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Old 28th July 2010, 05:13 PM   #1
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Default The Maggie factor

Hello tubers

I am currently in the processes of Designing/making a push-pull amplifier. I am using the KT-120 in the output stage. I would run this amplifier in PP Triode for all of my cone-based speakers, with plenty of power to boot. I also want to use this amplifier in Pentode mode (maybe UL) to power my planar magnetic Magnepan SMGs. I think two KT120s could drive these speakers reasonably well, but there are is a question I have about picking an OPT.

Unlike cone speakers, the Impedance of my Maggie's is a steady 4 ohms. from DC-Cosmic ray (excuse my hyperbole) they always have a 4ohm impedance. How should this affect my decision of which OPT to buy? the KT-120 datasheet says it wants a primary Z of 3K, but we all know that primary Z will be a lot different than 3K at most frequencies for traditional speakers.

am I over reacting? any help would be fantastic,
Thank you
-Moose
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Old 28th July 2010, 05:50 PM   #2
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Why not get a OPT that has 4 and 8 ohm taps?
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Old 28th July 2010, 06:58 PM   #3
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perhaps I am being unclear. I am not really worried about being able to use different impedance speakers. I am worried about the output stage being able to accurately reproduce every frequency at 3K ohms because theres no speaker reactance for the amplifier to hide behind.
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Old 28th July 2010, 07:05 PM   #4
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Quite the opposite, this will be kinder than nearly any other speaker from the standpoint of the output stage. IME, Maggies were the least amplifier-critical speakers (other than efficiency) that I ever owned.
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Old 28th July 2010, 07:32 PM   #5
20to20 is offline 20to20  United States
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Quote:
Unlike cone speakers, the Impedance of my Maggie's is a steady 4 ohms. from DC-Cosmic ray (excuse my hyperbole) they always have a 4ohm impedance. How should this affect my decision of which OPT to buy? the KT-120 datasheet says it wants a primary Z of 3K, but we all know that primary Z will be a lot different than 3K at most frequencies for traditional speakers.
Quote:
Originally Posted by alexmoose View Post
I am worried about the output stage being able to accurately reproduce every frequency at 3K ohms because theres no speaker reactance for the amplifier to hide behind.
The best anyone can do is to pick the OPT primary Z to match the output tube data sheet recommendations. Not much choice. Are you asking if there is a particular brand of transformer that is designed to be a perfect match to your Mags or any other speaker with superior reactance characteristics?
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Old 28th July 2010, 08:12 PM   #6
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Originally Posted by SY View Post
Quite the opposite, this will be kinder than nearly any other speaker from the standpoint of the output stage. IME, Maggies were the least amplifier-critical speakers (other than efficiency) that I ever owned.
Alright, Thank you very much. That exactly what I was wondering.

What kind of Maggies did you/do you own? did you ever find a tube amplifier that produced satisfactory results?
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Old 28th July 2010, 08:30 PM   #7
SY is offline SY  United States
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MG-1. Worked very nicely with some amps I built with Dynaco Mk III iron, 7027s in the output, trioded, driven AB2. That was, omigod, 30 years ago.
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Old 29th July 2010, 12:44 AM   #8
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Quote:
Originally Posted by SY View Post
Quite the opposite, this will be kinder than nearly any other speaker from the standpoint of the output stage. IME, Maggies were the least amplifier-critical speakers (other than efficiency) that I ever owned.
Quite agree, found this to be the case with both the MG1.4 and the MG1.6QR.. They are just power hungry due to their relatively low efficiency, and they are rather revealing. Used these both with heavily modified Citation II and later 300B PP amps..
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Old 29th July 2010, 12:49 AM   #9
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Copied from there: SF - Vinyl Records and Turntables Are Gaining Sales. - Page 13 - Style Forum

My favorite component is my Wavebourn Pyramid VII, Prototype 1, built to my specs and as far as I know, the only one in existence. I originally bought the Pyramid V, also a prototype that was damaged during shipping (as seen below). I always wanted to try a tube amp but I've got some terribly inefficient Magnepans and the tube power needed to drive them was just too cost prohibitive. After searching for months I rolled the dice on the Wavebourn and it's been the best stereo purchase I ever made. The designer, a Russian dude from Cali, was basically going to lose his home unless he raised some quick cash...so I got this amp for less than the cost of the power supplies. The V was originally designed to be used in a PA system and as a guitar amp. After seeing it on Audiogon I researched Anatoily, the designer, and what little I could find out about him he seemed very well respected among his peers. When the V showed up the power supplies were literally ripped from the chassis so, to make a long story short, it took six months but he tweaked the circuitry and I ended up with the Pyramid VII. I've had Acurus, Rotel and some other lesser SS amps in this system and the Wavebourn is by far the best sounding. Very, as they say, musical...and not fatiguing at all. The truth is that I bought this amp because I liked the way it looked. I love it for how it sounds and I'll never part with it because of the history I have with it and the uniqueness/cool factor. At 80W X 2 it drives the Maggies but not quite as loudly as I like when cranking NIN, Rob Zombie, etc. For classical, jazz and blues though...

The damaged Pyramid V as I received it...



Click the image to open in full size.
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Old 29th July 2010, 01:19 AM   #10
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That looks sadly familiar.... At least it still works..
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