Zero Feedback Impedance Amplifiers

[enochRoot]

i just moved to ohio about a month ago. raining and 30-40 degrees here. just haven't updated my profile yet. but yeah...it *was* great living out there, and i blew off work quite often to walk the dog down to the beach (i was bout .4 miles). and i could even see catalina from there (on a really clear day).

now i have nothing *but* diy to keep me going

[bear]

Darkmobius - you should have NO problem finding surplus heatsinks and parts up the wazoo out in LA. I know I did. Wished I had a tractor trailer to haul stuff back east!!

If Rockwell still has their surplus shop - that's a best bet.

I think ALL Electronics has stuff, and I found a ton of other places... there's one in Pasadena "C&H"?? and others about. Plus places on the web. Heatsinks should be a no brainer.



_-_-bear

Yeah, and there is a big "swapmeet" once a month too... made out like a bandit there... forget the name, what they called it.

[darkmoebius]

Originally posted by bear
Darkmobius - you should have NO problem finding surplus heatsinks and parts up the wazoo out in LA. I know I did.

Hey Bear, that's really good news to hear.

If Rockwell still has their surplus shop - that's a best bet.

I used to go to TRW's swap meet in El Segundo on the last Saturday of every month. Get all kinds of test equipment, etc. I think that is the one you are thinking of. They still have it like clockwork, although resellers have discovered it and the deals aren't as great as they used to be.

I think ALL Electronics has stuff, and I found a ton of other places... there's one in Pasadena "C&H"??

I'll definetly look around for these places, thanks.

[Susan-Parker]

Hi Darkmoebius

Originally posted by darkmoebius

Aaaaah, a decent shock every once in a while is good for the circulation

In reality, your amps are no more expensive to build than a lot of the SE & PP tube amps I was considering - especially the 300B variants. In that case, I would still have to buy the driver/output tubes and the the output and interstage transformers. Filament transformers, cockets, designers capacitors, PS filtering components, etc.

The chassis and connector costs would be the same no matter what topolgy, so in that light your amps are reasonable.

That's a relief

Although, those SK158 heatsinks are another shocker $270 EUR/$360 US.

I was quoted UKP 80 but I had to buy five to get this price.

You can use another type of heatsink by changing overall size to get an equivalent heat dissipation rate. The SK158 is one of the better ones for surface area and although expensive is relatively compact.

Extruded aluminum heatsinks are primarily priced on weight although complexity of profile does have some bearing.

As Bear says stuff is available from various sources but I have to specify commercially available items.

Is it also possible to buy the bobbins for the input transformer also? If so, what EI and stack size is the bobbin/laminations?

That might help bring the total purchase within my price range.

I will add some more information here.

Patience & time are two things that I have an abundance of, as compared to money. I could easily construct a reliable hand-crank winding system w/ a turns counter.

I now use my lathe with a handle on the spindle as I can hold the bobbin more securely.

I was trying to work things out in my head last night - here's a partial list of needs:

(2) EI-120 x 50mm/2" two-chamber bobbins
(2) sets of EI-120 x 50mm M2 .007" Super-Orthosil laminations (Thomas & Skinner)
(?) 0.8mm enameled magnet wire.
(2) sets of EI-120 transformer frames
(8) non-magnetic lamination screws & bolts

The winding geometry has me a little confused. For the Sowter 9840 type output, is the winding geometry like your example "Version 2 Windings" here?

You need to be looking at

http://www.susan-parker.co.uk/zeus-out-tx-75w.htm

Wire diameter is 1.0 mm for the EI-120 laminations.

The bolts and nuts can be steel but one uses fiber washers and insulation on the internal thread so there is no magnetic circuit.

Or one can use austinetic stainless steel.

I will reorganize the website to try to make it clearer about the correct transformer information.

In that example, I assume for each chamber that we first wind all 12 layers(2 wires) of the primary around the bobbin first, then 6 layers of the secondary(2 wires) - loop out for midpoint taps - then continue the final 6 layers of the secondary. No insulation or paper between windings, except between primary and secondary.

Although, your "start/finish" numbers make me think that you suggest interleaving the primary and secondary. Is this right?

Almost

All four wires are wound simultaneously.

Using the dual chamber bobbin one quad filar winds about 75 turns to get a full chamber. Then turn the bobbin around and wind an identical set of turns.

