Posted by Al Sekela on October 19, 2003 at 09:44:06:
In Reply to: Re: Re: Re: Re: Re: Re: efficiency of your? posted by marcos augusto on October 19, 2003 at 03:13:07:
I have an InnerSound ESL Mark I, late production, with the WBT binding posts (the feedback was changed with the introduction of the WBT posts, and is the same as the Mark II: you don't want an earlier Mark I). Thanks to Travis, who insisted I try the amp.
If you get a used one, be sure to take the top off and check the main circuit board under the 2-watt power resistor to the left of the ribbon cable connector for the front panel LEDs: on some units, this resistor is undersized and the board will be charred. Simply unplug the LED display if you find this.
For US$3K, it is a very nice-sounding amp. However, with a few tweaks, it gets much, much better.
The basic problem is in the casework design. The front, rear, and top panels are lightly supported and ring. This interferes with accurate rendering of the sound-stage. The power transformer is bolted near the center of the bottom panel, which is only supported by four feet at the corners. The bottom panel plus transformer ring at a low frequency, which causes muddy bass.
I reduced the resonances on my amp by clamping a wood panel to the front panel, resting a heavy cutting board on Deflex sheets on the top panel (with room to allow air circulation from the vent holes), and removing the stock feet and resting the amp on a very heavy, butcher-block cutting board with a shallow hole drilled to accommodate the head of the transformer fixing bolt.
I monitored my progress with each step, and each reduction in casework resonance added more depth and clarity to the sound-stage. I am tempted to use some silicone rubber strips and devise a clamp to dampen the heat sinks, but I have not yet gotten to this.
The amp also provides better deep bass if it has a dedicated power circuit with maximum capacity.
It sounds better when driven through the XLR inputs. Part of the reason is the low input impedance, which provides proper loading of the interconnect cables. On my amp, the RCA inputs are fed through blocking capacitors.