inspiration
ive come across this thread a while ago, since i've owned this amp for 10 years now
just a pic;
notice that the ac-wires are thin and the dc-wires are thick
powersupply-voltage +/- 47.7 v
standing current per output device =500 mA(250mv/0.5ohm)
comments and questions r appreciated (i own a dynatek and i know how 2 use it)
Klaas
ive come across this thread a while ago, since i've owned this amp for 10 years now
just a pic; notice that the ac-wires are thin and the dc-wires are thick
powersupply-voltage +/- 47.7 v
standing current per output device =500 mA(250mv/0.5ohm)
comments and questions r appreciated (i own a dynatek and i know how 2 use it)
Klaas
Re: Only if Loek had seen Gengis's avatar
So when's your 14th birthday then?
Hi Klaas, and welcome to the never ending story!
The thicker wires from the caps are possibly an attempt to reduce the impedance of the PSU, though for an amp run primarily in class A like the Krell it isn't quite so much of an issue as it is with class B amps. It is also only usually seen after the PSU caps, but I suspect that the thicker cable in yours was just to make assembling the wiring looms easier.
loek said:
So when's your 14th birthday then?
Hi Klaas, and welcome to the never ending story!
The thicker wires from the caps are possibly an attempt to reduce the impedance of the PSU, though for an amp run primarily in class A like the Krell it isn't quite so much of an issue as it is with class B amps. It is also only usually seen after the PSU caps, but I suspect that the thicker cable in yours was just to make assembling the wiring looms easier.
wires again
thx pinkmouse for your welcome
about your comments on wire-thickness;
its not the dc-wiring im wondering about ; i think its there for obvious reasons -low impedance- as you stated.
i'm more curious about what you people think about the extremely thin ac-wiring.i'm pretty sure Krell put it in for a reason
maybe to add resistance without adding a resistor
Also the powersupply-voltage has me puzzled
the Krell KSA-50 Building Wiki states "In the original Krell it was ~37.5 VDC"
I'm pretty sure i've got the original here, after a few hours of warm-up (should i say heat-up
) i still measure 47.3 VDC
Kind regards,
Klaas
thx pinkmouse for your welcome
about your comments on wire-thickness;
its not the dc-wiring im wondering about ; i think its there for obvious reasons -low impedance- as you stated.
i'm more curious about what you people think about the extremely thin ac-wiring.i'm pretty sure Krell put it in for a reason
maybe to add resistance without adding a resistor
Also the powersupply-voltage has me puzzled
the Krell KSA-50 Building Wiki states "In the original Krell it was ~37.5 VDC"
I'm pretty sure i've got the original here, after a few hours of warm-up (should i say heat-up
) i still measure 47.3 VDCKind regards,
Klaas
Hi Kvh,
500mA per device. Are there two or three pairs of output devices per channel?
Total standing current (output Iq) = 1A or 1.5A.
Peak ClassA current is 2A or 3A giving 16W or 36W into 8ohm.
This implies a low ratio of ClassA power to ClassAB power in the Mk1.
Can you confirm?
It may be that the Iq is set too low and allowing the Vrails to rise.
Was the Mk1 all that different?
500mA per device. Are there two or three pairs of output devices per channel?
Total standing current (output Iq) = 1A or 1.5A.
Peak ClassA current is 2A or 3A giving 16W or 36W into 8ohm.
This implies a low ratio of ClassA power to ClassAB power in the Mk1.
Can you confirm?
It may be that the Iq is set too low and allowing the Vrails to rise.
Was the Mk1 all that different?
K-amps, my ac mains is ok (225 Vac) so no problems there
Andrew T., this amp has got 2 pairs per channel
just to be sure i measured the other channel, 240mv after a few mins of warmup.
i'm pretty sure turning the standing current up to 2 amps per channel wouldnt cause a voltage-drop of 10 V, i think the powersupply is wayy too big for that to happen.
Also, judging from the heatsink-temperature now i'm 99 % sure i would fry the thing - after being fully warmed up its HOT already
Jacco, does this mean i've got a different ksa-50 than the one you're cloning here ?
with kind regards,
Klaas
Andrew T., this amp has got 2 pairs per channel
just to be sure i measured the other channel, 240mv after a few mins of warmup.
i'm pretty sure turning the standing current up to 2 amps per channel wouldnt cause a voltage-drop of 10 V, i think the powersupply is wayy too big for that to happen.