This quad filar winding is important to get the best performance from the output transformer.

I am going to make one this weekend and will put up some pictures.

And those in charge tell us this is good for Americans May be good for exports, but sucks for importing.

Unstable economies are not good for anyone, even if there is short term gains one way or the other.

Best wishes,
Susan.

[keypunch]

Hi Susan,

I just discovered this thread of your various personal DIY audio deversions. Just so you are aware, if my typing looks odd I think I can be or am "dslextic" as well . I have nto had time to read all the way through the thread yet. I have made it about a 1/3 of way. I will have to catch up on the thread later. For what it is worth, I agree the transformers are the key part. I have look at your site and links a bit. I like to determine if I can wide up one of the two transformers. Heck I might, I am patient, tru to wind up the other one two!

I wanted to at least place a message her to say another silent reader that has viewed part of the thread has come out of the "box", but has lots to catch on. Though I only discovered the thread today.

All the best to your steam locomotive building project if it is not past its deliverly date yet.


Regards,

John L. Males
Willowdale, Ontario
Canada
10 December 2004 19:33

[darkmoebius]

Originally posted by Susan-Parker
I was quoted UKP 80 but I had to buy five to get this price.

The UKP 270 price was from Borberly Audio , perhaps there was a slight markup in that price

You can use another type of heatsink by changing overall size to get an equivalent heat dissipation rate. The SK158 is one of the better ones for surface area and although expensive is relatively compact.

Extruded aluminum heatsinks are primarily priced on weight although complexity of profile does have some bearing.

As Bear says stuff is available from various sources but I have to specify commercially available items.


Re purchasing pre-wound input transformer bobbins:

I will add some more information

Sounds very promising.

You need to be looking at http://www.susan-parker.co.uk/zeus-out-tx-75w.htm...
Wire diameter is 1.0 mm for the EI-120 laminations.

I have a tendency to overcomplicate things, don't I? Now, I get it - just wind all four wires until the bobbin is filled(approx 75 turns). Can't get anymore simple than that. Repeat in both chambers, then cacume impregante w/ varnish.

Thanks so much for setting me straight on this, I really appreciate it.

[Susan-Parker]

Hi Darkmoebius,

Originally posted by darkmoebius

The UKP 270 price was from Borberly Audio , perhaps there was a slight markup in that price

Okay, having had a look at their site I note that that price is for two off, so not quite so horrendous although there is still quite a mark up.

SK157 200
FISCHER Heatsink
300x200mm, black anodized, not drilled
Pair: Euro 270.00

Also it's the SK157 profile as shown in my quick 3D CAD sketch, rather than the higher SK158. However I specified the latter at 150 mm length and the SK157 at 200 mm should be about the same.

My UKP 80 each ( = about Euro 232 for a pair) is for 150 mm lengths of SK158. I was quoted UKP 47 each for the SK157 X 150mm profile.

I have done some more searching and Aavid Thermalloy

http://www.aavidthermalloy.com/

have a suitable extrusion section OS245 which looks to be roughly equivalent to the SK158:

http://www.aavidthermalloy.com/bin/e...00&TReff=0.210



200 mm lengths of this should do the trick

Might be cheaper or at least easier to get from the USA?

Part 0S245 (VIS#400908)

http://www.aavidthermalloy.com/company/locations.shtml

I have asked for a quote.

I have a tendency to overcomplicate things, don't I? Now, I get it - just wind all four wires until the bobbin is filled(approx 75 turns). Can't get anymore simple than that. Repeat in both chambers, then cacume impregante w/ varnish.

Yes, this is correct

It's not complicated ONCE one has got one's head around the ideas and techniques. But like anything that's different it can seem very complicated at first. Don't forget it took me two years of pretty intense development work to get to the point of being able to understand what I was doing.

Even now when I talk to some transformer manufacturers they keep telling me how to do it "properly" with separate winding layers etc. and these are people who live and breath transformer technology on a daily basis.

If you can't vacuum impregnate then painting each layer with varnish as you go will work just as well (although perhaps be a bit sticky).

I don't use any varnish for my development work as I sometimes strip down a bobbin for reuse. However I can hear the windings singing on the test bench so for a final build transformer some form of impregnation is better.

Sound coming from a non-designated source is distortion after all.

