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OK, I've got two unanswered questions in this here thread that have been dissed worse than an Orphaned Kenny.

1.) Milford, spill beans, please, about that Bottlehead 2A3 kit. You likey?

And 2.)

steve wrote:I will biuld a small power amp. I have a design

I'd be interested in hearing about it, if you have two minutes to type out the particulars.

The Bottlehead "Paramour" 2A3 kits are very nice. They make good music for a reasonable price plus a decent platform for experimenting . They were a vast improvement over my Altec 353a integrated.

They will have more power than your Decware amps. I find them to be slightly underpowered for my 93db AudioNotes. I will be moving up to a 300b amp in the next year or so. But for now the Paramours make me happy.

Cheers,

Chris G wrote:I'd be interested in hearing about it, if you have two minutes to type out the particulars.

It's more of an educational exercise for me than anything else. I wanted to design an amp without having a schematic or kit or anything to force me to go through all the design restrictions and math, so that I would learn how to do it rather than just making something that someone else did the hard part for.

The VA section is a cathode-biased single 5703 subminiature triode -- excellent bandwidth and about 20V p-p available. The power section couldn't be simpler: a single 6B5 tube. This is an unusual and long-outdated dual-dissimilar triode tube that has its own driver triode internally cathode-coupled to a triode power section. This saves me the trouble of designing as driver, one of the most contentious areas of amplifier design, and one that would surely cause me much hemming and hawing.

The output transformer is a custom Electra-Print. This company was fast and easy to deal with, and I recommend them.

The power supply is a C-L-C Pi filter. Haven't decided whether to use diodes or a couple of 3A3 rectifier tubes I have laying around. I'll probably use diodes on the breadboard until I'm sure everything is working, then try it with the rectifier tubes. I'm a little concerned about the complexity I'll be adding with another filament transformer dust for the PSU, and these tubes were originally intended for high-voltage clipper use, and I don't know how well they'll work as PSU rectifiers.

toomanyhelicopters wrote:
and as far as the cables go, i have to say that i've tried interconnects made from Wrigley's Spearmint, Juicy Fruit, you name it. the Big Red provides an unparalled transparency. and the Mouse-Tail speaker cables cannot be beat. it's really the magic spell incorporated by the witch children. but DO NOT let them use rat tails or weasel tails or anything else. it HAS to be mouse tails, in accordance with The Prophecy. otherwise you lose all kinda detail in the 38-45KHz range.

Awesome. I used to use weasel tails myself, but the guy in the shop convinced me I was fooling myself. Do you power-condition with black arthronite from the mines of Krung or thousand-year-old Granglan's Superb? Or are you a 'custom dude'?

ok, I gave in and bought some cable today because of you guys
my girlfriend could not help giggling when the guy explained that those he was selling us were made so that different sounds travelled in different parts of the thread so that they would synchronize at the end (he looked at her and said "but this is the TRUTH) and the killer part was that there was a way for them to go out of the amp and in the speakers, that totally sold us and now I've to wait until monday (my birthday) to try them out with the mummies single we also bought as well as a Monks reissue vinyl that this other guy was keeping behind the counter for some undisclosed reason but was happy to sell us

VPI Scout w/ Grado Platinum cartridge

Sony XA 777 ES CD/SACD player

Bryston BP-25 preamp

Bryston 4B ST power Amp

Infinity Quantum 4 speakers

Kimber cables (8TC for speakers, Silverstreak for the rest)


I'm really happy with the Infinity's, but now there is a France VS. England battle for the upgrade (Focal JMLab 926 VS. B&W Nautilus 803). I also covet the Dunlavy's I heard at Trevors Mastermind studios here in Milwaukee, $$$, I have to sell more stuff.

a phase linear 400 power amp

a carver c-1 preamp

a pioneer pl-518 turntable with the grado gold cartridge that was on it when i bought it for $80

a tascam 302 dual cassette deck

my laptop's cd player

an old and very large pair of technics speakers (my next upgrade)

and a pair of sony headphones, the ones that say "studio monitor" on them.

oh, and pere ubu's the modern dance, their first, and perhaps second best lp.

steve wrote:It's more of an educational exercise for me than anything else. I wanted to design an amp without having a schematic or kit or anything to force me to go through all the design restrictions and math, so that I would learn how to do it rather than just making something that someone else did the hard part for.

