filament currents are important when designing power trafos, you add all the filament currents to determine wire size to use in filament windings...
really, it is the filament voltage that matters, the nominal 6.3 vac can be as high as 6.9vac or 5.9 volts...
i design my power traffos with the assumption that the 6.3 volts filament winding will be 6.9 ~ 7 volts open or unloaded...
unlike the ht windings, the lv filament windings do not vary as much with primary voltage fluctuations...
really, it is the filament voltage that matters, the nominal 6.3 vac can be as high as 6.9vac or 5.9 volts...
i design my power traffos with the assumption that the 6.3 volts filament winding will be 6.9 ~ 7 volts open or unloaded...
unlike the ht windings, the lv filament windings do not vary as much with primary voltage fluctuations...
very clever power supply, i like it.....so how is the regulation? i mean, what is the unloaded voltage readings? and when all filaments have warmed up....thanks..
btw, i specially like the way you put in higher rails on your front end stages, not many amps are made that way that i know of...
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i see so many coupling caps in the signal path, care to explain why?
an old guru told me, when it comes to coupling caps, use the smallest value you can get away with....
I love Kodabmx's circuits. I looked at my notes and I was getting 174vpp at the MuFollower a bit less at the phase splitter. I actually used (slightly modified) Kodabmx's 6SN7GT input and direct connection to a 6SN7GT phase splitter in another circuit. The currents were the same between the two tubes. I will post a pdf of the MuFollower as soon as I figure out how. Its a work in progress but the front end works, still working on the power supply. I'm working on my version of a Brook 10C with ABC...
I managed to find out how to upload, so here is the MuFollower. I was pretty impressed with its performance. I actually built the front end and its power supplies. This circuit is here on my desk so I can run this to take measurements this weekend if anyone is interested...as you can see I like to design them in LTSpice then build. This design is still in design so to speak..
Unloaded it approches 700V (the quadrupler) but by the time the tubes warm up we have ~560V on the 600V caps (because 2k).
The regulation is good enough that I don't think about it. The extra voltage on the input stages minimizes distortion and allows the many volts needed to drive the output stage to full power
That's how it works best in this scenario... All the poles seem to be low enough not to interfere, and the toroid transformers allow for more gNFB than you would think would be stable with these caps... I suggest 2k only because you need too much gain with 1k (like 6V for full output), otherwise it's stable here.
Thank you. Let us know how it goes and share the circuit, won't you? EDIT: See following post.
As I said (indirectly), I want the -3 to be lower than 2Hz. This easily does that. And the price was right
Plus it seems to play nicely with the rest of the poles in the amp gNFB.
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Ok I see now. Where Tony was like "so many caps" I'm like "So much DC coupling" but if you can make it behave, why the hell not? Same as me from the other direction I guess? I just like cap coupling because all the tubes play nicely over time and vast differences in aging (read - I don't need matched or otherwise special tubes for my designs... that's a design goal for sure!).
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As I said (indirectly), I want the -3 to be lower than 2Hz. This easily does that. And the price was right
What reasoning to have an amp play down to 2Hz?
Perhaps to use as a rumble/subsonic testing amp?
Nothing more than a flat response from 20Hz up... I listen to a lot of "modern" electronic music that easily makes good bass down to the 20-30Hz range, too. I haven't needed a "tone stack" on any tube amp I've built because I like to see the speaker wiggle to 5Hz if I choose It always makes me smile, just how low of a frequency I can pass through transformers
It always makes me smile, just how low of a frequency I can pass through transformers
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I did that on my first amp - a Williamson with the standard DC coupled first stage. Worked well
enough but I then opted for more "modern" designs that frankly work better if you have the "iron". Still, my design could be traced back to it's Williamson roots in some way?
Do you wind toroidal transformers, Tony?
Also - Sorry to the OP for kind of hijacking the thread.
Run your tubes with a voltage source. As Mr. Fahey pointed out, the tubes will still work with your current source... But just plug them in and listen to them... Try not to waste time and effort on the diminishing returns of current vs voltage for the heaters... What if I told you the true magic lies in using a battery? Maybe it does! Maybe it's horses**t...
enough but I then opted for more "modern" designs that frankly work better if you have the "iron". Still, my design could be traced back to it's Williamson roots in some way?
Do you wind toroidal transformers, Tony?
Also - Sorry to the OP for kind of hijacking the thread.
Run your tubes with a voltage source. As Mr. Fahey pointed out, the tubes will still work with your current source... But just plug them in and listen to them... Try not to waste time and effort on the diminishing returns of current vs voltage for the heaters... What if I told you the true magic lies in using a battery? Maybe it does! Maybe it's horses**t...
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Nothing more than a flat response from 20Hz up... I listen to a lot of "modern" electronic music that easily makes good bass down to the 20-30Hz range, too. I haven't needed a "tone stack" on any tube amp I've built because I like to see the speaker wiggle to 5Hz if I choose
I see....
As for me, there is nothing exciting about music below 30ish Hz, other than power-robbing subsonics like rumble.
I much prefer my amps to utilize their power in the hear-able zone. 30Hz to 15kHz.
Oh mine will use the power in the band, but they extend down to the 8Hz required by "bach on the biggest" Robert Elmore - Bach On The Biggest (1958, Vinyl) | Discogs
That record has the lowest frequencies I've seen on a useful recording.
That record has the lowest frequencies I've seen on a useful recording.
Here's a good example track, although the vinyl sounds better obviously...
Urbandawn - Black Notes (feat. Daniel Baeder) - YouTube
Urbandawn - Black Notes (feat. Daniel Baeder) - YouTube
And this: #DSOLive Encore: Anne Akiko Meyers: Mason Bates Violin Concerto - YouTube
So good IMHO! If you have the dynamic range for it.
So good IMHO! If you have the dynamic range for it.
I had a similar experience with some EH 6922s a while back, and started a thread here. Their filament current was quite different from the nominal one, which meant that in current regulated mode they were operating significantly under the rated voltage. I ended up voltage regulating them.
Alex
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