Search found 758 matches

by jjman
Mon Feb 25, 2008 8:47 pm
Forum: Trainwreck Discussion
Topic: V4 / 5 1.5K grid resistor wattage
Replies: 9
Views: 1515

Re: V4 / 5 1.5K grid resistor wattage

Normally there should be no current flowing thru the grid stopper so I'm not clear on how the type would affect noise level. I guess the voltage swing can be corrupted by "noisy" resistors? Using a higher wattage resistor in a location subjected to heat is a good idea. Such as across a tube socket w...
by jjman
Fri Feb 22, 2008 5:51 pm
Forum: Trainwreck Discussion
Topic: volume
Replies: 7
Views: 1192

Re: volume

thanks guys, previously i had a marshll TSL100 through a 1960AV cab and that sounded fine at room levels (considering its not a particularly good sounding amp IMO) but that had a master volume and a pentode/triode switch. I am not a fan of low wattage valve amps, i find that they just dont have the...
by jjman
Thu Feb 21, 2008 12:14 am
Forum: Technical Discussion
Topic: What five tools have helped
Replies: 31
Views: 5952

Re: What five tools have helped

benoit wrote:
Mickey_C wrote:Toss the CAD, and get on the Alibre Design bandwagon. Once you do solids, you'll never look back. It's never been cheaper or easier to use!
Google sketchup (http://sketchup.google.com/) is pretty easy to use and is free.
Is Google sketchup free forever or will it expire or something?
by jjman
Wed Feb 20, 2008 2:29 am
Forum: Trainwreck Discussion
Topic: Power Up; Time to push some electrons!
Replies: 59
Views: 7099

Re: Power Up; Time to push some electrons!

Could also be a switcharoo in the PS between B3 and B4 ?

But I'm guessing that slajeune is correct on the 100k vs 10k switcharoo.
by jjman
Wed Feb 20, 2008 2:24 am
Forum: Trainwreck Discussion
Topic: DC idle current flowing thru presence pot for PI cathode
Replies: 2
Views: 639

DC idle current flowing thru presence pot for PI cathode

I'm looking at the Express presence pot and all the dc for the PI's cathode appears to flow thru it. Isn't that taboo? Is it a wire-wound pot? I'm trying to draw it using a 5k resistor for the dc and a pot wired as a variable resistor for the 0.1u cap. I'm thinking the pot would need to be no-load o...
by jjman
Tue Feb 19, 2008 6:29 pm
Forum: Technical Discussion
Topic: When wiring a pot as a variable resistor...
Replies: 6
Views: 1106

Re: When wiring a pot as a variable resistor...

When used in a bias or presence circuit you are "safer" using the "unused" lug for the reason above.
by jjman
Mon Feb 18, 2008 6:01 pm
Forum: Trainwreck Discussion
Topic: Power Up; Time to push some electrons!
Replies: 59
Views: 7099

Re: Power Up; Time to push some electrons!

With no tubes in there DC should be all about the same on all PS nodes, as you are seeing. This is because there's no current flowing thru tubes to drop the voltage down on each rail node. You could check the primary ac voltage coming in to the amp to get an idea of how low the heaters should be. Wh...
by jjman
Fri Feb 15, 2008 6:13 pm
Forum: Trainwreck Discussion
Topic: Transformer Availability?
Replies: 6
Views: 1178

Re: Transformer Availability?

I received my set from toneslut.com last week. They shipped out a week later than originally mentioned. I used the "place order" email link (orders@toneslut.com) on the site and paid with paypal.

Those are some heavy ass trannies! :shock:
by jjman
Thu Feb 14, 2008 9:52 pm
Forum: Trainwreck Discussion
Topic: Heaters.
Replies: 11
Views: 1495

Re: Heaters.

That's why I save pins. Ever since I pushed one out by mistake once.

Never know when you might need one.
by jjman
Thu Feb 14, 2008 9:43 pm
Forum: Technical Discussion
Topic: wire gauge on builds
Replies: 24
Views: 6345

Re: wire gauge on builds

I found the teflon shielded wire to be too hard to strip w/o also stripping the sheild. I like Hoffman for it.
by jjman
Wed Feb 13, 2008 6:30 pm
Forum: Trainwreck Discussion
Topic: Low Frequency Noise (Express)
Replies: 5
Views: 959

Re: Low Frequency Noise (Express)

mumford wrote:.........The low frequency hum is only audible when I'm not playing/unplugged.....
If it hums with nothing plugged in, and doesn't hum when plugged in, the jack is not "shorting" properly when unplugged. Did you use a shorting type jack and ground the shorting tang?
by jjman
Wed Feb 13, 2008 6:11 pm
Forum: Technical Discussion
Topic: wire gauge on builds
Replies: 24
Views: 6345

Re: wire gauge on builds

Only the heaters and speaker see anything close to significant current.
by jjman
Wed Feb 13, 2008 12:47 am
Forum: Trainwreck Discussion
Topic: relationship of cathode voltage to noise?
Replies: 21
Views: 3063

Re: relationship of cathode voltage to noise?

Now that I'm home I can see the scheme. Both v1 plate resistors come off the same PS node and are the same value. The higher v1b K resistor means an expected cooler idle which mean less voltage drop on it's plate resistor. So the v1b plate should have a higher voltage than v1a's plate to some extent...
by jjman
Tue Feb 12, 2008 9:55 pm
Forum: Trainwreck Discussion
Topic: PPIMV ?
Replies: 45
Views: 7764

Re: PPIMV ?

I'm gonna try one in the "Express" I'm building soon. It's not a true "clone" so I'm not subject to the negative karma from a PPIMV right? I read (here) that the Express OP tubes clip 1st, then the PI, then the 3rd stage. So I figure I could let the PI clip 1st, then the 3rd stage by using a PPIMV a...