Also, judging from the heatsink-temperature now i'm 99 % sure i would fry the thing - after being fully warmed up its HOT already
Jacco, does this mean i've got a different ksa-50 than the one you're cloning here ?
with kind regards,
Klaas
Klaas,
you have one of the first series, yours should not have mk-2 inscribed on the front plate Krell Logo.
Your KSA50 has regular type resistors on the boards, the MKII had Dales (all brown, no color rings)
Most here build the KSA clone like a KSA100, with 2 heatsinks and vents, yours has 1. You own the real Classic KSA50.
you have one of the first series, yours should not have mk-2 inscribed on the front plate Krell Logo.
Your KSA50 has regular type resistors on the boards, the MKII had Dales (all brown, no color rings)
Most here build the KSA clone like a KSA100, with 2 heatsinks and vents, yours has 1. You own the real Classic KSA50.
thx Jacco for your reply, i guess ive got a mk1
btw, my pcb looks like this:
the damage to the top of the pcb came from a breakdown due to faulty power-eletrolytic$$$$$ when the amp fried it took a dynaudio 17w75 with it
anyway, muchos gracias for your response (or should i say "bedankt"? )
Klaas
btw, my pcb looks like this:
the damage to the top of the pcb came from a breakdown due to faulty power-eletrolytic$$$$$ when the amp fried it took a dynaudio 17w75 with it
anyway, muchos gracias for your response (or should i say "bedankt"?
)Klaas
Hi All sorry for the absence, I had to leave the state for the weekend and did not have / take time to log on while gone...
Anyway, I hear that the kits are ok EXCEPT the diodes and Zeners.
How may I ask was that determined? Reason I ask is because I took them out of the Mouser bag and taped / labeled them. SO obviously they were incorrect in the packages from Mouser.
I hope to test some of them tonight. The only way I can think of testing them is to throw a meter across them and the diodes should conduct when positive is on the Anode (black stripe) and the Zener will conduct on the Cathode (no mark). My Fluke 87 has a diode tester setting, but I think that is only to check if the diode is good or not... Not to test if it is a Zener or not.
Thanks again and sorry for the confusion...
Anyway, I hear that the kits are ok EXCEPT the diodes and Zeners.
How may I ask was that determined? Reason I ask is because I took them out of the Mouser bag and taped / labeled them. SO obviously they were incorrect in the packages from Mouser.
I hope to test some of them tonight. The only way I can think of testing them is to throw a meter across them and the diodes should conduct when positive is on the Anode (black stripe) and the Zener will conduct on the Cathode (no mark). My Fluke 87 has a diode tester setting, but I think that is only to check if the diode is good or not... Not to test if it is a Zener or not.
Thanks again and sorry for the confusion...
Klaas,
good guess is that your Krell is a mark I and has been updated to a MKII.
(in the late 80s it was possible to have a KSA250 converted to a monaural unit without a charge, the MDA500)
Means the 50 volts on your Krell is what it should be.
Btw, the fan on your KSA50 has been reverse mounted on the cool tunnel.
I would like to see a close-up picture of the front end/driver board of your Krell, if possible. I can only see 2 Toshiba devices, the KSA circuit that was posted had 4 .
good guess is that your Krell is a mark I and has been updated to a MKII.
(in the late 80s it was possible to have a KSA250 converted to a monaural unit without a charge, the MDA500)
Means the 50 volts on your Krell is what it should be.
Btw, the fan on your KSA50 has been reverse mounted on the cool tunnel.
I would like to see a close-up picture of the front end/driver board of your Krell, if possible. I can only see 2 Toshiba devices, the KSA circuit that was posted had 4 .
rabstg said:
If you referring to my comment, the parts are correct. The label just may have been switched on mine Z = Diode D = Zener. The Diodes are easier to identify - as you roll them you will see:
41
48
That, to me, would refer to a 1N4148 diode. the zeners are a little smaller and say 27 on them. (I'll double check all that when I get home)
You went way above and beyond with the taping/sorting/labelling etc. Thanks for all your efforts, man!
Seriously, let us all know what the differential payment per kit is, so that for those who feel so inclined (as I am sure most/all of us do) can make up any differences that your now out of pocket on.
~Brad