The components
just a couple questions to update me the components....
in the krell's chematics avaible on internet, the components udes are:
MJ 15004/5 for the outputstage drivers f
MJE 15030/1
i could't find these followings components:
2SA 9688
2SC 2238
2N 6431
2N 6433
...come questions about this.... where can i find that components?
...and....dtalking about hi grade componets..andd quality in general........i know...that the same devices can be made from motorola ...or other companies.
does the fact that the componet is made from a company rather than another make digfference talking about audio quality.
More....talking about resistence and capacitor where can i find a good company that makes hi-quality components? for instance.....Infinity cap (for the capacitors)......
i'm looking forward to hearign your suggestions.
Stefano.
just a couple questions to update me the components....
in the krell's chematics avaible on internet, the components udes are:
MJ 15004/5 for the outputstage drivers f
MJE 15030/1
i could't find these followings components:
2SA 9688
2SC 2238
2N 6431
2N 6433
...come questions about this.... where can i find that components?
...and....dtalking about hi grade componets..andd quality in general........i know...that the same devices can be made from motorola ...or other companies.
does the fact that the componet is made from a company rather than another make digfference talking about audio quality.
More....talking about resistence and capacitor where can i find a good company that makes hi-quality components? for instance.....Infinity cap (for the capacitors)......
i'm looking forward to hearign your suggestions.
Stefano.
Stefano,
Try MCM On Line. They have all the semi's that you need for the Krell....
Mark
http://mcm.newark.com/
Try MCM On Line. They have all the semi's that you need for the Krell....
Mark
http://mcm.newark.com/
Just insert a CL-60 inrush limiter in series with the power transformer promary. I use them in all my priject amps and it eliminates all the BS circuitry for a relay type soft start. Cost is about 2 bucks!
Mark
Mark A. Gulbrandsen said:
i would probably do that if i knew i wasn't going to be frequently powering up/down my amp. from what i read though, thermistors don't provide much protection once they've heated up, so powering it down and them turning it back on in a short time would be almost the same as there not being any protection at all. is this a really big deal?
actually, i had an idea that i came up with when i was looking at a device that attaches between power supply and fan in a computer. the idea is to run the fans for a few minutes after the computer's been shut off, to cool the processor/GPU/etc suitably since apparently temperature rises a fair bit after power to cooling fans has been cut off, even if the processors are no longer processing.
i was going to use a fan tunnel to cool my KSA50. the sound of a fan doesn't bother me in an amp, and if it's a silent one, i'm happy to deal with there being a fan there if i can make the whole thing more compact. i thought it would be neat to use those aircraft-style switches with the flip-up cover on them...maybe have a switch labeled "power" that turns on lights, fans and other bells and whistles, and another switch labeled "arm" that powers up the actual amp. the idea being, aside from having a cool-looking switch that says "arm" is that you would be able to turn the amp on and "arm" it, then when done with it, you "disarm" the amp but leave the fans and stuff running for a bit, then kill it. alternatively you could just turn them off together but i figure, not much more effort and it'll extend output device life if used as intended.
also, on the "making it more compact" thing, i have decided to go with a capacitance multiplier supply. does anyone have any experiences with these? i've read as much as i could find about them and it seems simple enough if the wires are laid out correctly. i guess i will need slightly higher secondary voltage to make up for the loss.
in the link that oyu sent me....i couldn't find the semicondactor that i need in order to built the amply.
i wasn't able to find the 2sa9688 and the 2n6431.
....but i found just the 2sc2238.
is anyone ale to explain to me why there is this huge difference in prices betwen toshiba and panasonic? (from 1.20$ up to 6$ for the panasonic)
....could anyone give me some suggestion about the capacitors resitor trasformer diode....good company....with hi grade components?!
for insatance...capacitors infiniticap....
does anyone has a feedback on this? could someone help me so see some of the catalog?
i wasn't able to find the 2sa9688 and the 2n6431.
....but i found just the 2sc2238.
is anyone ale to explain to me why there is this huge difference in prices betwen toshiba and panasonic? (from 1.20$ up to 6$ for the panasonic)
....could anyone give me some suggestion about the capacitors resitor trasformer diode....good company....with hi grade components?!
for insatance...capacitors infiniticap....
does anyone has a feedback on this? could someone help me so see some of the catalog?
got the mistake....the 2SA 968B is used .... not the 2SA 9688....
wich drivers for the differential input stage are used in the mkII version??
....now that i'm getting into the project....i 'm undertanding something about the mkI mkII.....staff like that......
has anyone never experimented the difference on the sound betwen this two versions?
i mean...is it not correct that krell officil sell just krell ksa 50? not mkI mkII.....so shouldn't they sound the same?
