Clementine confusion

[croudyj]

Well... it works... and it sounds amazing. All my worries about hum were completely unfounded. This is the quietest amplifier I think I've ever heard. That is until I play some music through it and turn the volume up. My wife came home while I was testing it so I put some jazz on (something she can appreciate) and her jaw hit the floor (which, believe me, is not a common sight). I've heard the sound will improve over the next few days as it 'burns in'. What? It can get better?

The sound is strange -- hard to describe. It's really clear and detailed while at the same time kind of full and deep. The bass is amazing and it has this old-time fullness that is often lacking today; I guess that could be the 'triode' sound. Whatever it is, it's great. It's also amazing how loud 5 watts per channel can be. I was expecting much less volume at maximum. It's way more than enough for my living room. This was definitely worth all the blood, sweat and tears. The only thing left to do is put the feet on the bottom plate.

Thanks to everyone, in particular Tom, without whom I would probably not have succeeded. And Shannon, if you're reading this, thanks for making your designs and circuit boards available for everyone to enjoy.

I'm very happy

John

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[TomMcNally]

Beautiful ! Great job John, and it's always nice when you turn it on and it just works fine ! I turned one on with no fuses recently, haha. I would suggest jumping pins 1 and 8 on the outputs (maybe you did it up top?) I didn't have a good experience on the Russian 6n3c-e tubes without the jumper. What outputs are you using ?

It was a pleasure giving you some advice gained from building a literal ton or so of amps ! Hopefully your experience will get some other guys going too.

... tom

[croudyj]

Hi Tom,

Thanks! I'm using Sovtek 5881 / 6L6WGC output tubes. I didn't connect pin 1 as I'm not planning to do any tube swapping.

I have a couple more questions. Although the amp was running for a few hours with no sound problems, I did notice the pilot light changing brightness every now and then. It would randomly go a bit brighter, then a bit dimmer, with no pattern. There was no glitching in the audio though. I put a voltmeter on my power strip and it read an almost constant 121.5 volts. How could a constant primary voltage result in a fluctuating secondary voltage? Perhaps my lamp is glitchy; it's just a flashlight bulb in a cheap holder. I think I might try cleaning the contacts.

More worrying is the temperature of the output transformer. It got so hot that pressing my hand against it for too long would burn me. This is about the same temperature that my Fat Man iTube 252 got to after some hours. But I wouldn't have expected this one to get that hot. Could something be wrong?

I measured the current draw to the heaters (J8) and it was 2.1 amps. That's pushing the 2.5 amp limit but I'm sure it was part of the design. I noticed that you seem to parallel your 6.3v secondaries. Is this the reason you do that?

Thanks,

John

[TomMcNally]

I've always paralleled the 6.3 windings for extra current. Others have done what you did , using the second winding for a pilot lamp. There has been some controversy in the past over how to determine the correct phase of the two windings. There is the scientific method, and mine ... I connect one wire (you can use the adjacent empty holes or stuff the wire into the connector) then with a voltmeter across the 6.3 volt connection, quickly tap the other wire across. If you get a spark, reverse it - if it's correct you'll still have 6.3 volts. It works without a meter too. That method takes like 1 second, I forget how to do it "safely"

I've only built one amp with pilot lights, green for filament, red for plate. I wound up putting higher voltage bulbs in the sockets to dim them down.

My latest Edcor Chubby Clementine power transformer runs cool enough to keep your hand on it. There have been many discussions over "the hand test" and what to expect.

[croudyj]

Hi Tom,

Thanks for your reply. My guess is you put both windings into a 2-channel scope and make sure the sine waves are aligned. Your method made me cringe but it can't hurt if you do it real quick. I wonder what would happen if you left it connected wrong? Perhaps the transformer would melt! Ahh... but the fuse would blow first, I hope.

I'm thinking I should parallel mine too and feed the lamp off J8 as well. That might make it run cooler. Worth a try. Part of my problem might be the fact that it's already getting hot here in SoCal. If things get out of hand I'll arrange to have a quiet fan running behind it.

John

[TomMcNally]

cool it down like Sal did with a Dynaco SCA-35



The paralleled windings should help. A quick spark won't hurt anything !

[katabatic]

Beautiful, John!

[croudyj]

Thanks, katabatic.

Tom: Ha ha ha -- that's a bit over the top. I might put a small computer fan behind it. I still don't know if that kind of heat is acceptable. I estimate it gets to about 140 or 150F after 2 hours. The 10-second finger test is a bit too much for comfort. I paralleled the 6.3v secondaries, but it didn't make a difference to the heat. However, the pilot light is now stable. I don't know if that's related.

The chassis also gets quite warm and I noticed while testing that the CL90 gets very hot indeed. Is that right? Is it supposed to have a heat sink or is it happy to get that hot?
This heat makes me pretty nervous. I keep expecting something to blow up -- I am a nervous type as it is

John

[soundbrigade]

The only thing that really concerns me now is the metalwork. I'm much better at soldering than I am with power tools. I'm thinking of using the 12 x 8 x 2 black steel Hammond chassis but I don't know how I'm going to make those large holes. I only have a battery powered hand drill. Is there some kind of special bit I can use or do I need to buy a whole new tool for punching steel?

Thanks again,

John

If you check www.vt4c.com, you will find a sort of drill that looks like a router tool. They come in sizes especially made for varous kinds and sizes of tube sockets.

[croudyj]

Thanks Magnus. That site is a bit weird! Well, I think I can stop worrying and just enjoy this thing. Of course the CL90 is supposed to get hot, that's how it works! I tried pointing a fan at the transformer and it's amazing how it gets rid of almost all the heat. The chassis still gets warm near the tubes but I'm sure this is normal.

I think that's the end of my Clementine Confusion. Thanks again to all those who helped me get this done. I'll stick around and see how other people get on. It's always nice to see pictures of new builds.

John

[TomMcNally]

The best way to cool a tube amp is to use a device designed for that purpose back when everything had tubes. Now manufactured by Comair-Rotron, the Whisper fan is almost silent, and moves a good amount of air. Get the real thing. I've seen them last over 10 years running 24/7. Keep in touch John show us your future projects. You need to get your moneys worth out of that 1 1/16" Greenlee chassis punch.