Isolation transformer for SDA-1Cs?
PolksTillIDie
Posts: 102
Recent events have conspired so that I might have a chance to pick up a Rotel Michi S5 amp for a song to pair with my SDA-1Cs. The problem is I haven't yet gotten a straight answer as to whether or not its a common ground design, though being a dual mono-block, I think not. So this brings up the question what do I have available for an isolation transformer that will be worthy of this $9K amp. These speakers are no longer stock, having been heavily and gloriously modded by the late westmassguy, but are schematically the same with the exception of the Erse inductors making them 4 ohm units.
Any ideas, opinions? I've heard that the Dreadnoughts won't work with the 1Cs, true?
Again, thanks for the help.
Any ideas, opinions? I've heard that the Dreadnoughts won't work with the 1Cs, true?
Again, thanks for the help.
Polk SDA-1Cs with RD0194-1 upgrade tweeters, SoniCaps, Clarity PX, Gimpod boards, Cardas BPs, Erse inductors, Canare 4S11 IC; Michi P5; Yamaha M-80; Yamaha CD-S1000; Oppo BDP-95; Sony UBP-X800M2; EverSolo DMP-A6; Topping DX-7 Pro +; Technics SL-1400 with Ortofon 2M Bronze PnP; PS Audio Dectet; AudioQuest Red River ICs; AudioQuest NRG-Z3 PCs; RapcoHorizon High Def High 413-Strand 10AWG Speaker Cable; Auralex Isolation Pads
Answers
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99% sure that Michi is a common ground amp. Almost all Clas AB amps that share a single power cord (ie:not mono blocks) are common ground, even if the amp power cord isn't grounded. It's the Class D amps that are most always floating ground and not common ground.
Also, pretty sure most 1C work with an isolation transformer (aka Dreadnaught). I think as long as it is a Pin-Blade SDA connector, the transformer works.
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Almost all Clas AB amps that share a single power cord (ie:not mono blocks) are common ground
I disagree.
The Rotel in question has a true dual mono topology in a single chassis. Therefore, it cannot be common ground.
OP, why haven't you called Rotel to ask
them?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 -
Almost all Clas AB amps that share a single power cord (ie:not mono blocks) are common ground
I disagree.
The Rotel in question has a true dual mono topology in a single chassis. Therefore, it cannot be common ground.
OP, why haven't you called Rotel to ask
them?
Cannot be common ground? Surely you know better by now. Even if it has separate power supplies and separate transformers, if both channels have the negative terminals going to ground, it is a common ground.
If it is a fully differential amp it might have the negative speaker terminals going back to the amp boards and then it wouldn't be common ground. Dual mono doesn't necessarily mean non-common ground. The Parasound HCA-2200ii is dual mono but common ground. So is the Halo A21. This has been discussed many times and often, the worst case solution is to tie the negative terminals together with a separate wire.
I agree the OP should reach out to Rotel for a definitive answer, but if the amp can be gotten for a song, perhaps there isn't time to let that happen. I'd say get the amp and test for continuity with a multimeter on the negative terminals. Worst case, if there truly isn't any continuity, then build a Dreadnaught and he would have a killer amp and the ability to run SDAs.
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It's noted as having a completely dual monophonic circuit topology. Key word, completely.
One of my amps has a true (completely) dual mono topology with only one power cord, so I wouldn't use the number of
power cords as a gauge.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 -
Companies use terms loosely and they can say "completely dual mono" and still have both speaker negatives going to common ground. I can't find a service manual or schematic for it anywhere but since they are not advertising it as a fully differential amp, and it clearly doesn't use output transformers, I suspect it is a standard AB design with a common collector circuitry. Like I said, the test is simple with a multimeter.
