leadfootdriver wrote:Thanks for the heads up! Maybe I could use a DPDT to switch in a choke with the tube rec???
This stuff can get crazy with the constant mods...
Yes, modding can get crazy indeed. I went through a phase where I had a lot of mod switches on my amps. I think this helped me to answer the questions of what something sounded like over another and while it was very useful for where I was in ampbuilding, ultimately, I have adopted a more simplistic approach. I was told early on by Mark Huss (something of an 'involuntary' mentor to me -- thanks Mark ) to voice the amp once and voice it right the first time. This is sage advice. In other words, mods are nice but invariably, there are very few that are worth doing and as players we most often find one setting and leave it there. I have also found that more switching in the signal path sometimes can degrade the overall tone or lead to instability. I had to find this out firsthand even though I was told up front that this would be the outcome.
With the Trainwreck design, its virtue and purity in tone is due to that simplicity. I get that now having built and heard a Liverpool first hand. I can't believe the clarity and lament what I've been missing all this time! But I can't help but feel that I had to go through all that I did with other builds and experimentation to arrive precisely where I am right now. I'm looking forward to building my Express and Liverpool!
Sorry for the philosophical digression!
No problemo. Thanks for taking the time!
I've never heard or played a TW in person. I plan to do an Express after the new year. I'm working out the details here on the board, so I can go into the build with a game plan.
leadfootdriver wrote:Some of these power transformers come with the tube rec taps. It seem like it would be easy to add a DPDT toggle so you could select tube or silicon rectification.
Colossal wrote:I implemented such a switch on a 6V6 Plexi build. Academically, it was interesting to be able to hear the difference between tube and solid state but ultimately did not find the mod very useful as I preferred the solid state dynamic (higher voltages) over the tube rectifier and just left it. I love a good tube rectifier though so I think it depends on the amp.
As far as usefulness I agree with Colossal(depends on the amp)...although I like the tube rec sound better in the bat cat build.The SS switch does seem to give that design a nice aggressive tone change. Although I have not used one, maybe try the solid state plug as Reeltarded suggested.
My experience with the Bad Cat schematic was the opposite. I was using EL84s and the tube was night-and-day better. It might be because that tube is so sensitive to the sweet spot on voltages that I needed the voltage drop to make it right. Not a terribly useful mod and uses a lot of real estate. Switchable fixed/cathode bias is a better choice. sh
Luthierwnc wrote:My experience with the Bad Cat schematic was the opposite. I was using EL84s and the tube was night-and-day better. It might be because that tube is so sensitive to the sweet spot on voltages that I needed the voltage drop to make it right. Not a terribly useful mod and uses a lot of real estate. Switchable fixed/cathode bias is a better choice. sh
I used EL34's(JJ 6CA7)T Hot Cat design...and it's a screamer with a soft sided clean...both tube and SS sound good with it
"Switchable fixed/cathode bias is a better choice" is a cool idea.
leadfootdriver wrote:That looks cool. What about the GZ34, and the 5U4G? Could I just plug and play any of these along with the 5Y3?
You can swap rectifiers so long as a) you do not exceed the tube's voltage and current maximum and b) your tube rectifier winding can deliver the necessary current. A GZ34 has the least voltage drop, followed by the 5U4, then the 5Y3 which drops quite a bit. However, the 5Y3 can't deliver as much current as the other two.
I take that back, because I didn't take the filtering into account. I would blow up any of the rectifiers. The Express has 2-40uf's in parallel for 80uf right after the recs. POOF...
leadfootdriver wrote:I take that back, because I didn't take the filtering into account. I would blow up any of the rectifiers. The Express has 2-40uf's in parallel for 80uf right after the recs. POOF...
The Express does not have a tube rectifier because this would affect the overall voltages, changing the dynamic compression characteristic which is in part responsible for the amp sounding/playing the way it does. The Express should be solid state rectified so that no ghost noting or motorboating occurs because of compromising the reservoir capacitance value in order to use a tube rectifier (I am sure Ken tried this already). The Komet K60 does use a GZ34, even with the high amount of filtering (80uF), so it has been done.
High capacitance in excess of the recommended limit in front of a tube rectifier will not necessarily blow the tube outright (unless it is just ridiculously oversized capacitance). This limit depends on the peak current the tube will be expected to deliver. So if you are using fairly high or (slightly) over the recommended limit of capacitance but at a low current maximum, the tube may be ok. Still, I doubt anybody blew up a tube by following the RCA Receiving Tube Manual The only tube I would probably try this with is a real Mullard GZ34 which would probably take the abuse. But I wouldn't because they are expensive and increasingly rare.
Colossal wrote: The Komet K60 does use a GZ34, even with the high amount of filtering (80uF), so it has been done.
TW Rocket too; jus' sayin...
D'oh! (slapping forehead) Good call Martin. The Rocket is a good example where even though the reservoir capacitance is 80uF and above the recommended maximum, the DC load current and ripple current is within reason and is probably not gonna hammer the rectifier.
) to voice the amp once and voice it right the first time. This is sage advice. In other words, mods are nice but invariably, there are very few that are worth doing and as players we most often find one setting and leave it there. I have also found that more switching in the signal path sometimes can degrade the overall tone or lead to instability. I had to find this out firsthand even though I was told up front that this would be the outcome.
Good call Martin. The Rocket is a good example where even though the reservoir capacitance is 80uF and above the recommended maximum, the DC load current and ripple current is within reason and is probably not gonna hammer the rectifier.