lgreen said:
Hi lgreen!
That does indeed seem very odd!
I own a KSA-50S, and I wasn't aware of this problem. My assumption has always been that Iq is instantly increased as soon as you hear the relays clicking. To be honest I find it hard to understand how it could be any other way? (But I haven't seen the schematics for the 50S..)
Regards
awpagan said:
A safe 2-bias cicuit always keeps one resistor in/out the circuit and then switches out a second parallel resistor that will cause an increase/decrease in Class-A bias current. There is never an open circuit.
The bias current changes instantly, but it takes a few minutes to reach thermal stability. Many of the Vbe multiplier circuits include a parallel capacitor which can help filter the switching glitch.
Hi
I have a KSA200s with the sliding bias and in my experience it only sounds really good when it driving low impedance speakers. With normal speakers it sounds fine but hook it up to a set of Martin Logans running at .5 ohm and then the hairs in your neck start to raise. Could this be due to the sliding bias arrangement ?
The amp also has LED's showing the bias levels and I have always been amazed that even at low volume -say playing at 10-15 watts that the bias would sometimes show peaks up to 75% of its rating.
Jozua
I have a KSA200s with the sliding bias and in my experience it only sounds really good when it driving low impedance speakers. With normal speakers it sounds fine but hook it up to a set of Martin Logans running at .5 ohm and then the hairs in your neck start to raise. Could this be due to the sliding bias arrangement ?
The amp also has LED's showing the bias levels and I have always been amazed that even at low volume -say playing at 10-15 watts that the bias would sometimes show peaks up to 75% of its rating.
Jozua
4 boards to sell
Unfortunately, I will not have the time nor money to finish my boards in the foreseeable future. Thus I am willing to pass them on to others.
On the wiki page there is a column at the end called Spares. Is this a list of people interested in buying cards? This is my first post to diyAudio, so I am still under moderation and therefore not able to send email directly to anybody on the list asking directly.
Harald R.
Unfortunately, I will not have the time nor money to finish my boards in the foreseeable future. Thus I am willing to pass them on to others.
On the wiki page there is a column at the end called Spares. Is this a list of people interested in buying cards? This is my first post to diyAudio, so I am still under moderation and therefore not able to send email directly to anybody on the list asking directly.
Harald R.
Alas if you have already paid for PCB's in the G.B. as far as I'm concerned they are yours. Please don't e-mail me asking me to send them to a second party. Post them for sale on the "Electronics and Parts" thread or "Market Place" that they are available and that you don't want them and deal directly with the new party that wants them after you receive them.
Boards are set to ship to me right around Jan. 30th so I will have them shortly there after. Its difficult as it is keeping track of everyone so its up to those in the G.B. to Pass on boards you decided you don't want.
Thanks!
Mark
Boards are set to ship to me right around Jan. 30th so I will have them shortly there after. Its difficult as it is keeping track of everyone so its up to those in the G.B. to Pass on boards you decided you don't want.
Thanks!
Mark
Hi Mark,
I haven't tried to email you, nor I have diffrent understanding from what you described. Yes, I paid for boards and I am not expecting anything else from you but just boards. It was logical to me to mentione here if there is anyone interested who came late in the game and didn't have chance to order. It is my responsibility to deal with my change of plans.
I haven't tried to email you, nor I have diffrent understanding from what you described. Yes, I paid for boards and I am not expecting anything else from you but just boards. It was logical to me to mentione here if there is anyone interested who came late in the game and didn't have chance to order. It is my responsibility to deal with my change of plans.
Mark A. Gulbrandsen said:Thats ok!! I just wanted to make clear that all boards will still be shipped to their buyers. Its up to the buyers to dispose of them however they want to. I'm sure if you send em to ZenMod he'd build it
Mark
nope;
I'm in diff mood in last time - I'll make phono toob preamp with them
just in case that you send me (eventually
) promised souvenirs ....I'll certainly make Mini KSA50 ...........or KSA5 !!!ya remember that Krell make nice hphone amp(s) ........
anyway,almost all my spks are just as hdphns,just little bigger
I just received offer for my boards, but since I have 4 I decided to split and let go two and to send two to Zen Mode as present. I would love to see how someone makes tube pre amp out of these boards. 
