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PostPosted: Thu Jan 01, 2009 7:20 pm 
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Isn't ~400v a little high for class A? Haven't done the math...just seems high.
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PostPosted: Thu Jan 01, 2009 8:16 pm 
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Quote:
Isn't ~400v a little high for class A?

Yeah.....sorry I wasn't clear. Per Zaphod's recommendation, I'm shooting for ~350v. I originally spec'd a tube rectifier, which brought the voltage down. With diodes, I'll need to either use an alternate PT (275-0-275 maybe) or find another way to knock the voltage down....possibly with zeners.

One major issue here is that the original power section was largely lifted from someone else's 6V6 design and I'm making an educated guess as to the PT specs that were used. Now that modifications are being made, I'm in unknown (for me) territory....which is actually very cool, since I'm wanting to learn as much as I can from this.

Keep those comments and suggestions coming! :D

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PostPosted: Thu Jan 01, 2009 11:45 pm 
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There's actually a nice sweet spot for Class A-ish SE amps with 6V6s, at around 350V. You also lose about 20V at the cathode, which is something I have also factored in. The tube then runs at the borderline of Class AB, and gives great power amp distortion. :D BTW as a comparison, the Fender SF Champ runs its 6V6 power tube somewhat above 400V - IIRC it's somewhere around 420V.

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PostPosted: Sun Jan 04, 2009 1:04 am 
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Question - If I were to connect the PS heater center-tap to the pwr tube cathode, could I eliminate C1 and R1?

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PostPosted: Sun Jan 04, 2009 10:13 am 
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Yes, but using C1 & R1 is a little more effective, since you would normally get a higher elevation voltage that way. If you have a cathode follower, it's even better that way, as it helps prevent cathode-heater insulation breakdown. I would even recommend using a 180k/47k (vs your 220k/20k) combination to get the elevation voltage somewhat higher.

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PostPosted: Sat Jan 17, 2009 3:39 pm 
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Finally came up with a layout.....man, is THAT a brain-cramper. The turretboard pattern is based on a Watts (turretboards.com) "Large Universal" board....using eyball-guesstimated spacing.

http://www.burntmonkey.net/chimp/ChimpLayout0.95.jpg
http://www.burntmonkey.net/chimp/ChimpSchematic0.95.jpg

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PostPosted: Fri Feb 13, 2009 7:10 pm 
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Ya know what's fun :shock: :shock: :) :) :) :)

Finding a cool schemo and thinking .... hmmm....
Do I have some 47/500's around????

Oh yea, I've got 3 :D :D
I could actually build this.

Thanks b0b0,
for a great design

:D :D :D :D
Later


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PostPosted: Fri Feb 13, 2009 7:12 pm 
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hell, I even have the dual-ganged :shock: :D


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PostPosted: Sat Feb 14, 2009 1:57 pm 
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I just noticed one more thing :oops: You will need blocking resistors of around 100k to 220k in series with the grids of the 2nd and 3rd stages, to prevent farty sounding distortion setting in.

This amp will have a lot of gain!

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PostPosted: Sun Feb 15, 2009 2:43 pm 
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I am very pleased with the interest that has been shown in this project. I will be modifying the design per zaphod's latest input, but it will probably be a few days before the revised docs will be posted.....I lost the original Visios last week in a hard drive crash. :shock: :bugeye: :damntech:

...life goes on....

jac - It'd be VERY cool if you decide build one of these! I'm planning to start work on mine in a few weeks (shortly followed by a TC-15, I hope). I'm sure you already realize this, but I feel obligated to point out that since this is an untested design, post-build tweakage will almost certainly be needed......but that's half the fun, eh?

Updates soon.....

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PostPosted: Wed Feb 18, 2009 1:21 pm 
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Ok...here's the latest.....

Image

A higher resolution version can be found at:
http://burntmonkey.net/chimp/ChimpSchematic0.96.jpg

Starting from scratch on the layout, so it'll be a while.

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PostPosted: Thu Feb 19, 2009 6:47 pm 
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Go figure, the only password I remember. :lol: :lol: :lol: :lol:
At least I remembered the right one :lol: :lol: 8)
BoBo, send me an address on the side and I'll send you an RCA 6V6 for the "Chimp" !
Yes the real deal :D :D
Later.

