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Take a look at Don’s new 6C33C amp. The top plate is ABS plastic, the base is Australian Spotted Gum. There is a power tranni for the HT and a toroid for the 6C33C heaters. Two chokes are used to split the HT into two channel PS. Four separate DC supplied lay under the bonnet. This is a three stage amp with 6SL7 driver tubes. The two 6SL7 triodes are linked with a cap but the second triode drives the power tube direct. Each power tube will run up to 220mA but even at 150mA the power tranni gets real hot. Don’s work is ultra neat but I had to correct all the wiring around the 6SL7 for him to get the amp to go. It sounds absolutely fabulous. Has to be Don’s best to date.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
Follow Ups:
that when he builds an amp that he gets it running correctly before going on to another? Seems a lot of the learning comes from correcting the mistakes before you move on. Just a thought.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
What keeps Don busy (in his retirement) is tube amp construct, chasing down NOS 45s or 6A3s or getting a good price for Psvane 300Bs and suitable schematics. He fills in his day bringing all this together to construct an amp. Yes it would be nice if it worked first-up. His age and limited skill for fault finding, schematic following and "electronics sensibilities" often works against him though his wood work and construction is sheer perfection.
I give him points to check and procedures to follow to assist him to fix the amps himself but this never works. It's time for me to assist those who are prospering the art but not always able to bring their builds to final fruition. Time for me to help where in the past I was helped. If I didn't help Don a dozen non-working amps would be sitting on dusty shelves. Right now Don has eight working beautiful amps and three more on the way. Today I took a quick look at his parallel 6C33C which has some serious PS issues. Soon I will help him to get this going too.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
I have lost my glasses so maybe I am misunderstanding here. Are you saying your good freind Don has built you his best amp yet that you love but despite that you felt compelled to come in here and publicly rubbish it and him by saying it never worked properly until you with your superior ability's rewired it? And even though its a great build it still is running red hot?
I am confused because I don't understand why you wouldn't just build your own amp and leave you mate Don to build fabulously stuffed amps for other more grateful friends.
There appears to be some confusion about what I posted earlier so I will try to make the post as clear and as I can with relation to Don's 6C33C amp.
1 - My good friend Don built a 6C33C amp for himself.
2 - The amp failed work and Don could find no reason why.
3 - I volunteered to give Don a hand to make it go.
4 - The driver stage was rewired according to the schematic.
5 - The amp works as it should.
6 - I auditioned the amp and it sounds excellent. Don did a great job.
7 - Don has HIS amp back.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
Thanks!
There are a few names but I would just call them biasing points. As you know you drop a meter into them and a adjust a pot (in the middle) to obtain a certain bias current.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
or test point jacks
Yes probably test point jacks is a better name. There is a 1ohm resistor in the cathode leg of the 6C33C. These test points are wired across the 1ohm resistor. By adjust a 25 turn trim pot the voltage (which is about 0.2V or 200mV) across this resistor varies as the 6C33C passes more or less current due to changes in bias.
The current changes are reflected directly across the cathode resistor (as voltage changes) and can be read off a inexpensive meter from the test jacks.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
Just so he could find them!
Nice amp, by the way.
Just what I needed to know. Thanks!
I didn't make it clear but Don is a fellow tube amp builder who lives near by. He is well past his 60's and has little idea of electronics. This doesn't stop him building nearly a tube amp a month. The last four have not worked on completion and I take them on to get them going. Other amps Don has built are: 300B, 2A3 (stunning sounding amp) an early 6C33C (recently rebuilt), EL34 and currently working on a parallel 6C33C and a 45.
retro-thermionic
http://www.retro-thermionic.blogspot.com.au/
Mongrel Dog Audio
http://mongreldogaudio.blogspot.com.au/
:-)
nt
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