It’s 12:11am, August 12, 2010, and I just gave up doing my College Physics to replace the first stage preamp cathode bypass resistor as noted in V1.3 schematic. I sure wish it wasn’t half past midnight :). I have it on 10° or less volume, and 45° EQ, give or take a degree. I’m just guessing. I really want to crank it up to see if the tone and distortion sounds better. 9-6-2010 – It does need some circuit tweaking. It doesn’t sound good to me after all.
I just had to turn it down some. I can just imagine my wife hearing me play and having a moose because it might wake the babe.
The link is to the circuit design blog. I wasn’t extremely thorough in describing the ins and out of designing because the AX84 project, as noted in the blog, can do a much better job.
I also bought some 6DG6GT tubes…to see if my other tube amp can sound better. At $3.50 each from Tubesandmore.com, I couldn’t pass up a chance at trying it out. I had to buy two Marshall style input jacks for the Marshall repair job so I decided to go in halves for the shipping. I am going to rebuild my first tube amp to make it at least half as good as the new one. Check out my first tube amp here—> Building a Tube Amp from Scratch: Crazy!
I have played the 6DG6GT tube amp described and depicted in the Crazy! blog for hours each week since January 2009. It started to hum really bad a few months ago, even after changing the preamp tube to a 12Av7 tube. That is a low gain tube, and yet the humm is ridiculous!!!
The other issues with this amp is that the power transformer’s screws came loose from the cabinet, and it rolls around. That is bad news if it hits a tube, especially the zillion dollar rectifier tube. That might actually explain why it sounds so bad. It probably cracked an envelope on the power tubes. I shook them just for fun, and something is rattling around in the Tung-Sol one. that’s probably not a good thing.
Anyhoo, I’m going to sign off and play a few more tunes before I pass out from exhaustion. I’ll try to get a video up on the tube for everyone once I crank the volume up and see if I like what I hear.
“It’s more than just a project”… Tonight, it has become an obsession.