I know, I know it is not guts out of my Treshold , but ... it is Krell.
Send me your address, since you are the third party... and Mark...
(just a joke Mark)
I know, I know it is not guts out of my Treshold , but ... it is Krell.
Send me your address, since you are the third party... and Mark...
(just a joke Mark)
Well if you want to use the KSA as headphone amp you'd have to reduce the 28dB cloesd-loop gain considerably to something like 6dB.. which could lead to instability issues. Keeping that gain with a normal source will blow your ears off with even the most insensitive phones, and the high gain with a low-gain signal source is likely to produce hiss. 50V DC rails for a headphone amp is also somewhat unrealistic, and for the rails and gain to be reduced the circuit has to be adapted somewhat.
A huge dropping resistor in series with the load instead of the normal 120ohms is IMO just stupid, although it's the easiest for those with existing amps who want to experiment before connecting the output stage I suppose. Since I'm toying with the headphone idea I'll simulate the stability margins sometime.
Those with iPods may be fortunate; apparently Apple had to lower the gain after somebody sued due to hearing damage.. its maximum output is now -10dB referenced to its source signal. The thing measures up damn good on my AP though, had to retake the tests just to make sure. The moment you add a load things deteriorate rapidly, even at 300ohms the harmonics rose terribly. The KSA's 47k input impedance should make an iPod sing like never before.. wonder if it will retain the Krell bass
A huge dropping resistor in series with the load instead of the normal 120ohms is IMO just stupid, although it's the easiest for those with existing amps who want to experiment before connecting the output stage I suppose. Since I'm toying with the headphone idea I'll simulate the stability margins sometime.
Those with iPods may be fortunate; apparently Apple had to lower the gain after somebody sued due to hearing damage.. its maximum output is now -10dB referenced to its source signal. The thing measures up damn good on my AP though, had to retake the tests just to make sure. The moment you add a load things deteriorate rapidly, even at 300ohms the harmonics rose terribly. The KSA's 47k input impedance should make an iPod sing like never before.. wonder if it will retain the Krell bass
PWatts said:Those with iPods may be fortunate; apparently Apple had to lower the gain after somebody sued due to hearing damage.. its maximum output is now -10dB referenced to its source signal. The thing measures up damn good on my AP though, had to retake the tests just to make sure. The moment you add a load things deteriorate rapidly, even at 300ohms the harmonics rose terribly. The KSA's 47k input impedance should make an iPod sing like never before.. wonder if it will retain the Krell bass
Effing knew someone had to go and ruin a good thing. Consumers are idiots...
Here are a few quick pics of the boards. I still prefer the look of the gold plated board... That Hewlett Packard look is hard to beat... but ok... the blue solder mask is certainly very romantic as well!
The gold plating on these is so shiny that you'd think they were form King Tut's Tomb!
The gold plating on these is so shiny that you'd think they were form King Tut's Tomb!
Attachments
Ok... The blue solder masked ones are at least ok looking .
Anyway... I am hiding from work today so I can start shipping these out. I think you will all be very impressed with them. Thanks again to PWatts for all his effort in the design and in putting up with all of our silly requests and to all those who participated in the Group Buy.
I expect to see photos of at least 50 finished 100 MK2's's in the next two months
.
Mark
.Anyway... I am hiding from work today so I can start shipping these out. I think you will all be very impressed with them. Thanks again to PWatts for all his effort in the design and in putting up with all of our silly requests and to all those who participated in the Group Buy.
I expect to see photos of at least 50 finished 100 MK2's's in the next two months
.Mark
