OK, I admit I was bored last weekend, the wife and kids where away visiting family and it was to hot to leave the air conditioned shop. So I scrounged up some leftover and salvaged parts and decided to try the Matchless Spitfire circuit. I needed something simple with a max of 4 nine pin tubes to fit in this 7.25"x4.5"x3" cast aluminium chassis. It uses a really small PT from a reel to reel machine, delivering about 300 volts to the plate of the EL84's and gets a bit warm after an hour or so of playing. The OT is from a stereo that was running 6V6's so it a good match for these tubes with a 4 or 8 ohm speaker. I used terminal strip point to point construction and kept most of the components mounted right to the sockets, pots, etc. The controls are volume, tone and master which work well to dial in the amount o ...

Just finished up a the C14 and new circuit I'm experimenting with. It's based on a brownface princeton with a few modifications. It's running 6V6's at about 320 volts on the plates(for approximately 14-18 watts) close to the BFP specs but with a larger output transformer. The phase inverter was modded to a fixed bias design and switches where added to lift the negative feedback (Soul) and disconnect the first preamp tubes cathode cap (Fat). All this results in an amp that has nice warm tone with smooth break up. You end up hearing the 6V6's going into overdrive before the OT saturates. It's kind of a hybrid of a blackface princeton power section with a tweed princeton preamp section, a nice mix IMO. It also has a very lush bias vary tremolo with a standby switch, bias jacks and adjustment pot that are nice modern conveniences. I used this at rehears ...

I finished up the C60 in the industrial powered coated steel cage head chassis. I changed a few things since it was first fired up. I added dual bias pots so the prime old stock KT88's (unmatched) or any other tubes could be dialed in to an optimal range. Removed the master volume, I didn't like the sound of it in this amp. Plus it already has preamp, volume and level controls to adjust the overall loudness as well as a very effective tone stack. The bass, midrange and treble controls really work in this circuit allowing many different tones. The presence and meat (adjustable nfb) do a good job finishing off the highs and lows for the user. I experimented with the preamp voltages and lowered them a bit for a smoother sound. This amp is very sensitive to preamp tubes also, tried a bunch from my stash and ended up with RCA's V ...

I've been working on a new circuit based on the *umble schematics circulating around the net. It's a dual channel switching amp with a clean and overdrive channel. The single white knob is a pull switch that activates a boost by bypassing the tone stack. Resulting nice midrange/ gain boost  that makes leads cut through the mix rather well. I'll probably end up wiring it up to a footswitch along with the channel switch. It also has a switch on the back to disconnect the negative feedback for even more gain and a nice open tone that works well at lower volumes.  I used some salvaged transformers for this prototype that came out of an old Dynaco mono block along with it's choke and KT88 output tubes. I'm still in tweaking stage at this point but it has a nice range of clean and crunch tones with plenty of sustain and controllable feedback. It's going up to Optimus studios next week for a test run through their 4x12 cabinets and hopefully I'll get to hear it in a band situation. More in ...

Here's an interesting repair, we had an Orange AD30TC in the shop that came in dead. It already passed through another local shop without being repaired correctly. I had a blown HT fuse on arrival and since these EL84 amps normally run the tubes hot I figured it was a tube failure. But after pulling the chassis I found a burnt cathode bias resistor and capacitor, as well as a couple surrounding toasted resistors. Replaced them and retubed the power section and all is well. BTW, this is a great sounding amp when set up properly.

It was Marshall week at the the shop this week. I had two JCM 2000's in for a check, retube and bias. One of them was blowing fuses, turned out to be a bad output tube. The JMP 100 watter needed a new input jack and a check and bias.

Just finished up Cam's silverface Bassman mod/ conversion to a AA165/ AA864 hybrid. We did a full cap job and service to amp while it was in here. Also included a half power switch and a presence boost switch on the back in existing holes. Plus a mid control for the bass/ tweed  channel in the #2 input hole. Check to service page or email me for more info on this mod. Or check Harry J. gear page for sound clips of the one I did for him.

http://www.harryj.net/gear_page.html

Got some clips done of the C35. Sound recordings and video recordings, so go to our Clips section to see them (some are still in edit). Everyone remarked how great the amp sounds, I think so too!

I finished up the Purple C35 this week. While listening and tweaking it I decided I liked 6L6's in this one. They seem to have a nice clarity to the low end and still crunch up nicely in the low power and tweed modes. At a high volume test I weeded out another bad preamp tube, this time it was a NOS Jan 12AT7. It was breaking up at the end of loud sustained chords, but with a new one in there all is well. A quick list of features on this one is as follows.

• Half power - pentode / triode switch which works very nicely in this amp to know down the volume enough to crank the amp into overdrive.
• Pull switch on the volume pot that changes the preamp voicing from blackface to tweed.
• Soul switch disconnects the negative feedback for a gain boost that ...

I finished up the chassis assembly on the C35 today. All went well on the initial test except one bad preamp tube. I added an extra feature while building this one, it is a dwell control for the reverb. It will have to be a set and forget type of control as it's located on the bottom of the chassis. But it does let the owner dial in his reverb preferences. Next is tweaking and testing, then final assembly.