One further thought on modified and tube rolled Moscode 600's.
George once told me that he had bridged some 600's for a famous record maker (to remain un-named), because that is what they wanted. However, in his opinion they did not sound as good bridged as they did vertically bi-amped.
Never the less, based on experience with a different pair of amps in the late 70's. I kept trying to bridge them.
First I used a transformer input. Interesting result, but George was right. Later I bought a SS bridging unit with absolute polarity switching, still not as good as vertical bi-amping.
Eventually I bought a preamp with balanced out, but no absolute polarity switch. I built a little box to convert the balanced out to single ended with switches for absolute polarity. The box also gave me the ability to bridge the amps.
WOW, WOW, WOW!! That was what I was looking for.
I now have two preamps with balanced out, one SS, one tube. They both do a fabulous job of bridging the amps into 1000+ watt monoblocks into an 8 ohm load.
The good news is that the amps were originally stable into very difficult loads. Because they are bridged into a pair of Martin Logan Prodigy they need to be stable. These speakers are nominally 4 ohms with a dip to 1 ohm above 15kHz. Running the amps bridged the amps effectively see 1/2 that load, so a dip to 1/2 ohm.
If you are willing to do a little, to a lot, of work with them the 600's can really shine.
George once told me that he had bridged some 600's for a famous record maker (to remain un-named), because that is what they wanted. However, in his opinion they did not sound as good bridged as they did vertically bi-amped.
Never the less, based on experience with a different pair of amps in the late 70's. I kept trying to bridge them.
First I used a transformer input. Interesting result, but George was right. Later I bought a SS bridging unit with absolute polarity switching, still not as good as vertical bi-amping.
Eventually I bought a preamp with balanced out, but no absolute polarity switch. I built a little box to convert the balanced out to single ended with switches for absolute polarity. The box also gave me the ability to bridge the amps.
WOW, WOW, WOW!! That was what I was looking for.
I now have two preamps with balanced out, one SS, one tube. They both do a fabulous job of bridging the amps into 1000+ watt monoblocks into an 8 ohm load.
The good news is that the amps were originally stable into very difficult loads. Because they are bridged into a pair of Martin Logan Prodigy they need to be stable. These speakers are nominally 4 ohms with a dip to 1 ohm above 15kHz. Running the amps bridged the amps effectively see 1/2 that load, so a dip to 1/2 ohm.
If you are willing to do a little, to a lot, of work with them the 600's can really shine.