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Old 21st May 2006, 10:51 AM   #1
TBM is offline TBM  Norway
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Default WE417/437 with battery or RC on cathode

Hi

Anyone with experience with using battery (2x 1.2V NiMH) on the cathode of 6C45pi, 417, 437 or similar, driving a 300B output tube? Some says RC (in parallell) is better sonic wize? Agree?

Pros, cons and comments much appreciated.

Cheers,
Tom, Norway
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Old 21st May 2006, 10:59 AM   #2
SY is offline SY  United States
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(c) None of the above.

This is a prime spot to use an LED.
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Old 21st May 2006, 01:33 PM   #3
lndm is offline lndm  Australia
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I agree with SY. To directly answer your question, I believe the battery is the preferred choice. In particular, there is a lack of bass rolloff (mainly a lack of phase shift) that gives the bass a much cleaner sound IMO. This effect resembles one improvement that LED's offer.
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Old 21st May 2006, 02:00 PM   #4
TBM is offline TBM  Norway
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Hi Sy,

that sounds very interesting. Could you be so kind to enlighten me on the subject? Simple schematics if possible and what you have of experienced.

Best,
Tom
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Old 21st May 2006, 05:52 PM   #5
rdf is offline rdf  Canada
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Hi Tom, I'm playing around with that configuration on a couple of amps - a 6C45-KT100 (soon to be GU-50) and a 6C45-EL84. It's the all-purpose front end.

You might find the attached graph interesting. It's zipped to get past the forum size limits without reducing resolution. It shows a spectral analysis of a 6C45 biased with two series green LEDs and an IXYS solid state current source for a plate load. The output is driving a 100 kohm resistor at about 95 volts peak-to-peak. The operating conditons are as specified in the PNG's name, 3.9 Vdc grid to cathode, 5.4 ma plate current. This places the plate at ~200 Vdc, nominally 50 over limit. I've had no issues, this tube is tough as nails and others have abused it much harder. Static plate dissipation is barely a watt, less than 20% rated. THD is about 0.2% as shown and nearly pure second harmonic. The junk above 10 kHz is a measurement artifact. The LEDs are unbypassed. Bypassing with a 1000 uF cap actually brough the 3rd harmonic up a few dB. The LEDs' internal resistance apparently generates a little negative feedback. It had almost no effect on the 2nd.

This will be as good a starting point as any at driving a 300 with a single stage of 6C45. Don't most 300's bias around 100 Vdc? Four volts bias on the cathode doesn't leave much headroom and the gain of ~40 will require significant drive voltage from the source.
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Old 21st May 2006, 09:16 PM   #6
TBM is offline TBM  Norway
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Thanks for your good inputs!
I don't have a CCS on my 6C45pi, but I am using a beefy PSU with LCLCRC with BG and grid choke; running 12mA. I am not a tube specialist, but can I substitute my NiMH 2x1.2V battery with one LED with Vf about 2V for improved sonics? I don't think I will go for CCS now, perhaps later.

Cheers,
Tom
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Old 22nd May 2006, 12:33 AM   #7
arnoldc is offline arnoldc  Philippines
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Here, here!

My Tri-amp (300B/10Y/50) uses 417/5842 as the driver and I must say I'm a recent convert to the LED bias

I changed the cathode resistor to LED (Orange) that gives me 1.9V on the cathode. I should say the improvement is unbelievable for just two LED. Mine is unbypassed, by the way.

My 45 amp with the same driver was the first conversion.
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Old 22nd May 2006, 12:54 AM   #8
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by arnoldc
Here, here!

My Tri-amp (300B/10Y/50) uses 417/5842 as the driver and I must say I'm a recent convert to the LED bias

I changed the cathode resistor to LED (Orange) that gives me 1.9V on the cathode. I should say the improvement is unbelievable for just two LED. Mine is unbypassed, by the way.

My 45 amp with the same driver was the first conversion.
gimme your overall xperience with 10Y..........

on your site that line is gray .......
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Old 22nd May 2006, 01:24 AM   #9
arnoldc is offline arnoldc  Philippines
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choky!

re: 10Y-

I've heard a pair at a friend's house driving a vintage Altec and has glorious mids.

After that I searched for them tubes You might remember that I posted here sometime back (How fragile are Sylvania 10Y tubes?) about a pair that was broken, which the seller said is caused by the filament voltage I used.

Anyway, since I liked the 5842 as a driver and the grid voltage to drive is it similar to the 45 (in fact a bit lower) I thought it would work out just right.

I got it to sound to my liking in this prototype -

And I used it for months, until friends saw them and thought they're ugly. So I looked for a "nicer" chassis which I posted at the pictures section of diyAudio (bad pic actually)

In the end I was gifted a pair of 50, made sume adjustments and I posted the project here - My simple 5010 amplifiers

I guess that's the story and thank you for reminding me that I don't have anything about that project on my site
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Old 22nd May 2006, 01:41 AM   #10
arnoldc is offline arnoldc  Philippines
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Here they are now in a "nicer" chassis-

It uses a 417A variant- the Amperex gold pin 5842 and now uses LEDs on the cathode.

My 45 uses plate choke on the drivers but in this chassis I don't have a place for another transformer so I will be putting in a pair of diyAudio's CCS boards in a coming experiment.

Why the 417A (and variants)?

1) Simple to implement (1 tube)
2) Have balls as a driver
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