...the only other ksa 50 that i know is the ksa 50S ....am i wrong?
so...when i read that the best krell ever buit is the first version of the ksa50.....are they referring at the ksa 50.....or specifically at the ksa50 mkI ?
because to chach that one you should open and see the devices used...because i don't thinkk that they made a logo on the krell with mkI and mkII......right?
...anyway could anyone give me any answer on about the differencial stage..wich devices are used....and....about the quality of the components (the prewious post)?
wich drivers for the differential input stage are used in the mkII version??
....now that i'm getting into the project....i 'm undertanding something about the mkI mkII.....staff like that......
has anyone never experimented the difference on the sound betwen this two versions?
i mean...is it not correct that krell officil sell just krell ksa 50? not mkI mkII.....so shouldn't they sound the same?
...the only other ksa 50 that i know is the ksa 50S ....am i wrong?
so...when i read that the best krell ever buit is the first version of the ksa50.....are they referring at the ksa 50.....or specifically at the ksa50 mkI ?
because to chach that one you should open and see the devices used...because i don't thinkk that they made a logo on the krell with mkI and mkII......right?
...anyway could anyone give me any answer on about the differencial stage..wich devices are used....and....about the quality of the components (the prewious post)?
Whew! I've been following this thread since day 1 and have forgotten most of what I've read. With so many other projects I've always told myself "self, your gonna have to get some boards someday and build this thing". Thanks to MikeW someday is now. See what you've done Mike, dag nabbit🙂 By the way, that mosfet 40 is nice...The bass is solid and it sounds real good. I still have yet to hear better mids than the A30 though😉
Need I mention this thread is long? Need I mention that getting info out of it is very difficult? These things lead me to a few questions if you folks don't mind.
All are in relation to Al's boards, I'm currently 'parts gathering'...
1) Rail voltage. I see that it is normaly -+ in the high 30's. Due to parts availability I may end up in the -+42 volt range. ? I know I'll make a bit more heat and etc. but my worry is that something may not like the slightly higher voltage Is this a problem? If so, I will implement some kind of a CRC.
2) Bias. I see that this thing does ~50wpc class A and 75wpc AB under normal conditions. If I lower the bias will I just lower the power into class A but retain the 75w AB level? Will it current limit like an Aleph with lower Bias?
3) Does anyone have any MJW1302/3281 they would be willing to sell me? I'm looking for 3 or 4 of each. Or maybe someone knows who stocks them
.
sorry...one more:
5)Q111 on Al's BOM says MJE15032 OR MJE15030..Is one preferred or does it not matter?
Thanks a lot Guys! I don't want any
flames on this one.... I'm talking 'bout the real flames...you can make fun of me all you want🙂
Need I mention this thread is long? Need I mention that getting info out of it is very difficult? These things lead me to a few questions if you folks don't mind.
All are in relation to Al's boards, I'm currently 'parts gathering'...
1) Rail voltage. I see that it is normaly -+ in the high 30's. Due to parts availability I may end up in the -+42 volt range. ? I know I'll make a bit more heat and etc. but my worry is that something may not like the slightly higher voltage Is this a problem? If so, I will implement some kind of a CRC.
2) Bias. I see that this thing does ~50wpc class A and 75wpc AB under normal conditions. If I lower the bias will I just lower the power into class A but retain the 75w AB level? Will it current limit like an Aleph with lower Bias?
3) Does anyone have any MJW1302/3281 they would be willing to sell me? I'm looking for 3 or 4 of each. Or maybe someone knows who stocks them
.sorry...one more:
5)Q111 on Al's BOM says MJE15032 OR MJE15030..Is one preferred or does it not matter?
Thanks a lot Guys! I don't want any
flames on this one.... I'm talking 'bout the real flames...you can make fun of me all you want🙂
Ok, here we go...
1) Mine is running quite happily, (or was, I took it apart to case it up properly and haven't quite got round to finishing it yet), with a 30-0-30 with the aforementioned 42V rails. CRC might be fun to try, but it's not essential.
2) In my purely practical experience it seems to, but I'll wait for someone with a better grasp of theory to confirm.
3) Sorry, no. I'd like some more as well as it happens...
4), What happened to four?
5) Both work equally well in listening tests, but the 15030 is a slightly better rated component for the voltages we're using. Jacco raves about the original Japanese tranny, but he seems to be one of the few people that can get hold of them.
I hope this helps.
1) Mine is running quite happily, (or was, I took it apart to case it up properly and haven't quite got round to finishing it yet), with a 30-0-30 with the aforementioned 42V rails. CRC might be fun to try, but it's not essential.
2) In my purely practical experience it seems to, but I'll wait for someone with a better grasp of theory to confirm.
3) Sorry, no. I'd like some more as well as it happens...
4), What happened to four?
