2) The "Strat-friendly" switch - put the two halves of V1 in parallel to add a lil' gain and complexity as well as reduce a lil' noise due to common mode noise rejection (move the second stage to V2a, cathode follower on V2b). Nothing new - it's the same thing as presented in many of the Matchless builds (see the Lightning schematic).
Steve Bench did a little article on this...the results may be a bit surprising. The article is here.
I actually did build mine like that (paralleled V1) even though I had read Steve's article beforehand. My intention was to do some testing on my own but I never did. Probably will someday.
2) The "Strat-friendly" switch - put the two halves of V1 in parallel to add a lil' gain and complexity as well as reduce a lil' noise due to common mode noise rejection (move the second stage to V2a, cathode follower on V2b). Nothing new - it's the same thing as presented in many of the Matchless builds (see the Lightning schematic).
Steve Bench did a little article on this...the results may be a bit surprising. The article is here.
I actually did build mine like that (paralleled V1) even though I had read Steve's article beforehand. My intention was to do some testing on my own but I never did. Probably will someday.
RJ sent me a copy of the Bench report - looks like the issues raised by Bench are related to input voltages of 20 or 30V and greater. That's not the case of using the parallel triode in the first gain stage of a guitar amp where voltages are typically less than 1.0 V.
1) In RJ's picture, there remains the opportunity to add the "Chime" switch - inserting the bypass cap on the output cathode resistor.
2) The "Strat-friendly" switch - put the two halves of V1 in parallel to add a lil' gain and complexity as well as reduce a lil' noise due to common mode noise rejection (move the second stage to V2a, cathode follower on V2b). Nothing new - it's the same thing as presented in many of the Matchless builds (see the Lightning schematic). TubeDogSmith may have hardwired it on his early Rocket build as I recall.
Hmmm - Zippy was kind. I would've titled that post "what happens when you forget the cathode bypass caps"... The shocking news is that the sound really didn't change all that noticeably when I added them in. I'll keep playing with it but I'll say I was disappointed that I didn't hear more.
I went ahead and did the parallel gain thing... the jury is in session.
rj
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RJ Guitars wrote:I went ahead and did the parallel gain thing... the jury is in session.rj
"The Jury" wants to hear his Strat and some P-90s through that amp.
I'm with ya, I thought we'd hear a lot more from the bypass cap on the outputs but it was pretty subtle. But, as my friend in Texas would say, that amp ain't no dawg.
1) In RJ's picture, there remains the opportunity to add the "Chime" switch - inserting the bypass cap on the output cathode resistor.
2) The "Strat-friendly" switch - put the two halves of V1 in parallel to add a lil' gain and complexity as well as reduce a lil' noise due to common mode noise rejection (move the second stage to V2a, cathode follower on V2b). Nothing new - it's the same thing as presented in many of the Matchless builds (see the Lightning schematic). TubeDogSmith may have hardwired it on his early Rocket build as I recall.
Hmmm - Zippy was kind. I would've titled that post "what happens when you forget the cathode bypass caps"... The shocking news is that the sound really didn't change all that noticeably when I added them in. I'll keep playing with it but I'll say I was disappointed that I didn't hear more.
I went ahead and did the parallel gain thing... the jury is in session.
rj
In the Dan Torres book (not exactly in the same category as The Bible or The Koran) he says that the cathode resistor bypass cap is mainly required if the output tubes are not well-matched. I've always used them, although sometimes I'll wire them up to a switch to select between 25uF or 100uF for a subtle change.
Steve
Last edited by steeve_a on Thu Nov 10, 2011 10:38 pm, edited 1 time in total.
Well, I decided to revive this old thread so that I could add a few more tweaks to the Rocket build options.
I finally got around to tweaking and listening to my parallel gain stage mod. I actually went with some input from Skippy and Blind Lemon (https://tubeamparchive.com/viewtopic.php?t=7493) and adjusted both the plate resistor and the cathode resistor on those parallel stages.
I changed out the plate resistor from 220K to 100K and then split the cathodes altogether. On one side I went with the 1.5K resistor and a 25uF cap. On the other side I also went with a 1.5K resistor but no bypass cap. Seems like it has some good harmonic stuff going on, but I want to play with it a bit more.
I've also finished my Rocket build with cathode biased Octal output tubes. It has it's own thread but it's relevant to this Rocket tweak stuff because it has a bunch of useful mods. https://tubeamparchive.com/viewtopic.php?t=7300
I made several tweaks to this build that are visible in the pictures immediately above and blow.
1) Add variable mid control.
2) Move the cut control wiring over so that it cuts as you turn it up rather than backwards as it was in all my other Rocket builds.
3) Put in balance pot for the phase inverter - Don't bother!
4) Replaced the cap on the 1st gain stage with a 50uF (wanted more low end).
5) Added a gain boost via a switchable bypass cap on the 2nd gain stage (not there yet in the front view photo but added before I took the gut shot)
6) Added a direct line out option.
Hey RJ, looks good. Let us know what you end up with on the cathodes. How the gain and the noise? Try the NFB but if the gain and noise are OK I don't think I'd like the NFB. It'll cut its balls off................
