Cambridge Audio 851W common ground?

hauxon

I'm able to get a 6 months old Cambridge Audio Azur 851W power amp at a very good price. My speakers, Polk Audio SRS 1.2TL require a common ground amp. Does anyone here know if the CA 851W is a common ground design? ...and yup I don't have a dreadnought (yet).

Schurkey

Contact Cambridge Audio?

hauxon

I sent an email to the but no reply so far.

gyosa

I bet it is , unless it’s a true dual mono ....

For example , the ps Audio s300 is a true dual mono and it’s not common ground ....

Bk

hauxon

It is common ground. I measured it with my multimeter. I bought it.

hauxon

Official answer arrived from CA:

Thank you for contacting Cambridge Audio.

I'm pleased to say that it is a common ground design.
Best regards,
Chris

Cambridge Audio

The amp has been connected to my SRS 1.2TL over the weekend. I looks like a good match to my speakers. Compared to my NAD C272 I feel it's more secure footed and smooth. It's also dead silent, not even a faint hiss at loud levels with my ear against the tweeters. The difference in power is only 50 watts or 33% and should thus not be easy to detect but to me it seems more. The NAD is rated 150 wpc for both 8 and 4 ohms. The 851W is however rated 350 wpc into 4 ohms. If I recall correctly the SRS 1.2TL should be around 6 ohms and probably lower after I built the new crossovers with lower resistance Jantzen inductors. At least it sound noticably more powerful to my ears.

The only negative I can think of is of generated heat from the amp. It runs way hotter than the NAD. Actually I never felt any heat to speak of coming from the NAD power amp. The Cambridge Audio is not a conventional class AB amp but something what they call Class XD which runs closer to Class A but without the excessive heat generated by Class A. Probably similar Class A / AB implementation to what's found in amps from Parasound, Vincent and more. It still runs very hot, you can touch the top of the amp but barely so. All the ads I've seen and setup from shows have the amp on top of the matching 851 streamer /preamp, probably for a reason. So I moved my NAD M51 dac/preamp below the Cambridge amp to allow better ventilation and get the M51 away from the heat. I might even make ventilation holes in the back of my cabinet (IKEA Stockholm TV bench).

I've been using Kimber RCA interconnects between the NAD components but decided to used balanced XLR between the amps since the CA offers balanced inputs. After doing some reading I just bought pro-audio XLR cables from a music instrument store selling gear for recording studios for $35. Seems like the recording studios are not using "audiophile" grade interconnects. Probably less need with balanced audio.

Hrannar

westmassguy

Those C-Coil Inductors drop the impedance quite a bit Hrannar

Clipdat

hauxon wrote: »

After doing some reading I just bought pro-audio XLR cables from a music instrument store selling gear for recording studios for $35. Seems like the recording studios are not using "audiophile" grade interconnects. Probably less need with balanced audio.

You might be surprised. Even with inexpensive XLRs, there are plenty of audible differences. I explored this and wrote about it here: https://forum.polkaudio.com/discussion/186671/four-way-xlr-cable-shootout

Schurkey

gyosa wrote: »

I bet it is , unless it’s a true dual mono ....

For example , the ps Audio s300 is a true dual mono and it’s not common ground ....

Bk

Technically true...but misleading.

The S300 is dual mono. The S300 is not common ground.

But "Dual Mono" is NOT why the S300 is unfit for SDA speakers without using an isolation transformer.

The S300 is a balanced amplifier. Neither of the output jacks are referenced to ground. Therefore they cannot be "common ground", they aren't ground at all.

It's the balanced part, not the "dual mono" part that makes the S300 incompatible with SDA (requiring an isolation transformer.)

This is fairly typical of "dual mono"--IF (big IF) the amp isn't bridged/balanced, they typically are either common ground or they can be made common ground by strapping the negative terminals with a jumper wire. I suppose there are exceptions, but I don't know of any.

hauxon

Clipdat wrote: »

hauxon wrote: »

After doing some reading I just bought pro-audio XLR cables from a music instrument store selling gear for recording studios for $35. Seems like the recording studios are not using "audiophile" grade interconnects. Probably less need with balanced audio.

You might be surprised. Even with inexpensive XLRs, there are plenty of audible differences. I explored this and wrote about it here: https://forum.polkaudio.com/discussion/186671/four-way-xlr-cable-shootout

Would be interesting to do a test but I'm not a "cable guy" and don't believe there is much to gain with spending hundreds of dollars on cables. I still buy what I call good quality interconnects and speaker cable. When interconnects start to cost hundreds or thousands of dollars I'm out. I'd rather spend my money on better components. I might spend $100 on RCA interconnect cable just to buy something that's well constructed and not of low quality. However here in Iceland (350k inhabitants) there are not many audio stores and not all of them have XLR interconnects. I can get XLR interconnects from Chord ranging from $200 to $1500. Too expensive for me and I see nothing wrong with the current Cordial CMF XLR cables I'm using. (https://www.thomann.de/gb/cordial_cfm_05_fm_sw.htm)

Clipdat

Yeah I'm not saying there's anything wrong with yours or that you have to spend a lot of money. That was pretty much the point of my post, that there's still fairly dramatic differences among under $50 XLR cables.