5) Both work equally well in listening tests, but the 15030 is a slightly better rated component for the voltages we're using. Jacco raves about the original Japanese tranny, but he seems to be one of the few people that can get hold of them.
I hope this helps.
Stephanoo, a small suggestion.
As the major part of the cost of this amp is chassis, PSU, and heatsinking, then I would just build either of the clone boards in this thread to get started. Once you have done that, you can swap out exotic transistors, components, and even circuit boards if you like. At the moment you seem to be working totally on the Krell's reputation, ( no real problem, it's a great amp), but rather than spending loads of time and money on tracking down all this exotica, build a clone and then see how you want to go from there. You know it makes sense. 🙂
As the major part of the cost of this amp is chassis, PSU, and heatsinking, then I would just build either of the clone boards in this thread to get started. Once you have done that, you can swap out exotic transistors, components, and even circuit boards if you like. At the moment you seem to be working totally on the Krell's reputation, ( no real problem, it's a great amp), but rather than spending loads of time and money on tracking down all this exotica, build a clone and then see how you want to go from there. You know it makes sense. 🙂
That helps a lot. Thanks!
OH..Question 4 was: Gee, do you think my heatsinks are big enuff?
you are very perceptive for a mouse🙂
Re: question 3: This seems like it might be the toughest question of all. My availability of these is a total of 4 each, instead of 6. Can I get away with 4 per channel instead of 6? (well, I know I can..but will it severely limit low impedance use?)
Is there a VERY suitable replacement that is readily available?
OH..Question 4 was: Gee, do you think my heatsinks are big enuff?
you are very perceptive for a mouse🙂
Re: question 3: This seems like it might be the toughest question of all. My availability of these is a total of 4 each, instead of 6. Can I get away with 4 per channel instead of 6? (well, I know I can..but will it severely limit low impedance use?)
Is there a VERY suitable replacement that is readily available?
Well, it's your choice if you only have a pair. Drop the voltage, or forget about stupidly low impedance loads. (What are you planning, welding or something?). Though personally I suspect that if you get the heatsinking sorted, you will likely be ok with normal use. Best to check the SOA chart in the device datasheets.
I'd check for you, but the work computer I'm currently on doesn't like the Onsemi site. Obviously a hotbed of porn or something... 🙂
I'd check for you, but the work computer I'm currently on doesn't like the Onsemi site. Obviously a hotbed of porn or something... 🙂
This has not been a problem for me nor has it been for Pass Labs who uses these in many of their amplifiers. I've never blown a fuse with these in place even when powering down and then right back up again. For 2 bucks I would reccomend you try it unless you're building a huge version of the KSA-50. Then you may want to think soft start. Keep in mind that these don't go to zero resistance even when they are hot!
For those that are leary of running fans because of the noise will want to investigate this . Bill WW brought one over and with it connected to 120 volts this Sunon Fan fan is completely inaudible at 2 to 3 feet. It is a bushing style motor plus speial "quiet" blades. It is definately alot qiueter than the ball bearing Papst fans I bought. My 2 120 volt fans are running connected in series in my KSA-50 and they are very quiet but not like the Sunon was. Note that there is also a 120 volt version of this fan available.
Mark
pinkmouse said:
Huh ?
It's the Czech former Mosfet amp designer P. Dudek who likes to show his amps but not his face who raves about the 2SC3955 for Q111.
The one who is very pleased with the original Toshiba combo for the Vas instead of the MPSA's is me. Just this week i received a bunch of complementary 200 Mhz Toshiba devices for Chocoholic and me. When the KSA50s are finally locked and loaded i'll try using these for the vas in stead of the 968/2238s.
You are right that i'm a good shopper, probably still one of few who has a source for the complementary Sanyo 2SA1540.
Attachments
Hi Mpmarino,
using a 30Vac transformer will cause no problems with the amp.
As you surmised the dissipation of most components goes up due to the +-42Vdc rails. But the spare capacity keeps all except the Drivers and Output Stage well within safe levels.
For drivers ensure you have an adequate heatsink and preferably not the output stage sink which could be running at over 50degC and even much worse.
For the Output Stage try to keep the device dissipation below Krell's dissipation of 35W (ratings 250W 200degC) and below 30W with plastic packages, but aim for <25W/device, particularly with the 150W,150degC MJW package.
The ClassA rating of the push pull amp is directly related to the quiescent current. Push pull does not limit (overload) like the single ended examples you mentioned.
If you reduce Iq you will reduce the peak ClassA current.
A consequence of reducing Iq is a small increase in Vrail, leading to a small increase in instantaneous ClassAB power. The continuous AB power will be the same whether the Iq is set low or high.
Drivers see reactive loads just like the output stage.
