silpakorn
8 posts
Jul 17, 2010
4:10 AM
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After searching this forum and reading Greg's article I kinda get the idea of how it works to make a pro jr more harp friendly now. But just one simple question; is it as simple as changing a light bulb ? Does it need rebiasing or something ? and do the valve jr and princeton need swapping tubes to make them more harp friendly too ?
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hvyj
459 posts
Jul 17, 2010
6:51 AM
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My experience w/my Princeton Reverb Reissue is that no tube swaps are necessary. However, I thought the Ruby Tubes that came w/ the amp sounded a little harsh for harp (maybe okay for guitar, though). So, I replaced them with JJs from Eurotubes which I think sound warmer.
Btw, the owner of Eurotubes (Bob Pletka) is VERY knowledgeable about tubes swaps or replacements to voice a guitar amp for harmonica and doesn't mind answering questions. There's nothing about harp on the Eurotubes website, but Bob has quite a bit of experience retubing amps for harp players. You can call and leave a message and he'll call back or email him and he'll reply. Very nice guy, too.
Last Edited by on Jul 17, 2010 1:07 PM
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Kingley
1326 posts
Jul 17, 2010
7:00 AM
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You'll most likely only be swapping the pre-amp tubes (12AX7) for lower value ones. So you will not need to rebias the amp.
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Paul "Kingley" Routledge
My YouTube Page
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LittleJoeSamson
354 posts
Jul 17, 2010
12:12 PM
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Circuits that are self biasing such as cathode biased or grid resistor biased are OK to swap power tubes, as long as same type and good quality. ( However, it is a good idea to check..if you have the know-how or a friendly tech ).
As Kingley says, swapping pre-amp tubes is more typical. Voicing for harp is as individual as the situation...given differences in other gear ( mics, speakers, even cords ), playing styles, and personal taste.
Brent Jesse's www.audiutubes.com has a good comparison chart on different valves and variants of similar types ( such as 12AU7 & 5814 ). Thankfully, there are plenty of fairly priced equivalents of good make, that testing different values needn't be cost prohibitive.
[ A friend has a Pro Jr. that sounds good with a 5814A in V1 and a 6829 in V2. I put a 12DW7/7247 Mullard in V1 & a 6829 in V2 of my Blackheart Handsome Devil. ]
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silpakorn
9 posts
Jul 17, 2010
12:39 PM
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Thanks a lot you guys for the infos ! I really hope that it's as simple as you guys said, cause since I'm living here in thailand it's almost impossible to get an amp that's originally made for harp. So getting one of those guitar amps and changing tubes seems to be the way to go for me. By the way, this is going to be my very first amp so which one out of these three would be a good choice to practice at home and hopefully a gig in the future, a valve jr, pro jr or princeton ( this one maybe too big ) ? or any other choice ?
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Kingley
1328 posts
Jul 17, 2010
12:57 PM
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My favourite all time amp for harmonica is the Fender Princeton Reverb. I'd highly recommend it.
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Paul "Kingley" Routledge
My YouTube Page
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hvyj
460 posts
Jul 17, 2010
1:09 PM
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Princeton Reverb Reissue is a great amp. Big enough for smaller gigs, and, IMHO, not "too big" for anything.
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Joe_L
468 posts
Jul 17, 2010
2:05 PM
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When I owned a Pro Jr, I screwed around with tube swaps and settled on an ElectroHarmonix 12ay7 in v1 and left the 12ax7 in v2 I tried a bunch of lower gain tubes and didn't dig the change in tone.
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N.O.D.
43 posts
Jul 20, 2010
7:06 AM
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Hi Bro's i been messing about with my Fender Blues Junior it's heavly modded after market tranys & few other things, fitted a vintage 1960 10" 20 watt Magnavox speaker in it today,
I'm running stock tubes, what are some of the combo's you guys prefer to run in V1 V2 V3
Does any one ever swap out the EL-84s
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Cheers Bro's
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LittleJoeSamson
359 posts
Jul 21, 2010
12:16 PM
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Doing the pre-amp rolling gives many different voicings...given all the variants with a nine-pinout available and the gain characteristics / plate resistance configurations.
Not so many choices when it comes to octal based tubes. There, the choices are in brands and dates of manufacture.
What I have found is that changing the rectifier tube has the most noticeable effect on sound. I recently installed a Bendix 6106 ...and it provided a smooth sound, but it did not give the punch of the Matsushita 5CG4.
I've tried '50s Tung-Sol 5Y3GT/VT-197A's and they also have a boost over ordinary 5Y3GT's. 5Y3WGTB/6087's are midway between the 6106 and the 5CG4, and are also a step up.
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Joch230
250 posts
Jul 21, 2010
1:19 PM
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The Valve Jr. has a solid state rectifier. No rectifier tube to change.
