Je labs 300b DIY project for NG?

[TubeHound]

Hello,

New here and lurking for a little while. Want to build my first amp. What about the JE labs 300b amp?

Would this be unrealistic for a first time project ? I will ask many questions in the near future, some not so brilliant, so forgive me in advance, Thanks.

Paul A.

I borrowed the parts list from Audio Illusions website,(thanks).

General Parts List
Quantities are for dual mono construction
· 1.....2 req - Angela Universal Power Transformer - 380-0-380V / 200mA
· 2.....2 req - Hammond 1627SE Output Transformer - 2k5/160mA/25W/4,8,16R
· 3.....2 req - Hammond 193J Enclosed Choke - 10mH/200mA/82R
· 4.....2 req - Angela Oil Cap 15uF/600VDC
· 5.....2 req - Angela Oil Cap30uF/600VDC
· 6.....2 req - Angela Oil Cap50uF/518VDC
· 7.....2 req - Angela 0.22uF/630V Paper in oil, Copper Foil
· 8.....2 req - Black Gate 100uF/100VDC bypass cap
· 9.....2 req - Black Gate 47uF/160VDC bypass cap
· 10...4 req - 100K /1W
· 11...4 req - 220K /1W
· 12...8 req - 47K / 1W
· 13...4 req - 1K /1W
· 14...2 req - 470ohm/1W
· 15...2 req - Angela 880ohm non-inductive 25W Cath Res
· 16...2 req - Dale 50K / 25W power supply bleed res
· 17...2 req - 3k3 /5W metal-oxide power supply res
· 18...2 req - Clarostat 75ohm/2W wirewound pot
· 19...2 req - General Electric 5U4GB ( or Mullard GZ37/GZ34) rectifier tube
· 20...2 req - General Electric 6SN7GTB
· 21...2 req - JJ/Tesla 300B Tubes
· 22...2 req - China Ceramic silver 300B Socket
· 23...2 req - Octal CeramicSocket for GZ37 tube
· 24...2 req - Octal Ceramic Socket for 6SN7WGTA tube
· 25...2 req - Power supply cables
· 26...2 req - Speaker Binding posts
· 27...2 req - 100K log Pots - Bourns








Thanks in advance

[fdegrove]

Hi,

I'm not familiar with this particular circuit but don't see why anyone couldn't build it.
Have you got the diagram for the PSU?

People built this as yet?

Cheers,

[DaveInVA]

Here is a link to the site that has that amp and other projects:
JE Labs

Dave

[Ken L]

Keep one hand in your pocket and remember that tubes commonly run up to around 500 volts. Take your tiime, pay attention - be careful - ask questions when you need and you should be fine.

Until I started several other projects I was considering this as a first project. It came down to JE Labs 300B or one of the kits from any one of the sponsors on Audio Asylum.

I've had a good bit of grief from a nosiy Hammond transformer in one of my current projects. Several other amp builders have told me they had similar problems with Hammond. You might want to consider another brand.

OTOH, the best sounding amp I have ever heard, an 845 amp had a bunch of Hammond iron.

Hope this helps



Ken L

[TubeHound]

Thanks for the replys Folks,

I ordered svetlana's 300b's and they are on thier way, cool.


Now for the Questions:

I have a liitle more to spend on the output trannys, say in the $200-$300 range, any recommendations?

What about the power trannys? recommendations, things to watch for?

Which is the better rectifier tube and why? 5u4gb or gz37? both work with this amp, just curious.

The chokes are hammonds, any ideas in this area?

Which is the best ever 6sn7* type tube ever made and why?
( not wanting to start a big debate, just would like to know)

Thanks again everyone for your help, will post pics as this project progresses.

Paul A.

[Colt45]

Originally posted by maybeim

Which is the best ever 6sn7* type tube ever made and why?

that would depend on the following:
- personal opinion
- placebo effect
- how much crack you smoked the night before
- etc.

anything not chinese should be fine, IMO.

but then again, i feel the same way about brandname resistors, and stuff like that

[DaveInVA]

If you are building monoblocks and don't want to waste half a 6SN7 you can use a 7193/2C22 instead, its like 1/2 a 6SN7, sounds good and looks cool with both a plate and grid cap and they are dirt cheap...


Dave

[SHiFTY]

What about the power trannys? recommendations, things to watch for?

Get ones that have a large margin of safety, ie 1A over your filament ratings and 100mA over your B+ rating...

Last longer and run cooler that way.

[stigla]

[QUOTE]If you are building monoblocks and don't want to waste half a 6SN7 you can use a 7193/2C22 instead, its like 1/2 a 6SN7, sounds good and looks cool with both a plate and grid cap and they are dirt cheap...



A 6J5 is essentially a half 6SN7. 6J5-G has an ST shape an looks realy cool, like a small 300B, if you want

[Brett]

<b>I have a liitle more to spend on the output trannys, say in the $200-$300 range, any recommendations?</b>

<a href="http://www.lundahl.se">Lundahl</a> LL1620/80mA SE. Based on the results I'm getting with the LL1620 in PP, it will exceed the Hammond in performance. There are also the One Electrons (www.one-electron.com, www.tubesandmore.com) Magnequests (www.bottlehead.com) and Electraprints. The Lundahls are possibly the best value.

<b>What about the power trannys? recommendations, things to watch for?</b>

Don't use a torroid, an EI core is better because it has a lower bandwidth, so doesn't let a lot of the junk on the mains into the amp. Better not to let it in than try to filter it out later. Cheaper and simpler too. For the same reason, it's worth the extra to get a power trans with an electrostatic shield. Buy the largest one you can afford. Your circuit needs ~110mA, so don't buy a 120mA trans. I like to go double or at least 50% more than the circuit draws at maximum not idle. They run cooler, don't vibrate or hum as much and last forever. The Angela should be OK, one per channel.

I personally prefer fullwave tube rectifiers off a +-0-+ wound transformer, choke loaded, or at least one stage of a Pi. If for whatever reason I decide to use a DC filament supply, I use a seperate filament transformer to stop coupling of the rectification spikes into the B+, and a Pi filter and Schottkeys. Hammond chokes will be fine in a Pi filter, and should also be rated for a choke input too. If in doubt email Hammond and ask.

Put the PS on a different chassis from the amps if possible, connected by an umbilical.

For rectifiers, I only use TV damper diodes now, 6CJ3/6D22S. Much better than all the others I've used and not stupid money (cheap!!) like some of the NOS Mullard GZ37 etc.

Avoid electro caps in the PSU. PP and PP in oil are MUCH better.
Remember, all an amp does is modulate the PSU, so have a junk PS and you get poor results.

<b>Which is the best ever 6sn7* type tube ever made and why?
</b>

Who knows? Colt45 is right but forgot to add tube snobbiness and exclusivity. Why are the best tubes usually the rarest?

It might be worth looking at the Chinese <a href="http://www.diyhifisupply.com/tube_supplies/china_nos_tubes.html">6N8P</a> from Brian at www.diyhifisupply.com. I haven't heard them as none of my gear uses 6SN7s, but I've read a lot of good reports on email groups about them. Plus they're cheap, tested and traced, and Brian is good to deal with. More than good enough to start with.

Cheers
Brett