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PostPosted: Thu Oct 12, 2006 6:57 am 
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PostPosted: Thu Oct 12, 2006 7:38 am 
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And here's a pic of the GB150S2 PSU using a 10A bridge and +/-23,500uF 63V, bleed down resistors and optional 5 way terminal blocks possible for 2mm wire connections.

The PSU facilitates lower supply impedances that reduce Class AB commutation artefacts, reducing the loss of detail and imaging characteristic of Class AB.

Cheers,
Greg


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PostPosted: Thu Oct 12, 2006 8:31 am 
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Hi Greg,
amplifierguru wrote:
The PSU facilitates lower supply impedances that reduce Class AB commutation artefacts, reducing the loss of detail and imaging characteristic of Class AB.
you must be planning to supply the world with new PSU boards.
Your high PSRR amps are not supposed to need all this low impedance stuff, or are they?
Are you still recommending running two channels off a single supply?
Maybe that's why the better PSU is required?

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Andrew T.


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PostPosted: Thu Oct 12, 2006 5:33 pm 
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On the GB300 you use a full bridge rectifier for the + and - voltage. I wonder why you haven't considered a full bridge for the + and a full bridge for the minus voltage. Somewhere I read that that approach delivers a significant better sound. Have you ever tried it?

PS my 300VA R-core trafo's for the GB300 are finally delivered, I have my chasis so I can start finisheing those amps and evaluate them.
Wouldn't it be that we will move to a new house (planned to be effective half november). So I am afraid this GB300-project will have to be delayed again.

Are your buffer's a solution to connect the GB300's in a balanced way to a pre-amp. Like we discussed in our first emails last year.

Henk


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PostPosted: Thu Oct 12, 2006 7:55 pm 
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Hi Andrew T,

Quote:
Maybe that's why the better PSU is required?


The artefacts created by Class AB are equally generated in both channels and are only a few dB below their fundamentals -

http://www.diyhifi.org/amplifierguru/guru_011.htm

(see the blue FFT on a real power supply).

so the reduction of AB artefacts on a low Z supply can work equally well for the other channel's contribution and the combined C gives a 6dB benefit to both channels. Once the PSRR and supply Z is low enough, pure tone crosstalk also becomes negligible. In addition there is a beneficial 'across the board' L <--> R filtering effect which I will measure and post details as soon as I have a chance. :finga:

The wiring from the supply to the module is more of a concern as this highlights the harmonic artefacts. I will be posting some FFT's of this in the near future.

PSU's for the world - from moi? I don't think so, just trying to offer a simple and convenient low Z supply for consistent results with the GB150Ds.

Hi Henk,

The dual bridge arrangement is interesting , I may do a PCB for one in the not too distant future. There are advantages in reduced noise on the ground from unequal windings but, with negligible residuals in the amps already, there may, in reality, be only a feelgood advantage. :yawinkle:

Finally got the R cores AND a new house - that's an early christmas for you? :rolleyes: Yes the preamp can be set up as a balanced input buffer for the power amp - with it's own onboard 80dB discrete regulators!

Cheers,
greg

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PostPosted: Thu Oct 12, 2006 8:20 pm 
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Sheep
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Hi Greg,

that's some interesting stuff you've got there. Can you tell us anything about the topologies for the pre-amp and regs, for example what output stage do the pre-amps use? What sort of topolgy are the regs? How far does the 80dB extend to?

Dan


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PostPosted: Thu Oct 12, 2006 9:40 pm 
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Hi Dan,

Quote:
that's some interesting stuff you've got there


Thanks.

The pre- or linestage is similar to the SKA topology but without the intermediate emitter follower and using bipolars with emitter degeneration for the CE output stage. The bootstrap works from the degenerated emitters. It's very simple - bootstrap complementary differential first stage followed by a low gain CE output stage running Class A at ~ 6mA , in a x 4 (12dB) gain global FB loop. It is all DC coupled and has an offset adjustment trimpot. :rolleyes:

The regs are simple 2 transistor with bootstrap bias R and Vbe as reference. They run at < 10mA and use a BC546C (+reg) or BC556C (-reg) as the pass element. They are right where they're needed - onboard 'at the coal face'. The 80db extends beyond 20KHz. :finga:

Also included are 2A discrete bridge and 2 x 2,200uF 25V supply caps. All on a 50mm x 75mm PCB (one channel). A single gang pot will go onboard or a dual gang can be wired in.


Cheers,
Greg

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PostPosted: Fri Oct 13, 2006 2:03 am 
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And here's a better pic of the GB150S2 dual channel shared +/23,500uF 10A to 63V shared power supply for a pair of GB150D modules.

Optional terminal blocks in. Individual local star grounding. Dimensions are 158W x 49D x55H.

Cheers,
Greg


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PostPosted: Fri Oct 13, 2006 9:12 am 
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While on the subject of PSUs , here's the updated PSU for the 50W Class A configuration of the GB150D, or any other amp requiring +/- 28,200uF @ 35V.

It has the quiet star ground design with 6A bridge, bleed down R and LED.

Cheers,
Greg


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 Post subject: Simple Volume/Buffer!
PostPosted: Tue Nov 07, 2006 5:31 pm 
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Hen

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Hi Greg!

Do you still remember this project?
I know it is simple, but I like very much your design on the photo!
Is it possible to get you PCB plan for this volume/buffer?

Greets:

Tyimo


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PostPosted: Tue Nov 07, 2006 6:08 pm 
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What happened to Greg's web page link? :?:


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PostPosted: Tue Nov 07, 2006 6:26 pm 
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Hi Tyimo,

Welcome to DIYHiFi!

Yes I have it now on my website. There is also another thread here of a "Simple FET buffer" collectively honed.

Hi Jam,

I am reworking it right now - seems I loaded it with one too many amplifierguru folders. Arrggh! :rolleyes:


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PostPosted: Tue Nov 07, 2006 7:39 pm 
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Hi Greg, I moved the files one level up so the usual address should work. While we are at this, I'd recommend using subdomain URL, amplifierguru.diyhifi.org.

Pedja


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PostPosted: Tue Nov 07, 2006 7:50 pm 
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Hi Pedja,

Thanks but... I have to maintain the integrity of the links that are out there... and figure out how I managed to muck it up. The website is all reworked as well with more pages and better (I hope) appearance.

Cheers,
Greg


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PostPosted: Wed Nov 08, 2006 7:59 am 
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Hi Greg,

I was thinking to try buffer between 10k DACT and GB150. Do you recommend Fet-buffer or SKPre for my purpose ?
I was thinking to instal buffers inside my Orion EQ + DACT passive enclosure, where i have good quality +/- 15VDC available.

As i have told, i have not any sonical "broblems", i want try buffer only for curiosity.

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