The Steel Guitar Forum

Hi there,

I just bought a Fender Blues Junior amp for use with my National New Yorker lap steels. I really like the tone (my main concern is a warm, clean sound), but I would like to make it hum as little as possible. I've heard that there are several ways to upgrade this amp, but as my experience in upgrading a tube amp is nil, I thought I'd see if anyone here has some good advice to offer?

One thing I read about was "getting a Mercury Magnetics Blues Junior output transformer". How exactly would this affect the sound of the amp?

Another thing suggested, to get more clean headroom (which is something I'm interested in), was to change the preamp tubes to 12ay7.

In short, my main objective is to minimize hum. What would be the essential mod(s) to achive this?

Any advice would be most appreciated!

Cheers,

Fred

Hi Fred,

Replacing the output transformer is pretty major surgery and I’m not sure that it would solve your hum problem.

I had a Pro Junior and it was really sensitive to different preamp tubes. I would try some different tubes in the socket that’s farthest to the right (looking at the amp from the back) to see if you can find one that the amp likes a little better. This would also be the place to try a lower gain tube like a 5751, a 12AY7 or even a 12AU7 to see how they affect the headroom on the amp.

Good luck,
Dave

I can't speak to the upgrades or mods, but as to hum...

If the amp hums all by itself, with no instrument plugged into it, it needs a trip to the shop...probably for some new filter caps. But if you're refering to hum, only when an instrument is plugged in, you'll need to deal with the instrument side of things.

Single coil pickups are notorious for picking up unwanted hum, and it's very difficult to eliminate. A humbucker might be required.

Also, consider that bad, or cheap, guitar cables could be the cause. Just replace them with high quality cables...like George L's....but there are other good brands, too.

And one last thought, don't put any signal processing equipment, like stomp boxes, on top of the amp. they'll pick hum from the amp's power transformer.

Hi Dave,

Many thanks for your input! Do you know a good place online to shop for tubes? Or is it better to buy locally, considering the fragility of these things? (I buy 99% of my musical supplies including instruments from the US as the prices are almost half of the European prices).

Thanks!

Fred

Thanks Mike for your comments!

I'm referring to the "natural" hum of the amp itself. Maybe I'm just hyper-sensitive to it as I mainly play acoustic lap steel, and the hum is never an issue while playing, as it is low compared to the signal. I just want to make it as silent as possible.

Speaking of cables, these old lap steels have an "amphenol" connector, so there is not much choice. Elderly carries a C.B.I. cable like this, and that's what I've got.

Cheers,

Fred

If you play in and record with a band, a little amp buzz may well go unnoticed. If you perform and record solo, and mic the amp, gate it a tad so the buzz won't be heard while you play.

Or live with it. I play my T-8 Stringmaster thru a Blues Jr. and love the amp.

cheers,
Drew

Drew Howard wrote:If you play in and record with a band, a little amp buzz may well go unnoticed. If you perform and record solo, and mic the amp, gate it a tad so the buzz won't be heard while you play.

Drew, I play and record solo, so that's the thing. I also make quite "quiet" music with a lot of space. Any suggestion for a good affordable gate?

Thanks!

Fred

Sorry, I should have been more specific. A comp/limiter would help, set it long so it doesn't cut off your notes.

Alesis 3630 $99 @ Musician Fiend

cheers,
Drew

Fred,

KCA Tubes (http://www.kcanostubes.com/content/) is the only retailer I've ever dealt with and they were fine. Shipping shouldn't be an issue if the tubes are well packed.

Since your amp has three 12AX7s in it I would just try switching them around first to see if it changes anything for you. I think a certain amount of background hum/hiss is par for the course with these amps but the right tube may lower it some.

Dave

Hi Fred,

As the owner of a Fender Pro Jr that also had a hiss and a hum, I'd second the tube swapping idea. I had to try several different tube types/brands to find some that worked well in my amp (although they worked perfectly fine in other amps). I ended up switching to a lower gain 5751 tube(a Philips GE 5751, I think) in the first spot (furthest to the right) and put a better 12ax7 (Tungsol) in the other position (the Pro Jr only has 2 12a_7 spots). These changes quieted down everything, and the tone improved a ton. I also changed the power tubes, which improved the tone some but didn't change the hiss/hum.

I bought mine from www.thetubestore.com. Their service was excellent and they have some good reviews/comparisons of different tubes on their site.

Fred, as mentioned KCA is a great source - so is Lord Valve in Denver Colorado. Both test their tubes and offer warranties. IF you decide to use newly-manufactured tubes, I'd highly recommend JJ's. They approach the vintage tone of Sylvanias, RCA's etc. I use them day-to-day in my Pro Reverb and Vibroverb, switching out for NOS tubes for sessions.

The suggestion for a MM transformer is a result of many discussions on how to get a more "raw" blackface-type tone out of a modern amp. Certain models of MM (they make hundreds of transformers) designed for vintage Fenders have been installed as output transformers (the "heart" of an amp) in these newer models with nice results - the transformers "saturate" sooner, providing a warm tone with earlier, smoother breakup. As mentioned, it's a job for a REALLY good tech who knows guitar amps - he'd have to select the right model along with doing installation.

As far as the preamp tube goes, yes, a 12AY7 will lower your gain and give you a bit more (sometimes a LOT more) headroom. It's a no-brainer - remove the 12AX7 for the channel you use (you'll need a chart that shows which tube is which) and pop in the 12AY7 - no other adjustments needed. Same with a 5751, which has a gain level between a 12AX7 and 12AY7.

The other thing that can be done - again by a tech - is rebiasing your output tubes a bit on the colder side. You will gain headroom, but lose some warmth. It's a yin-yang thing...to get one you give up the other.

