Jeff Rowland

Hello Al, Ricred, Kijanki, and all,

After reading this thread, it has led me to question my intention of using a second Class D CDA 254 amplifier, thus allowing me to use the two of them in bridged mode as monoblocs.

My speakers are of course different, they being Tannoy HPD 315's, 94 db sensitivity and 8 ohms. I don't know if you can draw any conclusions without specific test results, which in any case, wouldn't be available.

My particular application of these drivers are in custom 150 liter bass-reflex enclosures.

I have written to Tom, at Class D Audio, about this, but the expertise available here is without peer.

I'll be thankful for any information that can be provided.

My apologies to Ricred for hi-jacking his thread.

Regards,
Dan

Those Wireworld cables have a lot to do with your system's excellences

Stringreen,
Do I detect a little sarcasm in your comments?

Richard, the safe/conservative approach is not to add a second M525 chassis for a bridged configuration, but to move up the chain instead with an amp that inherently delivers greater power....

Within the Rowland line, that means the Continuum S2 integrated, which is also said to enhance all those audible parameters that you already like on M525.

On the other hand, there are reasons why Rowland was comfortable enabling bridging via a simple toggle on the rear panel... According to all reports I have heard, M525 in bridged mode does not degrade the sound quality, and delivers larger stage/images, and greater authority.

Of course, things might be different with speakers having relatively low impedance.

G.

Hi Dan (Islandmandan),

I found this impedance curve for the HPD 315he, which confirms (as might be expected for a Tannoy) that its impedance characteristics are very benign. (If the link just opens at flickr.com instead of opening at the specific photo, paste the url https://www.flickr.com/photos/89700142@N03/8344329373 into the address bar of your browser). Note, btw, that in contrast to most such curves that are presented this one extends down to 1 Hz. So the somewhat low impedance magnitudes at the left end of the curve essentially represent DC resistance, and are reasonable values that can be expected to be inconsequential.

I also looked at the web pages on the amp module and the kit, and the manual.

The bottom line is that I don't doubt that the amp can drive the speaker in a reasonable manner in bridged mode, but of course how the resulting sonics would compare with stereo mode is speculative.

Another possible concern, though, is that I note that the amp module's input impedance is spec'd at a low 7K, and I suspect that in bridged mode it is likely to be around half that amount, or only 3.5K. That will be non-optimal for many preamps, especially the many tube-based preamps which employ coupling capacitors at their outputs, the capacitors typically resulting in substantial output impedance rises at deep bass frequencies.

But if you don't specifically envision an impedance incompatibility with the preamps you may use, given the very low price of this kit it would seem to be a reasonable risk. Also, perhaps it might be helpful in reaching a decision to try providing the kit you already have with a mono signal and running it in bridged mode with one speaker.

Best regards,
-- Al

P.S: Kijanki, thanks for both the input and the compliment :-)