Metropoulos Forum

Hello everyone, this place is awesome. I built a 45 kit from George awhile ago and love it. I used Larrys grounding and amp is real quiet. Does anyone know about changing the layout by moving resistors on board to lengthen plate and shorten grids of output tubes? I'm sure someone here has read the same book I did, but did you get hosed by same on a repair? Thanks to all and enjoy the weekend.

What happened?

I apoligize for the misunderstanding. What I am courious about is the layout of a 45. I built a kit awhile back and used Larry grounding . Everything is very quiet , I used 5.6k grid stoppers but there is still some of that presence hiss. I read in Gerald Weber's book about the larger chassis in the 45 vs 5f6a creating a problem with a longer run of grid wires. His suggested solution is to put the 220k grid return resistors on the top of the board and move the 82k and 100k on the bottom to shorten grid wires to output tubes and lengthen the plate wires. This is supposted to quiet things down. Anyone have any idea if this is worth doing ? Thanks for everything.

Oh oh I see.

Honestly, I am not sure about that. These things all hiss at volume. The best resistor choices on the front end will do that. Is the hiss worse than any other similar amp? When even my higher gain amps are hissing pretty loud, when you roll up the volume and hit a chord, everyone dives for cover. It's pretty negligable while playing.

I played 2 or 3 supers at volume for years. The hiss level on stage was like a waterfall on a mountain creek, but the volume would flatten that mountain when the drummer counted us in. Gerald kind of talks to talk.. Maybe he's right, I just don't know how much. Gainy amps hiss, no?

charles anthony wrote:I apoligize for the misunderstanding. What I am courious about is the layout of a 45. I built a kit awhile back and used Larry grounding . Everything is very quiet , I used 5.6k grid stoppers but there is still some of that presence hiss. I read in Gerald Weber's book about the larger chassis in the 45 vs 5f6a creating a problem with a longer run of grid wires. His suggested solution is to put the 220k grid return resistors on the top of the board and move the 82k and 100k on the bottom to shorten grid wires to output tubes and lengthen the plate wires. This is supposted to quiet things down. Anyone have any idea if this is worth doing ? Thanks for everything.

Here is one a guy on PP posted, he did this mod:http://photobucket.com/jtm45 some other bad things too, I doubt that this solves the problem

In my experience hiss comes from gain in the early part of the pre-amp, so good quality resistors go a long way. Also if you have big bypass (bright) cap on the pot of lead channel you will be creating (or should it be liberating/selecting the hissing frequencies). You can tell this when you plug into a silent normal channel and turn up - no hiss, but plug into bright channel and turn up his++. To me this suggests that the noise is not generated in the grid wires of the PI output. Using the original layout has never been an issue for me. I use twisted wires and grid stoppers on the socket, that will usually block any unwanted transients anyway.

Thanks , I built my kit as per Georges instructions except for Larry's grounding and had some issues until I saw here the grid stoppers everyone installed. I cleaned up wiring in that area, mounted resistors and played around with presence pot wire. As you mention normal channel is silent....unless you either dime presence or raise bright volume. I was so proud and excited about this build/amp I'm just being crazy ! Gerald's idea seemed to make some sense , but I value the opinions offered here more. Overall I am super pleased with the 45 and sort of feel left out when it comes to mods. This thing rocks stock . Sometimes what you don't know does not hurt. Thanks again for the input. This place rules ,time to play some guitar.

I can't imagine any significant hiss reduction by shortening power tube grid wires. As has been stated, most hiss is generated early in the preamp and amplified in the following stages.

While I'm not familiar with the specific remedy you mentioned, I would suggest taking most of what Gerald Weber says with a grain of salt, at least based on what I've read by him.

Yes, I do agree with you regarding Weber . But as I do not own a computer his books gave me something to read to satisfy my need to know. I found out the hard way from his repair service that it was time to go a different route regarding my quest to inform myself and this place has been a blessing. Building Georges kit was a great learning tool.... or a great excuse to own another amp !!

charles anthony wrote: Overall I am super pleased with the 45 and sort of feel left out when it comes to mods.

While it's all well n good to know about mods ( and you'll probably pick up a few in time) IMHO the JTM 45 sounds best when stock with good parts.I even think the shuggy KT66s sound good. Put in some old stock pre amp tubes and yee the falk haa.

Coot Boy wrote:

charles anthony wrote: Overall I am super pleased with the 45 and sort of feel left out when it comes to mods.

While it's all well n good to know about mods ( and you'll probably pick up a few in time) IMHO the JTM 45 sounds best when stock with good parts.I even think the shuggy KT66s sound good. Put in some old stock pre amp tubes and yee the falk haa.

I concur, to nail the tone don't deviate from the benchmark. Good tone caps and pre's with the Shug's kill.

OnTheFritz wrote:

Coot Boy wrote:

charles anthony wrote: Overall I am super pleased with the 45 and sort of feel left out when it comes to mods.

While it's all well n good to know about mods ( and you'll probably pick up a few in time) IMHO the JTM 45 sounds best when stock with good parts.I even think the shuggy KT66s sound good. Put in some old stock pre amp tubes and yee the falk haa.

I concur, to nail the tone don't deviate from the benchmark. Good tone caps and pre's with the Shug's kill.

what he said

I just switched from Shuguangs to Gold Lions and couldn't be happier. Gold Lions are smoother, less harsh on the top end, but have good grind.

BrianH wrote:I just switched from Shuguangs to Gold Lions and couldn't be happier. Gold Lions are smoother, less harsh on the top end, but have good grind.

I have not had a chance to reply. Thanks for all the insight . I have a pair of tung sol 5881's from a old neighbor still in brand new orignal boxes I can't wait to try. I still think my build could use some more time to break in. I have had good luck with the valve art KT66's George sent with kit. I have tried some GE pre's I had laying around but, still have to select best ones from my stash. Honestly my build sounds so much cleaner than most clips posted here.....delicious none the less. It seems to flub out past 8 on bright volume. I cant stand pedals so I am happy with plugging straight in a staying a little cleaner.

charles anthony wrote:

BrianH wrote:I just switched from Shuguangs to Gold Lions and couldn't be happier. Gold Lions are smoother, less harsh on the top end, but have good grind.

I have not had a chance to reply. Thanks for all the insight . I have a pair of tung sol 5881's from a old neighbor still in brand new orignal boxes I can't wait to try. I still think my build could use some more time to break in. I have had good luck with the valve art KT66's George sent with kit. I have tried some GE pre's I had laying around but, still have to select best ones from my stash. Honestly my build sounds so much cleaner than most clips posted here.....delicious none the less. It seems to flub out past 8 on bright volume. I cant stand pedals so I am happy with plugging straight in a staying a little cleaner.

What OT did you use?

neikeel wrote:

charles anthony wrote:

BrianH wrote:I just switched from Shuguangs to Gold Lions and couldn't be happier. Gold Lions are smoother, less harsh on the top end, but have good grind.

I have not had a chance to reply. Thanks for all the insight . I have a pair of tung sol 5881's from a old neighbor still in brand new orignal boxes I can't wait to try. I still think my build could use some more time to break in. I have had good luck with the valve art KT66's George sent with kit. I have tried some GE pre's I had laying around but, still have to select best ones from my stash. Honestly my build sounds so much cleaner than most clips posted here.....delicious none the less. It seems to flub out past 8 on bright volume. I cant stand pedals so I am happy with plugging straight in a staying a little cleaner.

What OT did you use?

The stock Heyboer 784-103