Looking for 300B or 2A3 design suggestions......gearing up for a new project

[jmillerdoc]

Hi,

I have been thinking of building a big tube SET amplifier for some time now. I am looking for some suggestions on good, proven designs.

Would love to get some input from a few of you out there who have built and know of some excellent performing amp designs using the 300B or 2A3 (or variants) or similar "big power" tubes.

Thanks!
Jeff
Lawton, USA

[andyjevans]

The type of SET design I use constantly is a three stage design with all DHTs. There are several variations. Input tube can be 26, 01A, 30sp, or even 10Y, driver can be 31, 71A, 46 or 10Y. Output is 300b normally. Any of those variations will give you superb transparency, timbre and realism and a really delicate and detailed treble. I think this sound is a trademark of DHTs in general so I use them all the way through, not just the output.

Couple these how you like - transformer, good russian teflon cap etc. I usually use a wirewound resistor on the cathode - others use battery grid bias which is probably better. I went off red LEDs though did give them a go. Plate load can be an active IXYS cascode or a choke. Or just start with a resistor to get it going.

Filaments are just Schottky diodes, big cap like 15,000uF and LM1084 ccs. But you need a filament supply for each tube, so that's 6 supplies. least hungry are 30sp into 31, and that's cheap and a very good sound. 30sp (VT67) is less microphonic than the plain 30. 01A into 71A is better still and still not so hungry. 26 into 10Y is getting seriously good, but filament supplies start to need big heat sinks. Given the 6 filament supplies, it's a pretty easy decision to use a seperate box for the power supply. That leaves you with choices for umbilicals. I use Amphenol AP 4 pin for HT and earth and XLRs (4 pin mostly) for filaments, or Speakon 8 pin connector for drivers and outputs and XLR for inputs.

Lots of information about this in the current 26 preamp thread.

andy

[jmillerdoc]

Andy,
Thanks for the great advice. I am not quite to the point where I can create a design de novo.....you wouldn't know of any good schematics that are proven would you?
Thanks,
Jeff

[45]

Originally Posted by jmillerdoc

Andy,
Thanks for the great advice. I am not quite to the point where I can create a design de novo.....you wouldn't know of any good schematics that are proven would you?
Thanks,
Jeff

Katelelo by Ciro Marzio is an excellent 300B amp. The circuit is shown here (post #6): Katelelo
For some reason the original article has been removed from the net.
You can use the 26 instead of the rare PT8 as input triode. The driver options are: 71a, 45 and 2A3. Also, as suggested by Andy, the 31, 46 and 10Y are excellent drivers, too.
The 4-300BLX was a special titanium plate 300B made by Golden Dragon and was discontinued a long time ago.
The original OPT's, chokes and supply transformer are available. However you can use other similar types for you own realization.
Cheers,
45

[45]

This is the bigger brother:
211 SE2

[dsavitsk]

Electra-Print.com 300B DRD Amplifier
Electra-Print.com 2A3 DRD Amplifier
TubelabSE
Unnecessarily complex 300B amp
http://www.hagtech.com/pdf/clarionarticle.pdf

[azazello]

Jmillerdoc, You have a PM.

[dr.fishbacher]

for the PSET 2A3 - 2A3 PSE - Parallel Single Ended

for the SE 300B- 300B PSE - Parallel Single Ended

for the PSET 300B- 300B PSE - Parallel Single Ended

[Ty_Bower]

Originally Posted by jmillerdoc

...amp designs using the 300B or 2A3 (or variants)

If you're looking for something less ambitious, you could try Shannon Parks' Get*Set*Go. It's a proven design, closely based on the JE Labs Simple 2A3. The amp is built on a printed circuit board so it's easy to build. I built one this spring, and I really enjoy listening to it.

[88man]

I am thinking of building this after my SET 6N1P/KT88 amp... It's very complete, proven, and reproduced by many. Just look at the gallery of builds.

300B Mk1 Triode Amplifier