For this reason current capacity at elevated voltages is important, but not overiding.
The 50V capacities of the Onsemi devices are
15030 280mA
15032 600mA
15034 1000mA
Most of the other specs show the 15034 to be the best of the bunch. I would recommend it from it's peers. If you want something better try the 2sb649/d669 (300mA @50V) but only for higher impedance loads i.e. 8ohms or 6ohms or 4 to 8ohms. They may work with 4ohm loads but no guarantees.
However reducing the number of output devices increases the loading on the driver and inturn on the VAS.
If you are in the market for alternatives to MJW1302, try MJL4302 (3pairs) or 2sa1943 (4 pairs for 4ohm and 3pairs for 6ohm or higher)
using a 30Vac transformer will cause no problems with the amp.
As you surmised the dissipation of most components goes up due to the +-42Vdc rails. But the spare capacity keeps all except the Drivers and Output Stage well within safe levels.
For drivers ensure you have an adequate heatsink and preferably not the output stage sink which could be running at over 50degC and even much worse.
For the Output Stage try to keep the device dissipation below Krell's dissipation of 35W (ratings 250W 200degC) and below 30W with plastic packages, but aim for <25W/device, particularly with the 150W,150degC MJW package.
The ClassA rating of the push pull amp is directly related to the quiescent current. Push pull does not limit (overload) like the single ended examples you mentioned.
If you reduce Iq you will reduce the peak ClassA current.
A consequence of reducing Iq is a small increase in Vrail, leading to a small increase in instantaneous ClassAB power. The continuous AB power will be the same whether the Iq is set low or high.
Drivers see reactive loads just like the output stage.
For this reason current capacity at elevated voltages is important, but not overiding.
The 50V capacities of the Onsemi devices are
15030 280mA
15032 600mA
15034 1000mA
Most of the other specs show the 15034 to be the best of the bunch. I would recommend it from it's peers. If you want something better try the 2sb649/d669 (300mA @50V) but only for higher impedance loads i.e. 8ohms or 6ohms or 4 to 8ohms. They may work with 4ohm loads but no guarantees.
However reducing the number of output devices increases the loading on the driver and inturn on the VAS.
If you are in the market for alternatives to MJW1302, try MJL4302 (3pairs) or 2sa1943 (4 pairs for 4ohm and 3pairs for 6ohm or higher)
yes it does make sense!
It's not like you say....if you want to use real good components...you ill end up spending more than the double than using normal components.
For instance...there are particular trasformers that costs like 500Euro.
Or...capacitor than can cost like 10times the normal one.....
you understand better than me.....that in this way it's gonna cost much more.
But like you said.....that's not the problem.....i have to built first the krell than see.
But i still want to first projet eerything.....i prefere to see first where i can go and then actually do it!
...anyway noone answered at my questions yet 🙁(( ....about the soncs difference betwen the mkI and the mkII .... and which drivers the krell uses on the differential stage.
Someone knows a link where i can order heatsinks?.....is it true that there are audiophles heatsinks?.....what's the difference(if there are!)?
It's not like you say....if you want to use real good components...you ill end up spending more than the double than using normal components.
For instance...there are particular trasformers that costs like 500Euro.
Or...capacitor than can cost like 10times the normal one.....
you understand better than me.....that in this way it's gonna cost much more.
But like you said.....that's not the problem.....i have to built first the krell than see.
But i still want to first projet eerything.....i prefere to see first where i can go and then actually do it!
...anyway noone answered at my questions yet 🙁(( ....about the soncs difference betwen the mkI and the mkII .... and which drivers the krell uses on the differential stage.
Someone knows a link where i can order heatsinks?.....is it true that there are audiophles heatsinks?.....what's the difference(if there are!)?
just a fast question: hte devices used on the original krelll mkII are 2sa968B and 2sc2238 .... or .......a968b and c2238 ?
are toshiba those one? could anyone give me some information about this?
can someone explain me why the 2238 from toshiba costs much less then the same 2238 from panasonic?
are toshiba those one? could anyone give me some information about this?
can someone explain me why the 2238 from toshiba costs much less then the same 2238 from panasonic?
Thanks for all your awesome replies guys!
I truly wonder why every plastic packaged power BJT suggested is made of unobtanium right now. Do I have to resort to using steel devices or...maybe... Mosfet KSA50 anyone😎
kidding.
I truly wonder why every plastic packaged power BJT suggested is made of unobtanium right now. Do I have to resort to using steel devices or...maybe... Mosfet KSA50 anyone😎
kidding.
Stephanoo, I don't know the answer to your questions about the transistors. It won't cost much more to build a basic amp then upgrade, I would guess the hardware and case will be 75-80% of the costs. As for Audiophile grade heatsinks, I think someone is having a joke with you...