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Old 19th January 2009, 05:57 PM   #11
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Thanks! The case is a standard 12x8x2" Hammond aluminum box with pieces of urethane-sealed wood bolted to the sides..
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Old 19th January 2009, 07:41 PM   #12
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Nicely done! Watch that middle transformer tab (UL tap), it's a dousey!
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Old 19th January 2009, 08:11 PM   #13
athos56 is offline athos56  United States
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Hehe, I imagine, after getting a dose of a faulty aquarium heater I wouldn't want a taste of the UL tap...
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Old 19th January 2009, 10:23 PM   #14
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Hi your SET AMP looks very nice well done.

Hi Tube Lab
I in the proses of building PSE Amp with xxxx Tube
was thinking D3a Driver-Inter-stage TX to Output Tube
Output TX 50% UL running the Amp 290 Volts 60mA
by the way i Run the same Configuration with 300B
sounds Excellent WAT YOU THINK
Thanks
Rudi
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Old 24th January 2009, 03:12 AM   #15
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nicely done.

i am interested in building one as well. whats the wattage?

thanks, Erwin
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Old 24th January 2009, 07:18 AM   #16
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Quote:
Originally posted by milen007
nicely done.

i am interested in building one as well. whats the wattage?

thanks, Erwin
Thanks! I expect the wattage to be similar to a 2A3 circuit, around 3 to 3.5 watts.
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Old 8th February 2009, 11:56 PM   #17
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Default 6**5GA [the tube we dare not speak its number] SE with 6SL7s

Inspired by George aka tubelab I have been hacking around with the tube that shall remain nameless, trying different operating points & drivers, naturally searching for Nameless Tube Nirvana.
I am using Edcor 5K:8 OPTS, always wired ultralinear.

I seem to have settled on a "slightly hot" operating point, with B+ around 360-370V with bypassed cathode resistors of about 920 ohms. This gives about 59-60V at the cathode, for about 65 mA plate current and 19.6 watts plate dissipation. My Nameless Tubes are Sylvanias, and they don't show any signs of distress here at all.

I like SorenJ07's 12AV7 SRPP implementation (esp all them Henries in the P/S; that's heavy iron after my own heart), but I wanted to try the IXYS CCS chip.

I have about 2 dozen 12AV7s and clones, and I expect that would work well with the CCS (sort of a sand variation on the Soren SRPP), but the tube that fell to hand was an old 6SL7WGB.

The 6sl7 chart revealed what appeared to be a VERY linear area around 2mA and -2.0V grid. (It turns out that Horizontal Load Lines are really easy to eye-ball!) Wasn't sure that the IXYS chip would work well at such a low current, but it looked worth a try.

I "biased" the chip with 1.8K (with the 1K "snubber" that George recommends), and used LITHIUM AA cells for battery bias.

Dropped the B+ to around 250V to feed the CCS and let her rip.

I had never used Lithium cells before, and the ones I used were NOT fully charged; figured I would let the bias current do the charging for me. HOWEVER, while charging they sounded like they were "leaking" (scratchy, like a loose connection). Neither NiMH nor NiCad cells do that. For a second I thought I had made a huge mistake, but after ~15 minutes they cleaned-up completely.

Without getting too hyperbolic about it, this set-up works great.
Plate current is a little higher than I wanted (2.15 and 2.13 mA measured at the pins, with the tube out), and the Lithium cells bias up right about 1.73V...If I do it again, I may use a slightly higher value to bias the CCS chip, say 1900 or 2K ohm.

Obviously, the 6SL7 is pretty darned linear to begin with, but now there's PLENTY of driver gain (the chart says a real 70, although i haven't measured) and between constant current on the plate and ~constant voltage on the cathode, this thing is EXTRA clean.

I'm not sure about "the octal sound" that some DHT folks talk about (psychoacoustics?), but this foundling 6SL7 in this circuit is at least as clean and open as the best of my 9 pins (some Mullard 5751s, if I had to choose).

I'm using the Tubelab local bypass cap (1500uF, IIRC) on the Nameless tube, and on some pieces (e.g. Folsom Prison Blues), I think I need to pad it down with a pot as the bass is overwhelming. Great stuff. Easy, simple, cheap. I'm going to have to replicate this one on a "keeper" (aka High WAF) chassis.

I'll post photos and a schema if there's any interest.

hareynolds
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Old 9th February 2009, 12:50 AM   #18
isaacc7 is offline isaacc7  United States
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Has anyone tried running this unnamed tube in pentode with partial feedback ala the RH807? Just curious....

Isaac
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Old 9th February 2009, 05:42 PM   #19
Jeb-D. is offline Jeb-D.  United States
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That's a nice looking tube (and amp). Checking out the datasheet for that ****, indicate a linear screen drive. Mmmm, future project idea.
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Old 9th February 2009, 09:45 PM   #20
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Thanks! hareynolds, I'm very interested to see your implementation. Pics + schematic please!
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