SET Asylum

Single Ended Triodes (SETs), the ultimate tube lovers dream.

Return to SET Asylum

Message Sort: Post Order or Asylum Reverse Threaded

These 300B came in today and they Tube DIY asembled but didn't work

97.95.41.11
Posted on April 12, 2014 at 20:00:29
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005






They have regulation in the filament and the High Voltage B+ along with an all film cap high voltage power supply and I can tell you honestly that I really love how these they effortlessly power the big full range ribbons.I hooked them up to the ESLs and they got right on it.They have many PP amp characteristics with the energy in the bass and treble region.In other words,they aren't rolled off or tubby in the bottom octaves.I really like 300Bs and I would love to hear a pair of paralleled 300BXL running about 800 volts or a PP 300B amp(s).
I fixed a hair line cracked board in the one but I put in a reg in the other one because I couldn't trigger the negative bias voltage and it taps off the,much like a switch mode supply..
He did send the PSvane 300b tubes with the amps but I prefer the Shuggie Treasures but they are similar in most ways.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

Hide full thread outline!
    ...
RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 11:26:51
Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999
 Hi Michael,

Just a note, there is no SCR (Silicone Controlled Rectifier) in this.

If you need help trouble shooting, drop me a line.

The Mosfet's on the Main Power Boards (IRF830 for +B and some 500V Fairchild P-Channel ones for the -C - sorry I forgot the part number) are a bit fragile. When they go usually the SMD LED's too go as do a lot of other 2 and 3 legged fuses on the boards.

If something blows up, best action is to completely re-build the boards, with all semiconductors replaced.

Also,try Raytheon 5687WB as driver and real WE 310A/B as Input Tube.

For rectifier I like brown base Coke Bottle 5R4G best, not greatly fond of the Chinese GZ34 that seem to be fitted, the Shuggie 274B is also a decent rectifier choice.

Best 300B to my ears in these where Full Music and KR/Vaic.

When in good nick and with decent tubes you should get around 15-16W RMS out of these Amp's, Class A2 past maybe 12W...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

 

RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 13:35:55
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Ciao
I realized that after I had typed it because what I was looking at it on the schematic and there were the words SCR all over the place which I realized meant the capacitor brand..I changed Q2 which I had a close match in stock because it wasn't turning on to give me my negative bias voltage so after fixing the slight crack in the board,the 300b was dropping half of its source voltage across the tube so that's when I changed Q2.
I thought using SCRs were unusual because they are very noisy. I was amazed when I scoped the B+ rails at how low the ripple content was.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 13:42:56
Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999
 Michael,

A lot of really cutting edge technology was designed into these Amp's, if I may say so. They are not your average 300B Amp's. A PP Version of these could be totally killer.

Sadly DIY insisted on cramming it into too small chassis and their QA/QC was not great, in part due to employing workers with poor skills.

If you have a good working pair of these Amp's they should be great. Rehousing them into a bigger chassis that optimises arrangement of the magnetics better should be able to drop noise below 0.1mV (unweighted).

If you need the schematics of any of the boards used in them, I have partial sets here.

Also, if you actually can fix them, I know one or two people with Amp's that need fixing that other tech's failed to do (despite full schematics - I suspect they were good on toobz but poor on 3-legged fuses)...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

 

RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 13:52:15
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 I thought that they had an unusual amount of power.Can you really get 16 watts with a standard 300B? I know the 300BXL that KR makes can produce those numbers but I didn't think the standard 300 could.I just crossed the number on Q2 and I did have an 82v zener that opened which is rare but that could have been due to mechanical stress from the crack in the board because it was snapping really loud..I love working with solid state circuity but many times it's over engineered from what it has to be.
I was thinking about implementing your circuit in these.The 5687 runs at a blistering temp but that's because it's almost like a small power triode lol.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 14:02:05
Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999
 Hi,

> I thought that they had an unusual amount of power.
> Can you really get 16 watts with a standard 300B?

Yes, the output tube runs at > 400V / 80mA (pretty much the legal limits) plus 3K load. And the grid circuit with two parallel 5687WB can put a lot of power into the grid when called upon (Class A2 on peaks).

> I just crossed the number on Q2 and I did have an 82v zener that
> opened which is rare but that could have been due to mechanical
> stress from the crack in the board because it was snapping really
> loud..

Could be. These amp's are a bit cramped, there are cables under the board that need routing carefully to avoid stressing the board.

> I love working with solid state circuity but many times it's over
> engineered from what it has to be.

These units may (or may not) be guilty as charged. I did try to max out certain things.

> I was thinking about implementing your circuit in these.

They implement my circuits... 100%.

;-)

Keep them as they are, they are quite a bit special.

> The 5687 runs at a blistering temp

That is the heater alone, the current is low...

> but that's because it's almost like a small power triode lol.

Yup and it is used as a cathode follower with a choke in it's tail. It has control over the 300B Grid well past "Iron Fist" levels. And no Velvet Glove either...

I'd avoid overly expensive 300B's, because the Amp's does run them hard, the price to pay for power.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

 

RE: These 300B came in today and they Tube DIY asembled but didn't work, posted on April 13, 2014 at 14:50:32
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Ciao
I did notice on the 310a on one of the amps,when you pull off the grid cap,you get a really loud buzz thru the speaker like when you touch an unloaded RCA input jack on center but the other amp is only a slight buzz when doing that...The amps are a slightly different layout from each other but both play really well.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

I figured out why the loud buzz on the one amp when pulling off the grid cap., posted on April 14, 2014 at 00:34:05
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 The 310a has issues.Its microphonic but also the five pin sockets need a little tightening.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

Page processed in 0.019 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]