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Old 12th March 2011, 04:53 PM   #1
cricha5 is offline cricha5  United States
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Join Date: Jan 2011
Default Two amps done and done!

I completed the DC coupled SE amp about a week ago. Built out of spare or pilfered parts and using a 5y3 rectifier with a 6ea7 dissimilar triode and an ipod input going from stereo to mono. It was destined for my kitchen, so fidelity was never a top priority. However, I must say it sounds loads better than the basic computer 2.1 system, even in mono. The interesting thing about this one is the direct coupling between the stages. Less components in the signal path, but omg does it waste heat through those power resistors, about 10 Watts. Those heat sinks were not in the original plan, but they are definitely necessary.

I just built the single ended ultralinear 5y3 rectified 6sl7 6v6gt tube amp. I have been waiting over a month for the transformers and they just came in yesterday. I have to say I really like Edcor's quality and price, just not their shipping time. Sounds super awesome betterthananythingyouhaveeverheard, but I might be biased having built it. It's based on the Boozehound design, but I changed the cathode bias due to larger than expected B+. The power supply design he had showed ringing in psud, so I changed that too. I also switched it to ultralinear instead of triode strapped. Wow, did that wake the amp up. Big difference. The original design did not have the front plate, everything was supposed to be mounted on top. The problem came when I received the 100uF 500V cap. That thing is huge! I had no idea from the picture on the website. It caused me to rearrange the whole layout since I had already built the box and top plate. The 6v6's are running a bit hot, but I don't want to lower the load line any more than I already have. They're cheap tubes, I don't mind if they burn up soon.

The amp has plenty of volume for the room its in, so I'd like to put the load line of the 6sn7 hotter and more in the linear region, but I keep reading and people keep telling me that the plate load resistor needs to be at least 2-3 times the internal resistance of the tube. Can anyone derive this rule of thumb or point me to a new reference that does?

Something that really surprised me about both of these amps is that there is no hum at all. I figured my first amps would have problems like that from lack of experience, but I guess I either lucked out or planned well.

Next up will probably be a push pull amp for a sub-woofer. That should be an interesting change from this singe ended madness.
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File Type: jpg 6v6_bottom.JPG (143.2 KB, 192 views)
File Type: jpg 6ea7_bottom.JPG (122.5 KB, 185 views)
File Type: jpg 6v6_top.JPG (113.9 KB, 189 views)

Last edited by cricha5; 12th March 2011 at 04:55 PM.
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Old 12th March 2011, 07:12 PM   #2
Helmuth is offline Helmuth  Netherlands
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recent projects :OB-mk1 /fatboy / monitor-xl / Horn-AM / dappolito / td124-mk1-rb301 / Hybrid-pse / Vfet
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