Thanks so much for setting me straight on this, I really appreciate it.

My pleasure. It is very heartening that you are interested enough to want to build my amplifier design and I do appreciate how much effort (and money) goes into building even this relatively simple design.

And I do want you to have the best possible outcome and be happy with the results.

Best wishes,
Susan.

[Susan-Parker]

Hi Keypunch,

Thank you for your post and you interest in my work.

Originally posted by keypunch
Hi Susan,

I just discovered this thread of your various personal DIY audio deversions. Just so you are aware, if my typing looks odd I think I can be or am "dslextic" as well .

Welcome

It's quite possible, there is a lot of us around and it is quite common although Dyslexia as a label covers quite a lot of ground. Thank goodness for computer and online spelling checkers!

I have nto had time to read all the way through the thread yet. I have made it about a 1/3 of way. I will have to catch up on the thread later. For what it is worth, I agree the transformers are the key part. I have look at your site and links a bit. I like to determine if I can wide up one of the two transformers. Heck I might, I am patient, tru to wind up the other one two!

Transformers are very underrated these days and all too often regarded as a nuscience.

The output transformers are quite easy to make and can be done by hand "in the hand" with a little care and patience.

The input transformer is not quite so easy and I would admit I haven't got round to making my own here either. This will require at least a little winding frame with a turns counter to get things even.

One way of ensuring symmetry is to wins both sides simultaneously, so then it doesn't matter if the number of turns between the inner and outer layer is different, as long as both sides are exactly symmetrical.

If one does get into winding bobbins regularly then a small lathe with a spindle handle (as one would use for manual turn thread cutting) becomes very useful.

I wanted to at least place a message her to say another silent reader that has viewed part of the thread has come out of the "box", but has lots to catch on. Though I only discovered the thread today.

Thank you for posting. It is very heartening to know that people such as yourself do appreciate this thread and helps keep me motivated to continue with the development and testing my end. I have spent a minimum of 40 hours a week these last couple of months supporting this one thread as well as buying components and upgrading test equipment and software. As you can no doubt imagine encouragement really means a lot to me.

All the best to your steam locomotive building project if it is not past its deliverly date yet.

Regards,
John L. Males

Thanks. My locomotive is a long term project but I am pleased to say that my first monoflue prototype boiler is now under construction.

Meanwhile Jan-Eric in Finland:

http://members.surfeu.fi/animato/steamloco.html

... has built two locomotives using radiant burner boilers based on my design concept - although he has a tri-flue and a bi-flue versions as he has 7-1/4" gauge locomotives.

We think he must have elves helping out in his workshop

Best wishes,
Susan.

[Susan-Parker]

Dear All,

Some updates to the Zeus pages, hopefully now a bit clearer.

Best wishes,
Susan.

[bear]

Arrgh... it ate my post in edit...

Ok.

You can get heatsinks of any size or shape to do the job.

Avvid and Thermalloy have pages to calculate the requirements.

Add 25% for safety - it is better to be too big than too small!

It's absolutely not necessary to use the same extrustion shape or size that Susan has spec'd!!

They're available cheap surplus - sometimes it is cheap enough to buy an entire chassis or subassembly to just take the heatsinks and some random parts...

Ok, here's the home brew method I use:

(ascii representation)

|E
|E
|E
| <---devices mount here

E = smaller extrusions
| = backing plate - MUST BE FLAT

mount the smaller extrusions w/ fins VERTICALLY, 90 degrees rotated from as shown w/ heat sink goo and multiple screws, flat and tight to backing plate.

backing plate must be >0.250" *minimum* - fatter is better.

or:

]|[
]|[
_| <--devices mount here (I had to put a _ in to get the "|"plate to align... but a fat "L" on the bottom is legal too...

For a two sided set up - gets you more dissipation in less vertical space.

Derate the composite heatsink by ~15% compared to an extrusion, because of losses in the coupling between surfaces - the flatter the better the coupling.

You can see a homebrew example of this on my website in the Amplifier pages with my SE Mosfet amp... the caps on the chassis are 3" diameter, for size reference. The backing plate is 0.375" and the fins are made in a metal shop.

It runs 120watts of heat all the time for a 30 watt SE amp using 6 Hitachi Mosfets biased at ~3 amps...

_-_-bear