6 ohms is fine, as speaker impedance dips go... and the dynamic impedance of any speaker is naturally all over the place.
The spec sheet in pdf says it all.
the transformer is a 1700va rated unit.
the maximum power draw is 1820va when in stereo mode, with 600 watts per channel continuous at 4 ohms. that’s the max power of the unit, that’s the rating of the transformer. The 1700v rating is an average long term thermal rating, as it is for all AC power transformers.
Dynamically, all transformers can handle higher intermittent short term dynamic loading, as in with bass transients. It’s just that the long term continuous loading is the ’toaster’ load rating. Ie, where the heat will go up to unsustainable levels.
The unit draws less power at 1000 watts mono at 8 ohms. 1330va....but the power draw will rapidly increase as you demand more power at lower impedance at 6 ohms.
The reality is that we rarely draw any real power continuously but mostly hit high power draw in peaks...
It should physically work, but how well, sound quality wise... is up to your testing/listening and how you feel about it.
It appears to be as if you would be stacking or bridging a pair of already bridged amps? Each channel is already a bridged design?
They are not giving you the slew rate, as that would generally be a dead give away if it is a balanced bridged design or not. Nor does my quick scan mention any thing about whether the grounds or negative terminal for the speakers is sensitive to being cross connected.
450 watts per channel into 8 ohms, tends to be saying it is a balanced/bridged design for each channel already, so I think you would be stacking balanced/bridge channels. Probably should not be run below 8 ohms (nominal) as speaker loads go.
You really need to look at your speaker’s impedance curves carefully. If the dip truly does not go below 6 ohms, then it might be fine.
Essentially, there is no assurance of anything for anything.
If this is your speaker, the impedance specs say it’s probably not a good idea.
Fine in stereo mode, though.
Thanks for the detailed information. I don’t understand everything you said...balanced bridge, grounds etc but these observations to date are throwing cold water on my possible plans. The speaker you reference is in fact the
ones I have. Perhaps the old Aragon Palladium
monos I have will be hard to beat without spending mega dollars ?
You could find someone competent with a history who can do a modification/upgrade of the palladiums, a minimal cost upgrade.
That may be a way of getting toward what you want without spending much at all.
cleaning up an amplifier can cause the dynamics we desire to come out of hiding from the noise the amplifier produces in sync with the signal. After all, this is what they are doing.
found this:" Plastic Binding Post outputs; replaced with CARDAS binding posts. Runs class A to 125 watts; generates a fair amount of heat. "
If this is true of the amps you have, then the heat will have by now wreaked havoc with the small electrolytic capacitors in the unit and its sound is going to be sub par from when new.
“found this:" Plastic Binding Post outputs; replaced with CARDAS binding posts. Runs class A to 125 watts; generates a fair amount of heat. "
If this is true of the amps you have, then the heat will have by now wreaked havoc with the small electrolytic capacitors in the unit and its sound is going to be sub par from when new.”
I don’t believe they ran Class A to 125 watts, but they were biased very high and run very warm. A shop that carried them that I used to go to (long gone) would kick them on in the morning to heat the room instead of a heater.
They were good amps, the biggest complain they were a bit edgy in some systems. I agree with you that the caps are likely heat degraded and recapping them would probably significantly improve the sound and newer, better quality caps could even improve it from there. For the cost, I would give that a try first.
The problem with bridging stereo amps is, if the speaker load is 8 ohms, then each channel sees a 2 ohm load when operating in bridged mode. Which is okay if the speaker really is 8 ohms. If it drops down to 4 ohms in certain areas, then each channel would see 1 ohm on those frequencies, which is NOT a good thing.
The fact that the Adcom 585SE’s maximum continuous power capability in stereo mode is only 33% greater into 4 ohms than into 8 ohms (600 watts vs. 450 watts), as well as the lack of any rating for a 4 ohm load in bridged mode, does not speak well of its ability to sound its best, or even to sound good, if it were asked to power the Revel Ultima Salon2 in bridged mode.
And although the speaker has a specified nominal impedance of 6 ohms, it has a specified minimum impedance of only 3.7 ohms, at 90 Hz. And Stereophile’s measurements state that its impedance is between 3 and 5 ohms from 17 Hz all the way up to 600 Hz, which encompasses a part of the spectrum in which music tends to have much of its energy.
Finally, in bridged mode the amp will see those 3 to 5 ohm impedances as only 1.5 to 2.5 ohms (in bridged mode an amp sees the speaker’s impedance divided by two, rather than divided by 4 as stated in the previous post), which certainly seems likely to be problematical for the amp. In the absence of information to the contrary I wouldn’t even rule out the possibility that the amp might go into a self-protective shutdown if asked to provide a lot of power into those impedances, given the facts I cited in the first paragraph.
Personally, I would consider using that amp in bridged mode with that speaker to be a non-starter.
Good luck. Regards,
Al, that’s what I thought originally as well, but I was correct by erik squires. It’s not half impedance, it’s actually quarter impedance.
If you look at Parasound A21 specs:
250 watts x 2 into 8 ohm
400 watts x 2 into 4 ohm
750 watts x 1 into 8 ohm (bridged)
If each channel of the amp only saw half the load in bridged mode, it would want to push 400 watts, not 750 watts.
Wow. You guys really understand how all these elements should mesh together. I almost think I
can understand what you are saying.
