avantgarde with SS amp recomendation

Herman: I'm curious as to why you say that the Pass Firstwatt is incompatible with multi-way speakers? While it was designed for use with single driver systems, i see no reason why it won't function with multiple drivers. After all, "personal preference" seems to be the rule of thumb here, so who is to say that someone wouldn't like this combo?

Ttrhp: You might want to look into some of the Monarchy Audio SM-70 Pro's. You can run this as a stereo amp by itself or run two of them, each in mono mode. With one amp in stereo, you have 25 wpc @ 8 / 40 wpc @ 4. Given that this amp is biased into a Class A mode of operation, it does run quite warm. It also avoids the crossover distortion that becomes unbearable on high efficiency horns, which is what makes most lower bias Class AB amps unusable with this type of speaker.

Running two of these units in mono, you'll end up with 80 wpc @ 8 / 120 wpc @ 4 ohms. In my experience, this is how the amps sound best. With the efficiency of your speakers though, you may not need the additional headroom that the dual mono-block configuration offers. Starting off with one would be an easy way to see whether or not you like the amp at all and find out whether that one amp would be enough for your specific listening requirements.

Either way, these amps are quite "tubey" sounding as far as SS goes. I'm not saying that they will duplicate the sound of your specific tube gear or offer the highest levels of resolution that SS has to offer, but i don't think that you'll find their presentation "offensive" in the least. Based on past experiences, i think that this series of products would be a much better match for a horn based speaker than the comparably powered Aleph series any day of the week. This is just my personal preference though, so take that comment for what it is worth i.e. "absolutely nothing" : ) Sean
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PS... Please keep us posted on what you decide to do and how things turn out.

The First Watt is a transconductance amplifier i.e. it maintains a constant output current for a given input voltage. This is in contrast to almost all other amps that are voltage amplifiers, they maintain a constant output voltage for a given input voltage.

The passive crossover networks in conventional multiple driver speakers are at least in part in series with the driver and are designed to act as voltage dividers. They will not provide the frequency response they were designed for when driven by a current source. For instance, a simple high pass filter puts a cap in series with a tweeter to decrease current and therefore power to the tweeter at low frequencies. This is ineffective with a transconductance amp as it will increase it's output voltage at low frequencies to overcome the increase in impedance and deliver within it's limits the same current and power to the tweeter at all frequencies. Of course the amp will reach it's voltage limit at some point and not be able to compensate any further (it will be clipping the current), but the tweeter will still operate well below it's designed cutoff frequency.

These effects would not be subtle, and if one prefered the resulting gross distortions in the frequency response of the speaker then I suppose it could be considered compatible.

The frequency shaping network for this amp should be a current divider in parallel with the driver. The tweeter in this case would have an inductor in parallel with the driver instead of a capacitor in series.

Herman: Simple and to the point response. Thanks for making me look at the situation a little more thoroughly. Given the "backwards" design of this amp, i was stuck in a more "conventional" mode of thinking. As mentioned though, i'm sure that someone will find this amp paired with a conventionally designed speaker to offer them "sonic nirvana". Even with all of the aforementioned potential for "sonic warts" and incompatibility issues, personal preference is personal preference. Sean
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Colin Newman: Provisionally Entitled The Singing Fish / redbook CD

You may also try a digital amp like the Tact 2150, it works very well with very efficient speakers (and with others speakers too).