Author Topic: Building power amps for SF-2 and others (Read 189 times)

fasteddy · « **on:** July 19, 2007, 11:26:14 AM »

Yes, I'm building amplifiers, mostly for fun. A couple of my nephews and a niece are into the pro side of music, so I thought I'd take a stab at building a pro / stage / road worthy amp = two channels, maybe 300 or 400 watts, each ,without noticable distortion = a voltage follower for use with high quality tube pre-amps like the SF-2.

Ideas about chassis, travelin' weight, construction materials, etc., etc. etc, or any other suggestions appreciated.

David Houck · « **Reply #1 on:** July 19, 2007, 07:48:00 PM »

Hi Ed, welcome to the board.

First, the SF-2 is not a tube pre-amp. The F-1X and the F-2B are. You can read more about all three of them here.

Our members use a wide variety of power amps with their Alembic preamps. One of the most popular is the QSC PLX series. They have a very good combination of weight, power, reliability, and features. Several of us use the PLX 2402; 700 watts per channel into 4 ohms, 21 lbs.

fasteddy · « **Reply #2 on:** July 20, 2007, 08:49:17 AM »

Dave: I was not aware that the SF-2 was solid state ... the amp I am working up is intended for use with XLR connected tube pre-amp. The main claim to fame would be lighter weight while maintaining plenty of guts, rugged chassis, etc. for the road.

I am familiar with some of the QSC equipment and have several very old 1400s. From http://www.qscaudio.com/products/amps/plx/plx.htm ... the specs for the 2402 would be very close to the amp I will be building except for: no short circuit or thermal protection needed, freq range would be a little broader (5 to 100k htz.), weight target is less than 15 pounds ... ~375 watts per into 8 Ohms (more into 4) with a little better clipping picture on the 'scope IMOP ... All squeezed into a one up rack mount case. Details not finalized, but this is my third iteration of a tried and true design. I am a few miles south of your factory and could do a show and tell at some point in the near future ...

David Houck · « **Reply #3 on:** July 20, 2007, 11:42:02 AM »

Actually, I'm in the mountains of North Carolina and it would be about a 2,630 mile drive. There may be some members in the Northern California area that might be interested though. A single space power amp that can meet all of the PLC 2402 specs would certainly be intriguing.

fasteddy · « **Reply #4 on:** July 20, 2007, 12:13:12 PM »

... A single space power amp that can meet all of the PLC 2402 specs would certainly be intriguing. ...

I thought so as well. So I have a bunch of parts and modules on hand and more coming (that's the fun part, buying all these toys and stuff) then I will put together the best of the breed(s) and try 'em under different circumstances. Target: 1up chassis, under 12 pounds weight, road worthy construction, better than 0.005 % THD + N, better than 120 db Signal/Noise, cold operation / high thermal efficiency, 375 watts per channel ~= one horse power :>) ... I'm favoring class AB power MOSFET with switching power supply. (QSC is class H / switching amp.)

BTW: One nephew is a pro DJ, another nephew is a dynamite semi-pro bass player (and wants an Alembic bass, bad) and my niece is building a garage band recording studio ... so I've got equipment critics available.

jacko · « **Reply #5 on:** July 20, 2007, 12:24:13 PM »

Actually, I'm in the mountains of North Carolina

Dave, I love the thought that you're living somewhere on Peggy peak off the Smokey Park Highway. We could do with some more interesting place names over here;-)

Graeme

fasteddy · « **Reply #6 on:** July 20, 2007, 12:31:54 PM »

... fishin's real good over by nags head / lake mattamuskeet ... :>)

David Houck · « **Reply #7 on:** July 22, 2007, 04:04:08 PM »

Graeme; I'm maybe 5 miles (8km) from Peggy Peak. I live in Bens Cove, on the side of a ridge that I think, looking at the topo map, runs down from, or perhaps is, Ripshin Mountain; right close to Pisgah Mountain.

And you guys have plenty of interesting place names!