Ok- so here is the thing
I am building a homebrew based on a Traynor YGM2. It's a push- pull 2x el 84 design with a 12ax7 pre-amp, (both triodes) and a 12ax7 PI. It also uses half a 12ax7 for a tremelo circuit. The other half is just sitting there and I am from Dutch background. We don't enjoy wasting things!
So the Dutchman on my shoulder says: switch the unused half if the 12ax7 in and out in parallel. I believe it can be utilized as a sort of boost to make the pre-amp tone a bit thicker and crunchier. -I want to do this as a simple toggle- atrangement. The noob in me says: how do we do this??
Here is the request if anyone is willing: Could you please refer me to a schematic to explain how to do this?
Or a verbal description if there is no scem avail. Also if possible, can I verify what the effect would be?
Thanks in advance - the folks on this forum are fantastic!
Look up 18watt.com for the downloads sections. I believe it is the III Lite that has a nice arrangement of using the input jacks to switch between single and parallel inputs. Very clean implementation.
Some of the Matchless amps used the parallel configuration too - don't know if they were going after a bit more gain or hoping to get more character in the sound.
I use the Matchless Lightning arrangement (parallel triodes into cathode follower into PI) with a cathode bias 6L6 pair. Very fat sound, though I admit I've tweaked my version for more mojo than the Lightning.
Now I'm considering building one in which the input goes into both halves of a 12AX7, then out separately--one to the rest of the preamp, the other side into a reverb circuit. That way the reverb isn't a parasite on the main flow of tone.
I love the Lite 3- what an elegant little design, and so simple!
Just waiting for some parts and then gonna fire up the soldering iron.
Most of the pre-amp board is done, just wanted to know about the parallell config.
I'm planning to do a closed cab combo design with the "shelf" between the speaker and the Chassis like the original Traynors used to have.
I love the Lite 3- what an elegant little design, and so simple!
Just waiting for some parts and then gonna fire up the soldering iron.
Most of the pre-amp board is done, just wanted to know about the parallell config.
I'm planning to do a closed cab combo design with the "shelf" between the speaker and the Chassis like the original Traynors used to have.
Best regards,
Markus V
I like the closed cab idea What kind of speaker are you going to put in it?
Question to everyone on the closed cab idea..
Do you think there's any benefit using a smallish sealed cabinet with a no NFB amp? Wouldn't it offer a little more control (damping) on the low end due to the acoustic suspension design? I would think yes, to a certain extent, depending on the parameters of the driver and box.
I'll be honest to say that I really don't know how a closed cab would interact with *no NFB as opposed to *with NFB.
Any insights?
I am considering 2 options
a) 2x 10 inch eminence alnico's (Legend) I already have that config in a closed back extension cab and I love them
b) 1x 12 Private jack or Governor
The dimensions of the speaker cab part of the combo will be pretty much Golden ratio so I hope that with closed back design they will behave well.
The dimensions are rougly 9"deep x 14" high x 22" wide.
With the chassis section on top this amp will be pretty much square if you look at it from the front
My aim is to obtain a really tight bottom end and some compression at higher gain settings amongst other things.
I welcome any input- this is really a prototype of (hopefully) a small production run for the future
Speaking of parallel triodes, I tried something new this weekend. I was working on this amp that a guy had given me to tweak--make it sound better so he could sell it. Well, I previously added a gain stage with an unused triode section. However, that resulted in too much PS noise. I went through and checked all the caps, beefed up the filtering, and still couldn't get it as quiet as I'd like.
So I decided to try putting that triode in parallel with the other first gain stage. I had already put a local NFB loop (22m/.047 mF) on it, and I wanted to keep it. However, I didn't like the idea of it on the "first" gain stage, lest the cap fail and B+ gets put on the grid...
What to do? Well, I linked the two triodes' grids via a .022 mf/630V cap as an extra safety measure. With the two triodes in parallel the amp was fatter and a bit browner and more agressive than stock.
And, since parallel triodes have good noise rejection, you have to crank the amp to "9" to hear any appreciable noise at all.
So, there ya go.
Also, yesterday I biased a guy's 1967 Marshall PA 100. Very cool piece of amp history. Twin full bridge diode rectifiers and monstrous amounts of filtering. At some point in its history V1 had been rewired to the Normal and Bright specs of a Plexi. Unfortunately, he got to my house so late that I couldn't do the job and take pics of its guts before I had to take the kids to the movies!
What kind of speaker are you going to put in it? 