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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: Re: 5998A SET
PostPosted: 14 Sep 2009, 12:22 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Looks great Magnus. So the LED in the knob, is it just a length of wire that moves back and forth?
Cheers

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 Post subject: Re: 5998A SET
PostPosted: 14 Sep 2009, 12:34 
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Joined: 02 Mar 2009, 12:41
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Location: Vänersborg, Sweden
I wound the cable (from a butchered cheap in-ear head phone) two turns around the axles so it doesn't brake at once.

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 Post subject: Re: 5998A SET
PostPosted: 01 Jul 2010, 10:22 
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Location: Vänersborg, Sweden
I have started next project on the same theme - Triodino 3:

Image

Same tube(s) but each tube has its both triodes parallelled, thus doubling the "effect" (power). I have all bits and pieces ready (though where all the resistors and caps went, I dunno :confused: ), but lese; sockets, transformers, connectors are all in place in the solid wooden chassis.
Image

I choose sold wood just to make the amp top stand out a bit, and to aim for a very lean design.
Image

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Potentiometer and mains switch are located inside the box to minimize length of wires.

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Many parts are re-used like the speaker terminals.
My biggest concern are the OP transformers - Edcor XSE15-8-2,5K. Will they survive the 90mA bias current? Edcore has not such info on their site any longer, so this will be a GO/NOGO test ...
Image

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 Post subject: Re: 5998A SET
PostPosted: 03 Jul 2010, 16:28 
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Location: Winnipeg, CANADA
Hi Magnus, nice chassis work. Did you use a forstner bit to hollow it out?
Cheers

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 Post subject: Re: 5998A SET
PostPosted: 03 Jul 2010, 19:28 
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Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Typically the sections on the 5998 don't match, and you so may have to use seperate cathode resistors to get the tubes to balance out.

Also if you do a 3rd amp, I suggest a 1K or less primary plate load. The RP of those tubes is very low, around 350 ohms.


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 Post subject: Re: 5998A SET
PostPosted: 04 Jul 2010, 02:34 
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Location: Vänersborg, Sweden
I had planned to use a router to "carve out" the piece of wood, but I ended up with a drillbit used for candle holders and finalizing with a chisel.

Right now when I am struggling myself, I could consider using soem 6L6 (I have a spare Chinese pair) instead but could a single 6SL7 be sufficient??

The idea with the 5998A amplifiers is simplicity. The first one is a stereo single output tube 3W amp and the second a 3 tube (4 with rectifier) 7W stereo amp. Therefore, If I was to use separate cathode resistors, I'd use the same value (1K). Also I am too lazy to spend too much energy and time to fiddle with my projects.

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“If you don't know where you are going, any road will get you there.”
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 Post subject: Re: 5998A SET
PostPosted: 05 Jul 2010, 17:18 
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Joined: 26 May 2009, 18:51
Posts: 130
Location: Lilburn, Georgia USA
Hello Magnus, what kind of B+ does this setup need? I know where to get the tubes, down in Florida. That place has actually milions of tubes.


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 Post subject: Re: 5998A SET
PostPosted: 06 Jul 2010, 09:44 
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Location: Vänersborg, Sweden
I really don't know, but Va=307V and Vtransformer is 2 x 270V.

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 Post subject: Re: 5998A SET
PostPosted: 22 Apr 2013, 12:35 
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Location: Vänersborg, Sweden
A short update.
Have had some problems with the amp. One channel muted so I started yesterday rebuilding the small board that houses various components. Still nothing worked. Rewired everything again using point-to-point connections. What surprised me was that there was no voltage on the cathodes. Some 2.7V would have been normal, but nothing! :confused:
"wobbled" the input tube and HEY! did that rock!!! Aha, bad sockets (again). Changed the socket and now all works OK.
Changed the LED-knob for a BIG brass nob. Photos to follow another day.

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 Post subject: Re: 5998A SET
PostPosted: 22 Apr 2013, 21:04 
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Joined: 06 Jun 2008, 18:23
Posts: 5144
Location: Australia
Great looking amp. I'd like to see the bare trannies and chokes covered.

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