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Old 5th April 2013, 06:15 AM   #8471
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Hi,Stuart Easson and Alibear

I'm also thinking to double output transistor amount.

My project based on Jim's PCB and there are 'options' KSA 50 or KSA 100. KSA 50 have one driver (MJE15032,MJE15033) for two (MJ15024,MJ15025) and re 0.5ohm. And KSA100 version the output transistor doubling is done that there are one more driver to other set of output transistor and re 1 ohm.

So my question is if I double my 4 pair (MJ15024,MJ15025) to 8 pairs and change re 1ohm to 2ohm should that modification works? Or should I do drivers something, change type(MJE15034/MJE15035) or something else?

-jussi
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Old 5th April 2013, 08:25 AM   #8472
alibear is offline alibear  United Kingdom
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Hi Stuart, thanks for the reply. Did you also say that one pair of drivers ( as per Jans PCB) would be OK for the extra output pairs? I think this is the question Jushuota is asking as well.
Also can you see any problems with using a seperate supply for the front end of the amp., Re. my post of a couple of days ago.
Thanks for your help
Alan
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Old 9th April 2013, 07:50 PM   #8473
henryve is online now henryve  South Africa
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I have been listening to my KSA50 now in the nude for the last 2 weeks. In this time I replaced the Panasonic FC caps in the C102/C103 position with Nichicon KA caps. I have Elna Silmic IIs also but they are just too big for the space provided on the PM boards

It is funny how a good Class A amp can lay bare how bad some of my old CD's were produced (sound engineering). Some of the U2 recordings are not impressive at all while I was pleasantly surprised by how well the Level 42 recordings were produced.

Now I am moving upstream to sort some of my sources out. Pre-Amp is next in line. Someday I also would like some decent speakers like Martin Logan ribbons.

Damn, my wife is gonna eat me alive as I am also busy with an F5T. And my long term KSA100 project.
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Old 10th April 2013, 10:21 PM   #8474
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Quote:
Originally Posted by henryve View Post
I have been listening to my KSA50 now in the nude for the last 2 weeks. In this time I replaced the Panasonic FC caps in the C102/C103 position with Nichicon KA caps. I have Elna Silmic IIs also but they are just too big for the space provided on the PM boards

It is funny how a good Class A amp can lay bare how bad some of my old CD's were produced (sound engineering). Some of the U2 recordings are not impressive at all while I was pleasantly surprised by how well the Level 42 recordings were produced.

Now I am moving upstream to sort some of my sources out. Pre-Amp is next in line. Someday I also would like some decent speakers like Martin Logan ribbons.

Damn, my wife is gonna eat me alive as I am also busy with an F5T. And my long term KSA100 project.
I don't buy that mate. That's actually is discouraging to hear. In my experience with building tube amps the better they get. the lower distortion they are and the more forgiving of source material they become. the more neutral and less colored a amp is the better it will do on poor recordings. It sounds like the ksa 50 amp is not going to be too good full range. How is the bass performance?

I also bought a ten watt zen amp board too for a try at full range. Perhaps it will sound more smoother.

Last edited by fatbattery; 10th April 2013 at 10:22 PM. Reason: spelling
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Old 10th April 2013, 11:13 PM   #8475
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Quote:
Originally Posted by fatbattery View Post
...the more neutral and less colored a amp is the better it will do on poor recordings.
Depends on what you want to hear in a recording.

Quote:
How is the bass performance?
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Old 11th April 2013, 04:01 AM   #8476
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Very Good I got mine today? Did you use chokes in the power supply's? I am thinking a small hand wound choke coil in a lcr on the output might help with stability. Perhaps it could explain its revealing nature. I notice despite the Chinese Lehman headphone amps having nothing on the output my Altronics version has one for stability. So yea... chokes in the power supply and output might smooth them out beautifully! Of course I wouldn't consider my idea until somebody with some knowledge of ss amps hopefully chimes in and legitimizes my guess work!

Last edited by fatbattery; 11th April 2013 at 04:10 AM.
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Old 11th April 2013, 05:36 AM   #8477
henryve is online now henryve  South Africa
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I have no Zobel or Thiel network on the output.

I disagree with your point of view. The lesser amount of distortion or colouration an amp adds to the source signal, the more of the actual source signal is amplified and less harmonics added to make the sound either pleasing or horrible to listen to. You know, garbage in, garbage out.

Bass is deep and slamming, but only if there is actual bass in the original recording. You hear this quite well with a recording like Insomnia by Faithless. I must also add that my speakers do sound a bit dry.

Just build the bloody thing alright! Don't let subjective stuff get in the way. It's a good beginner's Class A SS amp to build. This was my very first electronic project that I actually finished and has no vices to catch out a noob.

Chokes in the PS is a good thing in any big PS, although I might add that I believe that the KSA50 has a better PSRR than most other Class A designs.

Last edited by henryve; 11th April 2013 at 05:47 AM.
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Old 11th April 2013, 06:43 PM   #8478
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Originally Posted by henryve View Post
I have no Zobel or Thiel network on the output.

I disagree with your point of view. The lesser amount of distortion or colouration an amp adds to the source signal, the more of the actual source signal is amplified and less harmonics added to make the sound either pleasing or horrible to listen to. You know, garbage in, garbage out.

Bass is deep and slamming, but only if there is actual bass in the original recording. You hear this quite well with a recording like Insomnia by Faithless. I must also add that my speakers do sound a bit dry.

Just build the bloody thing alright! Don't let subjective stuff get in the way. It's a good beginner's Class A SS amp to build. This was my very first electronic project that I actually finished and has no vices to catch out a noob.

Soon as I can scrounge up the trans. It quiet a expensive power supply with it 2 sets of rails. Thanks for your input buddy. btw My ten watt zen will come first because its going to fit straight into a old 80watt amp chassis that has even the right trans sise and taps and even the heat sinks will fit right. I love it when I can recycle some thing old and crap into something special.

Chokes in the PS is a good thing in any big PS, although I might add that I believe that the KSA50 has a better PSRR than most other Class A designs.
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Old 28th April 2013, 09:01 AM   #8479
alibear is offline alibear  United Kingdom
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Hi all,I have been constructing a KSA50 for quite some time. The first attemp was using passive cooling and I found it difficult with the heatsinks I was using to succesfuly manage the temperature. I then decided to use fan cooling with two tunnel heatsinks as per original KSA100 amplifier. This was fine, but of course there was the problem of fan noise. I now want to construct a final version of the KSA50 and would really like it passively cooled.Has anyone managed to construct a passively cooled version that was successful and if so could they post pictures or dimensions of their build, not for me to copy, but to point me in the right direction.Any information greatfully received.
Many thanks
Alan.
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Old 28th April 2013, 01:12 PM   #8480
henryve is online now henryve  South Africa
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Ali

I have my KSA50 running successfully on passive cooling. My heatsinks are on each side as follows:

Depth (front to back of amp) : 508mm
Hight (of amp, whick would be the lenght of the extrusion) : 200mm

Width of my case with the heastinks is 482mm.

Heatsink Profile info:
Height (Fins + Base ) 76mm
Base : 16 mm
Fins : 60 mm
Fin Distance : 13mm

Here are some photos of the amp while in my garage while for final casework. I still need to drill the venting holes and do some finishing, anodising the heatsinks and do final wiring up etc.

I ran the amp for 3 weeks biased at 1.95A and the temperature at Ra = 25 deg C were never higher than 50 deg C.
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