NAD 2200 or Adcom 545

[sdabeliever]

I have a (new) pair of sda 2's and an adcom gfp 555 what do you think would be a better sounding amp with this setup?

NAD 2200 power envelope or
ADCOM gfa 545

post you opinions!

[dorokusai]

You might as well stick with Adcom. Out of the two amplifiers, I prefer the NAD. It's a great amp.

[George Grand]

2200PE's are boss.

[anonymouse]

The 2200PE is *not* common ground.

[hoosier21]

The 2200PE is *not* common ground.

your right

[BigMac]

deleted.

[DaveMuell]

Are any of the other NAD amps common ground?

[anonymouse]

Are any of the other NAD amps common ground?

I do not know. The 2200PE is a very interesting beast. It has an innovative power supply. Because both channels share the same power supply, they invert one channel's input so that when a massive peak demand exists e.g. a bass intensive kick, both halves of the power (+ve and -ve) are working, rather than one side only. At the outputs, one channel is also inverted.

Another way to look at the output is that if you have a multimeter, you will see that one ground is connected to the positive on the other channel. Now will this work with SDA's? It might, *but*
1) make *very, very sure* that the SDA cable you are using does not connect the two grounds together.
2) Because there is a connection between the two channels in the amp (they both share the same power supply) , the SDA effect *might* still work.

[BigMac]

Found this looking for an answer to the common ground issue.

http://www.polkaudio.com/forums/arch...p/t-25249.html

[sdabeliever]

Uuhhhmmmmm. I bought the NAD today for $200. was that a mistake? I'm hearing you guys say this may not work. correct? please say it's not true!!

[sdabeliever]

Now will this work with SDA's? It might, *but*
1) make *very, very sure* that the SDA cable you are using does not connect the two grounds together.

what do you mean?

[anonymouse]

Do you have a multimeter? If so, hook up the amp, to the speakers, connect the SDA cable, but do not power it on. Check the ohm resistance between the two black terminals on the amp. If the reading is zero (or almost zero), then disconnect the SDA cable. You will need to build a new SDA cable which does not connect the common ground.

[sdabeliever]

sorry for the noob question ....How do I build that cable? (where do I look for the info? )

also does this mean in the meanwhile I can disconnect the SDA cable and use the 2200pe?

[anonymouse]

What model of SDA's do you have? Is it a blade-blade or a pin-blade?

And yes in the meantime, it is safe to disconnect the cable and use the 2200

[sdabeliever]

sda 2 with the blade blade
..

sweet!

[anonymouse]

To be honest, I'm not sure whether the blade-blade type shorts out the grounds. Others will need to chime in on this. Get a multimeter for $10 at the hardware store or $3 at Harbor Freight and do the test I suggested before you worry further.

[sdabeliever]

will do. Thank you...It'll be a couple of days b4 I get the amp.

[sdabeliever]

And you're right. it is boss. It honestly puts our onko m504 to shame : (

anonymouse RE: the OHM's I hooked up a multimeter as you suggested.. everything hooked up with the sda cable connected and nothing turned on. OHMs are about 1/3 of an ohm at the two negative terminals.

I also hooked up our M504 and got the same reading...?

so is a 1/3 of an ohm bad?

[sdabeliever]

I couldn't edit for some reason...

so another way to ask the question is. Does a reading of 1/3 ohm indicate common ground or non common ground?

I'm getting the same reading when the onkyo m504 and we've had that hooked up to my father in laws 2.3's for a year.

[anonymouse]

It would appear to me that the interconnect is shorting out the grounds. I would _not_ advise you to use that interconnect.

What is the ohm reading without the interconnect between the two negative terminals at the amp?

[sdabeliever]

It's exactly the same with SDA cable or without and with either amp.

