Members potaetoes Posted April 23, 2009 Members Share Posted April 23, 2009 preface: i have this awesome handbuilt princeton reverb clone. it's been upgraded with the OT of a deluxe, screen and control grid resistors, GZ34 rectifier, and a 12" weber california speaker. as it was, it sounded clean, pure, smooth, and beautiful. but it had insane bass. like crazy whoop-ass bass you wouldn't believe. i had to dial it down so low (7) to get a balanced clean tone. still, it sounded great, albeit a bit mellower and less chimey than i'd prefer, but whatever. enter distortion pedals. ick. weird, congested, nasal icepick highs and thumpy lows, and where did the mids go? oh yeah, they went straight to ground through that bass pot that was turned almost all the way down. rather than try to juggle all the various princeton mods that are out there, changing coupling caps, messing with NFB, changing the bias and B+ on various preamp tubes, etc. etc., i just decided to try something simple: a bright cap, like on fender's bigger amps... typically a 250pf across the volume pot. so i stuck a 250pf across the volume pot. blammo, cleans sounded balanced, chimey, and vibrant with treble and bass at 5. just what i always wanted! perfecto!... almost. re-enter the distortion pedals. ACK! much better, but now there was a weird-ass high frequency hair/fizz everywhere. curses! so i added a little helper to the bright cap - i call it the dull cap i put a 75pf cap to ground on the volume pot, hoping it would drain off some of that weird fizz. it worked perfectly! all the chime and detail and presence loveliness is still there, the low end is still huge and fat, the mids are a lot wider and more vocal, and all that crazy high end hair is gone. it's awesome. i can't believe how easy that was. while in there i also added a bias adjustment pot (yes i drilled a hole - not it's not a vintage chassis). this amp now slays. last week i was contemplating selling it, but now it blows my mind. and it only cost about $5 to do both the bias and the bright/dull mods. hells yeah! here's the bias mod. the weird orange material between the pot and chassis is a piece of silicone sheet to serve as an insulator. Link to comment Share on other sites More sharing options...
Members DirtyBird Posted April 23, 2009 Members Share Posted April 23, 2009 In all seriousness, that's pretty cool! Link to comment Share on other sites More sharing options...
Members HKSblade1 Posted April 23, 2009 Members Share Posted April 23, 2009 but yeah, pretty cool Link to comment Share on other sites More sharing options...
Members potaetoes Posted April 23, 2009 Author Members Share Posted April 23, 2009 mmm, cookie. Link to comment Share on other sites More sharing options...
Members potaetoes Posted April 23, 2009 Author Members Share Posted April 23, 2009 princetons seem to get no love on here... Link to comment Share on other sites More sharing options...
Members scud133 Posted April 23, 2009 Members Share Posted April 23, 2009 how about a before/after clip? Link to comment Share on other sites More sharing options...
Members potaetoes Posted April 23, 2009 Author Members Share Posted April 23, 2009 how about a before/after clip? those'll be coming in a day or two. Link to comment Share on other sites More sharing options...
Members pine Posted April 23, 2009 Members Share Posted April 23, 2009 Awesome post! This is what the amp forum should be about. I copied it and printed it out to save in case I need something like that for one of my amps. Very useful knowledge! Link to comment Share on other sites More sharing options...
Members newholland Posted April 23, 2009 Members Share Posted April 23, 2009 nice there, spuds! oh.. it's not that the amp forum as a whole doensn't give the princeton luv... just PART of it does... a lotta guys just wouldn't know what to DO with an amp like that! I'D like that amp.... there's one for sale nearby.. but it's too rich for my blood... $1100! but don't think i didn't THINK about it.... Link to comment Share on other sites More sharing options...
Members jimijam Posted April 23, 2009 Members Share Posted April 23, 2009 :love: Lotza Love for da Princeton here good job! Link to comment Share on other sites More sharing options...
Members eyeball987 Posted April 23, 2009 Members Share Posted April 23, 2009 I wish I knew how to do this kind of stuff. I would probably start a business creating my own amp and pedal mods if I did. I am getting really tired of working for somebody else doing things that I don't really like doing. Link to comment Share on other sites More sharing options...
Members phyrexia Posted April 23, 2009 Members Share Posted April 23, 2009 That's cool man. I'll to try that out when I buy mine back. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted April 23, 2009 Members Share Posted April 23, 2009 I applaud your approach involving a few caps that cost practically nothing instead of wasting hundreds on different speakers and tubes. I have had the same problem with a 70's Princeton Reverb that had previously been modded to blackface specs but still had way huge bass. It already had a Stokes mod which was a big improvement, and the speaker was a Jensen C12-N. Here's a Princeton Reverb's tone stack: What I did instead of adding stuff to the volume pot was to go right to the tone stack. This little program might interest you: http://www.duncanamps.com/tsc/ Click on the program at the bottom of the page and install it on your computer. It's a great little program that shows you what will happen to your tone by modding the tone stack with different caps and resistors. What you find if you use the program is that you can reduce the value of the bass cap and reduce bass that way. the princeton was designed to get more bass out of a 10" speaker. Now that you are using a 12", the bass is overwhelming. If you reduce the bass cap to something like .022uF (BTW that's what Fender uses in the tone stack of the Blues Junior...a similar power amp with a 12' speaker)...you can tame that extra bass. Now the MID cap is a different story. Increasing the mid cap value will cause more mids to drop out...giving you more of a scooped mid sound. I actually decreased my mids there a bit by soldering an extra cap across that cap. (Remember that caps act opposite to resistors. When two are in parallel you ADD them for total capacitence) If you solder an extra .022UF cap across the mid cap, for example, you'll get a total capacitance of .044, MORE mid scooping, and maybe tame the bass a little in the bargain too. I'm not saying you did anything wrong. There are many ways to skin a cat. I like working in the tone stack area more because you can use the calculator and it's a little more fine tuning in that you can alter specific areas of the response curve more. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted April 25, 2009 Members Share Posted April 25, 2009 ...You know out of curiosity I tried your approach last night. I put a brightness cap on the volume pot and returned the mid cap value to .022uF instead of .044uF. I left the bass cap reduced to .022uF though. I have to admit I like your mod better. The increased mids takes pedals better. You get the sparkle and presence without the loss of body to the notes. Works better with reverb too. I never thought adding a brightness cap could tame bass so well..I always assumed it just added brightness. The amp sounds more like a single channel Deluxe Reverb now....with a little different character. Link to comment Share on other sites More sharing options...
Members EvilMeow Posted April 25, 2009 Members Share Posted April 25, 2009 MAN I {censored}IN LOVE PRINCETONS! In fact, I'm so sick of buying all these high gain amps and never being happy. I was happiest with a Super Reverb! Link to comment Share on other sites More sharing options...
Members guitarcapo Posted April 25, 2009 Members Share Posted April 25, 2009 I have a Super Reverb reissue I love a lot. I've occassionally thought about selling it because I'm not gigging anymore and realy don't need that much power for what I'm doing lately...but I keep it around because I can set a head on top of it and use the 4 speaker cab. It does sound glorious on it's own though. I'm not a fan of really gainy amps either for what I do. Every time I hear one I think of 80's shredders which isn't what I do. I live in that world of mild distortion to clean. Link to comment Share on other sites More sharing options...
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