[guest1632]

Hi all,

I'd like to continue the discussions which were  in the marketplace, and deleted concerning the  SKA amps which are being marketted in kit form by Greg Baal.

My purpose is to help others who wish to build it, and are looking for various resources to buy items as well as to discuss any circuit improvements etc. If you wish to do any reviews, I would ask that you link them to another thread somewhere else, maybe in the Critics Circle. I'd like to keep this mostly technical. To Paul, the moderator, if this is not the place to have this discussion, then you are welcome to have this moved accordingly.

I will start out by saying that I had in the thread about the DIYEnclosures that appears to have been deleted, that Mike can accomodate the 300D module's heatsink situation.

Once more I will make this offer. i will be happy to go back to Thermaflo, and see what I can work out as far as a price goes. They do have a minimum of a $125 order. I have 2 people who are interested.
For that part of the discussion, you can email me directly:

raybronk@comcast.net

So let the discussions begin. The table is now open.

Regards,
Ray Bronk 

[amplifierguru]

Hi Ray,

Maate, thanks for your support!

I have a chassis /HS guy with CNC machinery working on complete DIY enclosures for both models (and DIY amps in general) behind the scenes with custom faceplate, etc... possibilities. As soon as I can the contact will be 'outed' for all to access. You won't have to worry about that $125 min HS order - I hate those imposts.

I have a thread up and running and a new website about to appear -courtesy of an Aussie DIYer who was so inspired by his SKA amp he contacted me with a new website. Its a knockout compared with my effort.

Thanks
Greg

[ooheadsoo]

For the diy impaired, what do you estimate the build time to be if I ordered everything as assembled as possible?  Is it just a matter of wiring up jacks and switches?  How involved will the casework have to be?  What if all I had was a cheap soldering iron and weak drill (and screwdriver and wrench) but no other specialized hardware?

[amplifierguru]

Hi Ooheadsoo,

I used to teach electronics at a tertiary college many years ago, and I  built my first amp at 17. I've been designing amps for 35 years. I hope there's a mower repair forum somewhere though! Seriously, the GB150D, even though it's 150W max, it's a simple 4" x 2" module and if you can solder and follow a DMM measurement routine you can build it! The satisfaction is enormous from your first successful build and suddenly a whole new perspective emerges...

Check ahead on my other thread as I'm working with a CNC machine guy to come up with case solutions that are simple and/or made to order.

You can buy kits, or fully built modules or 1 built as a physical guide.

With this amp it's can be as good as the effort YOU put in to build it. Build time - spare time over 1 week with all parts available.

Cheers,
Greg

[JoshK]

Greg, what does this:

I used to teach electronics at a tertiary college many years ago, and I  built my first amp at 17. I've been designing amps for 35 years. I hope there's a mower repair forum somewhere though!

Have to do with answering his question?  How much education I have or don't have also has nothing to do with technical discussions and diy building tips in the lab.  Staying on topic can certainly only help your cause with the powers that be. 

[woodsyi]

Greg, what does this:

I used to teach electronics at a tertiary college many years ago, and I  built my first amp at 17. I've been designing amps for 35 years. I hope there's a mower repair forum somewhere though!

Have to do with answering his question?  How much education I have or don't have also has nothing to do with technical discussions and diy building tips in the lab.  Staying on topic can certainly only help your cause with the powers that be. 

But Josh, it's fun to meander with tertiary topics.  If you were only focused on the primary topic, think of all the secondary fun you would miss out on.  Innovations have started as tangential ideas. 
What is a tertiary college?  Is it a three year school?  Or is it a third rate school? 

BTW, I don't know why this is in Lab circle to begin with.  Sorry for my levity, Paul.

[guest1632]

Greg, what does this:

I used to teach electronics at a tertiary college many years ago, and I  built my first amp at 17. I've been designing amps for 35 years. I hope there's a mower repair forum somewhere though!

Have to do with answering his question?  How much education I have or don't have also has nothing to do with technical discussions and diy building tips in the lab.  Staying on topic can certainly only help your cause with the powers that be. 

But Josh, it's fun to meander with tertiary topics.  If you were only focused on the primary topic, think of all the secondary fun you would miss out on.  Innovations have started as tangential ideas. 
What is a tertiary college?  Is it a three year school?  Or is it a third rate school? 

BTW, I don't know why this is in Lab circle to begin with.  Sorry for my levity, Paul.

Hi Woodsyi,

Well, that's because I stuck it here. If you have a better suggestion, I'm open. I just want to see Greg get a fair shake to discuss the technical side. I figure you don't just build and design one of these amps just out of the blue. If some place like audio Central would be a better place, sounds good to me. I am not one to be PC, but I'm not one to wish to break any rules here either. So to Josh, and the current moderator of this thread, I'm open to suggestions.Just do the move, and all will be ok.

