Hi Warrenh,
Got your email and have some insight to offer. The Audion Sterling EL-34 is a fantastic first SET at current used prices. It is well made and pretty good looking, especially compared to the cosmetics of the new Audions.
The EL-34 version definetly falls on the warm/rich side, whereas KT-88's make the amp much more neutral and authorative. Different flavors for different moods and music.
The bass is surprisingly good for a SET amp in this price range(used). Not an iron-clad grip, but not loose and flabby either. But, in your case, that won't be much of an issue anyway since your Definitions place very little current demands on an amplifier at 11dB and with four self-powered woofers.
The place where the Sterling (and most SETs) shines is the midrange - it is lush and glorious with EL-34's. But, the amp still manages remarkable detail within that midrange richness. With KT-90's, you chould get plenty midrange "magic" without too much warmth.
The amp does a good job with soundstage width and depth is pretty good. Not the holographic image of 300B's, a more dense structure all it's own.
The highs are slightly subdued with EL-34's - not bad, just not as airy as my 300B monoblocks or PX-25.
One thing I should point out, is that the amp was intended to be used with speakers far less efficient than your 101dB Zu's and my 97dB Cain & Cains. As a result the gain structure is a little less than ideal - you'll be reaching full volume before using 20% of the volume dial. This can sometimes be a problem with late night listening if anyone else is in the house. Thorsten Loesch recommended the 6CG7/6FQ7 as the input tube to reduce the gain and allow a wider use of the volume control. Keep this in mind, just in case. It can save your life (or relationship). If you find the standard 6922 works well, try a Russian 6H23-EB which is a high-end version of the 6922 - enhances focus and detail.
As Bigshutterbug mentioned, go with an NOS Tung-Sol 5687 for the driver tube. Save yourself all the money and time experimenting, this really is about as good as it gets.
Finally, after getting used to the amp, find someone to swap out the stock 50k-ohm Alps Blue Velvet volume pot. That thing is really throwing a blanket over the amp's true potential. There is an simple $50 alternative that simply blows away the Alps - like throwing open heavy curtains on a bright sunny day. Everything improves.
Shoot me an email in a few weeks and I steer you in the direction.
Got your email and have some insight to offer. The Audion Sterling EL-34 is a fantastic first SET at current used prices. It is well made and pretty good looking, especially compared to the cosmetics of the new Audions.
The EL-34 version definetly falls on the warm/rich side, whereas KT-88's make the amp much more neutral and authorative. Different flavors for different moods and music.
The bass is surprisingly good for a SET amp in this price range(used). Not an iron-clad grip, but not loose and flabby either. But, in your case, that won't be much of an issue anyway since your Definitions place very little current demands on an amplifier at 11dB and with four self-powered woofers.
The place where the Sterling (and most SETs) shines is the midrange - it is lush and glorious with EL-34's. But, the amp still manages remarkable detail within that midrange richness. With KT-90's, you chould get plenty midrange "magic" without too much warmth.
The amp does a good job with soundstage width and depth is pretty good. Not the holographic image of 300B's, a more dense structure all it's own.
The highs are slightly subdued with EL-34's - not bad, just not as airy as my 300B monoblocks or PX-25.
One thing I should point out, is that the amp was intended to be used with speakers far less efficient than your 101dB Zu's and my 97dB Cain & Cains. As a result the gain structure is a little less than ideal - you'll be reaching full volume before using 20% of the volume dial. This can sometimes be a problem with late night listening if anyone else is in the house. Thorsten Loesch recommended the 6CG7/6FQ7 as the input tube to reduce the gain and allow a wider use of the volume control. Keep this in mind, just in case. It can save your life (or relationship). If you find the standard 6922 works well, try a Russian 6H23-EB which is a high-end version of the 6922 - enhances focus and detail.
As Bigshutterbug mentioned, go with an NOS Tung-Sol 5687 for the driver tube. Save yourself all the money and time experimenting, this really is about as good as it gets.
Finally, after getting used to the amp, find someone to swap out the stock 50k-ohm Alps Blue Velvet volume pot. That thing is really throwing a blanket over the amp's true potential. There is an simple $50 alternative that simply blows away the Alps - like throwing open heavy curtains on a bright sunny day. Everything improves.
Shoot me an email in a few weeks and I steer you in the direction.