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832A power amp

ab0ez said:
Soundmotor,

Yes, I have a couple of schematics for 6AR6 tube amps, let me see if I can dig them up.
Click to expand...

I appreciate that! Post them under a new thread. Years back I bought a pile based on how they looked (dead ringer for a 5881) and figured they had to have an amplifier application. I bet I'm not the only one who has some either.
 
Somehow missed this thread the previous 2 times around. VERY VERY NICE!

I have a few of those tubes, as well as a pair of the original amps used in this
thread, rebuilt them a year ago using 6N6P drivers to push pull triode EL84, the
output tranny's are not all that bad.

Congrats! Way cool amps!
 
That is a very cool tube and a great looking amp. I've never seen a PP in one tube. How is the sound and what is the WPC? That tube reminds me of a Hobbit. Cheers.
 
Thanks for the compliments. They sound pretty darned good. They are quiet, smooth, and with the QQV07-50 tubes in place of the 832A's the bass response is quite full and not wooly at all. I was very pleasantly surprised. As far as power output goes, about 18 watts or so....more than enough for my Khorns.
 
Wow, 18w is incredible output for these tubes. They are known to be fairly weedy tubes. I would expected power levels closer to 8-10w.


I might have to take another look at these.
 
The 832A is a pretty robust tube. Look at the construction in them. That being said, it is best to get NOS tubes as those that have been used were most likely used in an RF application and have many hours on them. With some of the old used 832A's and with the operating conditions as shown in the schematic, you will get a lightning show of arcing inside the tube.

My personal favorite brand is the GE GL832A. Overall, the 832A has plate characteristcs similar to the 6BQ5, so the power output will be comparable.

As mentioned before, get a couple of the QQV07-50's and try them. It is basically an improved 832A. Some of the 832A's had problems with the air seals due to the unusual tube shape.

Above all, experiment, find out what works best for you and HAVE FUN!!!
 
I have about 10 NOS 832As here, I was just going by what I had read from others who used the tube. 18w is very very encouraging, I was expecting half that. Thanks!
 
This might be a really stupid question, but could you double P-P them for even more power?
 
Done with my 832A amp

Help - How do I insert photos? Do they need to be on a web link or can I insert something from my computer?

The amp sounds decent. Lots of bass and lots of power. Seems like its more bassy but with less detail in the upper midrange when compared to a recent EL84 I built.

Glad I built it. I used a LM317 constant current source scheme set at about 78 ma for each pair of 832 's. A good rock amp, I'm giving it to my 18 year old nephew for Christmas.

Thanks for the insperation!
I'l try to post some photos.

(you guys have any idea how hard it is to type when the "Ppppp" key on your keyboard sticks?)
 
If you click on the advanced reply option, you'll see a paper clip icon above the message box. You can upload smallish pics via that method.

Or you can host on Shutterfly, Photobucket, etc and then link the image with
img ] tags on either side of the URL.
 
Thanks.

The OPTs are Hammond 1608 8K-8 10W on both the 832A amp and one of the EL84 (6BQ5) amps.

The other EL84 amp with the walnut case has some Dyna clone OPTs from Triode Electronics that came highly recommended. The switches on the amp are for changing from pentode to ultralinear operation. I am still sorting out this amp with the Triode OPTs so I can't really say yet how good they will be. I have an old factory wired & unmolested Dyna SCA-35 amp that has the same OPT and its sounds sweet considering its unrestored and 40+ years old.

I have used Hammond outputs a three times now and Hammond Power Transformers twice. I think the outputs are good quality for the price. Heck, the 1608s are only 40 bucks a piece and sound great. I think the Hammond PTs buzz too much and I have never had noise issues with recycled vintage PTs, so I'm not buying their PTs anymore.

My 832A amp is running at 320V B+ at 150mA, 316V Plates, 215V Screens, 6.8V Heaters.

I have an extra 100R power resistor bypassed with a 10uF cap at the end of the PS before it hits the actual amp circuit. I put this 100R resistor in every new (or new-to-me) amp before the maiden voyage to drop the B+ and limit current a little until I can get some real numbers on my meter. The voltage drop divided by the 100 gives me a running current. Why not make the math easy. I'm thinking of taking it out and the slightly increasing the screen resistor. I'm shooting for 330V on the Plates with 200V on the screens just to see what it does. Who knows, I may go right back to the initial set up.

I am currently using a 5U4GB rectifier because I have some on hand and I knew they would handle plently of current. I'd like to try a 5AR4 as soon as I get my hands on a decent one, so that I get the soft turn-on feature that the directly heated 5U4GB doesn't have.

Later...
 
Some final numbers...

Did some tweaking to my 832A amp. Sounds good. Very powerful. Mid-Bass just a little muddy when turned up loud - sounds like its from the inexpensive OPTs. Overall I'm very happy with it and have been listening to it alot.

Now running 335V B+ at 150mA, 330V Plates, 205V Screens, 6.8V Heaters. Set the two LM317 CCS circuits for 70mA per tube.

I have a pair of new RCA 829B tubes and I tried them in this amp. Sounds clear but a little anemic - I suspect that the driver arrangement is ok but that they need both more plate voltage and more overall current. Oh darn, I'll have to build another amp - my wife is gonna kill me.
 
That makes sense, the 829B more closely resembles the plate characteristics of two 6L6's or 807's in a common envelope. Hmmm, I gotta build a pair of monoblocks using those tubes!
 
Good day, understand that this is a pretty old post. However, I just completed this 832A amp few weeks ago. I used Hammond 1650E OPT. It sound pretty decent in general. Cheers.
 
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