[kevtn8]

When switching the output impedance with the transformer, the lower impedance option will present a higher impedance load to the output tube, and should give you better bass response (because of more damping from the transformer) and lower power output. Steve uses a pretty high primary impedance on his output transformers already, so that may be why you don't really notice a difference between the settings.

After talking to Steve the other day regarding this UFO mod, the flexibility of having both 4 and 8ohm impedance on same amp was just an afterthought and a bonus. The real emphasis was on the overall sound quality and how much flatter the frequency response was and the extension on both ends. Its a much better transformer made to a much higher level of precision, thus the increase in price of the amps. Basically he not only improved on his already excellent transformers but he also managed to cram both of the Zen's 2 transformers ( stock and optional ) into one. Now the Zen amp's audio potential is not only taken up another notch but the amp itself is more flexible with different speakers. A brilliant move. 

Kevin

[kevtn8]

Thanks Kevin, I forgot about the bias switch. 

My Select was in the build queue when Steve came out with the Super Zen (the basic came first), so he made mine a Super Zen Select, but with the white top without meters (the Select with black top and meters came later).  Mine also doesn't have the dual inputs in the true sense of the word, or a switch, but the second set of inputs is for running it as a straight power amp.  Possibly the simplest Zen Steve ever built.  I believe the Zens with the UFO OPT have a switch to choose between 4 and 8 ohm, so between the input selector and impedance switch there's 2 switches where there was none before.  The Basic black Zen has 3 switches: bias, impedance, and inputs.

All of his amps with the new UFO transformers will have an impedance switch near the speaker binding post ( one for both L and R) and this is part of the transformer design and won't add anymore variable to the sound according to Steve. Although there are 2 impedance taps on same transformer, new UFO are made to a much higher standard with emphasis on sound quality and thus the positives far outweigh the insignificant and minor negative of having more than 1 tap on same transformer. The only other switch on my Zen Select is in the front for toggling between the RCA and XLR balanced inputs. Still a very simple and pure design while retaining the flexibility of the dual UFO impedance for different speakers.

Kevin

[ozoid]

Thanks, Kevin & Nailbunny. Now that I know what to listen for, I'll concentrate on the bass and see if I can discern a difference. Very glad to know there isn't a "right" position.

After six weeks, it and the Omegas are still opening up!

[Nailbunny7]

Thanks, Kevin & Nailbunny. Now that I know what to listen for, I'll concentrate on the bass and see if I can discern a difference. Very glad to know there isn't a "right" position.

After six weeks, it and the Omegas are still opening up!

Yep, in tube audio, there is seldom a 'correct' setting. The option that gives the most power often also produces the most distortion. Transformers that produce the widest frequency and support high power output almost always have more inductance, causing upper most frequencies to roll off a bit, same goes with when you use the 4 ohm output instead of the 8 ohm output on the transformer. Some people love the type of distortion single ended tube amps produce (since it's almost all even order harmonics) and some people don't like bright amps, but love tight bass.
The point is that everything has tradeoffs (though in many cases, these may be desirable). Happy listening

*Random unrelated piece of advice: Many people spring for expensive upgrades to their already great equipment, but it would almost always be better to get your listening room treated instead. It really makes a much bigger difference than things like capacitor upgrades, etc.

[Nailbunny7]

After talking to Steve the other day regarding this UFO mod, the flexibility of having both 4 and 8ohm impedance on same amp was just an afterthought and a bonus. The real emphasis was on the overall sound quality and how much flatter the frequency response was and the extension on both ends. Its a much better transformer made to a much higher level of precision, thus the increase in price of the amps. Basically he not only improved on his already excellent transformers but he also managed to cram both of the Zen's 2 transformers ( stock and optional ) into one. Now the Zen amp's audio potential is not only taken up another notch but the amp itself is more flexible with different speakers. A brilliant move. 

Kevin

Yep, Transcendar makes a good transformer. I immediately recognized the ones he used in his UFO change because I ordered the same custom transformers a few months ago from them (their custom transformers look different from the pictures on their website, but look identical to the ones in the Zen user manual). I'm also pretty certain the ones he used before were made by Edcor, since some of mine look exactly like the ones he used to use. Almost all transformer makers have their own look from their design type, so it's pretty easy to recognize them once you've ordered from several people.

