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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Amp for Magneplanar 1.6

Jde

Member
2010-12-21 1:44 am
Hello, this my first post and I hope will not be my last. I would like to build a tube amp for my Magneplaner 1.6's. I have rebuilt a Dynakit ST70 as a class A amp and enjoy its sound quality when driving my efficient cone speakers. But of course the ST70 can not drive the Magneplaner at any volume without clipping and blowing the speakers fuse. I have a pair of Dynakit Mark 3's that need to be reworked, could these 60 watt amps drive these speakers? I would prefer not to spend the money on the Mark 3's and then find out that they can not drive the Magneplanars. I think an amp able to produce 100 watts would work, are there any recommendation? Thanks.
 
A Stock ST70 was only able to output 25 Watts RMS with the Stricter FTC guidelines. Class A1 would cut it to maybe 12W? Its not unheard of to get 50W from a PP KT88 / 6550 in class AB. Is that enough? More than 50 Watts involves sweep tubes in near class B, More than one pair of tuber per channel, or very high voltages and transmitter tubes. Good Luck.

Doug
 
Several of us visited a stereo shop in Santa Clara to check out Magneplaner speakers in 1978. It was almost closing and they put on a good show for us. As we were leaving they hooked up a set to 110VAC to break them in. The mylar film when taught has little bass. I was shocked that this was possible, but was told that they are very inefficient and it was the factory recommended procedure. Scott bought a set and drove them from an amp with 120 watts/channel. Still lacked low bass. There is a Dynaco ST120, 70 on steroids at 60 watts/channel for around $900, or build your own. KT88, KT90, KT120 tubes are available for PP or PPP configuration, Hammond has iron 1650 R or T at 100-120 watts/channel.
 

kevinkr

Administrator
Paid Member
I ran a pair of MG1.6QR with my 30W 300B triode monoblocks for a couple of years, sounded quite good..

A Dyna MKIII ought to have sufficient oomph to drive a pair without much difficulty, whether or not you like the resulting sound of the stock MKIII with the 1.6 is another question.. Might want to consider a higher performance driver board.

The Citation II would be an excellent choice as well, achieved very good results with a heavily massaged unit with the older MG1.4...

Use the 4 ohm taps on all amps in question..

Note: The 1.4, 1.5, and 1.6 will not survive being connected to the AC mains.. (Their efficiencies are in the low to mid 80s, and is IIRC rated at 2.83V)
 
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I ran Maggie SMG panels off a Leak Stereo 20 in a small room. Sounded better than a CJ Premier 4, believe it or not. Take note of Kevin's choice of 300b monobloks. These speakers reward quality. Don't be too hung up about quantity unless you play music really loud. There's a lot of mythology about 200 watt amps with Maggies. Take it with a pinch of salt. A friend of mine drove SMGs with a PPP amp with 6SN7 outputs!! Did clip a bit but sounded great.

Andy
 

Jde

Member
2010-12-21 1:44 am
Thank you for all the feedback! “Triode Electronics” has a Mark 3 driver board and capacitor upgrade modules, any opinion on these units? The price is within my budget. I used Joe Cursio modules for my ST70, but the prices are now much higher then I remember, it's been 10 years. If I build a new amp, could the driver module for a Mark 3 be used to drive four KT88's or 6550 when using a Hammond 1650TA transformer. Is the Hammond transformer a good choice?