pretty high impedance, so I'm assuming the base current is negligible.
At 23k, If you use a 10u capacitor the -3db point is <1hz, even a 1u cap gives <10hz...personally I've used a higher quality but smaller, value...IIRC a 2.2u polystyrene, it's large, over 1"x1/2", but I feel better about it than a regular electrolytic.
HTH
Stuart
Hi,
With a DC blocking cap the DC resistance to ground will be enormous, theoretically infinite...measuring might not be useful.
Based on the 1k input resistor and the 22k resistor to ground, for audio frequencies I think you're going to find it's ~23k.
The input transistors have pretty high gain driving a pretty high impedance, so I'm assuming the base current is negligible.
At 23k, If you use a 10u capacitor the -3db point is <1hz, even a 1u cap gives <10hz...personally I've used a higher quality but smaller, value...IIRC a 2.2u polystyrene, it's large, over 1"x1/2", but I feel better about it than a regular electrolytic.
HTH
Stuart
Bikehorn
You asked about sonics. This is my subjective opinion only!
The 2 I have finished with about 50 hours therebouts- matched mpsa's 800va Avel mono's Dale panasonic FM/FC wima bypasses
I have the Quads (first version) also a set of Martin logan SL3's and AudioConcepts Sapphire (DIY matched drivers wilson watt look)
Right now and probably not broken in yet, overall the sound can be considered very smooth- maybe just a little too much so. The high's seem a little down in amplitude compared to mid's and low's, however, (I think) so far, the sound keeps getting better and broader and might change when everything settles in.
Also, summer listening is not my favorite time to get serious about sound, winter time seems to grab my attention more, so this should be factored in.
My next set will use different input trannies, caps/bypass and outputs, with different wire to see if it can improve on anything.
Best matched with brighter speakers IMHO. The Quads rank 1st and sound great, ML 2nd (their highs start shelving down around 10 or 11K by themselves) also work very well. Seems to drive these without any load issues whatsoever
This is afterall, a mid 80's design and regulation would do wonders for bass tightness and top extension, but for what it does,
it does it very well !
Regards
David
You asked about sonics. This is my subjective opinion only!
The 2 I have finished with about 50 hours therebouts- matched mpsa's 800va Avel mono's Dale panasonic FM/FC wima bypasses
I have the Quads (first version) also a set of Martin logan SL3's and AudioConcepts Sapphire (DIY matched drivers wilson watt look)
Right now and probably not broken in yet, overall the sound can be considered very smooth- maybe just a little too much so. The high's seem a little down in amplitude compared to mid's and low's, however, (I think) so far, the sound keeps getting better and broader and might change when everything settles in.
Also, summer listening is not my favorite time to get serious about sound, winter time seems to grab my attention more, so this should be factored in.
My next set will use different input trannies, caps/bypass and outputs, with different wire to see if it can improve on anything.
Best matched with brighter speakers IMHO. The Quads rank 1st and sound great, ML 2nd (their highs start shelving down around 10 or 11K by themselves) also work very well. Seems to drive these without any load issues whatsoever
This is afterall, a mid 80's design and regulation would do wonders for bass tightness and top extension, but for what it does,
it does it very well !
Regards
David