Regards,
Ray

[JoshK]

I was only commenting on Greg's self promotion.  I just didn't feel it was necessary in the context of the thread. 

[guest1632]

I was only commenting on Greg's self promotion.  I just didn't feel it was necessary in the context of the thread. 

Understood. I figured that was where you were coming from. That's why I suggested to move the thread.

So let's get some discussion started.

Regards,
Ray

[amplifierguru]

My apologies to Ooheadsoo, for answering his questions incompletely at the end of a 16 hour day.

Josh what I should have added was that I (believe I) am well (qualified and) able to provide the support and detail that a first time DIYer may need to succeed in such an endeavour. Would you be seeking investment advice from an unqualified source. Indeed the courses you may choose to take are by qualified people, yes? Audio is no different - without a scientific foundation we have only belief. A newbie doesn't need confusing information.

My apologies if it seemed like self aggrandisment it was not meant that way.

Hi woodsyi,

What is a tertiary college?  Is it a three year school?  Or is it a third rate school? 

I am a B.Sc in Physics/Math. After grad I worked p/t in the Uni labs as a tutor/prac class in the Physics labs while undertaking private research on Audio Engineering Techniques. I was offered the lecturing position at a TAFE (technical college) proving Diploma Courses in Electronics and Communications for Telecoms Techs, referred by the head of the school of Physics at the Uni.

If everyone is agreeable I am happy to provide some insight into the development of the SKA. Light theory not mired in maths. This would qualify this thread for the LAB. Where to start....

Cheers,
Greg

[woodsyi]

Greg,

I remember very early on I had a question on your topology but never got around to ask it.  I would love to hear about the science behind your amplifier.  As all gear design is full of compromises, I would love to hear why you took the path that you did and what alternatives you discarded.  Also, it would be immensely helpful, to me, if you explain why you chose your parts and what specs and tolerance you were looking for in the parts you used.

[amplifierguru]

OK here goes.

Class B and Class AB amplifiers are notorious for the generation of switching or crossover distortion especially at higher frequencies related to the on/off switching speed of the push-pull output stages.



When amplifying a pure sinewave (of which all music is composed) one half of the output stage switches on for half the time, and then the other, so they produce half of the output signal each. In Fig 1 above Zl is the speaker. The full sinewave cycle is shown to the right. This is shown as a current across the speaker load.

more to follow...

[amplifierguru]

So we have a Class B amplifier gain block of gain G outputting a sinewave to a load Zl, and, for simplicity, we'll consider the case of a resistive load so Zl = Rl and the current and voltage at the output are thus in phase.

So the half waveform above the line (+ve going signal) will be supplied by the upper half of the push pull output stage and the half below the line from the lower output stage half.

So we have two half wave waveforms from the two halves of the output stage combining in the load to give the final output sinewave. These will alternately draw current from the power supplies as the current is demanded to maintain the waveform across the load. Shown in Fig 1 are the current waveforms drawn from the supplies, above and below the output waveform.

These currents can be shown to have the fourier series as in Fig 2



So our Class B amplifier generates a spray of harmonics of the pure sinewave signal frequency in both supply currents according to the coefficients in front of the terms cos2wt (second harmonic) , cos4wt (4th harmonic), etc... relative to the fundamental frequency term sinwt.

more to follow...

[amplifierguru]

tutorial on SKA development and innovation unwanted at AC.

farewell all.

remember to support SKA - I'm not dissappearing just because AC can't take innovation and value.

Cheers,
Greg

[Greggo]

Well, that was fun while it lasted.  Too bad, I was very interested in learning more about this here.  Mods, what's the deal?  Did Greg Ball need to start a manufacturers circle to post in the manner he did, or did he just flat out push someone's buttons?  I am not saying you owe me an explanation or anything, I am just curious... want to get a better understanding of how things are supposed to work around here.

Regards,

Greg Jensen

[TheChairGuy]

This thread is now locked.

[Occam]

tutorial on SKA development and innovation unwanted at AC.

farewell all.

remember to support SKA - I'm not dissappearing just because AC can't take innovation and value.

Cheers,
Greg

Greg,

I want to make this clear to you and everyone else -

The reasons for your exile have nothing whatsoever to do with the value and/or innovation of your products. The causal factor in your predicament rests solely on YOUR behavior on these circles. You have been warned, cautioned and disciplined over your repeated infractions of rules explicitly explained to you. If you choose to perceive your treatment though myopic paranoia, that is your choice, but that does not change the reality of this situation.

Wishing you all the best in your search for venue of communication more appropriate for your needs,
Paul, Moderator of the Lab Circle