Another Liverpool question

[Tdale]

As I understand it, each Trainwreck is made differently. But I have always heard that you need at grid resistor for the preamp, but the Liverpool doesn't always have on on the input of the first tube.

But on one of the layouts, there is a resistor on the first grid, but none on the second grid?

Is there anything that's "right" on this amp? Should I go for grid resistors on both grids, on just one of them...or none?

Tommy

[CaseyJones]

As I understand it, each Trainwreck is made differently. But I have always heard that you need at grid resistor for the preamp, but the Liverpool doesn't always have on on the input of the first tube.

But on one of the layouts, there is a resistor on the first grid, but none on the second grid?

Is there anything that's "right" on this amp? Should I go for grid resistors on both grids, on just one of them...or none?

Tommy

You're talking about a "grid blocker". Fender used 68k, Marshall copied Fender so they also use 68k. Fender and Marshall wire their inputs so one input goes through the 68k, the other goes through 68k divided by 2. The closest readily available resistor would be 33k. Values between 33k and 100k between the input and the V1 grid are common.

They're called "grid blockers" because they block a bit of RF and crosstalk. Mr. Fischer didn't believe in them so you won't see them in Trainwrecks.

Your replica isn't a Trainwreck no matter how accurate a copy. If you want to save yourself some aggravation at least use a grid blocker on V1. Don't work it backwards and think that because your Trainwreck replica doesn't have a grid blocker you can get away without one in all of your amps.

[skyboltone]

++1 on Brother Jones comments.

[Tdale]

Do we know why Ken Fisher got away using no grid blockers, and most other amp builders need them?

There is no harm in trying without any blockers, just to check how it sounds, right? If it's no good, I'll just add a resistor..

Tommy

[dartanion]

Certain amps don't need grid stoppers, others do. It's a crap shoot at best, but Ken tried to eliminate anything that he thought would be a tone suck in the Wrecks. Ken also spent a good deal of time dialing in each amp, so I would imagine that he did whatever he thought was necessary to meet his design requirements.

This is sort of like the no attenuation between gain stages. Hard to do without attention to detail in your layout. Easy to do if you dump gain between stages to make it stable.

[CaseyJones]

I see similarities to motorcycles in Ken's amps. Rumor has it Ken was into old BSAs, there's a Quixotic old scooter for ya! Never mind that I have one in a spare bedroom in big chunks, another "someday" project. Don't worry, there's plenty of shit that runs in the garage! Anyone know what H.A. Dumble rides?!

Anyway, here's the motorcycle analogy: There's a certain school of thought that stipulates that the bike should be stripped down to the bare essentials, no crap on there that doesn't earn its keep. Even better if one part or one fastener can perform multiple functions, that cuts the parts count even further. A Dumble by comparison is the Honda Valkerie of amps (sorry Howard, I mean H. Alexander), it will do a lot but it's heavier and more complicated than it needs to be to perform any one task well. Besides functioning as a two wheeled Buick Electra so to speak.

SO in that light take another look at an Express. Anything that could be left out... was left out. Careful layout and lead dress negates the need for grid blockers.

[Tubetwang]

even with the grid stopper...it is still a great amp...

[Doug H]

s there anything that's "right" on this amp?

I think the answer is what is "right" is what sounds "right" to you and what works. Grid stoppers can effectively tame oscillation and RF. They can also provide a little high freq rolloff. Use them if you want or don't use them. The choice is yours. Don't worry about what other people think.

[CaseyJones]

The choice is yours. Don't worry about what other people think.

Sure, no argument from me on that. I'm not prejudiced... I give everyone an equal hard time about everything!

Seriously, my point is to understand what it is and why it is that way. Industrial design is some of the best art... if you know what you're lookin' at the designer's intent is very clear. It's like takin' a trip to The Phillips and embossing yer butt cheeks into that worn leather bench in front of The Boating Party. It sure is purty but so are the paintings they sell for $100 each over at The Holiday Inn. The Picasso hangin' across the room doesn't get anywhere near that kind of attention.

You may "meet the nicest people on a Honda" but I wouldn't suggest that you ride one to Sturgis. I mean, -I- would but that's because I really and truly don't give a rat's ass about what other people think.

[Lonely Raven]

Since you brought it up...I have a friend that took is Suzuki TL1000 sport bike (bright red and silver) to Sturgis this last year. He said he expected more grief, especially at random gas stations along the way where you typically run into A-holes...and he said *everyone* was very accepting of him and didn't care what bike he rode...just that he rode and quite well at that.

It doesn't hurt that he's a cool dude and gets along with everyone.

[jaysg]

Most of those amps with 68K's in parallel (34K) are done with single conductors. KF used coax with a grounded input jack. TW inputs would be problematic with a Cliff jack and one wire to V1.

[CaseyJones]

Since you brought it up...I have a friend that took is Suzuki TL1000 sport bike (bright red and silver) to Sturgis this last year..

It must be the "V" motor. Seriously, when I see a Rebel Without A Clue on a Honda-Davidson (a Japanese Harley copy like a Shadow or something) sometimes -I- want to kick his ass! It's about pretending to be something you're not and not even bein' cool enough to fake it. Some jerk in a plastic Nazi helmet and a cutoff denim vest just doesn't do it for me. I used to dress up like that for Halloween when I was 8 years old!

He said he expected more grief, especially at random gas stations along the way where you typically run into A-holes...and he said *everyone* was very accepting of him and didn't care what bike he rode...just that he rode and quite well at that.

It doesn't hurt that he's a cool dude and gets along with everyone.

I bought an old Triumph from some back alley bad-asses in Somerville a while ago. These guys were draped over bench seats salvaged from various old cars and drinkin' beer in the Summer sun. This was behind an apartment building, one of those places that has a dozen or so peeling wooden garages out back. It was like the freakin' "Price is Right", an outlaw (the town doesn't know about it) motorcycle shop was concealed behind two of the doors, then they rolled up a couple more doors to reveal some high end customs. "My" Triumph was stashed in one of the bays with a stack of old Harley parts, the guy told me to get it out of there right quick (in more colorful language) before they beat it flat and burned it because it wasn't a Harley!

You'll have that. It helps to know what it is and why it is.

[Tdale]

It's interesting, and a bit hard to understand, to see this debate about Honda/Harley etc.

Coming from a country that doesn't make either cars or bikes, all cars and bikes are imported, so it's not really an issue here

Tommy
Norway

[Doug H]

Sure, no argument from me on that. I'm not prejudiced... I give everyone an equal hard time about everything!

No worries here. I don't even remember if I read your post.

I wasn't referring to anyone specifically.

[CaseyJones]

It's interesting, and a bit hard to understand, to see this debate about Honda/Harley etc.

Coming from a country that doesn't make either cars or bikes, all cars and bikes are imported, so it's not really an issue here

Tommy
Norway

Yeah Tommy, I apologize for yankin' your post off-topic but it's what I do best!

Scandinavian bikers are among the most serious on the planet as near as I can tell. You're right, they're not picky... everything is an import. I think they're as serious as they are because the ridin' season over there is only about two months long, less than that if the sun goes behind a cloud! It's cold enough to freeze the balls off a brass monkey for six months of the year. What to do, then? Sit in the sauna and think about how hard you're gonna ride durin' those two months!