So I will ditch the Adcom idea
the Aragon Palladium’s I have are the original
preferred model. That was determined by the
fact that they only have a balanced connection, no single ended like later models. These have
the preferred Toshiba metal film caps that are
harder to find than unicorn nuts
i have a great tech but assume he would have
to replace every cap , total number unknown
so is that a practical upgrade that doesn’t run
the risk of ruining the sound?
No, you were right the first time, and if Erik disagreed he was uncharacteristically incorrect.
From the perspective of each amplifier channel a given output voltage will result in twice as much current being drawn from that channel in bridged mode than in stereo mode. That is because in bridged mode a voltage that is equal in magnitude but opposite in polarity will appear on the other side of the load, driven by the other channel, resulting in twice as much voltage across the load than each channel is outputting individually.
Twice as much voltage across a given load means twice as much current, of course, per Ohm’s Law (stated for this purpose as I = E/R; if E is doubled and R remains constant I is doubled). And from the perspective of each channel having to deliver twice as much current for a given output voltage corresponds to each channel "seeing" the load impedance divided by two, again per Ohm’s Law (stated for this purpose as R = E/I; if I is doubled and E remains constant R is halved).
The factor of 4 relates to power, not to impedance, as doubling the current into a given impedance corresponds to a 4x increase in power. As I’m sure you realize, for a resistive load Power = (Current squared) x Resistance.
So for an ideal design a bridged amp can deliver 4x as much power as each channel can deliver by itself, in stereo mode. In practice, though, current capability and thermal limitations usually reduce the factor of 4 significantly.
@blueskiespbd - The Aragon sound is a very warm sound with slightly rolledoff / smooshed highs. The highs are there, but they definitely rich sounding and slower than other amps. The Aragon doesn't have a huge amount of attach / resolution / detail. If you love this sound, then great. Generally speaker, older amps may need to replace the electrolytic capacitors as they can dry out.
At this point, the only reason to change amps is if you're looking for different sound. Monoblocks such as Bryston 7B series or Parasound JC1 will have a lot more detail and attack than the Aragon. It's really a personal preference. The Aragon Palladium will have enough current to run your Revel speakers.
Auxinput 7-1-2018Hi Auxinput,
My previous response, while accurate, did not specifically address this comment.
As I’m sure you realize, for a resistive load P = E x I, where P is power, E is voltage, and I is current.
The increase in the maximum power rating of solid state amps which occurs when load impedance is reduced from 8 ohms to 4 ohms reflects the fact that nearly all solid state amps act as voltage sources. Meaning that they will maintain an essentially constant output voltage as load impedance varies, as long as they are not asked to exceed their maximum voltage, current, power, and thermal capabilities.
So the increase from 250 watts to 400 watts that you referred to reflects I (current) increasing substantially as a result of R decreasing, ***but reflects E remaining the same.*** And as I’m sure you realize, some amps can provide up to 2x as much power into 4 ohms as into 8 ohms, reflecting a 2x increase in current due to R being cut in half while E remains constant.
In bridged mode, on the other hand, E across the load and I through the load ***BOTH*** double (compared to stereo mode, and provided that the amp can supply the required current), while R remains the same. Therefore, since P = E x I, ideally P can increase up to 4x, as I said in my previous post.
I agree with auxinput regarding the Bryston or Parasound monos. As stated - running brigged stereo is self defeating when driving low ohm speaker loads. I believe that either the Bryston, 7Bsst monos @ 600/900 W or the Parasound, JC1 monos @ 400/800 W would do a great job at driving your Revels without breaking a sweat; well except the Parasounds do run in class A for the first 25 W, so it’s their nature to run hot.
Either of those two sets of amps would be very hard to beat at anywhere near their cost. IMO....Jim
Nothing at all against the Adcoms. I have a Adcom GFA - 5500, as my back up amp and it has served me very well and I’m always amazed at how well it sounds and performs, when compared to other much more expensive amps.
I think you would be surprised how well a single 585 SE would drive your Revels. Not quite on the same level as the Brystons or Parasounds, but, dollar for dollar - very good...Jim
I agree with passet02 Maybe not with quite the finesse for words.
I’m not sure, but 450 watts in stereo mode may just be adequate power for these speakers. I’d really be interested to see if anyone has heard these. It would also be interesting to know if they were still following the framework that Nelson did on the old GFA535/545/555 or are these a truly completely different design.
I think we all have the tendency to judge based on the name Adcom, but to be fair, we need to hear these amps. They could be poor, so so or even fabulous.
The following statement appeared in the OP:
I am thinking this could be fun to buy 2 of these place in bridge mode and get about 900 watts of juice each side.
The "S--t" Passet02 classily referred to was entirely relevant to that question. Also, included in that "S--t" was a significant misstatement about how an amplifier responds to speaker impedance when used in bridged mode. That in turn necessitated a correction and an explanation.
What? Adcom changed the landscape because their Nelson Pass designed amps were the equal or better than your Nad level gear of the mid 80’s. For much less.
I have been able to contact Adcom when needed and suspect the above poster just didn’t find the contact page. I’m an owner of the current oroduction Adcom 555 SE amp, and it is superior in some ways to the Parasound Halo A21, my former amp.
People that bad mouth these new Adcom amps in some cases are just piling on. Mine gives a very accurate piano rendition and I can’t comment on sax since I have no music with sax in it.