Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Tode => Topic started by: Doc B. on August 23, 2012, 12:33:40 PM
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There are a whole bunch of them out there now. You guys are making me antsy!
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Its killing me to have it sit there. I'm working on a custom enclosure but I'm having to practice my woodworking skills first. Then I need to ensure the way I want to mount the front panel to the baffle will work.
I received my stereomour today, so maybe I can take care of my soldering jones with that while I'm working out the particulars on my amp cabinet.
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I'm building without any modification, so shouldn't take me too long. Trying to do a little each day. But the kids are going back to school next week; the confusion from that might slow me down a little!
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Doc,
I just finished mine a few minutes ago, but seem to have a problem. Resistance checks are good, but I'm getting 15.6v at term 2, 20.0v at term 5 (both on the front), and no sound (speaker or headphone). The other voltage checks are all close, I have LED glow, tube glow on the EL84. EF86 I'm not sure... I'm checking for bad soldering joints now.
Cheers,
Bill
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Completed the wood "base" assembly, gluing and metal brackets, not yet decided how to finish it.
Back plate and PSU completed and checked out, it works properly.
Completed the front panel assembly, just finished the ground buss and "scoop filter" wiring.
Taking my time, no need to rush it... ;D
/ed B in NC
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Sorry Bill, we had a surreal day today (cover emails...check ebay auctions...pack all the assembled amps that are queued up... by 3... don't forget to drive to Port Townsend by 4:30 to pick up Mom's ashes!) and I didn't get a chance to look at the manual to understand what the terminals in question are connected to. I will take a look when I am back at the office tomorrow. If you can tell me what those questionable terminals should be reading I might be able to figure out what they have tied to them and give some suggestions. If it's just those two terminals, start there and make sure that everything that should be connected is connected to them. Sometimes the "no sound" symptom is due to the signal getting grounded out somewhere in it's path from the input to the output. It might be something like an errant whisker of shield wire on the coax cable shorting against the center conductor.
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Dan, given your day I'm amazed you pulled off answering posts at all! I'm sorry that anything to do with the loss of a loved one gets associated with a timeline-- we'll keep you and your family in our thoughts and prayers.
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Just finished building my Tode, works perfectly, sounds very nice. Only minor voltage check discrepancies are all related to the EL84 cathode voltage, I have approx 28VDC across the 560 ohm 5W cathode resistor, which would equate to 50 mA cathode current.
37VDC across it would be closer to 68 mA, which would likely give the EL84 / 6BQ5 the dreaded red plate syndrome :o
I left the front and rear plates their natural aluminum, I like the swirled brushed finish as it is, and I had no "bubble wrap" markings - mine were swaddle in non-adhesive bubble wrap, so no sticky footprints to deal with ;D I painted the power tranny bell with a brown rustoleum finish, I figured it will look good with the finished wooden cabinet.
So, all the voltage checks which indicate approx 35-37 VDC, are approx 10 V lower. I tried the supplied Sovtek EL84, and a couple others (J/J and EI) that I had on hand, and observed nearly identical voltage measurements. In both cases, the EL84 control grid voltage is about 16VDC, that would make the grid to cathode differential about 12 VDC, whic is spot-on for these tubes, at 50 mA.
I get approx 350 VDC on the "hot" end of the power supply's 47 uF / 450V cap, and 432 VDC at the "hot" end of the voltage doubler, and approx 82 VDC drop across the 1.6K, 10W power resistor.
I haven't yet applied any varnish / finishing to the wooden cab, so I am testing it "bare naked", just with the front and back plates assembled together. With nothing plugged into the input jack, it is dead quiet, no discernable hum, buzz, ripple, noise, a true "black" background. ;D
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Hey Ed,
Remember that the tubes are direct coupled, so the op point of the EL84 is somewhat dependent upon the op point of the EF86. I'll check the voltages in mine when I have a chance. Meantime, could just be the tubes need to cook a while and form their cathodes before the voltages settle in.
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I do have some Tungsram, and a couple of "mystery" Russian made EF86s (which I got from Triode Electronics, for an ST-70 mod project, a LONG time ago), buried deeply in the tube stash, I'll try them out, when I can excavate them from the mountain of boxes... Meanwhile, I'll just let the supplied Svetlana and Sovtek tubes burn in.
/ed B
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Doc,
I think you've really nailed this one! I have a feeling that this one will be a success with the broader musician community in addition to those of us more rooted in the playback side of things. It's addicting... the more I play with it, the more drawn in I get! ...Now if it could only help my technique!
Cheers,
Bill
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I've built mine and it sounds very good. The Fender tone setting sounds good with my pedal steel guitar (I don't play no stinkin' 6 string twangers!). The line out to my WGS- EV-SRO clone into a closed cabinet sounds great and darn loud too. Some Tode pix:
http://s660.photobucket.com/albums/uu330/piperbob_photos/Tode/
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Wow! You ought to post the first picture in the Gallery. I like the red and green finish to the front plate.
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Love your soldering iron rest.
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37VDC across it would be closer to 68 mA, which would likely give the EL84 / 6BQ5 the dreaded red plate syndrome :o
Remember, 4-5ma of that cathode current is flowing through the EL84 screen, and a teensy tiny bit through the EF86 screen.
I think the tubes we used during the writing of the manual were pretty well thrashed (mostly by me) during the prototyping stage, so some variation doesn't surprise me at all.
-PB
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Doc, your instructions were very well done. I've built about 20 guitar amps from instructions all the way to crappy pictures and grainy looking schematics. This would have been a tough build for me going point to point in three dimensions without your instructions. My reason for buying this amp was to try the EF-86 flavor. I can't figure out if it is better than a 12AX7 or 6SN7/6Sl7 that I have used in the past. I'll have fun trying to find out.
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There's a lot going on in the amp that will make it sound different than a typical 12AX7 input kind of thing. The EF86 has enough bias on it that you would usually need a pedal with some boost to overdrive it, even a humbucker is barely going to get the EF86 crunching. On the other hand that single EF86 has a ton of gain and drives the bejeezus out of the EL84, particularly with the feedback rolled off. That's how the amp is capable of putting out around 10W distorted. So the sound is not only pentode distortion-dominant (duh), it's also output stage distortion-dominant. It gives it a wee bit more of a "big amp" sound that one would expect from a little practice size amp. In clean mode it's probably going to sound closer to a 12AX7 input amp, but the direct coupling and fairly high amount of global negative feedback that can be dialed in (about 20dB) should at least in theory make for a "cleaner clean" than some other amps are capable of - a bit more snappy and articulate.
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I should have posted these earlier:
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Very cool! The leather handle looks nice. I wish we could include those in the kit, but it would drive the price up.
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It's a strap from a trunk restoration site. It really didn't cost too much (for those thinking about it) and I even got the replica brass nails to attach it.