Bi-amping with Rotel RA 971 MK2 & RB 971 MK2

[gramps23]

Hi folks,

I'm having a little quandry and hoping that someone will be able to help.

I currently use a Rotel RA 971 MK2 integrated amp with my B&W DM601 S2's (soon to be replaced with Dali Zensor 3's), and have been offered a 'matching' RB 971 MK2 power amp for very good money. The intention was to use the amps configured to bi-amp the 'speakers, but I've just been having a flick through the manuals (I've put links to both at the end of the post. Outputs haven't changed from mk1 to mk2 btw) and it appears that the RA 971's output is rated at 60w, the RB's at 70w.

With the amps having different outputs, whichever elements get the RB 971 powering them will get more current, right..? There's no way to attenuate the output of either amp and balance their outputs, so this means that the two units are incompatible in the configuration that I want to use them...? It seems a bit weird if so, as all of the other manufacturers I know of, that offer integrated amps with a matching power amp, engineer them to be able to work together, and offer a clear upgrade path.

If someone could help to shed light on whether my thoughts are on line, or not, it would be very much appreciated!

Warm regards

PDF manuals for both units are here- http://www.rotel.com/content/manuals/ra971_eng.pdf http://www.rotel.com/content/manuals/rb971_multi.pdf

 

[jiggyjoe]

From the info on dali's website it looks like the zensor 3 is single wire only, so you wont be able to bi-amp.

 

[gramps23]

From the info on dali's website it looks like the zensor 3 is single wire only, so you wont be able to bi-amp.

Ha! Well, that was easy. Thank you jiggyjoe

I'm going to get the RB anyway, seems silly not to at the asking price, and hope that another one comes up so I can run the pair in bridged mono. In the meantime I'll try using the RA as a pre only - see if there's any improvement with a few extra watts from the RB and having the two stages running seperately from each other. Might be interesting for a few hours of beard stroking..!

 

[stevebrock]

i used to own a RA 971 Mk2 - great amp, you can only bi-amp by adding 2 RB 971s

 

[gramps23]

i used to own a RA 971 Mk2 - great amp, you can only bi-amp by adding 2 RB 971s

Thanks Steve.

If that's the case then running the RA 971 as a pre-amp only, with the power-amp stage sitting there doing nowt seems a bit silly. Maybe it's time to see if I can sell the unit and get one of the RC 971 pre's instead - hopefully having less electrickery buzzing around in the box will improve things?

 

[stevebrock]

i used to own a RA 971 Mk2 - great amp, you can only bi-amp by adding 2 RB 971s

Thanks Steve.

If that's the case then running the RA 971 as a pre-amp only, with the power-amp stage sitting there doing nowt seems a bit silly. Maybe it's time to see if I can sell the unit and get one of the RC 971 pre's instead - hopefully having less electrickery buzzing around in the box will improve things?

No thats isnt correct really, the only part redundant is the power amp stage in the RA 971 redundant, you will be using the power amp in the RB971 which in theory should be better than the RA 971 power amp.

 

[gramps23]

i used to own a RA 971 Mk2 - great amp, you can only bi-amp by adding 2 RB 971s

Thanks Steve.

If that's the case then running the RA 971 as a pre-amp only, with the power-amp stage sitting there doing nowt seems a bit silly. Maybe it's time to see if I can sell the unit and get one of the RC 971 pre's instead - hopefully having less electrickery buzzing around in the box will improve things?

No thats isnt correct really, the only part redundant is the power amp stage in the RA 971 redundant, you will be using the power amp in the RB971 which in theory should be better than the RA 971 power amp.

Sorry, didn't word my post very clearly Steve.. Yep, I understand that - was just saying (in a slightly complicated fashion!) that it would be a shame to have an integrated amp sitting there and only using the pre-amp stage, so might be better off getting the pre-amp on its own. Hope that makes sense now!

Cheers

 

[stevebrock]

yep get ya now, probably best to get a better Integrated amp then, think i paid £299 for my RA 971 MK2 many years ago and I thought it was a great punchy ideal for Dance & Rock.

 

[stevebrock]

i would have no hesitation in two RB971s with the RA971 as a pre!

 

[gramps23]

Not sure if I'll be able to better the Rotel combo for the monies - the RB 971 mk2 is costing me £90, an extra one of those will be £100-150 when the time comes, and the 971 pre-amp shouldn't cost any more than I can get rid of the integrated for (I could spend a few extra quid and get a better second hand pre, I guess).

So, I'll end up spending £200-250 for a combo with a dedicated 180w amp firing into each speaker. I've read that the Rotel power amps take on a new dimension when they're bridged, and I can't imagine that I'll be able to better them with an integrated costing anywhere near that budget, even send hand? I was looking at a NAD 372 a while ago, and very impressed by the sound, but got scared off by a friend who's an electronics engineer and runs a little repair shop, and he says that and 1/4 of all the seperates that come in are NAD!

