Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: leevc5 on May 09, 2016, 07:00:24 pm
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How I modify my 5F1 kit to use and take advantage of the higher power output of a 6L6?
If not is there a way to put two 5F1 kits together and get one ~10 Watt amp?
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How I modify my 5F1 kit to use and take advantage of the higher power output of a 6L6? ...
What kit are you using? Is this a Hoffman board, using all the parts on the BOM (http://el34world.com/Hoffman/files/Hoffman_5F1_BOM.pdf)? Do you already have the power & output transformers, or are you in a planning stage?
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I already have the hoffman kit built.
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What specific power & output transformers are you using?
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What I did to my VibroChamp might help.
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Jjasilli,
Really been itching to build a SE 6L6. Is there anything you would do differently?
Any particular reason for using 2 Orange Drops to bypass V1, or just what you had? The 1uf/3k3 Bias on both cathodes I have seen in a Morgan Amp, but never done it myself. Did you do that to keep Bass frequencies off a smaller speaker or just like it?
The 330pf from pin 5 to 8, how effective is it?
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I am using W022772 PT and W022905 OT.
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What I did to my VibroChamp might help.
Jjasilli, what is the PT in your schematic?
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Thanks for all the help. This is great!
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The W022772 6.3v filament winding is rated @4A so no problemo there. Selectable 600v or 660v on the main secondary as well. That's a good little PT.
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What I did to my VibroChamp might help.
Jjasilli, what is the PT in your schematic?
My PT is stock Fender VibroChamp: 125P1B
Note: the filter choke occupies the spot on the chassis which formerly held the OT. The new, bigger OT is on a supplemental chassis mounted to an inner sidewall of the cabinet.
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Jjasilli, what is the PT in your schematic?
My PT is stock Fender VibroChamp: 125P1B
manufactured by whom?
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It's a SilverFace Fender VibroChamp with a stock PT. Don't know manufacturer.
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Documents on AX84.com cover just about every power tube.
May I suggest a choke between the "reservoir" cap and the OT node on the power rail? Much cleaner power supply. Might help even more with a 6L6.
Chip
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My PT is stock Fender VibroChamp: 125P1B
I am using W022772 PT ...
And the stock Princeton/Princeton Reverb PT. It and the W022772 PT are capable of 70-100mA on the high voltage winding, so powering a 6L6 (for actual increased power output) should be no problem.
... W022905 OT.
Okay, a 7kΩ:4Ω OT.
Assuming your B+ lands ~375-400v, you could bias a 6L6GB/5881 (or any 25w or higher variant) to ~62mA and get ~11w of output power. To get the most out of a 6L6GC (which would still only be a couple extra watts), you'd really like a 4-5kΩ primary impedance (probably what Jjasilli is using with his Hammond OT).
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I sincerely thank you all for the help and advice but it looks like the bottom line is that where I am with the current kit it is not worth the effort to just get a couple of Watts.
I will save the schematic for my next build so that I can get the full advantages of using a 6L6. Or I might look at doing a dual 6V6 or 6L6 build, I'll have to do a cost analysis. The darn PTs and OTs cost are just killers when you want to build a kit I wish I could find a source that had better prices.
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That PT will support a 6L6. The OT will too. Connect a 4Ω speaker to the 8Ω tap. Then simply replace the 5Y3 and 6V6 with a 5U4 and 6L6.
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It's a SilverFace Fender VibroChamp with a stock PT. Don't know manufacturer.
If it has "606" printed or stamped on it anywhere it was made by Schumacher for Fender.