KSA 100 from Jim's Audio on EBAY

[Kaplaars]

Hi Spurtle,

It is a shame that I lost your respect. You are right, we have to obey the rules, I am no exception. From the other hand I think we don't have to be more Catholic than the pope when it comes to little off-topic phrases, just like our little chat about France.

To me the discussion about intellectual properties was not bickering, just a friendly discussion. I think Upupa feels the same. I just felt the need to give a explanation why I made the plates are the way they are. I also wanted to explain the legal issues. I use a lot of smileys to express my emotions, but maybe that is not enough and are my answers misinterpret, and is the friendly nature of the posts lost. I honestly want to excuse for that.

My intention was to give a nice overview of building a DIY KSA-100 clone, to learn more about the theory, and to make the amplifier better. So I spended a lot of effort to make nice pictures with a little story around it and try to formulate my questions as good as my knowledge of English allows me.

I am sorried for this off-topic answer. I am even more sorried that my reportage did not turned out so well as I intended. I am not realy a quitter, but I think it is the best draw a close to reporting my build in this topic, so I will. I want to thank everybody for the help they gave me, I've learned a lot :-)

[neychi]

I'm really sorry how this topic went wrong. Michael, you build an amp for yourself and if you want, you can put NASA stickers on it. It's really up to you. I did something similar like you on my amp and I don't care what someone thinks about it. Don't be angry because of some well-meant but somewhat poignant remarks.

Please, keep us informed and stay cool

[Jozua]

Mr. Michael

When are we going to hear if the amp is working !!!!

You might just motivate me to finish my KSA 100 watt clone - at least my PCB's have been buildt up for the past 3 years but the lack of having a professional looking case and heatsinks has been a serious drawback as I also want a near professional look.

I have noticed that with my KSA 50 clone that uses heat-tunnels some transistors are warmer than the others. Hence my interest in how your heat/bias management is going to be implemented. With unmatched transistors on a heat-tunnel you possibly need to be more careful with additional heatsinking compared to the commerical units?

Btw I remain impressed with the quality of your workmanship- especially for a 'poor' student you doing very well.

Regards


Jozua

[spurlte]

Originally Posted by Kaplaars

Hi Spurtle,

It is a shame that I lost your respect. You are right, we have to obey the rules, I am no exception. From the other hand I think we don't have to be more Catholic than the pope when it comes to little off-topic phrases, just like our little chat about France.

To me the discussion about intellectual properties was not bickering, just a friendly discussion. I think Upupa feels the same. I just felt the need to give a explanation why I made the plates are the way they are. I also wanted to explain the legal issues. I use a lot of smileys to express my emotions, but maybe that is not enough and are my answers misinterpret, and is the friendly nature of the posts lost. I honestly want to excuse for that.

My intention was to give a nice overview of building a DIY KSA-100 clone, to learn more about the theory, and to make the amplifier better. So I spended a lot of effort to make nice pictures with a little story around it and try to formulate my questions as good as my knowledge of English allows me.

I am sorried for this off-topic answer. I am even more sorried that my reportage did not turned out so well as I intended. I am not realy a quitter, but I think it is the best draw a close to reporting my build in this topic, so I will. I want to thank everybody for the help they gave me, I've learned a lot :-)

At the risk at falling into the same trap--Kaplaars, believe me when I say, I was not referring to your endeavors or posts. "Via la France." And you should not be intimidated by anyone else who may have OCD, a control issue, "Do it my way or the highway." Please don't be the quitter!!! We want to see the finished product, "Made in Holland" and more importantly, a finished " DIYAUDIO.COM PROJECT." In your words, ".... in all fairness...."

[Kaplaars]

Thanks for your support guys! You are right Dean, forgive and forget, fresh new start from here :-) And I want to motivate Jozua, because I want to see more DIY KSA-100's haha.

