Erik Mandaville Posted June 16, 2003 Share Posted June 16, 2003 Well, wouldn'tcha know it! "Crunch, crunch.....snap, crunch," was the sound I heard as I sat at my little workbench installing new filter capacitors on my preamp. "Neat!" I thought, "Kiko (1 year-old pooch that has to get new hips in 6 months)brought in one of his rawhide bones to chomp on while I'm working. In walks Marie after her morning bike ride, and says firmly, "Kiko, NO!!!" His ears flop down, and he quietly walks out of the room. I turn around with soldering iron in hand to see what he had been chewing on. It wasn't a bone at all, but a 10mf Solen capacitor. It had be chewed to pieces! "Ah well," I thought, "...at least he didn't swallow any of it!" Then last night, we hear a familiar platic crunching sound again in the hallway. There were three more Solen caps on the floor, all chewed to pieces! This little fella had to have gotten up on my workbench chair, and taken the capacitors off the top. They were in a convenient clear plastic bag, so he got a whole cache, not just one! Didn't eat any of them, just chewed them up. So I re-order the whole bunch again today But! JFL (Jean-Francois Lessard)sent me a link to a great place here in Texas that sells not only some pretty neat tube amps, but also some very fine chassis for a reasonable cost. My always very honest and awesome wife said, "Jeez! you need to get some of those instead that cheapo Hammond box you got! They look TONS better! Get two to make monoblocks, instead of a single stereo amp." So this is in the works, I guess... My 'cheapo Hammond box (It's really not that bad, but does sag ever so slightly under the weight of the big power transformer)had already been punched for two rectifiers, the 2A3s, the driver stage/s, and big filter capacitors, So maybe I'll just keept it for another project. I'm still waiting for the grid and plate chokes to come from Magnequest, and those should be here fairly soon, I think -- I hope And! I can't remember who it was who said he connected his CD player directly to his amps, but I tried that this weekend with my new, ultra-expensive KLH DVD player (which I got 'cause it has a decent DAC for strictly audio use). I had to make some shorter BNC interconnects -- I've got BNC input jacks on my amps, and used the remote for the DVD player to control volume. This was not bad at all -- in fact it was quite good! I used to use a passive preamp that I made on the cheap (as usual, with an even more of a 'cheapo' chassis from Radio Shack), but a furniture move required moving the system around a bit. My Moondogs are very nearly dead quiet -- just the slightest hiss from the Lowther and La Scala chirper (I mean, tweeter!), and so background noise was very, very low. It was much better sounding than my virtually antique and problematic Denon player used to be when used the same way. MUCH better, in fact. I think it was Leok who said some time ago that CD players have changed quite a bit in the last several years, and this I found to be absolutely the case. What I may do, though, use a transformer-based attenuator (Sowter makes an interesting looking one)to control volume and switch between sources, of which I have three -- the third being an old Heathkit AM tuner. Wish I had and knew how to post pictures of my projects -- one day I'll learn how! Edster has offered to help me with this, which is nice of him. Take care, Erik Quote Link to comment Share on other sites More sharing options...
AnalOg Posted June 16, 2003 Share Posted June 16, 2003 Whats the name and/or website that supplies the chassis? tom Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted June 16, 2003 Share Posted June 16, 2003 Erik, Too bad about the Caps. - At least they weren't the Paper in Oil Silver variety I can sure help you with the Pics. Lord knows you helped me enough with my Moondogs! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted June 16, 2003 Author Share Posted June 16, 2003 Thanks, Kevin! Tom: that tube audio site is: www.iagaudio.com Hey: Any more work on the DC heaters for your Foreplay? (I can't believe you're selling your Paramours!) I'll bet the Dynacos are great, though. Quote Link to comment Share on other sites More sharing options...
AnalOg Posted June 16, 2003 Share Posted June 16, 2003 Hi Erik, I installed a 6v 800ma, wall wart from rat shak directly to pins 4-5 & 9 if memory serves me. Much better now, very quiet & blacker background, I also perceive better microdynamics. After I did this I wondered if going with what you recommended with better parts would take me to a higher level in sound quality. Thankx, Tom Quote Link to comment Share on other sites More sharing options...
