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Old 16th May 2006, 09:57 PM   #11
anatech is offline anatech  Canada
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Hi cjd,
Once you get into it again I'll try to give you a "hand". Phono fault included.

-Chris
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Old 22nd June 2007, 05:37 PM   #12
Heiney9 is offline Heiney9  United States
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Reviving this thread as I need some quick assistance. I'm considering purchasing a PA5 and I recently aquired a pair of Polk Audio SDA 1C's which can't be used in conjuction with a amp that is NOT common ground. I assume the PA5 is common ground but I need to be absolutely sure.

TIA

H9
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Old 22nd June 2007, 09:39 PM   #13
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I'm pretty sure it has a common ground on the (-) output.
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Old 22nd June 2007, 10:08 PM   #14
Nanook is offline Nanook  Canada
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Default Nakamichi Stasis ...

I sold the recievers and amps when new. They were quite nice to listen too. At the time one of my favourite setups to sell, an SR2, OMS2 (or 3), a Revolver turntable and DCM or B&W speakers--DM1600s. (I'd love to get a pair if I could find them and/or afford them). Really a very nice set up--and lower B&W speakers worked well to.

Compared directly to the then current NAD 3240PE, and the HK PM635(?), and a Bryston 2BLP/.5 combination, the Nak ran a close second to the Bryston setup. Yes, the Bryston had better bass. (the 2BLP/.5B was combined into the BP20 or whatever the intergrated was/is called).

I recalled the SR2 , and decided to buy one. I think I paid under $50 USD including shipping off of epay. The little reciever still sounds very good.

Is it a threshold? nope. But it held it's own against the Bryston pair and at a substantially lower cost. Currently I use it in my bedroom, but hope one day to create a "museum" of equipment in my livingroom. Kinda like pick and play.

anyone interested in a more modern look at the Nakamichi SR4 should look here , at the Feb 06 issue.
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Old 22nd June 2007, 11:08 PM   #15
anatech is offline anatech  Canada
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Hi Nelson,
Quote:
I'm pretty sure it has a common ground on the (-) output.
How can you be so sure??



I imagine you have a better idea than most of us, but I'll confirm that you are dead right.

H9,
Quote:
I'm considering purchasing a PA5 and I recently aquired a pair of Polk Audio SDA 1C's which can't be used in conjuction with a amp that is NOT common ground.
I think you have that backwards. Those speakers need a solid ground between channels or it will smoke the input stage grounds. Trust me on this.

Hi Nanook,
Quote:
Is it a threshold? nope.
Yup, just a little different and mechanically cleaner in build quality.
Quote:
Yes, the Bryston had better bass.
The Statis design takes the feedback from the drivers a little further back. The output is therefore running open loop with zero feedback. It will have a lower damping factor due to this. One of the advantages is that the amplifier only has one input (instead of two) now and does not respond to a speakers antics. It also doesn't receive radio stations quite as well as other amps may. But you can't compare it to amps of normal design really and it does have much better mid and high resolution. Yes, it has it's characters, but all in all I'd rather listen to a PA-x over any Bryston of that period (horrid construction BTW).

I still use a TA-2 in my bedroom.

-Chris
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Old 22nd June 2007, 11:16 PM   #16
Nanook is offline Nanook  Canada
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Default anatech

well, I am, nor ever will be a technician.

I recall the explaination for "Stasis" as follows:

basically a high quality input driver (operating in class 'A' or near class'A'), that is used to drive a class 'AB' output.

really, kinda like using a class A tube amp as an input to an AB output that uses no or little feedback.

Really quite a good idea. And I do love my old SR2, it is an early production one as the ones I sold were after 1989, and the "2" had terrible spring loaded speaker connectors.


hmm if low dampening factor than a nice match for my Hemp FR8 drivers
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Old 22nd June 2007, 11:37 PM   #17
Heiney9 is offline Heiney9  United States
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Quote:
Originally posted by anatech
Hi Nelson,

How can you be so sure??



I imagine you have a better idea than most of us, but I'll confirm that you are dead right.

H9,

I think you have that backwards. Those speakers need a solid ground between channels or it will smoke the input stage grounds. Trust me on this.

Hi Nanook,

Yup, just a little different and mechanically cleaner in build quality.

The Statis design takes the feedback from the drivers a little further back. The output is therefore running open loop with zero feedback. It will have a lower damping factor due to this. One of the advantages is that the amplifier only has one input (instead of two) now and does not respond to a speakers antics. It also doesn't receive radio stations quite as well as other amps may. But you can't compare it to amps of normal design really and it does have much better mid and high resolution. Yes, it has it's characters, but all in all I'd rather listen to a PA-x over any Bryston of that period (horrid construction BTW).

I still use a TA-2 in my bedroom.

-Chris
You are right (as usual Chris) I used a double negative in the sentence and confused everyone, including myself. Polk SDA 1C's can only be used with a common ground amp unless you utilize a special cable (AI-1) which incorporates a transformer for non-common ground amps like mono blocks. This is of course for the inneraural crosstalk cancellation feature of the speakers. I don't have the special interphase cable ( I just have the std. SDA cable) and I don't want to build one. I've heard they degrade the sound anyways.

On the Adcom GFA5500, 5800, 5802, 565's and 585's you can tie the negative output terminals together and they can be used with Polk SDA's. I was just wondering if the NAK isn't common ground, could the negative speaker terminals be connected (with approriate size cable) if need be.

I sold NAK and Polk way back when and I don't remember this being an issue, but memory can fail so I figured this would be the most accurate place to get the info

Regards

-Brock-
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Old 23rd June 2007, 02:57 AM   #18
anatech is offline anatech  Canada
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Hi Brock,
You should be fine. The only issue is that the SDA's force heavier currents between the negative speaker terminals than was thought of when the amp in question was designed. A heavy wire link between the negative terminals is recommended (just like Adcom 555 type amps).

We were authorized warranty for both Polk, Adcom and many other amps. I still fail to see why Polk released these darn speakers on the market without very clear warnings. I can't tell you how many customers had to pay for repairs not covered under warranty due to these speakers.

-Chris
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Old 23rd June 2007, 03:08 AM   #19
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Default Re: anatech

Quote:
Originally posted by Nanook
basically a high quality input driver (operating in class 'A' or near class'A'), that is used to drive a class 'AB' output.
What looks like a driver is a Class A bipolar follower pair coupled
to the load through about 1/2 ohm, which is capable of bypassing
the outputs and driving the load directly.

I suppose you could think of that as a feedforward approach.

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Old 23rd June 2007, 03:10 AM   #20
anatech is offline anatech  Canada
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Hi Nanook,
I used to be in audio sales and moved into service. Couldn't stand most other salesmen.

Anyway, the output of a Stasis amp is class AB, but biased on higher than normal AB. Nelson could give some rough figures off the cuff, and correct me if I'm wrong here (please, feel free to correct me!). The output stage is not contained in the feedback loop. The more output transistors there are run in parallel, the lower the distortion and the higher the damping factor will be. They do not sound as good into low impedance loads as they do into 8 ohm loads.

I must say that a Statis amplifier is darn hard to kill. It can be done, and I am impressed when it happens. My only repair of a PA-7 was the unfortunate victim of one of those really large copper box staples that fell inside. It's the only one I ever saw fail.

-Chris
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