Well that is going to be a big challenge for me too Jozua, the transistors I use are from the same batch, though I have not matched the transistors specificly. I use 1 ohm emitter resistors so I hope due to the large emitter resistor value bias current will distribute more equally. If this works and heat is distributed equally I want to try 0.47 ohm emitter resistors because I've red this would be better for the sound quality (I do not really understand why this would improve quality, maybe someone can explain?). If heat becomes a real issue I think I have to bias less. Hope I don't have to, but from the other hand it is maybe not a very big problem. I never listen to music very loud, so at worst case scenario even 25W of power would be more than enough. When I am right voltage across the emitter resistors for 4 ohm loudspeakers than have to be P=I^2*R --> 25 = x^2*4 so x = 2.5 Arms, thus 2.5 / 0.707 = 3.54--> 3.54 / 8 (=output devices) = .442. So I have to measure 442 mV across the 1 ohm emitter resistors. By the way, this raises another question, I've red the original has about 625 mv across the 1 ohm emitter resistors. This would mean the KSA-100 is only full biassed at 8 ohm. At 4 ohm bias has to be 884 mV when it is full biassed because: 100 = x^2*4 so x = 5 Arms, thus 5 / 0.707 = 7.072--> 7.072 / 8 = .884 mV, or am I wrong?

By the way, I ordered a few days ago a push button. It has a nice ring around the button itself which is lit white by a led. Drilling the hole into the front plate was a real hurdle to me. Although the front plate is made from aluminium, it is still 10 mm thick. But actually it was more easy than I thought. When drilling through aluminum you have to drill really slow. It is almost like when you think you are drilling too slow, you have the right speed. I also added some WD40 to lubricate the drill a bit. Worked like a charm. I also mounted the front and backplates. Some pictures:



And the back plate. Like you can see I have just enough room to mount the speaker terminals :-)

[AVWERK]

I used .47 ohm emitters on mine and from the same batch. The mv spread across all TO3,s was less than 15mv so no problems with current hogging as far as I,m concerned. Simply measure each output transistors emitter and write down the value and compare them. If one is way off just replace it and remeasure to get the total average down.
Changing to .47 ohm results in a change in output impedance and a resultant bias change remember
A lower bias had no detrimental effect that I could detect sonically
It did take a good 60 hours or so of running in before the sound fully came into its own and settled down to its smooth and detailed sweet self. Happened within about 2 or 3 songs and was a shocker on how this developed so quickly. Can,t explain why this should be, but has stayed that way ever since.
Burn in is real so don,t expect great sound at first start up!

Regards
David

[AndrewT]

Originally Posted by AVWERK

I used .47 ohm emitters on mine and from the same batch. The mv spread across all TO3,s was less than 15mv so no problems with current hogging as far as I,m concerned............

What is the tolerance of the 0r47 Re?
add that tolerance to the variation on the 15mVre and you may find that your bias currents could be anywhere, or very close. One simply doesn't know if one doesn't hand select the Re to better than 1% and preferably <0.2%

[AndrewT]

Kap,
the KSA100 is specified as a 100W ClassA amplifier. That 100W is delivered into an 8r0 load.

If you want/need/require a 200W ClassA amplifier for a 4r0 load then you should be looking at 200W into 4r0 ClassA amplifiers.

There is some evidence that lower emitter resistor values do result in lower output distortion. If this holds true for ClassA operation, then reducing the Re from 1r0 to 0r47 may give a small benefit. Keep in mind that with 4pairs of output devices the effective re was 0r25 and will become 0r118 for the proposed change. That is quite low for a +-52Vdc supply. Maybe Krell knew a thing or two after developing and building dozens of high power amplifiers.
Cordell has written a lot about this Re value and supply Vdc and Thermal Stability relationship.

[spurlte]

Originally Posted by AndrewT

Kap,
the KSA100 is specified as a 100W ClassA amplifier. That 100W is delivered into an 8r0 load.

If you want/need/require a 200W ClassA amplifier for a 4r0 load then you should be looking at 200W into 4r0 ClassA amplifiers.

There is some evidence that lower emitter resistor values do result in lower output distortion. If this holds true for ClassA operation, then reducing the Re from 1r0 to 0r47 may give a small benefit. Keep in mind that with 4pairs of output devices the effective re was 0r25 and will become 0r118 for the proposed change. That is quite low for a +-52Vdc supply. Maybe Krell knew a thing or two after developing and building dozens of high power amplifiers.
Cordell has written a lot about this Re value and supply Vdc and Thermal Stability relationship.

Thanks AndrewT, Stuart Easson gave me a bunch of 0R67--he has a ton of them, just send a private message to him--he said the same, but said I could experiment. I will read Cordell just to understand a new subject involved here--"Thermal Stability relationship."

[AVWERK]

From the same batch means the TO3,s and I did check the values of the emitters to see they were close enough not to lose any sleep over it

BTW Andrew, did you ever get your krell from the ksa 100 thread to finally work?

David