Balanced SET? North Audio

That means it is a push-pull amplifier.

Their amps can only be used with a fully balanced pre amp. They take the + and - and amplify individually. They come together at the output transformerwhere and the noise cancelling happens. This is not push-pull. Any tech nuts out there that might have better understanding of this. If anybody is really interested contact www.northaudio.com . I am not any way connected to North Audio. I just got very sold on the idea when I met him on the phone. He was doing some work on my pre that I just bought. I haven't listened to them either. They are located just out of Ottawa. I am in Vancouver. Is there anyone in the Ottawa area that would be interested in checking them out. The owner Steve sounds like a nice guy and has a showroom at his house. He was also telling me about his new proto type 45 balanced monoblocks. He sounds very proud of them and says with the right speakers that nothing can touch them. Let's not rule out something new before someone gives it a chance.

12-15-06: Sdrsdrsdr They come together at the output transformer where and the noise cancelling happens. This is not push-pull”

Actually, that is exactly push-pull is. Push-pull or single ended refers to the output of an amplifier. That amp as a push-pull output. Period.

A SET and all other SE tube amps uses a single ended output transformer. In short, the one primary tap will have a + bias source from the power supply, the other tap will be coupled to the anode of the output tube.

This is not the case for North Audio – their amp clearly uses a push-pull output transformer, as do each and every push pull transformer coupled tube amp.

And if you think what they are doing is new, unique or special, I suggest you have a look at Cary’s V12 series of amps. They are also pairs of 100% single ended amps (also EL34, 6550 or KT88) wired into a push-pull configuration via a single push-pull output transformer. And I believe V12s have been around for 10 years. You’ll probably see many other manufacturers with similar designs if you care top do a bit of research.

“Any tech nuts out there that might have better understanding of this.”

I have built amps (tube and transistor, single ended and push-pull) for more than 10 years, although I do not consider myself a nut of any kind. What I am not, is totally naïve.

“[Steve] sounds very proud of them and says with the right speakers that nothing can touch them.”

I would be surprised if he didn’t. That is exactly what I think of the amps I build.

“Let's not rule out something new before someone gives it a chance.”

Of course not. But then the design has to actually be new, which this clearly isn’t. At best it is a slight variation on a design that is more than 50 years old.

BTW, I am not saying North Audio are frauds, or that the owner is a bad guy or that their systems sounds bad. However, they won’t be the first audio site to sell vaporware. Particularly funny are their “feedback less“ mosfet amp and their “balanced” (i.e. un-rectified) HT supply. (tip, rectified HT power is better in tube amps)

Kind regards
Paul

I know North Audio, have met Steve a number of times, heard some of his equipment and have been to his home/store. He is actually a service tech for an elevator company who eventually realized he could turn his expertise to designing and building audio equipment (absolutely nothing wrong in this). He is very opinionated on some subjects (eg. the cheapest Dale resistors are far superior sounding than Vishays etc.). I have not had any of his equipment in my own system, although I have heard several pieces in other high quality systems and thought they sounded okay. All of his equipment is expensive (by my standards, anyway). There are several people living in this area (Ottawa) who think very highly of his stuff.

When stereo was new there was a brief interest in converting mono amps to stereo, without adding any output tubes or power supply. (Yes really). My memory of the circuit details is a bit dim, but it involved connecting the center tap of the output transformer through the primary of another transformer. One channel drove the output tubes in common mode, and came out of the auxillary transformer. The other signal drove the output tubes differentially, and came out of the original transformer. The signals involved might have been L+R and L-R instead of L and R. Certainly the rig would work better with the relatively small A-B being the common mode signal.

Anyway, such an amp might be described as push-pull and single-ended at the same time!!