Sound Lab vs Magnepan 20.7

Clio09, you should know by now that getting rid of the transformer gets you greater transparency :)

However direct-driving ESLs has its own set of problems- chief amongst them is how the amplifier can be safely connected to the speaker such that it does not represent a danger to the user. This usually means the amp is built into the speaker, and *that* usually means if you want to upgrade to a better speaker or more powerful amp, you have to start over...

True Ralph, but most serious junkies use a specific amp with a specific speaker anyway. Change one and you most likely will have to change the other. When an engineer designs a speaker/amplifier combination, he can tailor each to the other.

Ralph, yes there is a benefit in transparancy with the OTLs that I have realized but now I am putting that signal through a transformer with my Quad 57s. Previously that was not the case with my Jazz Modules. I was hoping someone could talk more about the use of a direct drive amp. I know Roger Modjeski builds one and some Acoustat users have modified their speakers to use it. But can it be done with other ESL designs such as Quad or Soundlab? At what level of complexity or risk. You pointed out a couple in your post but would like to hear more from you and others. Perhaps I should start a separate thread on that.

Acoustat actually made a powered direct-drive ESL. They had to integrate the amp into the speaker on account of the rather dangerous high voltages involved.

This will be the case with any direct-drive installation. Of course, any ESL can be direct-driven if you are willing to do the surgery. So it would be possible to do that with a Sound Lab. But with the voltages involved to bias the speaker, the amp would have some very high operating voltages which would make it a challenging amplifier to build and operate.

Clio, Modjeski is very familiar with the 57's, and makes custom amps. Give him a call (he's up in Oakland/Berkeley now, not Santa Barbara), and see what he says about making you a direct-drive OTL for your 57's. Then let us know what he says---I have a pair of 57's too!