AnalOg Posted June 16, 2003 Share Posted June 16, 2003 Erik, On the amp issue, I've aquired to many of them. I decided to go with the Marks because they give the best all around performance for me. At low volumes they can be sweet like SET (sorry guys, it's true to my ears), crank the attenuators clock wise and your ready to rock. Tom Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted June 16, 2003 Author Share Posted June 16, 2003 That sounds neat Tom! Your description of how you wired your heaters on the 12AU7s is curious is to me, though... Pin 9 is the heater center tap. Pin 9 should be connected to a lead which feeds it about 50 VDC (the schematic specifies 49 volts, if I remember right). And this is on only ONE of the two tubes. The heaters (pins 4 and 5)of each tube are connected in parallel, and thus a single pin 9 is common to both. Are you using a different tube, maybe...with a 6 volt heater supply wired in series? I'm interested in what you're doing, Erik Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted June 16, 2003 Author Share Posted June 16, 2003 Hey, no apologies needed!!! I have a couple of push pull amps myself that sound great. If you're getting the best of both worlds, then you've got it made! Erik Quote Link to comment Share on other sites More sharing options...
AnalOg Posted June 16, 2003 Share Posted June 16, 2003 Pin 9 is the heater center tap. Pin 9 should be connected to a lead which feeds it about 50 VDC (the schematic specifies 49 volts, if I remember right). And this is on only ONE of the two tubes. Erik, I don't claim to now what I'm doing 100% of the time, but I'm pretty good at following directions. As per mod I picked up on the bottlehead forum. You leave the above described intact, snip the green wires comeing of the transformer which feed 6.3vac 600ma to 4-5 & 9. Check for proper phase on the wall wart, negative going to pin 9, the other to pins 4-5. Then of course you have your jumper wire at 4-5 & 9 going to the other tube sockets 4-5 and 9. You end up with DC on the filaments. I think.LOL Tom Tom Quote Link to comment Share on other sites More sharing options...
prodj101 Posted June 16, 2003 Share Posted June 16, 2003 you should get some bigger caps, charge em up than let your dog have a go at them Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted June 16, 2003 Author Share Posted June 16, 2003 Tom: I was just curious about what you were doing..... BTW: Since you cut the green filament wires, go back and check your plate and cathode voltages. You will find B+ may have gone up as much as 15 volts because of clipping those green wires. You can bring it back down to within a few percent of the spec 157VDC by adjusting the dropping resistors in the CRCRC filter section. But aside from all that techno-stuff, I'm glad it's working for you! Erik Quote Link to comment Share on other sites More sharing options...
AnalOg Posted June 16, 2003 Share Posted June 16, 2003 Since you cut the green filament wires, go back and check your plate and cathode voltages. You will find B+ may have gone up as much as 15 volts because of clipping those green wires. Erik, Is this a bad thing, will it do harm to tubes and/or system? Will it better the sound quality to get it closer to specs? Give me your feedback! Thankx Tom Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted June 16, 2003 Author Share Posted June 16, 2003 Tom: The reason the plate voltage goes up -- actually all the voltages, since they all come off the same B+ rail -- is because the stock transformer no longer has to provide heater current. 157 on the plate is already pretty low for 12AU7s, and 15 more volts won't do anything. I just like keeping things according to the schematic. You may find that bringing the voltage down makes the preamp quieter, still... Just make sure you discharge those caps before you mess around in the power suppply. Use a power resistor of about 100ohms/volt to bleed the capacitors safely... Quote Link to comment Share on other sites More sharing options...
DRBILL Posted June 16, 2003 Share Posted June 16, 2003 Oh, yes! We have Boston Terriers. You would be amazed at what they have nabbed and eaten off my bench. And ever more amazed at what they have passed! DR BILL Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.