I tried both set ups on my father in laws' 2.3's and got the same results= ~1/3 ohm

[anonymouse]

Ok, heres what I want you to do - disconnect the speaker cables from the amp. Measure the resistance between the negative speaker cables (the disconnected cables), with and without the interconnect and report your results

[sdabeliever]

OK. 1/3 OHM with the sda cable connected on my SDA 2's VS. "off the chart" disconnected. (all the way at the other end of the gauge.)

[sdabeliever]

UPDATE:

my multi meter was not zeroed correctly. It's 1/3 of an ohm off.

I called my local stereo expert and he said the opposite of what you guys are saying. That if it reads zero that it is a common ground amp and that it's fine to use.

??

[heiney9]

UPDATE:

my multi meter was not zeroed correctly. It's 1/3 of an ohm off.

I called my local stereo expert and he said the opposite of what you guys are saying. That if it reads zero that it is a common ground amp and that it's fine to use.

??

Reread post #12.................that's what was said. If it reads 0 or close to it then it's common ground and safe to use. The SDA cable has nothing to do with your measurements. You are measuring at the receiver or amplifer's speaker terminals. Power off and speakers disconnected. And as an extra precaution power cord UNPLUGGED.

H9

[anonymouse]

OK. 1/3 OHM with the sda cable connected on my SDA 2's VS. "off the chart" disconnected. (all the way at the other end of the gauge.)

Ok, your SDA cable is forcing the common ground then. I do _not_ advise you to use this cable with that amp. The amp is not common ground. Your SDA cable is assuming it is common ground and will likely destroy one channel if you use it.

Your best bet is to source of build an A1 interconnect if you want to use that amp with those SDA's.

If you want to check what I am saying, ensure the amp is unplugged, and measure the resistance between the negative on one channel and the negative on the other channel. What you will find is that the resistance is nearly zero from the negative of one channel and the POSITIVE on the other channel, proving conclusively that this amp is not common ground. If it were common ground, the two negative terminals on the amp, with nothing connected should be common at zero resistance.

[sdabeliever]

Sorry guys I don't seem to be getting this. I know how to use a multimeter but have no idea how this common ground/ non common ground thing works electrically in regards to resistance..hence my confusion.

anonymouse:
I just did this last test and the results are as follows. (with the amp unplugged from the wall) I measured the resistance (the speaker wires were still hooked up) at the two black terminals on the amp= zero ohms. Also measured resistance between black on left and red on right=zero ohms.

You are saying this conclusively proves that it is a NON common ground amp...correct?
If so can you or someone please help me find how to build the A1 sda cable with a transformer (I've only been able to find mention of it on the forum so far)

Heiney9:
I must be misunderstanding what you wrote because to me you and anonymouse are saying the opposite. you said: "If it reads 0 or close to it then it's common ground and safe to use." Anonymouse just said: "What you will find is that the resistance is nearly zero from the negative of one channel and the POSITIVE on the other channel, proving conclusively that this amp is not common ground."

i just want to understand the bottom line not be a pain.

[anonymouse]

A common ground amp simply means that the left and right channel share a common ground inside the amp. The NAD2200PE does not have the left and right channel grounds connected internally. Therefore it is not common ground.

There are posts on here describing how to build the A1. Honestly though, your best bet would be to sell this amp and buy an Adcom or similar common ground amp. The A1 cable does not give you as good an SDA effect, and you will spend at near $100 building that cable.

[sdabeliever]

Thanks. sad news. nice amp :(

would it be cheaper to alter the cable I have? Do I need anything other than a transformer to do this? I'll lose at least $50 (shipping paid) on this amp if I turn around and sell it.

[Kex]

... The 2200PE is a very interesting beast. It has an innovative power supply. Because both channels share the same power supply, they invert one channel's input so that when a massive peak demand exists e.g. a bass intensive kick, both halves of the power (+ve and -ve) are working, rather than one side only. At the outputs, one channel is also inverted. ...

Is that what they call "Power Drive" technology, or is that something different entirely? A fairly recent review of the T955 highlighted this feature, and I'm just curious if it's useful, or if it's useless marketing blurb.

Sorry to derail, slightly, sdabeliever.