 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
72.201.10.143
I am going to use a Lundahl interstage double secondary transformer (the transformer splits the phase of the signal so a single tube can drive both tubes of the PP pair) to drive a pair of 300B's in PP for the gig boost stage of the guitar amp I've built for my son; assuming line level input to the driver tube (tone, overdrive, reverb, etc, already all taken care of, signal now at line level), what driver tube would be the best choice?All opinions greatly appreciated; I will then ask Lundahl for technical assistance on the final choice and which tx to use and post it here. :)
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
Follow Ups:
More info is needed. But in general you want the Rp of the tube to be 1/10 of the primary L at lowest hertz. A 5842 is a commonly used tube for IT driving a 300B. But a lot depends on what type of gain you have before the tube driving the IT. Don't be afraid to consider triode strapped 6v6, el84, 6l6. If the IT is used as a step up the miller capacitance of the 300B is stepped up by the square of the turns ratio so you want a driver that has some current. But most ITs don't like a lot of current.
Russ
The Lundahl LL1677, which is for SE to SE and for driving the 300B, has a 1:2 stepup ratio, will run 80 ma quiescent through primary, at 80 ma it's at 1.2 Tesla's leaving 0.4 T for swing (I'm assuming 0.8 T for peak to peak); the primary inductance is 24H at - shoot I forget, 30Hz I'm pretty sure - and will put out 410 volts peak to peak.Is this enough? Somehow I didn't get the primary impedance. I will also go on KandK, the forum's U.S. distributor for Lundahl, and see if they have some quick and likeable answers.
Could the 6L6GC drive this IT tx for the 300B? That would be ideal for me, I love this tube, and my circuit is already optimized for it.
Cheers. If I find out anything there I'll let you know, but by all means any ideas you have right now I would treasure, you know that. By the way, can I add on a complicated (maybe not) question?
I was surprised to see that most of the IT tx's were essentially 1:1; this is the only one I saw so far that stepped up. So, I'm confused here. Is the only reason we're using either a capacitor or an interstage transformer to couple a driver to an output tube the expense of an additional power supply? Why not just direct drive? Or does it also have to do with limiting parasitic oscillations and eliminating lots of really high frequency power robbing extraneous stuff? Explanations most appreciated; I AM starting to understand them. Thanks, as always. :)
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
....Lundahl along with current specs (I do remember they list the current max's, will check for the rest of the specs). I really like the idea of using 6L6GC triode strapped as the driver; already like the tube, already getting great sound out of just that, just want more power from a true triode SE, I could breadboard this right on to Max's first prototype guitar amp, it would be quick and easy (except for building the second power supply, which I want to do anyway: full wave LC input critical inductance L but low DCR from center-tapped secondary, two sets of tube diodes in parralel so current surges don't overpower one by itself - by the way, which current-production power supply tube diode do you recommend cost vs. quality?) Thanks!! This is starting to cook!! I will print out the 300B graph today and finally teach myself how to draw the load line for the output tx I'm going to use, and then I'll know the max peak to peak voltage that has to be applied to the 300B for maximum volume, correct?
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
I think the russian 6d22s is still being made. Or you can go with the old 6c*3 family. These diodes are very rugged and I don't think the low DCR transformer nor a decent sized cap will cause them to break a sweat. If you go choke input then your current spikes are eliminated and are not a concern. These are single diodes so you will need a pair....but they have a low enough impedance and high enough current rating that you don't need to double up on them. Watch the tube sockets needed as they aren't the normal types!
Russ
for vacuum tube diodes, and Lynn Olsen published some time ago that they have the cleanest shut-off of any diode - less high frequency garbage than anything else around. Plus they also give a slow high voltage turn-on, allowing the signal tube filaments to warm up before the high voltage is applied. They do have a fairly high filament current demand, though, otherwise, what's not to like?
....tx, (long story I will post in a few days after i get my patent application in on simple idea but i think a good one, will happily share idea with all diy'ers, just want to protect idea), i like putting a thermistor in front of the plate supply tx so the plates come on after the filaments warm up; with these slow turn on diodes it gets even better. thanks for the info.
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
thanks
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
Rad
I have a SE AES/CARY 811 amp which I drive the sv572 output with,you guessed it,6L6gcs. My altec 1570b's which Im modding with Tom Tutay's circuit,Im using 6L6gcs once again.I have thought about using the 300b to drive them but I always seem to end up back with the 6L6.
Mikey
...design this guitar amp around parralelling as many 6L6's as needed for as much power as I want - have given that serious consideration - but I have to confess that one of the reasons I want to build the second prototype guitar amp with 300B's in the output is simply the esthetics of it. The way I'm doing the amp, the tubes are all visible on top under a VERY strong steel reinforced plexiglass cover (with positive ventilation), and the 300B's LOOK SO COOL. I want Max and his friends to go wow over it. Just for the sheer fun of it, and if I do end up making this into a kit I can sell a few of (trust me, I'm not planning to takeover Marshall) the visual wow factor of the amp is an important factor. But right now it's just for fun - and it will be interesting to see if the tone can improve by going from the 6L6 to the 300B; the tone is already so fabulous I'm not sure it can get better - just louder.
"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.
Yes it is........., Because of bieng so hot here I decided to play outside last night & cracked my Soldano & my KT-66 amp to WAY godly levels on a couple 4x10 Marshall 65a/b cabs & everybody in a 10 mile radius got there fill of what I do on the side.. Goldtop & Dimarzio Sd's getting with it.. Would love to see that 300B guitar amp when finished..I am a tone junkie from way back..................
I run 6L6gcs and KT66s in my dynaco st70 with the vta boards and they are such a marvel now that you have a circuit that can drive the tube.Bill Johnson did the same thing when he redesigned the st70 with his circuit and used 6L6gcs and it was quite the amp.
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