 

[MUSICRAFT]

Hi gramps23

Providing the RB-971 MK2 is gain matched to the RA-971 MK2 and that the speakers can be bi wired/bi amped then you can use a RA-971 MK2/RB-971 MK2 pairing to bi amplify speakers. You'll have to check with Rotel regarding the former.

Bridged RB-971's are superb :twisted: however when used in this configuration the speakers need to have an impedance of 8 ohms.

All the best

Rick @ Musicraft

 

[gramps23]

Hi gramps23

Providing the RB-971 MK2 is gain matched to the RA-971 MK2 and that the speakers can be bi wired/bi amped then you can use a RA-971 MK2/RB-971 MK2 pairing to bi amplify speakers. You'll have to check with Rotel regarding the former.

Bridged RB-971's are superb :twisted: however when used in this configuration the speakers need to have an impedance of 8 ohms.

All the best

Rick @ Musicraft

Hi Rick,

Thanks for the advice, much appreciated.

I've just spoken to a very friendly chap at B&W, who seem to be in charge of Rotel now (?), and he said that though the amps weren't gain matched, they should be useable together without a perceivable difference, particularly if the power amp was used to drive the bass element as it would 'soak up more energy'. Apparently there's people using Classe amps together, which have over 100w difference in output, with some of B&W's largest models, and there's no issues there either.. All sounded a bit odd and doesn't quite add up on an academic level, but I wasn't going to argue!

It's a little frustrating if the Rotels won't drive anything less than an 8ohm load when bridged. I've just spent a couple of weeks audtioning new speakers, and the Zensors were certainly top of the pile on the budget I have, but have a 6ohm load.... Ho hum.

Is it possible that the amps will be ok with the 6ohm load if not pushed hard? In the past I've had to use PA amps in emergencies, on loads that they're not recommended for, but nowhere near their full output potential, and had no problems. We've got pretty sensitive neighbours, so the Zensors will never be run beyond about half their potential max SPL, which won't be much above tickover for a 180w amp. Any thoughts..?

Warm regards,

Lawrence.

 

[Dougal1331]

As long as you don't party too hard, bridged 971s would drive the Zensors no problem- just ensure plenty of ventilation as they may run a bit hotter.

You'd be in for a real experience too, I'm familiar with the 971mk2 integrated, and it will suit the Zensors perfectly. Bridged mono 971mk2 is even better- I'd say go for it, personally. And prepare to have to your socks knocked off.

 

[MUSICRAFT]

Hi gramps23

Providing the RB-971 MK2 is gain matched to the RA-971 MK2 and that the speakers can be bi wired/bi amped then you can use a RA-971 MK2/RB-971 MK2 pairing to bi amplify speakers. You'll have to check with Rotel regarding the former.

Bridged RB-971's are superb :twisted: however when used in this configuration the speakers need to have an impedance of 8 ohms.

All the best

Rick @ Musicraft

Hi Rick,

Thanks for the advice, much appreciated.

I've just spoken to a very friendly chap at B&W, who seem to be in charge of Rotel now (?), and he said that though the amps weren't gain matched, they should be useable together without a perceivable difference, particularly if the power amp was used to drive the bass element as it would 'soak up more energy'. Apparently there's people using Classe amps together, which have over 100w difference in output, with some of B&W's largest models, and there's no issues there either.. All sounded a bit odd and doesn't quite add up on an academic level, but I wasn't going to argue!

It's a little frustrating if the Rotels won't drive anything less than an 8ohm load when bridged. I've just spent a couple of weeks audtioning new speakers, and the Zensors were certainly top of the pile on the budget I have, but have a 6ohm load.... Ho hum.

Is it possible that the amps will be ok with the 6ohm load if not pushed hard? In the past I've had to use PA amps in emergencies, on loads that they're not recommended for, but nowhere near their full output potential, and had no problems. We've got pretty sensitive neighbours, so the Zensors will never be run beyond about half their potential max SPL, which won't be much above tickover for a 180w amp. Any thoughts..?

Warm regards,

Lawrence.

Hi Lawerence

Your welcome.

I wouldn't use amplifiers to bi/tri amp speakers if they weren't singing as one.

I would not use the Rotel power amplifiers in bridged configuration with speakers which have an impedance of less than 8 ohms. Even with speakers rated at 8ohms the bridged Rotel's will see a load of 4 ohms, 6 ohms - 3 ohms, etc. This could limit stability and narrow the margin for error regarding useable output.

601's with RA-971 + two RB-971's (bi amp or bridged). Then replace RA-971 with RC-972 or RC-995.

or

Zensors with RA-971 + RB-971. Then replace RA-971 with RC-972 or RC-995.

All the best

Rick @ Musicraft