-John
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toddlgreene
1580 posts
Jul 21, 2010
1:26 PM
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On this subject, I have a harp-modded Epi V Jr. with stock tubes. I'm wondering if anyone has taken out the EL84 and replaced it with a Mullard or JJ-did it make a substantial difference? Again, I don't want to change value, just brand of tube.
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Crescent City Harmonica Club
Todd L Greene, Co-Founder
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toddlgreene
1581 posts
Jul 21, 2010
1:31 PM
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HvyJ-thanks for the heads-up about the eurotubes site. Here is what he has to say about EL-84 tubes:
EL84/6BQ5
Sovtek EL84: This tube has a very harsh mid and upper mid-range. If I had to describe the tone in one word I would call it "cardboard". They make your amp sound like a big Wheaties box. The low end is flabby and only gets worse as more lows are dialed in. The highs are piercing and brittle. These tubes are just flat and lifeless sounding without much harmonic content. When over driven they get real grainy and the break-up is quick and not smooth.
Sovtek EL84M: This tube has the same tonal characteristics as the standard Sovtek EL84 and is even more lifeless and less touch responsive.
Electro Harmonix EL84: These are sovtek tubes and all the above applies.
mullard reissue EL84: These are sovtek tubes as well and are absolutely nothing like the original Mullard EL84's. It should be against the law to muddy a good name like this...
EI YUGO EL84: This is a pretty good sounding tube. The problem is finding good ones that are matched. They have nice harmonics and break-up pretty evenly. They don’t have a strong low end but dynamic response is good. The upper mid and highs are this tubes strong points. Nice detail even when distorted.
PHILIPS 6BQ5: Even though these are out of production NOS tubes are still fairly available at a decent price. These are nice, warm sounding tubes with good dynamics, nice harmonics. This tube has good definition but is hard to drive into distortion. A nice tube overall but I would use the EI before spending the money on these. They work pretty good for Hi-Fi.
JJ ELECTRONICS EL84: This tube has the deepest and tightest low end of any of the tubes reviewed here. The mids are thick and harmonically complex. The highs are sweet and smooth. These tubes are very punchy with a nice chime. When over driven they get nice and thick and do not loose their detail. The break-up is very smooth and linear and they are very responsive to touch.
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Crescent City Harmonica Club
Todd L Greene, Co-Founder
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Joe_L
474 posts
Jul 21, 2010
1:33 PM
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Todd - Tubes are pretty cheap for a Valve Jr. Pick up a couple and try it. It never hurts to have a spare or two on hand. Those things come in sockets for a reason, i.e. they don't last forever, so you might as well have a couple of extra laying around.
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toddlgreene
1582 posts
Jul 21, 2010
1:35 PM
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I think we posted at the same time, Joe. I agree, and any other amp I've owned, I always had at least one spare tube or set;I'm just looking for a tube that sounds better than stock to get two of(one as a spare)-and that Eurotube info saved me a lot of trial and error. He has the same info on many popular tubes. Good stuff.
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Crescent City Harmonica Club
Todd L Greene, Co-Founder
Last Edited by on Jul 21, 2010 1:36 PM
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hvyj
467 posts
Jul 21, 2010
1:46 PM
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@NOD: I sold my BJ to buy a Princeton Reverb Reissue when the PRRI came out. No regrets.
But when I had a BJ, I re-tubed the preamp stage as follows: V1-12AT7 (ECC 81) V2-12AX7(ECC83S) V3-12DW7 (ECC832). I used JJ Electronics tubes which i think have a warm sound for harp.
Didn't change the power tubes, but I did replace them w/JJs of the same kind.
BTW, Ruby Tubes makes a replacement reverb tank for the BJ that has a deeper and better sound than the stock reverb tank. You may want to check it out. You can't use an Accutronics replacement tank because they are TOO BIG to fit. I think the stock reverb sounds tinny. Really cheesy. I had the reverb circuit modded on my BJ--but that was before the Ruby Tubes tank came out, which would have been a better alternative than a mod.
I also bagged the tank. Mojotone sells small reverb tank bags that will fit either the stock BJ reverb tank or the Ruby Tubes replacement reverb tank. The reverb tanks in my PRRI and my Super Reverb Reissue are bagged. That's how they come from the Fender factory. The stock reverb on the Princeton (and on the Super) is much deeper and richer than the stock reverb on the BJ.
Last Edited by on Jul 21, 2010 3:13 PM
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hvyj
468 posts
Jul 21, 2010
2:00 PM
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Btw, I put a set of 14" Fender tilt back legs on my Princeton Reverb RI. I really like the way the tone of the amp opens up when it's tilted back. Very useful mod, and inexpensive.
If you do this, you have to replace the the little metal feet/tabs on the bottom of the amp w/ Fender sphinx glides since you will want to put metal corners on the amp to protect it when it's tilted back, and you need to remove the feet to install the corners. The sphinx glides are nicer than the feet anyway. Fender also makes the metal corners you need to put on to protect the rear corners of the amp if you tilt it back, but I put corners on both front and rear bottom corners of the amp which is a good idea anyway.
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