Common ground amps
analogluvr
Posts: 72
My sumo Polaris gave up the ghost yesterday which was unfortunate because it was doing a great job. I'm going to be looking for a replacement and I have my eye on and Adcom 555 or an Adcom 545. Does anyone know, are these common ground amps?
Comments
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My SDAs are blade blade so I need common ground amps.
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Yes,they are both common ground.Get the 555 if you can.2 Channel
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Thank you for that I really appreciate it! I will try to land one. It is actually a 555 version II. I assume this is still a common ground? Sorry I should've mentioned that the first go-round.
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Yes it is common ground also. If you can, check the D.C. Offset on the Adcom. Use the search feature on here and you will find how to do it and what readings you're looking for.2 Channel
Polk 1.2tl's Modded with dreadnought
Musical Fidelity M6Si
North Star Intenso Dac
Auralic Aries Mini Streamer
Oppo 103
Pangea PC
Wireworld Equinox 7 interconnects
Wireworld Equinox 7 Speaker Cables and Jumpers
Backups 2.3tl, Crs+ pin/blade with stands.Monitor 5 peerless,Monitor 4 peerless,Polk R200,McCormack Dna 0.5 Deluxe McCormack Dna 1,Dared Sl 2000A,Dayens Ampino Rogue Magnum 66 pre -
Thanks for the tip, is that a common problem with those? If you get a high reading is it just not indicative that the power supply capacitors need to be replaced?
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DC offset is not adjustable on a '555. As I recall, high offset means a fault in matching of some smaller transistors, meaning one has gone bad.
I'm no expert--that's just what I've read. Others may have a better diagnostic.
Corey Greenberg seemed to prefer the '555 II to the Polaris II, but he also wound up with two semi-defective examples of the Sumo.
http://www.stereophile.com/solidpoweramps/491sumo/index.html
I'm not saying there's anything "wrong" with the '555, but they made some design choices that rub me the wrong way. Lack of protection circuitry, and an inability to adjust DC offset being the main two. The power transformer is large, but not Krell (or even Aragon) huge.
Don't forget to look at B&K and Acurus, both of which have products in the same general price and age ranges, but which might be better-built. My Acurus 200X3 is common-ground. I am beyond satisfied with my Aragon components. I had a single warranty claim with my preamp/processor, and one used amplifier was delivered to me with a popped fuse--which I replaced and has never popped again. For all I know, it failed from vibration in shipping. The Aragon amp driving my SDAs requires a jumper wire--or isolation transformer in the SDA interconnect--because it is almost common-ground, having ~20 ohms between the negative terminals of two channels.
Carver is well-regarded here, when in good condition. Heck, maybe upgrade to a Sumo Andromeda! (Ooooops. No. Andromeda is not common-ground.)
ANY amplifier from the era of the '555 is likely due for service. Maybe you're better-off getting the Polaris rebuilt. You already know it's history, and you know that you like it. -
yes I read that about the Polaris. That thing has shocked me with every comparison I've made. I used to have a pair of apogee divas and I was running the mid frequency and high frequency ribbons with an Ayer V5 xe. For some reason I ended up putting the Polaris in that position and preferred it over the ayre. A $400 amp over a $3000 amp. I also preferred the Polaris over a sonic frontiers Power 2 but I don't find that overly surprising as generally I don't like the sonic frontiers stuff.
Then when I got the polk SDA's I borrowed a Yamaha pro amp that my friend was quite happy with. It has something like 300 W the channel. The polaris smoked it, it wasn't even close. The Yamaha Had floppier bass less midrange and certainly more irritating highs. Now since I've blown up the Polaris that's all I have to listen with. So I won't be very patient! -
I guess by now you know the Adcoms are common ground and my gfa-555 rack face pushes any speaker I've ever owned and even did a stupid test w/ multiple speakers and handled the load w/ no ill effects.2chl- Adcom GFA- 555-Onkyo P-3150v pre/amp- JVC-QL-A200 tt- Denon 1940 ci cdp- Adcom GFS-6 -Modded '87 SDA 2Bs - Dynamat Ext.- BH-5- X-Overs VR-3, RDO-194 tweeters, Larry's Rings, Speakon/Neutrik I/C- Cherry stain tops Advent Maestros,Ohm model E
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leftwinger57 wrote: »I guess by now you know the Adcoms are common ground and my gfa-555 rack face pushes any speaker I've ever owned and even did a stupid test w/ multiple speakers and handled the load w/ no ill effects.
Not all but these we are discussing are ....just to clarify
many of the later 4 number series are not. -
Was Jimmy B still part of Sumo at the time the Polaris II was produced?
I have the greatest respect for Jimmy B as a designer/engineer. (I'm not so sure about his taste in clothing.) God bless 'im. I do not expect to own an Ampzilla 2000, but they'd be on my short-list if the Palladiums ever fry. -
Yes he was. Me too!