[IanOak]

A bit late to this thread as I've only just registered! I've been using a dynamo for nearly a year now and it sounds good. I will hopefully be ordering two zen se84ckcs amps in the new year though as from what I have read they should be a step up sound wise. I will pair these with a set of super alnico monitors, I'm using dm946 speakers at the moment, though I will definetly keep those. I haven't heard a rachel so can't comment on that versus a dynamo though.

[Nailbunny7]

A bit late to this thread as I've only just registered! I've been using a dynamo for nearly a year now and it sounds good. I will hopefully be ordering two zen se84ckcs amps in the new year though as from what I have read they should be a step up sound wise. I will pair these with a set of super alnico monitors, I'm using dm946 speakers at the moment, though I will definetly keep those. I haven't heard a rachel so can't comment on that versus a dynamo though.

Why would you order two?

[seikosha]

Why would you order two?

He probably wants to bridge them for more power.

[Nailbunny7]

He probably wants to bridge them for more power.

That's what I thought, but it's not the greatest idea. It puts the output tubes in parallel, and both the output transformers too. Always far worse than a single transformer. What it does best is sell twice as many amps. Much better off getting the Rachael if he's already buying from Decware. Although, tbh, a single SE84CKCS will have enough power for the alnico monitors unless you like your music very loud.

[Canada Rob]

Nailbunny7 is correct.  You only need one SE84CKCS to do the job if you're not into party volumes.

[IanOak]

I have read that but thought that each could be wired in series? Two would allow me to biamp the dm946, mono either these or my intended omega's or run the music room or tv room systems in a purist fashion. Two to me would provide more options and fun!  My other half liking music I don't and vice versa would allow me to retreat to the man cave while she listens to her Bon Jovi :-p
is there a real loss of transparency if run in mono? Some say yes, some say no?? Also XLR over single ended? As my main digital source has these is it worth the extra £400?? Questions, questions, though thanks for any input!!

[JLM]

It's been years since I kept up with Decware, but the XLR option cost more than my DAC/pre! and the recommended options almost double the price of the amp!

[Nailbunny7]

I have read that but thought that each could be wired in series? Two would allow me to biamp the dm946, mono either these or my intended omega's or run the music room or tv room systems in a purist fashion. Two to me would provide more options and fun!  My other half liking music I don't and vice versa would allow me to retreat to the man cave while she listens to her Bon Jovi :-p
is there a real loss of transparency if run in mono? Some say yes, some say no?? Also XLR over single ended? As my main digital source has these is it worth the extra £400?? Questions, questions, though thanks for any input!!

There isn't really any reason to get XLR over single ended RCA unless your DAC outputs audio natively through XLR (having balanced signals summed into single ended is almost always worse). But if your DAC's output is the same for both XLR and single ended RCA, just go with the RCA option. Adding the balanced option to the decware amp requires using a balanced transformer to the signal path, which costs a lot, while the only benefit is being able to accept balanced signals (DACs like the Schiit Mjolnir outputs balanced signals natively, so it might be of benefit there, but I still really doubt you could hear a difference). Basically, I think the money would be better spent on treating your room acoustically (something most people don't do, even though it makes a gigantic difference over expensive things)

[IanOak]

Thanks Nailbunny,
I have never gone the balanced route and the consesus of opinion seems to back you with these amps. It seems the more purist the better seems to be the way, which suits me to be honest!

[Nailbunny7]

Thanks Nailbunny,
I have never gone the balanced route and the consesus of opinion seems to back you with these amps. It seems the more purist the better seems to be the way, which suits me to be honest!

Yep, less transformers is always a good thing. No transformers would be best (if only tubes had low enough output impedance not to need them...). The Transcendant Sound amps do this, but you have to be ok with lots of feedback being used in the circuit (not as bad as everyone makes it sound) and buying a few hundred dollars worth of tubes every so often. Those ones also double as room heaters.

[IanOak]

Had some Croft otl's with loth-x horns years ago. That was a great system. I only moved it on because the amps were so unreliable. Probably my favourite system I ever had! Definitely better than the more expensive Leben system I had after that!