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In Reply to: RE: From what I understand the Zero's... posted by cpotl on May 10, 2017 at 05:42:05
With the Zero's that the amp was still an OTL in the purist sense. I was just asking about the speaker impedance matching with OTL's and how critical it was after reading that article. I just made the comment that the Zero's were not a OPT like you were trying to say they were. So please keep the facts straight on that just like you are about the OTL design.
Some speakers give OTL amps a rough time due to their impedance or reactance and the result is bad sound. Then the OTL's get a bad rap for not sounding good or thin. Some of us do not have the money to burn to keeping buying amps or speakers until we get a perfect match, so the Zero's are maybe the better way to go to match OTL amps with our existing speaker systems IF there is an issue with the matching (yes, like a crutch).
As you know, just because a amp and speakers look good on paper....doesn't mean it will sound good in your system or home together. So the Zero's are the next best (cheapest) thing until you can either make or buy some speakers that match the OTL amp you have properly.
So instead of just arguing about the OTL purist design and the Zero's being an OPT (which they are not), why not bring some good advice or examples of what OTL/ Speakers you have or others that actually work well together so we can all learn.
Edits: 05/20/17Follow Ups:
Well, my own OTL amplifiers are home-built. Two of them use 6C33C tubes in the output stage, totem-pole style. (One pair of tubes in the output stage.) These give about 25W maximum into 8 ohms. One of the OTLs is based on a design by Hans Beijner, the other a design by Tim Mellow. I built another OTL that is a circlotron, based on a design by Alan Kimmel. This one allegedly gives up to 100W into 8 ohms, but I've never tried pushing it to measure that. Finally, I have one I really built just for fun, loosely based on the very early Dickie-Macovski design, with no iron-cored components whatsoever.
The speakers that I use are all high or fairly high efficiency. Lowther DX3 drivers in bass reflex cabinets; Klipsch Forte II; and Paradigm Monitor 7. With these, I've had no problems at all driving them from any of the OTLs. In fact the Lowther DX3 drivers have paralleled Audio Nirvana drivers too, so I suppose they are then nominally 4 ohm. But the sensitivity is so high that running out of headroom is never a problem.
I fully agree with you that if you have already an amplifier and speakers, and if the amplifier is not able to drive the speakers comfortably because of impedance and current-delivery issues, then Zero transformers may well be a reasonable solution to the problem.
Personally, I would be left feeling slightly unsatisfied if I were having to do that with an OTL amplifier, since it does, to some extent that different people can hold different views about, partially negate the whole OTL philosophy. For me, if I ran into such a situation it would be fairly straightforward for me to rebuild one of my OTL amplifiers in a beefed-up form, for example by doubling up on the output tubes. (In fact it would give me an excuse to build another one, which I have been wanting to do for a while, but currently find it hard to justify the need for a 5th one!) I can see, though, that if one is buying ready made amplifiers the financial considerations would be somewhat different.
Regarding whether Zero transformers should be called output transformers or not, I think that all that can be said on the subject has been said already. My main point in my observations on the topic is that one is going to be somewhat hard pressed to come up with a universal definition of what is, and what isn't, an output transformer if the definition is not simply going to be crafted for the express purpose of "allowing" Zero autotransformers while disallowing everything else.
Chris, Thank You for the info. Now this is what I was looking for in replies. :)
I totally agree with you about either building a new amp or speaker if there was an issue with proper matching OTL amp and speakers. I have built a tube amp from kit and have done a few DIY speakers but I am no expert in building tube amps from scratch let alone OTL amps.
What got me interested in OTL amp designs is how people who owned them said they were the best sounding amps the have ever had but speaker matching was a must to get good bass. I would really hate to add anything between the OTL amp and speaker that would take away from what the OTL amp brings in sound. So I do understand where you are coming from.
I hear those 6C33C tubes are pretty nice? Are these largely available?
I now have got some good info and direction/s on what to do which will help me out big time. I just wish I could build that many amps from scratch. There are some OTL kits I could try and hopefully with the DIY GPA driver (Altec) based 2 way with Zilch Z19 xovers should be a good match. If that doesn't work out I do have a Line Array design in the works with BG planars and Silver Flute 6.5 drivers I have already that I can arrange to get the proper matching impedance for the OTL amp/s.
I will look into some of those designs you mentioned
Thanks again for the info!
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