The Amp Garage

I was gonna say in a tube socket. Last octal based pre I fab'd I used a similar circuit but used a couple 12sl7 with the heaters run series as the cathode bias resistor for the 6l6 pair. Free regulated DC for the heaters, lovely tone but the draw back is warm up time. Second the recommendations so f...

Double check the entire amp pan for loose hardware as well. 67? Original OPT/PT? Give opt a thump test, eyeball the pt for rust. The potting, paper formers and rusty laminations can do weird things with age. I have had to replace the old wax pcb a few times for conductivity issues. Sometimes it impr...

Tektronix 2232 HP 202A Love the old boat anchor HP, gonna have to service the old thing eventually, sin/square/triangle and it's a low freq osc going up to about 1.5 k cycle, puts out enough juice 25 to 50 hz to test speaker resonance. Any basic oscillograph will do for simple tube circuits, good nu...

There's an evolution of design with screen grids and circuit designs, if you look at old schematic for long enough. Picture NO screen resistors and both screens of the P-P pair dressed directly to the center tap on the OPT. They were originally run positive relative to the anode, very early 6l6 powe...

Same amp,... different pre, blues jr has a SS verb and an extra gain stage with master. I like the pro jr for its simplicity, easy mod. Blues jr has the extra tube for high gain mod. You only get a pair of 6BQ5, fine for most things mic'd up, perfect for small venue. You can push them into clip easi...

I've taken to using an dryer heating element, clip on to the needed resistance, simple stupid. Rated to 5k. I know there's bones to pick with it, but heck,... free to cheap.

That a good question, I haven't seen that application, You might be able to get away it by dressing the pentode as a triode, simplify the circuit and still use the tube type. Ef86 pin out has separate pins for g1, g2 and g3. There are alternate ways to treat the pentode as a medium mu triode or a hi...

Plate dissipation,... not necessarily Wrms at output,.. even a pair of 6550 can dissipate 80w at design max, kt88 can go 90w. The max rating for the kt88 cathode is over 200ma. per tube. The current rating of an OPT primary becomes a limiting factor. I've made this very assumption,.. no fun when the...

Holy mosses, your all over it... Double check the the ma. rating of your OPT primary for a max design limit.
If you explore tube multiples p-p, or,.. the higher KT-- 's, the max dissipation can cook a meal and heat the shop thru winter.

Do you have a single generator with enough juice to figure the turns ratio of the OPT?
You can get creative to a certain extent with loading without swapping the iron out, but...
you need the turns ratio to provide the figure.

Okay,... I got digging in the heap and found one. A Sylvania, I can explore in a Champ. I think I have a 6w6 and metal type 6v6 to compare.
I did find a source for 6f6/vt66, metal and G/GT, pairs, quads, and matching. A bit surprised actually, positive motion.

I'm looking at a PT, it'll do 200 ma. at around 330v, a nice low B+ and 100 ma. at 50%. And as the mental mastication proceeds, starting figure just what to do with it. The low B+ allows me to explore power types that typically run from 250v to 300v plate voltage. So I start looking in the RCA appli...

I used a generic "bassman" PT and OPT as a standard bench circuit, a reference point. Its a good approach and saves a lot of time. If you are going to noodle with the high voltage mains with a switch, make sure you use a "break before make" switch, no sense shorting windings on your PT. Have fun wit...

Ahhh.... that aikido pre. Great pre, really good for hifi but not so much for guitar. A bass amp might be the best application, you need the bandwidth and clean drive there. SRPP, MU-followers and cascoded pre are almost too revealing in the mid, high mid and top end. Hi-Watt had a similar approach,...

Yes, this is very true. I like looking for the history, development and application of circuits. This particular is applied directly to a Garnet,..and carries into Train Wreck designs. It also follows into early tube analog computing circuits. The development of "television" led the way for a lot of...