2. amps-preamps
  3. 1038591857

Need advice from OTL experts

I have recently purchased a used pair Transcendent T8 OTL mono blocks (80 watts into 8 ohms) for my Quad 63 ESL speakers. For many years before this purchase, I have used ARC Classic 30, Classic 60, D115 and ASL Explorer 805 SET mono blocks with the Quad 63. I am a strictly vinyl person and my preamp is the ARC SP8 with a VDH Frog HO MC cartridge on a Oracle premier II TT. My speaker cable is MIT MH 750 extended, VPI phono cable and Cardas Decade interconnect from Pream to amps. The bottom line is I have never heard better sound and music coming out of these Quads before the OTL's and I am very pleased with this amp and speaker combination. The sound very pure, clean and precise without the typical tube coloration and faster than all the amps I had before. The gentleman whom I bought the OTL's from told me my SP8 preamp's output impedance at 1000 ohms is too high for these amps and speakers. I have owned this SP8 for many years because I love its phono section and I hate to part with it. My question is if this is a true statement with science behind it and if I would benefit from switching to a preamp with lower output impedance. I have looked at Transcendent web site. Their preamp has output impedance of 200 ohms and some other preamp brands have as high as 2000 ohms. Many thanks in advance.
blptwp

Showing 2 responses by sean

sean
6,231 posts
 
Given the figures that you've listed, i would not worry about impedances in the least. According to theory, the amp is in no way loading down the preamp. It should sound like "magic" and according to what you've stated, it is working as well or better than you expected. Enjoy and forget about the previous owners' comments. Sean
>
sean
6,231 posts
 
Brucegel: I think that OTL's are a LOT harder to get to work well than a standard tube amp with output transformers. The transformers lend a WIDE margin of "buffer zone" to a tube amp. Without that buffer zone, the linearity and overall performance of the circuit is forced to bare its' soul into whatever load you throw at it. Most designers / manufacturers aren't willing to risk their reputations by taking the chances that OTL designs and the various loudspeaker loads force upon them.

Like anything else, if you are good at what you do, regardless of what it is and what it costs, you will have people to market your product too. OTL designs are no different than any other part of the market, even though it may be a smaller segment overall. Sean
>
More to discover