The Amp Garage

I picked up a pair of EV SRO/12's in a Yamaha 212 solid state amp of some sort a bunch of years ago. Running my JTM-45 through one of them sounded awesome. I've still got them somewhere downstairs. They have a little bit of water damage from the surround to about a half inch in on the cone, but it d...

Your PI (V3) grid voltages (pins 2 and 7) look odd. Based on a sample I have of mine and 3 other builders' voltages, grid voltages should be 24-38V. I have been through that phase inverter circuit over and again and I see nothing wrong with it. I swapped in a brand new tube and checked again, same ...

Phil, not related to the question at hand, but the 6SJ7's control grid needs a ground reference.

Matt

xtian wrote:

Reeltarded wrote:Bed pans. Think about it.

The brown sound?

... and smell.

My fingers have become so immune to heat I burned my finger soldering i guess and didn't even notice till I Accidently ripped the blister open at work I knocked a nos 7591 of my bench it bounced 3 times on a tile floor I'm still using it Our cat knocked a KT88 off the window sill onto a carpeted fl...

Something else to look at is the Harmless project over at ax84.com: http://www.ax84.com/static/harmless/harmless_r0.pdf It's just a little single-ended amp using a champ OT as a pseudo-UL output. A couple of guys over there have built them and they're supposed to do pretty well for a low-budget tube...

I picked up a stromberg carlson console stereo that I was going to strip for parts, but it just sounds too good. I don't remember the model, but the power amp in it is an ASR-120 which is similar to the Dynaco ST-70, but with 7408 power tubes (6V6s) and no UL screen connection. It's got some hum in ...

A DR OT should have a 6k6 primary; even that seems rather low for 6V6 Use of an OT with a 4k primary under the normal DR operating conditions may result in the plate dissipation rating of the 6V6 being exceeded. Why is a 4k primary OT being used? The diagram on the mojo website shows a 7kΩ pri...

Thanks for that excellent explanation. I see it now. Before, I'd never use but one OT tap at a time, and make whatever connections were necessary to present the exact correct load to the corresponding secondary OT winding. This new way you explain opens up new possibilities and greater understandin...

............... when using two at the same time, plug a 16 ohm load into the 8 ohm jack and an 8 ohm load into the 4 ohm jack. This works because the speakers are now wired in parallel, making them worth half of what they are ................ A 16 Ω speaker in parallel with an 8 Ω speak...

Normally, that is the effect of a Post-PI MV but in the Spitfire, most of the overdrive comes from the power tubes. There is only one gain stage ahead of the PI so the PI will never clip hard. I once rewired one of my amps to the Spitfire schem, and turning down the PPIMV drastically changed the am...

I've got an H306 that I converted to have a 6G3 pre + 5E3 PI&Power stage. It's one of my favorite amps. Still has the 6SH7 trem that sounds really good. The guts on it don't look that great, but it works. :) First, set up a 3-prong plug and ditch the death cap if it still has it. Hot to fuse to swit...

As wyatt said, PPIMV is usually to get the overdrive from the PI. (Exceptions are things like power-scaling the output tubes only.) If the PI overdrives well, it will add some thickness to the tone. If it isn't designed that way, it can make things sound much worse. Personally, I don't like the soun...

No I was on the DC 1000v scale. Cheap Ideal dmm. Swapped out V1 and V2 for two other known good preamp tubes and walla! I' m rockin' now and all voltages are in line. I think one of the sidea on V2 might have been bad. I tested them on my BK700 and they were good but barely. Hard to test those ax7'...

Switch to a choke instead of a 1k resistor between B+1 and B+2. That will get the voltages on the screen, PI, and Preamp up. I use the standard fender deluxe style choke on lots of my builds when I need one. It's cheap and it works. Get rid of the resistors between the power tube plates and the OT. ...