My completed 6BQ5 PP tube amp!

audiozaz

audiozaz

rtfm!? - tl;dr
Here is what I started with:

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Details about the restoration can be found in the following thread:

http://www.audiokarma.org/forums/showthread.php?t=276264&highlight=6bq5

Here is the oak frame being glued together:

frame1.jpg

Here is the glued oak frame:

frame2.jpg

Here is the metal plate I installed under as a cover plus the rubber feet I installed:

under.jpg

Here is the assembled unit:

final.jpg

Here is the amp in my living room setup, wich has the only 8ohm speakers I have, the KEF 303:

final01.jpg

Closeup of that:

final02.jpg

continuing in reply...

az
 
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Here are a few other closeup views:

final03.jpg

final04.jpg

final05.jpg

I forget where I saw it, but I got inspiration for the angles on the front of the oak frame from another similar restoration I saw online, possibly on AK even, really beats me where!

I stained the oak with an Amaretto color water-based stain and gave it 4 coats of semi-gloss varnish. It fits perfectly with my latest flexy and flexy-style wall-mount CD shelf that were give the exact same treatment.

As for the sound of the unit, it's great! I first commented in another thread how the gain was low, but turns out that was only because of the 6ohm speakers I was testing it on. I was also having muddy bass and distorted highs on that. I would not have thought it would make such a difference to deviate only 2ohms from the OPT's rating. On my 8ohm KEF, it's simply wonderfull! The OPT's are quite adequate and provide all the low-end I need with those speakers. The midrange and highs are very sweet and pleasant.

I did not test the power output yet, as all my 3 scopes are out of order :thumbsdn:, but it's plenty enough for the 88dB sensitive KEF's. I rarely use them above approx 2-3 watts on the M-45's meter and my tube amp should be good for between 10-15W I was told.

I'll so do this again if I find a nice tubed console for cheap, this was a great learning experience. I went from knowing nothing about tubes to knowing a little less of nothing! :thmbsp: I also now have a nice amp that cost me around 60$ to buy and restore, not too shabby!

Many thanks to everyone here who helped me and special thanks to John at Pacific TV who provided me with a schematic when I had lost hope!

az
 
Very neat looking job. Wish I could do half as well with my wood work. If I ever get them done I will post pics of 2 speakers I've been working on since the holidays. They are approaching half done I think.
 
BEAUTIFUL!!!
I am tinkering with an amp I pulled out of an old Zenith television console. It works and sounds good. I broke a tube and am waiting on a replacement pair.
I am thinking about cutting the chassis to make it smaller. The power supply is on one side and the amp is on the other with a mass of emptiness and holes in the middle. I removed the tv components. I plan to dedicate this amp to use with a turntable.
 

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Beautiful work. I really like how you installed the caps. Any chance of getting a pick underneath. I would like to see how you installed - clamps or ???
Thanks!
Mark
 
Jcricket said:
Beautiful work. I really like how you installed the caps. Any chance of getting a pick underneath. I would like to see how you installed - clamps or ???
Thanks!
Mark
Click to expand...

Check the link I posted in the OP, on page 2 are pics of how I did it.

Thanks for the comments!

az
 
I got to spend lots of time listening to the amp during the weekend, both attentive and passive sessions and am trully impressed by the little beast! If nothing else, it's got a good synergy with my KEF 303. Those are usually spartan in the bass department, having a Qtc of 0.7 and -3dB frequency of 70Hz. They do sound very nice, but are a bit bass shy, even if whatever bass they have is very tight.

Seems like the low damping factor of the tube amp allows the KEF's to get as "loose" as they can in the bass regions. The sub-70Hz bass is now not as tight and is more lively, but still nowhere near boomy. It now sounds a bit like a very well tuned bass reflex would instead of a sealed enclosure.

I don't currently own another nice set of 8-ohm nominal speakers, but will try to check with friends about trying it with theirs.

I have been using my Denon DRA-545R receiver as a pre-amp because my Nakamichi CA-5 developed a buzz I have to find the source of and fix. It does an allright job, but I find it to be nothing special. I'm looking forward to try the Nak with the tube amp + KEF 303. The KEF's are naturally very smooth and laid back, if I may say so, in the upper-midrange and treble regions. The Nak pre is extremely transparent and precise, which I would expect to bring back a bit of the analytical sound I'm used to that complement the KEF's so well.

My main source was a 1985 Luxman D-103 CDP, which has a very nice and neutral sound overall, not being quite as precise as my TDA1541 Sony ES or Luxman DZ-112, but not feeling like it's lacking something either. It does not have the "harsh" sound that some older CDP's may have as well. I like it to evaluate new additions down the chain.

I'm also very pleased with the amp's form factor, meaning how everything is layed-out on the chassis. All three transformers well placed on the right side, all tubes well aligned in the front center place, with the capacitors hanging-out in the back. Some console amps are a bit wacky-looking and have things mixed-up all over the place, not that there's anything wrong with that, but I just like how neat mine looks. I was actually quite lucky to buy this one instead of the Fleetwood console that I missed by a few minutes! It was not as good lookin!

az
 
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Nice goin' zaz!

What did you use for coupling caps? I don't get all worked up about coupling caps, just curious about what you used is all.

You know...a scratch build can't be far off at this point...:thmbsp:

Best,

John
 
heekma said:
Nice goin' zaz!

What did you use for coupling caps? I don't get all worked up about coupling caps, just curious about what you used is all.

You know...a scratch build can't be far off at this point...:thmbsp:

Best,

John
Click to expand...

I left the original 0.27µF coupling caps, thinking that film caps last a long time. When I powered up the unit, I checked DC on both sides and I got the expected readings and they are not causing any noise either, the amp is dead quiet at idle. I changed the smaller pF value caps and the electrolytics only.

You can see 4 of'em in this picture, one better in the middle:

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Yeah, I'm starting to look into a scratch build now. Probably a SET or SE pentode. Edcor iron seems very nice and affordable. I won't do this for a while though, as I have another build from scratch in the works, SE class A SS amp with Cinemag IPT's. Still have lots of design and simulation to do before I can even start to assemble the circuit.

Thanks for the comment!

az
 
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