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Old 1st February 2009, 04:48 PM   #2351
sarrisk is offline sarrisk  Greece
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Default My SV811-3

my SV811-3 DHT SE amp almost ready
Click the image to open in full size.
Click the image to open in full size.
more details here : http://sarris.info/main/811a-single-...iode-power-amp

costas
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Old 3rd February 2009, 04:06 PM   #2352
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Quote:
Originally posted by wicked1
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Thank you for posting. Looks good!

Which rectifier tube are you using and when measuring bias (through those holes), are you using some kind of contact plugs?


Also, any pictures of those tubes glowing?
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Old 3rd February 2009, 04:24 PM   #2353
wicked1 is offline wicked1  United States
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Thanks! I'm so happy with it!
Rectifier is a 5u4g from aes. My hammond power tx just puts out way too much juice. I tried various tweaks to the circuit (smaller input cap, larger choke) and it still didn't bring the voltage down enough. I popped that 5u4g in there and it solved my voltage problem, as well as looking great.

Bias test points. The bare metal holes are screw holes for the bias adjust. The 4 black test points behind the power tubes (you can see 1 and 1/2 of them in that pic) are where I test the bias. I haven't tested it yet since I assembled it. I'm guessing I can just stick the ends of my multi-meter probes in them. There looks to be enough clearance around everything that I wont accidentally make any shorts.

Glowing tubes? Hopefully tonight! I finished the chassis assembly Saturday night, and when I snapped that photo Sunday morning, the wiring wasn't complete. I finished the wiring Sunday night. Had a busy day yesterday, and didn't want to take the chance of the first power up. SO, today. This should be the day for the glowing tube photo.. and I'll snap one of the under side while I'm at it, now that the wiring is complete.
I don't foresee any trouble w/ power up today. I have been using the amp for about a year.. it's just been all spread out on a plank of wood. So, basically just had to reconnect all the tx's in this new chassis.
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Old 3rd February 2009, 06:20 PM   #2354
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Quote:
Originally posted by wicked1
I'm guessing I can just stick the ends of my multi-meter probes in them. There looks to be enough clearance around everything that I wont accidentally make any shorts.
Very risky.

A pair of these panel mount plugs per each channel (+ and - test probe for each lead of R18 and R29) will make it much easier.
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Old 3rd February 2009, 06:26 PM   #2355
wicked1 is offline wicked1  United States
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Those are what I have on my test points! (except round ones, not hex on top)

Look right between the 300b's You can see a small black circle. That's one of the test jacks.
From the position of that photo, you can't really tell those are 3d test jacks and not just holes.

My amp is on, playing music! yay
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Old 4th February 2009, 11:33 PM   #2356
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Default My first Amp worthy of Display

This is a 6V6PP Fixed Bias. (excuse the one 5V6GT I could not find the fourth 6V6GTY I had squirreled away, then remembered it is on the Fender Tweed Deluxe Clone I built my Brother In-Law for his Birthday last year!)

B+ 250 - 6CG7's driver/splitter. Sounds Real nice driving my "Junk Pile" find Yamaha NS-A636's. Bass is a little "loose" or what I call "Boomy" or "Flabby" (left over from my Car Audio days) Not sure if that is just because these Yamaha's don't like anything below 40hz?
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Old 4th February 2009, 11:46 PM   #2357
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Default My first AMP worthy of Posting

6V6PP B+250 Fixed Bias, 6CG7 driver/splitter. No Feedback.
Sounds nice just a little bit "Loose" in the low end.
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Old 6th February 2009, 01:48 AM   #2358
JoshK is offline JoshK  Canada
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Finally have something to share. My first ever tube amp is complete.

It was actually done a bit over a week ago but couldn't find my camera's battery charger.

Still have a tiny bit of hum, but I think I know why.
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Old 6th February 2009, 12:37 PM   #2359
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Quote:
Originally posted by JoshK
Finally have something to share. My first ever tube amp is complete.

It was actually done a bit over a week ago but couldn't find my camera's battery charger.

Still have a tiny bit of hum, but I think I know why.

Josh,

Looks great. Well thought out layout. Didn't put the rectifier tubes on top of the input stages. Good going using two damper diodes, a superior setup to the overpriced 5AR4, IMO. I see two VR-tubes. Are they wired in between the KT-88 plate and screen grids so you can run the tube triode mode at decent plate voltages, or is this a G2 regulator and the tube is wired pentode mode?

What is the top deck plate made out of?
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Old 6th February 2009, 02:40 PM   #2360
JoshK is offline JoshK  Canada
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Thanks. This is Pete Millett's SE KT88 E-linear amp. I used his layout so I can't take credit. The VR tubes are for the D3A's G2. The KT88's are wired for UL and then plate to plate feedback is done from the UL taps back to the input stage.

The amp sounds great, despite a little residual hum left to track down. I am reasonably certain it is the AC heaters. Couple tricks left to try there.

The top plate is patina'd copper epoxied to a thicker piece of aluminum.
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