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Old 14th November 2007, 01:19 AM   #341
anatech is offline anatech  Canada
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Hi Charlie,
Why not use a SS rectifier? All you need to do is add series resistance for it to behave very close to a tube rectifier. You could add an RC network across the diodes to control and switching spikes, although the series resistance will take care of most of that.

Just a thought.

-Chris
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Old 14th November 2007, 01:55 AM   #342
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Charlie,
Sheldon is "spot on".
For your info - I have a pair of EL84 Baby Huey mono blocks 80% complete with SS rectification BUT choke input power supplies. They also have mosfet source follower buffers in each side direc coupled to the output tubes. This is a bit of an experiment to see if the loping, relaxed "pace" of the 6V6 Baby Huey is due to the tube rectifier or the choke input supply or just the tubes themselves. Will advise once they are done.

It will be some time before I get back to them as I undertook a design and build of a custom guitar amp (4 x Vintage 6V6G in parallel push pull) for a friend and have promised to have it done for Christmas. Thats my 1st priority right now.
Cheers,
Ian
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Old 14th November 2007, 02:00 AM   #343
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by cbutterworth
Ginger, please read Sheldon's last post to this thread and see if he's correct in his method of estimating current draw.
Ah, ye of little faith. No worries Charlie, if I'm wrong I want to know too.

One thing I did leave out in your B+ calculation is the drop over the output primary (center to end). You can measure the primary resistance when you have the transformers but meantime, estimate about 150R. The Plate voltage is measured from the input to the plate to the cathode.

Sheldon
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Old 14th November 2007, 03:04 AM   #344
chrish is offline chrish  Australia
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Charlie,

I am very interested in building a Baby Huey with tube rectification as well. Have started to source components - output transformers and some motor run caps etc. I am travelling to Beijing at the end of the month, so will be looking at power transformers and chokes there.

Keep us posted as to how you decide to go, as I am pretty new to all of this and it will be good to follow where others have gone before, rather than make my own mistakes

I guess I should be honest, my motivation for using tube rectification is that I bought a bunch of Russian 5U4Gs on Ebay and I think that they look cool, rather than having any specific technical reason

Along with that ebay purchase, I bought some 6P14P (stated as EL84 equiv) and 6P15P (EL83 equiv) output tubes and some 6N2P (similar to ECC83) driver tubes. I am aware of the slightly different pinouts and the different heater voltage of the 6N2P, but apart from that I was planning on using these tubes. Does any one have experience with these or see any problems? (note, am aware of 150V limit on G2 of 6P15P compared to 300 V on 6P14P)

Also, there are a lot of posts here to do with this amp, but very little in the way of photos. It would be a big help if some of you who have built this amp could post some shots to assist me with layout etc.

Thanks,

Chris
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Old 14th November 2007, 06:20 AM   #345
athos56 is offline athos56  United States
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Ok here it is! I change a few things, the .22uf/caps are orange drops from Angela, it added about $5 bucks, but I saved a bunch on buying the parts for my preamp CCS vs buying a kit. The trade off was that I had to stop ignoring the math and learn what was going on so that I could figure out what parts to buy You can ignore the 12b4a part list, but just in case I'll add the schematics as well.
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Old 14th November 2007, 05:26 PM   #346
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Quote:
Originally posted by gingertube

For your info - I have a pair of EL84 Baby Huey mono blocks 80% complete with SS rectification BUT choke input power supplies. They also have mosfet source follower buffers in each side direc coupled to the output tubes. [/B]
When you say "choke", do you mean "gyrator"? Have you already tried it?

Can you post a schematic of this amp, please? Iíve seen the 6V6 version but if I remember right, the buffer wasnít direct coupled to the output stage (I asked for this way of connection on post 199).

I'd like the idea of mosfet buffer because in this way Iíll be able to even try a PPP version of this amp.. more power and double Gm (good for feedback mechanism) but even double input capacitance (bad, frequency response limited due to Miller effect), so shielding the EL84ís grid to the high impedance node at the driver anode seems the right way to go. As a bonus the bloking distortion should be lower, that means faster recovery time.

Cheers

Mark
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Old 14th November 2007, 09:22 PM   #347
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Quote:
Originally posted by mark_titano
When you say "choke", do you mean "gyrator"? Have you already tried it?
I'd guess he means Choke as in a big chunk of "iron" since it is the input too a power supply. A gyrator usually refers to an assembly of active components, usually op-amps, that pretend to be an inductor in a filter circuit...

Ian?

dave
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Old 14th November 2007, 10:19 PM   #348
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Yes, I mean 8H 150mA Hammond "chunks of iron".

The MOSFET based gyrator (simulated inductor) is one of those "experiments to try when I have some spare time" things - don't hold your breath.

I'm a bit hesitant to post the current 6V6 design as I sort of consider the various 6V6 versions as a bit of a sidetrack . The best Baby Huey uses EL84s (or similar higher gm tube). What I can do, if you want, is sketch up a schematic for a tube rectified version of the monoblocks I'm now making BUT you'd have to appreciate that its "prototype" status - that is, not yet complete and tested, and the added complexity/expense not yet proven to be worthwhile.

For "newbies" I suggest you stick to the circuit posted back on page 1.

Let me know.

Cheers,
Ian
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Old 15th November 2007, 02:32 AM   #349
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Hi Chris,

If you email me I can send you some pix of my humble efforts. There's a couple of interior and several exterior that might help you with orientation. I'll try and annotate them.

There are some not-very-good ones on the thread already--Posts#251,263.

Let's know.

Cheers, Ken
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Old 16th November 2007, 04:33 AM   #350
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Ken -

How do you like those green K42's as couplers? I have a box of them that I intended to use for that duty but received a box of K40's shorly after. I ended up using the K40's and was so pleased, I never even tried the K42's. I'm curious if you've used enough varieties of coupling caps to form an opinion on the K42's and if so, would like to hear it.

Adam
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