Zero Feedback Impedance Amplifiers

[Circlomanen]

For me, Susan's system had a special combination of fluidity, detail and dynamics that I regard as the best I have heard to date. ( not bad considereing some of the systems mentioned above cost £50,000+ ).

Right on the spot.
(The amp that is. I cant comment on Susans system)

[Susan-Parker]

Dear Mike,

Thank you for your kind comments.

Originally posted by mikelm
.
A friend and I were lucky enough just over a week ago to get to audition Susan's Zeus amplifier along with the rest of her system and I have to say we were pretty impressed with what we heard ...

Susan explained that the system did not have any esoteric, hi end, expensive components - just stuff that she happened to have at the time when she built the system.

Of course, it is always difficult to know what is contributing what in an unfamiliar system but the overall sound cannot be better that the weakest link and overall sound was VERY good.

[snip]

For me, Susan's system had a special combination of fluidity, detail and dynamics that I regard as the best I have heard to date. ( not bad considereing some of the systems mentioned above cost £50,000+ ).

[snip]

mike

The setup was with my prototype CD-ROM drive CD player which uses ECL differential connection for the audio serial data to the preamp's DACs (MC10H124 Quad TTL to MECL > Ribbon Cable > MC10H125 Quad MECL to TTL).

Burr Brown 20 bit DACs (I will put up some information on the preamp soon).

Differential preamp line output is with OP275 opamps.

Zeus monoblock amplifiers in 4:1 output (15 watts max) configuration.

Beyond the Box floor standing speakers.

Best wishes,
Susan.

[Susan-Parker]

Dear All,

I have added a schematic for the STW34NB20 version to the "Building a Zeus" page:

http://www.susan-parker.co.uk/zeus-construction.htm

... and an intermodulation test to the 2SK1529 FFT test page.

http://www.susan-parker.co.uk/zeus-t...9-fft-1khz.htm

Still working on getting a definitive test set up configured

Best wishes,
Susan.

[darkmoebius]

Originally posted by Susan-Parker
Dear All,
Complete transformer is UKP 128.95 each.

I don't know how I missed this post

Yesterday, I made up my mind to simply go ahead and order the Sowter transformers. I figured $250 US for the input and probably an equal amount or less for the outputs.

So, I spent the afternoon driving around Los Angeles returning a bunch of tools, etc. that I never used to Home Depot and other stores. Came home with enough cash for the inputs and maybe some extra for the outputs - then I re-read your post.

$750 US for all four transformers!

Looks like I will have to get the inputs now and wind my own output is this amp is ever going to see the light of day in my house.

[Susan-Parker]

Dear Darkmoebius,

Sorry that you got a fright. Unfortunately the UK pound is strong versus the US Dollar and this is not helping either.

Originally posted by darkmoebius


I don't know how I missed this post

Yesterday, I made up my mind to simply go ahead and order the Sowter transformers. I figured $250 US for the input and probably an equal amount or less for the outputs.

So, I spent the afternoon driving around Los Angeles returning a bunch of tools, etc. that I never used to Home Depot and other stores. Came home with enough cash for the inputs and maybe some extra for the outputs - then I re-read your post.

$750 US for all four transformers!

Looks like I will have to get the inputs now and wind my own output is this amp is ever going to see the light of day in my house.

If you buy the wound bobbins only, and get the laminations and frames separately you should be able to get a good saving and much lower shipping cost than buying fully assembled transformers.

Winding the output transformers oneself on a EI-120 split bobbin (for the multiple option version) is not difficult although a bit of patience and care is required to count turns and get the layers even for both sides.

Winding on a single chamber bobbin with four 1.0 mm wires for the simpler 2:1 only configuration is a walk in the park (honest).

You can also use the finer M2 or M3 laminations from Thomas & Skinner which should push the distortion levels down further.

Best wishes,
Susan.

[planet10]

Originally posted by Susan-Parker
Unfortunately the UK pound is strong versus the US Dollar and this is not helping either.

More accurate to say that the USD has plummetted wrt most of the world's other currencies.

dave

[Susan-Parker]

Hi Dave,

Originally posted by planet10


More accurate to say that the USD has plummetted wrt most of the world's other currencies.

dave

Um, I guess.

I am doing my best to try to recommend components that are as affordable as possible. But unfortunately transformers and heatsinks are expensive to buy.

Here's a quick sketch of one way to build the amp:



Mono-block Amplifier with separate PSU in its own steel enclosure (this cuts down on the magnetic field radiation/pickup).

The amp is designed to be tall and not deep so as to sit behind or to one side of the speaker it is driving.

Heatsink (N.B. SK157 profile) 300 x 200 x 80 mm with a 300 x 150 x 80 mm steel chassis which sits in front of and at the bottom of the heatsink. The output transformer sits on top of the steel chassis, the input transformer is inside and thus screened from electrical and magnetic fields (including the output transformer's).

The PSU is in a separate 300 x 200 x 80 mm enclosure and sits under or to one side of the amplifier. Power connection is a (short) loop of cable with 4 pin XLR connectors.

I did a quick "back of envelope" costing as to how much each amp costs and buying all new from distribution is about UKP 550 per monoblock!

To be economically viable for me to build (i.e. putting aside my consultancy work and building audio kit instead) I would have to charge UKP 1495 (+ sales tax in the EU) each if I was building them for sale - and that would be "special direct 'dealer' price". Retail in the high street would end up being something like UKP 2495 each.

So UKP 4990 for a stereo pair. That's just for power output stage as well. Still need a preamp/line driver.

As in most things custom bespoke and just building in twos or sixes is expensive.

Its quite scary how quickly the costs mount up.

Best wishes,
Susan.

[darkmoebius]

Originally posted by Susan-Parker
Dear Darkmoebius...Sorry that you got a fright.

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

If you buy the wound bobbins only, and get the laminations and frames separately you should be able to get a good saving and much lower shipping cost than buying fully assembled transformers.

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.

Winding the output transformers oneself on a EI-120 split bobbin (for the multiple option version) is not difficult although a bit of patience and care is required to count turns and get the layers even for both sides.

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 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" [/B][/QUOTE]here?

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 seondary. Is this right?

Originally posted by planet10
More accurate to say that the USD has plummetted wrt most of the world's other currencies.

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

[enochRoot]

Originally posted by darkmoebius


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

ie: it's good for big business (who post record sales in times of a weak dollar), and bad for consumers...

[darkmoebius]

You're only a few minutes away from me in San Pedro. Nice to know there's another DIY'er in the area.

Originally posted by enochRoot
ie: it's good for big business (who post record sales in times of a weak dollar), and bad for consumers...

Yeah, they may have that on us but, there is one thing they can't ruin - it is currently 75-80 degrees (F) here at the beach in sunny Southern California. I can look out my home office window and see all of Catalina Island and the Channel Islands to the north. Clear with Santa Ana conditions.

No sign of Winter here, at all.

In celebration, I'm going to blow off all work today and take the dogs a few hundred yards down the hill for a hike through the canyons along the cliffs overlooking the Pacific ocean. May even hike down to the tide pools and let the dogs splash about.

Take that, all you East Coasters, Euro's, Brits, etc.