Jeff Rowland

Now if I can't use bridged 525s or can't find a used 625 that has the most recent updates, I may need to look at other options.

Richard, to be sure it's clear, using two 525's in a vertical biamp configuration completely avoids the potential issue that has been raised about using bridged amps in conjunction with low impedance speakers. At the same time, it very likely would provide sonic benefits that would not occur in bridged mode, and I suspect would have no downside relative to bridged mode aside from probably having a bit less maximum power capability (although maximum power capability would still be significantly greater than what you have now).

Good luck. Regards,
-- Al

Richard, I have no experience whatsoever with Rowland equipment, but I do have a suggestion I think may be worthwhile. When you get the new amp, in addition to trying the two 525's in bridged mode, try them in a vertical biamp configuration (which you can do with your speakers).

You would of course need an extra set of speaker cables and also probably a pair of XLR y-adapters (used at the amp inputs) to vertically biamp a pair of 525's, but for initial experimental purposes, at least, those things needn't cost much. And given the very low output impedance of the Bricasti M1, it won't have any problem driving two amplifier channels from a single one of its outputs.

Also, regarding Bombaywalla's most recent post above, I agree 100%. And the concern he expressed earlier about bridged mode perhaps being an issue when used with a 4 ohm speaker is certainly valid as a general word of caution. Not so much with respect to the amp's ability to function (at least in the case of a high quality amp that is presumably designed in a robust manner, such as a Rowland), but rather with respect to sonics.

In this case, as I have no experience with Rowland equipment I of course have no idea as to how applicable that caution may be to the specific amp in question. But I would cite several posts Atmasphere has made in the past in which he has asserted that ALL amps will sound better to some degree when driving higher impedances, such as 8 ohms, than when driving significantly lower impedances, such as 4 ohms. And (as Bombaywalla indicated) in bridged mode the amp will "see" the nominal impedance of your speakers as 2 ohms, and as not much more than 1.5 ohms at some bass frequencies which often require lots of energy.

Which is one reason for my suggestion of trying the amps in a vertical biamp configuration as well as in bridged mode. Another being that I wouldn't be at all surprised if vertical biamping were to provide a significant improvement in imaging relative to what you have now, that you are specifically looking for, without the possible sonic downsides of bridging. The possibility of improved imaging presumably resulting, at least in part, from elimination of the inter-channel crosstalk that inevitably occurs to some degree in a stereo amp, via grounds, power supplies, and other paths. In a vertical biamp configuration that is eliminated since the same signal is going through both amplifier channels.

Good luck. Regards,
-- Al

P.S: Here are some XLR y-adapters.

Regards,
-- Al

+1 Bombaywalla (with a slight qualification as described below).

Richard, I see that you are using some rather expensive interconnects and speaker cables. In part for that reason I would reiterate my earlier comment to the effect that you wouldn't have to double up on interconnect cables to implement a vertical biamp configuration. You would just use a short XLR y-cable at the inputs of the amp, such as one of those I linked to earlier, in conjunction with the same interconnect you would use for bridged mode.

You may have seen people claim at times that use of y-cables or splitters in their system resulted in some amount of sonic degradation. My strong suspicion is that in most of those cases the reason for that was not the y-cables or splitters themselves, but rather the inability of the component supplying the signal to drive the two sets of load impedances that were involved, and in many cases two sets of cables as well, in an optimal manner. That won't be an issue in your situation.

For example, it is sometimes reported that poor results are obtained when a y-adapter or splitter is used to route the outputs of a preamp to both a power amp and a powered sub. In those situations it tends not to be realized that the capacitance of the cable to the sub, which is often substantial due to the length that may be involved, will affect the signals received by the main power amp just as if it were added to the capacitance of the cable to the main power amp. It also tends not to be realized that the line-level input impedance of many and probably most powered subs is quite low, which will also affect the signals seen by the main power amp, especially if the preamp's output impedance is high. Yet the y-adapter itself will often be blamed for the less than optimal results.

None of those kinds of effects will be applicable in your situation, given also that the RCA outputs of the Bricasti DAC, which I assume you are using to drive your subs, are driven by output stages that are fully independent of those driving the DAC's XLR outputs (that often not being the case with lesser designs).

Finally, the very low output impedance of the Bricasti DAC, the fact that its connections to the amps are balanced, and the relatively short lengths that are involved, all work in the direction of reducing sensitivity to interconnect cable effects and differences. Including the effects of balanced y-cables that may be in the path.

Regards,
-- Al