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Actually sorry I'm not sure if he was for the Polaris ii but mine is a late eighties original. Although they do appear to be identical in design
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Actually I just read an article that said J B didn't like mosfets and his successor designed the amp. My bad
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I've been reading, always dangerous, and I am curious about the sumo nine. Whether it is common ground? I found this but don't understand it well enough to know what it means
While a derivative of the original SUMO Gold, the Nine Plus is both a product extension and a design refinement reflecting a clear understanding of Class A amplification. The Nine Plus is a balanced differential amplifier. Each side of the amplifier is active (as opposed to normal practice, in which one half is referenced to ground). -
By the description it has a balanced/bridged output stage so is not common ground and can not have its negative binding posts strapped together to make it common ground.analogluvr wrote: »... Whether it is common ground?..... The Nine Plus is a balanced differential amplifier. Each side of the amplifier is active (as opposed to normal practice, in which one half is referenced to ground). -
Is an Aragon 4004mkii common ground? It mentions in the literature that it is dual mono.
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Dual mono usually means non-common ground, but not always. Best to test it or call Aragon.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
According to the schematic there are a pair of 10 ohm resistors isolating the ground connection between both channels and safety ground.You can confirm with a multi meter, you should see 20ohms between the two negative speaker terminals.Strapping the negative terminals together would make it common ground as it does not have a bridged/balanced output stage.analogluvr wrote: »Is an Aragon 4004mkii common ground? It mentions in the literature that it is dual mono.
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The Aragon 8008BB (and the rest of the 8000 series, I'm sure) have the same 10-ohm resistors, 20 ohms between the channels. A simple jumper wire fixes that.
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According to the schematic there are a pair of 10 ohm resistors isolating the ground connection between both channels and safety ground.You can confirm with a multi meter, you should see 20ohms between the two negative speaker terminals.Strapping the negative terminals together would make it common ground as it does not have a bridged/balanced output stage.analogluvr wrote: »Is an Aragon 4004mkii common ground? It mentions in the literature that it is dual mono.
That might work, I'm just wondering if that might introduce some ground noise/hum.HT SYSTEM-
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The addition of the jumper across the negative terminals would place the 10 ohm resistors in parallel with respect to chassis safety ground.The resulting 5 ohms should still provide enough isolation to prevent a ground loop issue.
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According to the schematic there are a pair of 10 ohm resistors isolating the ground connection between both channels and safety ground.You can confirm with a multi meter, you should see 20ohms between the two negative speaker terminals.Strapping the negative terminals together would make it common ground as it does not have a bridged/balanced output stage.analogluvr wrote: »Is an Aragon 4004mkii common ground? It mentions in the literature that it is dual mono.
That might work, I'm just wondering if that might introduce some ground noise/hum.
There have been other members here that had them and no mention of hum. Me thinks you should be good.
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Strapping doesn't sound as good as using the AI-1or Dreadnought.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks for the help guys. I'm kind of all over the map inso far as searching for amps. And the price point keeps on creeping up LOL now I am contemplating higher power tube amps. I'm going to start another thread asking if there are any higher power tube amp users here. Generally I am more of a tube guy.
Basically I bought the speakers because I was curious about the technology. I do like what I hear a lot in terms of sound staging and bass response and so on. My only qualifying comment so far would be that perhaps there is a bit of detail loss. Right now what I'm hearing seems to be rich warm powerful sound that can be pleasant but not the ultimate in resolution. But I'm not sure if that's because I haven't used very good amps so far. The best I've heard them so far has been with the sumo Polaris. That is a MOSFET amp and stereotypically they do sound that way. So perhaps I need to go with something bipolar if I'm doing solid-state or go with higher power tube if they can handle the load. -
Strapping doesn't sound as good as using the AI-1or Dreadnought.
AI-1/Dreadnought is not an option here.analogluvr wrote: »My SDAs are blade blade so I need common ground amps.
The <12" jumper wire has been working beautifully for me for years. -
I realize that and yes, strapping can be an option in that case, but I've heard the difference on SDA's that could use the AI-1 or Dreadnought.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Good to know though as ultimately if I love the sound of these I'll probably end up with a pin blade pair down the line so that I can go with mono blocks and not be limited in my choices.
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What would happen if you didn't use the jumper wire? Also what would happen if you thought and amp was common ground but it wasn't and you hooked it up and used it?Strapping doesn't sound as good as using the AI-1or Dreadnought.
AI-1/Dreadnought is not an option here.analogluvr wrote: »My SDAs are blade blade so I need common ground amps.
The <12" jumper wire has been working beautifully for me for years.
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analogluvr wrote: »
What would happen if you didn't use the jumper wire? Also what would happen if you thought and amp was common ground but it wasn't and you hooked it up and used it?Strapping doesn't sound as good as using the AI-1or Dreadnought.
AI-1/Dreadnought is not an option here.analogluvr wrote: »My SDAs are blade blade so I need common ground amps.
The <12" jumper wire has been working beautifully for me for years.
Very loud sqealing and very possibly let all the magic smoke out. Trust me you DO NOT want to find out. Now you could use non common ground BUT you would need to NEVER use the SDA cable which negates all the special sound you enjoy from those speakers. -
As mentioned possibly some strange sound effects or potentialy nuke the 10 ohm resistors.analogluvr wrote: »What would happen if you didn't use the jumper wire?
Depending upon the amp you could have anything from a blown fuse,thermal shut down or worst case scenario blown output transistors.Also what would happen if you thought and amp was common ground but it wasn't and you hooked it up and used it?
