My latest acquisition.

Vibro Champ Update

The chassis prep is nearly complete. I have pots nearly all selected. I am adding push-pull pots to enable switching for tone stack and feedback loop. I've settled on a PS design with the help of the PSU design software from Duncan Amps. This allowed me to make use of a 4-part electrolytic capacitor. I had hope to use a 5.5H choke I pulled from a Knight-Kit, but an over zealous drill operator (guess who) over penetrated while drilling pot holes, and wrecked the choke. Import stuff: pilot light will be green. The 7C5 tube base had to be move from bottom mount to top mount. This 7C5 will be wired in parallel with the 6V6, which will allow "either/or" operation. Hope to have chassis fully loaded by end of August. If you get this update as an email remember to go to the blog to see full size photos.

Vibro Champ Clone

I've decided to postpone the Frankenstein amp (Conn 6020) and pursue a Vibro Champ (AA764) clone. Like the Frankenamp I have all of the parts that I need, but I believe the Vibro champ will be easier. With the other projects I have going I think it is a better fit. I have two solid state amps that will get attention soon. I will say this for the benefit of those who wanted to know how I was going to convert the Conn 6020, I am looking at the Ampeg Portoflex SB12 as a basis. As far as the Vibro Champ, I have one thing to resolve: the power supply. I have been rendering some old Knight Kits and one old Conar kit for parts. I hope to use a pre-Stancor Chicago Standard transformer and a 6X4 rectifier taken from a Knight-Kit O-scope.

Carmen Ghia Goof

It turns out that the problem I've had with this amp hasn't been a bad component but my error.  When I converted the Hammond AO-35 using the Phoenix schematic, I failed to ground a resistor that was tied to the terminal strip on the side of the chassis.  Grounding this resistor solved all of my problems.  My Dad found this problem while we were trouble-shooting this by phone.  Thanks Dad.  Click on the image to see it enlarged.

Frankenstein Amp to be "born"

It has been one year today since I last posted. Since then some caps on the Carmen Ghia have started leaking and producing awful noise. That project will be this summer. Now I am designing a "new" amp to be made from the main amp (model 6026) that came from the Conn Model 542 Minuet organ. What I hope to do with it involves adding a single preamp to drive the two power amps in parallel. The twist is that I hope to tie the two output transformers in series on the secondary side. Schematics will get worked out before November this year. I probably won't finish this until 2014.

Carmen Ghia clone Finished!

After 9 months worth of work on and off, I finally finished building a Dr. Z Carmen Ghia clone. I built it from the old Hammond AO-35 reverb amp, given to me by Ron Ashcraft back on Monday, May 12, 2008. Building the cabinet took more time, effort, and money, than did modifying the A0-35 circuit. I took lots of photos of the entire process. I will put them all out on a photo dump in the future. The amp sounds great but has more gain than I need around the house, so I've swapped the phase inverter tube from a 12AX7 to a 12AT7. The result is a little more clean headroom with a little less noise.
If you receive this blog update as an email, remember to use the link at the bottom of the email to get to the actual blog. Once there you can click on the photos and they will enlarge.

Dayton Hamvention 2012

I went to the Dayton Hamvention on Saturday. Tickets were a steep $25 at the door. My friend Brian landed a BOULEVARD PRINCE for $20. This is a tube powered PA amp from the late '50s or early '60s. As you can see in this photo I got a SHURE SM57 for $10, and a RAMSEY digital multimeter (ohms to 2M!) for another $10. I also bought a pair of 12AT7 tubes. All of these items worked for Brian and I, except for one. I bought a DIRECTV satellite box for $10 knowing it was a gamble. I plugged it in to the satellite dish and it worked, but too well. After it booted up it checked in with the intergallactic command center and then told me that it's registration had expired. In the trash it goes. If you get this update in an email, you can click on the link here and it will take you to the web site where you can enlarge the photo.