These new comps are well different. Vista sucks.
Have to remember my gmail password.
Later


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PostPosted: Mon Feb 23, 2009 8:00 pm 
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jac wrote:
These new comps are well different. Vista sucks.

jac...I am a Windows System Administrator and I can confirm that you are absolutely correct. Vista sucks.

On to other things....
Here's the latest layout:
Image

Higher rez at:
http://burntmonkey.net/chimp/ChimpLayout0.96.jpg

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PostPosted: Mon Feb 23, 2009 11:45 pm 
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Nice job on the layout. Did you use Visio?

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PostPosted: Tue Feb 24, 2009 10:29 am 
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b0b0, thanks for sharing your developing project with us. Thanks also to Zaphod and others making many contributions. A question for you: You initially mentioned Allen trannies. Is that still what you plan to use, after the various changes chronicled here? And, not being familiar with those, what are the specs on the PT and OT?


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PostPosted: Tue Feb 24, 2009 12:46 pm 
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coco wrote:
Nice job on the layout. Did you use Visio?

:) Thank you. Yes, I used Visio. I was sick/bored a couple of days last week, so I spent some quality time playing with Visio's Fill function. Here's the stencil, if anyone's interested.
http://burntmonkey.net/chimp/Amp_Layout.vss

I make no guarantees of the accuracy of the parts dimensions...I found conflicting information for some, and no information for others. I used mfg. data-sheets when possible.

HarmonyoftheSpheres wrote:
You initially mentioned Allen trannies. Is that still what you plan to use, after the various changes chronicled here? And, not being familiar with those, what are the specs on the PT and OT?

Yeah, I'm still figuring on using those trannies. I'm not married to the idea, but they do seem like a very good fit for this project. I really like that they publish the specs.....so many sellers just list amps their parts should work in without giving any real information as to whether they are original spec, upgraded spec, or just close enough for rock & roll. As far as the PT voltage specs go....I'm not terribly confident about my voltage calculations, so I'll be watching that closely and swapping components as needed to bring it all in line with Zaphod's recommendations.
Here's the spiff on the transformers:

TP25, Mfg- not specified
"310V-0-310V @ 150ma, 6.3V at 4.5A, 5V at 2A. 50V bias tap, center-tapped heater winding and internal hum shield brought out to a lead for grounding."

TO11c, Mfg- Heyboer
"Heavy-duty upgrade output transformer for single-ended amps using a 6V6, 6L6, EL34 or dual 6V6 power tubes"
"8,000 ohm primary to 8 or 16 ohm secondary for use with a single 6V6. 4,000 ohm to 4 or 8 ohm for use with a single 6L6, EL34 or two 6V6s in parallel. Rated 95ma continuous...."

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PostPosted: Tue Feb 24, 2009 4:24 pm 
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WHAT!!! :shock: :shock: :shock: :shock: :shock: :shock:
Trinity trannie's! :shock: :shock: :shock: :shock: :shock: :shock: :shock: :D :D :D :D :D :D :D :D
Betua they'll work the best 8) 8) 8) 8) 8) 8)


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PostPosted: Tue Feb 24, 2009 5:43 pm 
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I'd be glad to source the trannies (and pretty much anything else) from Trinity, but I haven't seen any SE OT's mentioned. The 18w PT looks great, but I'm unsure that the 290-0-290 will provide high enough DC voltage for 6V6/6L6....thoughts anyone?

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PostPosted: Tue Feb 24, 2009 9:21 pm 
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No SE OT yet. Not until we do the Tweedle. The PT wont reallt be enough hi V for you. Check out Musical Power Supplies for some iron. Be sure to get a big ass SE OT. Not some wimpy little Champ reissue style.

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PostPosted: Wed Feb 25, 2009 1:31 pm 
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big ass SE OT.


:shock: :shock: :shock: :D :D :D
BIG ASS ALL THE WAY
:D :D :D :D :lol: :lol: :lol: :lol:
8) 8) 8)


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