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THE MAG-1515 AND MAG-1515i POWER AND INTEGRATED AMPLIFIERS


                                                       With black chassis and SS rectifier.
 
 
 
 
 


 

And now the INTEGRATED!

    The MAG-1515 series amplifiers are designed and built for the audio enthusiast who wants high quality audio at conservative prices. These amplifiers use a technically simple circuit to keep the path for audio such as not to introduce much to cause distortion. High quality components are used where necessary (resistors, capacitors, sockets) as opposed to everywhere so as to keep cost down.

    This amplifier is based on the old Magnavox 15 watt per channel amplifier used in many of their high fidelity console stereo and television systems of the late fifties and early sixties. This version has been brought up to the 21st century with better quality components and modifications which brings the fidelity to higher standards. It is a push pull amplifier. While there are many tube enthusiasts that swear by single ended design, I believe that their opinion is based on a psychoacoustic response rather than a true reproduction of sound. A well executed push pull design can be as sonically pleasing as a good single ended design.

    The thought behind single ended versus push pull is that push pull eliminates the so called pleasant sounding even order harmonic distortion. I believe though that distortion is distortion. Reduction of much distortion at the output is a good thing if it can be done mostly by circuit design first. This does not preclude the use of inverse feedback.

    While many tout no NFB as a desirable feature, and one that is desirable for good high fidelity, I tend to disagree, and believe that it is a marketing ploy. NFB has been around since the likes of the first 45 and 300B amplifiers (1928) and is a very useful tool in the further reduction of distortion components, and the balance of frequency response. One must consider the fact that every amplifier involved in the recording of the music in the first place uses NFB everywhere. So the MAG-1515 uses a small amount of NFB.

    Another myth is that the power supply must be tube in order for the full nature of the tube amplifier to be realized. The fact is that tube rectifiers tend to have poor regulation, and cause the amplifier to change characteristics when under the load of heavy bass lines and hard transients, like percussion. The first thing to do is keep voltage more constant. One thing I do is use 300 µF of filter after the first filter capacitor and choke. This is true whether you choose the tube or solid state rectifier option. The second thing I do is use a rectifier with as low an internal resistance as possible. The 5U4 has an internal resistance of only 130 ohms at the needed 150 milliamps for full output. That means only little if any reduction of B+ under load. The third thing is the use of solid state rectification. Many claim that there is an addition of hash using solid state. However, the use of a choke eliminates any noise created by the rectifiers. This is because of the way chokes work. They make more resistance to higher frequencies. So hash does not exist after the filtering. The overall result is a wide dynamic range and well behaved bass, along with clean sound throughout the audio range.

    I believe the magic of this amplifier is in the use of a quasi-fixed bias on the output, coupled with a driver circuit that maintains the even order harmonic nature of triodes. It does so by the use of a phase inverter stage as opposed to a phase splitter. Phase splitters tend to cancel even order harmonics, while the phase inverter keeps it in there. The result is a balance of even and odd order harmonic content which makes the sonic character one of not "warm and fluid" nor "hard and harsh", but just right, or purist.
 

THE SPECS

So here are the figures:

Output Power:                       >15 Watts RMS per channel

Frequency Response:                 10 Hz ~ 45 kHz @ 15 watts (non inductive resistive load).

THD:                                <2% @ 15 watts; <0.5% @1 watt

Output impedance:                   4, 8 or 16 ohms (8 or 16 only with Magnequest)

Input impedance:
    Power Amplifier:                470 K
    Integrated amplifier:           100 K

Input sensitivity:
    Power amplifier:                1.7 volts for 15 watt output
    Integrated amplifier:           150 millivolts for 15 watt output

Power consumption:
MAG-1515                            With SS rectifier                   90 watts
                                    With Tube rectifier                148 watts

MAG-1515i                           With SS rectifier                   94 watts
                                    With tube rectifier                152 watts

Tube compliment:                    (4) Sovtek 6BQ5/EL84 (Matched Quad)
                                    (2) Sovtek 6EU7
                                    (4) 6EU7 for Integrated, (6) for Integrated with phono.
                                    (optional) (1) Sovtek or Svetlana 5U4

Upgrade to both :                    Sovtek EL84M (Matched Quad)
                                     JAN GE 6EU7 (for either amp)
 
 

                                            BUILT                    KIT

MAG-1515 Power Amplifier                      $699                    $549
MAG-1515i Integrated Amplifier                $799                    $649
 

WITH UPGRADE TUBES:                           Add $50 to the power amp, $70 for the integrated.

And NOW PHONO OPTION:                         Add $199

Future models: The MAG-4040 40 WPC Power Amplifier.
 

USER OPINIONS:

D.W. Fearn, engineer and manufacturer of professional tube microphone amplifiers:

"It sounds great! Even after all these years of proving to myself that you just can't get audio quality without using tubes, I am still amazed whenever I hook up something like your amp and hear just how good it sounds.

"It certainly eliminates a lot of the rough edges in the sound, especially from a CD.

"My ears tell me that the high-end is very extended. The lows are quite solid and robust. What distortion is present is obviously mostly second-harmonic."

Michael Donnely:

"Gabe, your amp rocks! As a guitar amp it seems to have more dynamic range and can be overdriven much better than any other design I have used."

Carl Hartman:

"I finished the amp on Saturday around 11:00 AM and proceeded to listen for the next four hours. Well, I was using a stock ST-70 in beautiful condition as my main amp.  The MAG-1515 blows it  away...period!  The bass is outstanding, tight, and well defined.  The mids are warm, and sweet.  It really is amazing to listen to CDs you have heard many times before and catch something you have never heard.  The highs are brilliant,  almost too much presence, or maybe I am just used to the severe roll off of the ST-70 due to its old coupling capacitors.  I am driving the amp with a Mackie mixer, so its easy enough to tweak the highs a bit, but I would rather leave it pure.  In any case, the overall sound is just great.

"Overall I am very pleased with the whole project and your prompt response to e-mails.  I will gladly recommend the amp to anyone, and you can use me as a reference."

Herbert Jeschke,

"Monday morning I was alone and could crank up the volume to my hearts content.

"First I have to say, when I turn the MAG-1515 on without signal wires connected it is dead quiet, no hum at all in the speakers!  Playing music wow what a soundstage, what detail and clarity. I have a cd with some repertoire of an Italian opera singer Katia Ricciarelli. It has live recordings on it. It was scary to hear the echo from the hall returning and enveloping her. You can hear the sand on the shoes of onlookers grinding on a stone floor and all the little stuff the members of the orchestra are doing while they wait their turn. Veil and veils are removed in listening with the MAG-1515 compared to my 300B amp. I had a few more sessions since. I am very happy with the definition in the low end as everywhere else in the frequency band.

"This is definetly the best amp I came across and I like listening to it very much. All my recordings become much more livelike, natural and true to the source. I think I might have to build another to use as monitor amp at work. This amp is a masterpiece to your credit. You made it work so it will play with most speakers out there. Thank you so very much for introducing me into this all new realm of listening."
 

TO ORDER:

Email your request and I will reply with postal address.

Money orders, checks or PayPal.

Please allow 4 to 6 weeks for shipping. Tubes are quality control checked and broken in for kits. Built units are tested for four days for quality control and break-in.

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