That's funny; about a year ago, I snatched up a crate of weird NOS tubes from Canal Street in NYC for about $20, and I've been looking up datasheets and designing and breadboarding weird amps ever since. Forcing myself to design an amp around a random tube is pretty rewarding and has led to some discoveries I don't think I would have otherwise blundered across.

I do have a couple of nice things that makes this easier though, such as a power supply bolted to a plank of wood, and a set of octal sockets with screw terminals on the topside, so I can get something up and working without even firing up my soldering iron.

steve wrote:The VA section is a cathode-biased single 5703 subminiature triode -- excellent bandwidth and about 20V p-p available. The power section couldn't be simpler: a single 6B5 tube. This is an unusual and long-outdated dual-dissimilar triode tube that has its own driver triode internally cathode-coupled to a triode power section. This saves me the trouble of designing as driver, one of the most contentious areas of amplifier design, and one that would surely cause me much hemming and hawing.

I'm seeing a lot of Internet schematics lately that call for the 5703. (And I think that tiny Z.Vex head uses them, as well ...) I'll have to buy a few and mess around with them.

One interesting tube I found: The 13EM7, a dissimilar dual-triode orginally intended for TV use; the bandwidth is also excellent. And, since they're TV tubes, the audiophile nuts haven't yet started hoarding them. I got a bunch for next to nothing.

steve wrote:The output transformer is a custom Electra-Print. This company was fast and easy to deal with, and I recommend them.

Wow. I just checked out their website ... $145 for a SE OPT that's flat out to 55kHz? I'll have to check out their stuff. Sounds pretty reasonably priced.

steve wrote:The power supply is a C-L-C Pi filter. Haven't decided whether to use diodes or a couple of 3A3 rectifier tubes I have laying around. I'll probably use diodes on the breadboard until I'm sure everything is working, then try it with the rectifier tubes. I'm a little concerned about the complexity I'll be adding with another filament transformer dust for the PSU, and these tubes were originally intended for high-voltage clipper use, and I don't know how well they'll work as PSU rectifiers.

I'm starting to like diodes rather than tube rectifiers, for a number of reasons:

1. As you mentioned, there's one less filament to power.
2. Reliability.
3. Less noise.
4. The bass is audibly better.

Granted, people talk about switching noise and "hash" with SS diodes, but the choke can pretty reliably kill that. Putting 0.1uF/1000V caps across the diodes helps, too.


How did you arrive at that choice of tubes, by the way? Were they just things you had laying around the workbench? Or did you choose them on their specs?

here is my set-up:

Lenco G75 re-plinthed and rebuilt by Jean Nantais
Denon DL-103 MC Cart with Mic transformer step-up (Beyer Transformers)
Audio research SP8 Pre amp Full of Bugle boy and Telefunken/RCA
Mcintosh MC 240 Amp full of Mullard/ RCA blackplates
Two set's of JBL's: L 100's on top, 4311B on bottom: LOUD!

The turntable is really something else, rebuilt by Jean Nantais, he is making this process almost as popular as the Garrard 301 and 401 rebuilds, absolutely stunning! (Can be done for around $200 as opposed to $12,000.00 with Hoome Despot parts) The Lenco is Swiss made and is an idler- wheel drive, no belts! Strong motor plus steady speed equals really good sound, PRAT, blah balh blah... Vive La Lenco!!!

Forgot to mention that I would like to build amps also: SET and Push Pull. Got a ways to go on that one...

I also build my own interconnects with Eichmann bullet plugs, 30 gauge fine silver and cotton sleeves. Speaker cables are cotton jackets with 1/4 inch flat bezel fine silver wire. They're fast!!!!!