6BQ5 / EL84 Power Amp, Based on Dyna Design

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G.Michael

6BQ5 / EL84 Power Amp, Based on Dyna Design
« on: 31 Dec 2007, 05:36 am »
Well, time has come to part with this beauty.  This was built by a friend of mine.  As you can see from the photos, he does nice work.  (High quality components, including very good coupling caps; ample power supplies; teflon-insulated wire.)   

Input tubes are 7199.  Output tubes are 6BQ5/EL84.  Rather sweet sounding and cleans sounding, as you might expect.  I'm not a fan of 7199's, but they sound good here and provide more than adequate drive to the output stage.. 

Given the hefty power supplies, it has a rather solid bottom end for such a relatively small and delicate amp.
Circuit design is Dyna-based, but there are a few mods to the design.  Power transformer and output transformers are Dyna.  Output tube plate voltage is 300V, which means it's gentle on output tubes.

This unit also has input level controls.  I've used the amp with and without good preamps, and I actually prefer the sound with no preamp.  I've fed a CD player directly into amp and used the input level controls to control the volume--with nice results..  I've also connected a switching box to the input, which effectively made for a nice integrated amp.

ONE OTHER THING YOU SHOULD KNOW: There was some slight shipping damage to the chassis, not real obvious, but it can be seen in the photos.  The top of the chassis isn't quite flat, and the end the chassis is dented in near one of the input level controls.  Doest not affect functionality, though.

IEC input.  Good input jacks.  The binding posts are better than they appear: They're laboratory-grade, with a lexan body, so they're plenty rugged and make a good connection.

Main Photo


Under Chassis Photo


Gallery of all photos: http://www.audiocircle.com/index.php?action=gallery

This is really a sweet amplifier.  (Selling it because I bought another EL84 that was built from the ground up by the aforementioned friend.) 

$335, shipping included.  This includes the 7199 tubes, but not the 6BQ5's shown in the photo.  However, I can get a set used of RCAs or GEs which will work nicely, and that probably will last a long time.  (Again, this amp is easy on tubes.)