6550 / KT88 ... pick me a set

[AwkwardLoudness]

Among the KT88/6550 options given, I suggest the Tung-sol 6550A set.

Personally, I like the Gold Lion reissue KT88s in my Hiwatt 400 amp.

 

[James Hart]

You, sir, have my full attention! Very nice!

Kudos James, those are some pretty ambitious specifications, especially for a first build! Who's building your transformers?

Well I come from an engineering family. I grew up being taught to over engineer everything and that big projects are really just a series of smaller one. I might be reaching a bit high... but I've got the theories worked out, I've got a bit of real world experiences that lend themselves to my task... and I've got a few places to turn with any snags I hit

My biggest obstacle this year has been the delay in moving into a place to set up shop (see my summer blog thread in OT for details). Once I get the renovations finished in the next few weeks I'll be able to focus on getting the equipment I need to get rolling.

I'm looking to go with Mercury but Edcor is also a thought.

Your amp design sounds real fine. There used to be some good transformer builders right in Trenton, too. Not sure if they're still there, though I'd doubt it.

Not sure of any quality local electronics places that aren't strictly .mil sub contractors these days... do you recall the name? It might be nice to use a local builder/supplier.

 

[iamdenialNJ]

That 1 kw amp probably weighs 175-225 lb. which is borderline portable. Going much past that, you or your roadies had better have a forklift handy.

 

[okcrum]

Not sure of any quality local electronics places that aren't strictly .mil sub contractors these days... do you recall the name? It might be nice to use a local builder/supplier.

Well, I've used NWL in Bordentown (not quite Trenton, but close) for everything from little power transformers to 20 kv/100 A for plate supply for 8973s. Trouble is, they don't seem to have much audio expertise, but you could give them a shout.

Better bets might be Glen Magnetics in Alpha NJ or Beverly Mfg. in Riverside. Both have audio specialty experience. Glen can do higher power units than Beverly, but both could do parts of the size it looks like you'd need. Are you thinking toroidal, E-I core, or something else?

 

[MAMMOTHvolume]

I understand. The first limit you hit with an amp like your older one or Chambers' is portability. It would be necessary to build it as a power amp only, on a wheeled enclosure, and use a separate preamp. That 1 kw amp probably weighs 175-225 lb. which is borderline portable. Going much past that, you or your roadies had better have a forklift handy.

Then there's the question of primary power. That monster will draw somewhere around 20 amps at 120 volts, so you couldn't just plug it into any old outlet at the club. Going to 240 volt mains means you'd halve the current draw, but could play only venues with that power available.

It seems the practical limit would be a 500 watt version of Chambers' amp.

<fantasy>
If one idly speculates about Disaster Area ("not only the loudest rock band in the Galaxy, but in fact the loudest noise of any kind at all" - Douglas Adams) class amplifiers, one could be done, with primary power supply, if you had oh, say, 6 flatbeds, a couple of semis, a box truck or two, a bus for the amp crew, a tanker (for the pair of gas turbine generators) and some serious cash. Use a pair of 8973s for the output stage and you could get a megawatt or so. Then you'd still need transport for the speakers.
</fantasy>

The craziest thing is, there are bands that already have transport logistics for something like that. U2 comes to mind. And a 1/2 megawatt audio amp was built as early as the mid-1930s as the modulator for the then-epic Invalid Link Removed.

Still, I wouldn't want to haul one to the gig.

Your amp design sounds real fine. There used to be some good transformer builders right in Trenton, too. Not sure if they're still there, though I'd doubt it.

the 1000 watt amp is awesome, It's a two man lift but you can do it on your own at a stretch. He got the front panels the other day so the amp should be ready soon!

In regards to the turn on, it's got a softstart so it doesn't take out the mains when you turn it on, all the lights still dim when you turn it on though

 

[okcrum]

the 1000 watt amp is awesome, It's a two man lift but you can do it on your own at a stretch. He got the front panels the other day so the amp should be ready soon!

In regards to the turn on, it's got a softstart so it doesn't take out the mains when you turn it on, all the lights still dim when you turn it on though

Oh yeah, soft start is a necessity with a unit like that - one of the relays is for that. I was talking about the peak mains draw in full operation. You have an advantage in having a higher mains voltage there. In thinking about the transformers, I bet if John went to Hypersil cores (if he hasn't already) he'd save 15-20 kg. off my weight estimate easily.