diytube.com

What effect would the James 5H choke have in the circuit instead of the 1.5H choke (i.e. sound, caps, resistors). Both are 200mA and 55 or 57 Ohms. I know that the James costs more.

Thank You,
Lee Hankins

the James would probably lead to decreased power supply ripple. ceteris paribus, more henries = better filtering. if you can spare the cash, a James PT, James choke and James OPT's would look pretty goddamn sweet.

A few years ago, at the NNETG meet at Gary K's house, one of the guys brought in a couple of very nice WE-91 "clone" 300B monoblocks, made in Taiwan, and all of the iron was James. The chassis were heavy steel, nicely chrome plated, they were a work of art, the workmanship superb, and they sounded great!

/ed B in NH

The James choke would definitely be a nice addition and lower the B+ ripple. I think you can sub this with no change to the circuit. But just in case...

One small caveat is the 'virtual hum pot' resistive divider I have across the 6B4G heater. Right now it is 51 and 47 ohms respectively. It might need to be adjusted to 50 ohms and 50 ohms with the larger choke. I think the extra little bit of offset in the current design nulls out what is left of the B+ ripple. Just a SWAG on my part.

A little "amp porn".....

The digital camera I was using at the time wasn't a really "great" one, only 640X480 pixels and it wrote to a floppy...

Note the nice "champagne" finished James Iron. Yes, these puppies
were HEAVY...

Tubes are TJ Meshplate 300B and WE 310A (with the plate cap) and rectifier - I think it was a vintage 5U4G, or perhaps WE 274B?

The circuit is similar to this one from the Bonavolta site:

http://www.bonavolta.ch/hobby/en/audio/300b_1.htm







Thanks to Shannon for linking these for me Yellow_Light_Colorz_PDT_03

/ed B in NH

Ok we have decided that the James choke is a good choice, and now discussion and pictures of an all James hardware amp, which James Power Transformer. Which one would work best with the Get*Set*Go.

This Amp is for my daughters college graduation/birthday (within the same week). She wants a system "hand made" by her father, also a set of "hand made" golf clubs, this is of course on top of the VW Jetta that was purchased for her graduation.

Lee Hankins

Of the two "closest" choices that I see listed on Euphonia's site, one is just a tad too "close" for current ratings, 300-0-300V @ 100 mA, and the other one is a serious "overkill", and weighs in around 15 pounds, and is expensive!.

http://euphoniaaudio.netfirms.com/ea/nf ... Path=26_22


Also, two independent 6.3VAC windings, of at least 2.5A each, are needed for the 6B4Gs, and the smaller James power trannie doesn't meet that spec.

This one does, but it's $208 and tips in around 13 pounds, and he has them in stock: (using the 280-0-280 winding)

http://euphoniaaudio.netfirms.com/ea/nf ... ucts_id=62


I am sure that there are others available from the manufacturer in Taiwan, and they will probably create any custom request, but at a fairly "stiff" cost...

The PA-774, with either nickel or brass end bells is decently attractive, and there is plenty of plate current "overhead", and the two independent 6.3VAC filament windings are what's needed.

Just my two cent's worth, I am sure there are other/better ideas out there...

/ed B in NH

Nice work on the power transformer research, Ed! Those seem to be some nice anchors. I shoot for a cap input full wave B+ of 380V (like the ST35) but take into account about a 50V drop from the 6AX5GT. With these James power trannies, some changes to the resistors at R17a and R17b might be needed. So we want to shoot for a B+ around 310V to 340V.

Lee, you think your daughter will be happy with 3W?

Shannon,

Yes, a 3W amplifier does have its problems, mainly speaker choice is limited. I have thought of my ST35 and or my Dynaclones but adjusting the bias is not something that I want her having to fooling around with, or even something she would do. Do have boards for both so could start from scratch.

Mostly, I believe it is the style or looks of the amps and preamps that she likes. I probably spend more time building the case and plate than actual solder time putting the units together.

Lee

THose James power trannies are a bit "rich" for my blood, but I did manage to save a beastly big power trannie out of a $5 all-tube laboratory pulse generator. dual 120VAC primaries, secondaries are 360VAC @ 500 mA and 6.3VAC @ 14 Amps :o (no center taps)

The bonus features included a LOT of 7119 dual triodes, 12AT7s, two 6080s, and some other really weird RF power triodes that must have been made on the Klingon Home World...

It's a tad bigger and heavier than the Triode PA-060 ST70 trannie, and is vertical mount, but I figure, use a full wave bridge of HEXFREDs and 8 EL34s in two channels of 4 PPP, for something resembling an "ST-140".

Yeah, I could use 6550s or KT88s but they'd be underfed... Oh, no, not another amp project :o Yellow_Light_Colorz_PDT_09 Yellow_Light_Colorz_PDT_21 Yellow_Light_Colorz_PDT_11 Yellow_Light_Colorz_PDT_02

/ed B in NH

FWIW,

he Russian 6C4C (6S4S) is the same thing as the Sovtek 6B4G, just doesn't have the fancy red paint job on the jug... Probably can snag these for dirt cheap on e-bay from the various tube sellers over there.

The Tube Store has this link including the PDF data sheet:

http://www.thetubestore.com/russian6c4c.html

And, apparently the Sovtek 6A3 is a 6C4C with a 4 pin base, rather than 8 pins, glued on.

/ed B in NH