OTL Tube Amps

[RDSChicago]

I’ve never heard one and am intrigued. I have Quad 57’s and Reference 3a Reflectors at 92 db sensitivity and impedance of 8 ohms with, I’m told, a fairly flat impedance curve. How good do these amps sound? I have heard listening to an OTL on the right speakers for the first time is a captivating experience. Please share your thoughts and recommendations. Of course Atma-Sphere is the first that comes to mind. Thanks.

 

[audio.bill]

Of course like any other audio gear their performance will vary depending upon their specific design and implementation. I've had the opportunity to hear several OTL tube amps over the years and the good ones have an alluring transparency and liquidity to their sound. Not necessarily the last word in dynamics but when matched with appropriate speakers (often high impedance which require less current) they can sound stunning. They also tend to run quite hot and radiate heat like few other amps, although that also depends on specific implementation and class of operation. Many years ago I had a buddy with Atma-Sphere OTL amps who just loved them, but when you'd visit for a listening session he'd often be down to his undershirt and shorts to deal with their heat. I'm not kidding!

 

[puroagave]

On Quad 57s, Ralphs M60 are sublime with that speaker. I heard them together prior to buying the speakers which were rebuilt by Sheldon Stokes. I tried the Graaf GM 20 OTL from Italy whose claim to fame was its circlotron circuit and a quartet of 6c33c tubes. That combo was less successful and lost out to a Beard EL84 PP amp we shot out. My most recent foray into OTLs was the Berning designed ZOTL 10 Mk II by LTA. It was paired with 18 ohm Avantgardes that are 107 db efficient. Up to the point i tired nearly a dozen SS and tube amps. The ZOTL was my favorite, easily besting the Allnic 300b I had on hand and my previous reference the Valvet E2.

 

[RDSChicago]

On Quad 57s, Ralphs M60 are sublime with that speaker. I heard them together prior to buying the speakers which were rebuilt by Sheldon Stokes. I tried the Graaf GM 20 OTL from Italy whose claim to fame was its circlotron circuit and a quartet of 6c33c tubes. That combo was less successful and lost out to a Beard EL84 PP amp we shot out. My most recent foray into OTLs was the Berning designed ZOTL 10 Mk II by LTA. It was paired with 18 ohm Avantgardes that are 107 db efficient. Up to the point i tired nearly a dozen SS and tube amps. The ZOTL was my favorite, easily besting the Allnic 300b I had on hand and my previous reference the Valvet 2se.

Thanks. I heard good things about the LTA Zotl's. I'm surprised the 10 watts was enough for the Quad's (mine were rebuilt by Electrostatic Solutions). I know they make a 40 watt power amp as well. Did you like the LTA better than the Atma-Sphere M60?

 

[puroagave]

Thanks. I heard good things about the LTA Zotl's. I'm surprised the 10 watts was enough for the Quad's (mine were rebuilt by Electrostatic Solutions). I know they make a 40 watt power amp as well. Did you like the LTA better than the Atma-Sphere M60?

As you may recall the ESL 57s I had rebuilt by Ken at ES are long gone. I still have the Stokes rebuilt 57s in storage but haven't brought them out since getting the Avantgardes so I haven't tried the ZOTL 10 on the 57s. LTA has a generous return policy if the marriage isn't successful, you'll prob want to use them with the Ref 3as, in which case Id get the 40w vers. That would be a great shoot out on 57s: M60 vs Zotl40