As far as the hum problem - it's almost always a bad tube, bad filter cap or ground problem. Test it in different locations to eliminate the power source as the problem, then see if you can borrow tubes from someone and swap them out one-by-one (except for the power tubes, where you swap the pair). IF tube-swapping doesn't do it, it needs to go off to a tech, probably for a cap job.

A compressor/limiter will only affect hum if it's coming from the guitar. If it's in the amp the comp/limiter will do nothing - except squeeze the life out of your tone. Not my favorite "effects" pedal.

Thanks so much everyone for all the very useful information! Now, having had the amp for two days, I'm not really concerned about necessarily getting more headroom - I love the clean tone as it is. But higher quality tubes that would reduce ambient hum and improve the tone is very interesting though. The stock tubes are:

2 x "6BQ5 (EL84"
3 x "12AX7" (the specs states "four" but I can only see three)

So I might try to swap the 3 12AX7s for 3 12AY7s.

From the weblinks you have provided, it seems "new old stock" tubes are the best (if a good brand) and that the JJ new tubes are a good choice too. What about the Electro-Harmonix? I'd rather spend a few dollars more on quality though, so what do you think the best choice of "new old stock" would be, in - say - the $20-$30 per tube region?

Many thanks again for the help!

Here's a little clip I recorded yesterday of the amp (it sounds better "in person" though).

http://www.youtube.com/watch?v=f-NZ1seHs6A

Cheers,

Fred

Fred,

I also own a Blues Jr. I love it! I'd suggest the JJ tubes. I tried a few different 'heats' of Groove Tubes, some Sovteks and Electro Harmonix ones as well. The 'blue' Fender Groove Tubes were nice, but didn't last. The Sovteks stunk. The Electro Harmonix EL84's got so hot that they melted paint off the back of my amp (mine's painted ash). The JJ's are sweet, and break up nicer too.

As for modifying a Blues Jr, Bill Machrone has a whole web site dedicated to this venture. I've ordered a few of his mods to clean mine up a bit and shape the tone a bit better. I'm waiting for my amp tech to have some free time to do the work!

Bill M's Blues Jr Page

Marc

Eurotubes has retube kits for the Blues Jr.

I haven't dealt with Eurotubes personally, so I can't give you a recommendation.

Lynn

This is a whole new can of worms!

Thanks everyone for the advice!

I have no prior knowledge of tube amp mods. From what I understand from Billm's Blues Junior mod page, the three 12AX7 serve different purposes, so it's not a case of simply swapping all three, but getting the right tube in the right place. He suggested a 12AY7 in the "V1" position and a 12AT7 on "V3" for a clean sound, so I guess that's what I'll try first.



Fred

Marc Jenkins wrote:The Sovteks stunk.

That's the stock 12AX7 tubes in my Blues Junior.

There are now so many options I don't know which way to turn! I think I will start with something reasonably priced - some JJ and JAN-Philips tubes - and see how that improves things, before spending loads on pricier new old stock tubes.

Do the quality of the two "6BQ5 (EL84)" tubes make any difference or is it only the three 12AX7 tubes that I need concern myself with?

Thanks again for your help (and patience)!

Fred

I found changing all the tubes to be important, but changing the EL84's made the biggest tonal improvement.

I've owned two of them and still have one, and they both hum. This web site addresses this problem: http://home.comcast.net/~machrone/bjr/bjrhum.htm
I haven't tried this remedy but it looks simple enough and worth a try

Fred,
I get all of my tubes from www.tubetown.de in Germany. They have got quite good prices, and you won't have to pay duties and taxes, since they are inside the EU. In their info section, they have got a "tube map" with quite good descriptions of different brands of tubes.

I also play a 2x EL84 amp (a Carvin Vintage 16), and for a warm sound, definitely go with JJ EL84 tubes (EL84 generally tend to be on the bright side, so stay way from Electro Harmonix, Sovtek, or Chinese tubes, if you are looking for warm tone - JJs are best for that, lots of warm midrange, but, naturally, also a bit less clean headroom - as always with "warmer" tubes).

You do have to set bias with any fixed bias (non-cathode-biased) amp like the Blues Jr. - it's not rocket science, but be aware of the high voltages inside tube amps, and read all the safety info; you will also need a multi-meter, and preferably, some tube-socket measuring kit (like that sold by TubeTown), to do that yourself...
(If you need more info, send me a private message.)
Also, I'm not sure whether the Blues Jr. does have a bias pot inside, if it doesn't, you will have to solder one into the circuit.

Oh, and I wouldn't spend money on a Mercury Magnetics tranny upgrade - sure, they are the "Rolls Royce" of tube amp trannies, but those stock Fender trannies aren't that bad, either...

If you end up getting inside your amp, it is worth reading through The Tube Amp FAQ safety information.

One of the easy'st mods is to put a high tolerance
insulated resistor on the input .. this is the Jerry
Garcia trick .. cuts down noise to the first stage
preamp tube ..

Hi Fred - it's sort of apparent at this point that your going about things in a "scattershot" way without any real idea of what effect each component has, or even which component is which (i.e. the idea of subbing all the 12AX7's with 12AY7's - you had no idea what any of those tubes do, thinking they are "preamp tubes" - a meaningless phrase when it comes to specific tube types and their application).

I strongly suggest you stop and regroup. First, read up on amplifier safety (as previously suggested). You need to know what will kill you and what *might* kill you, and basic amp safety - discharging filter caps, working with only ONE hand in the amp, using non-conductive tools (the "chopstick" method) - is your #1 priority. Until you understand that stuff, you should not even be peeking at the circuit boards.

You're getting a lot of good advice on tubes, but some variations - and you have NO way of knowing what's right.

I realize you are eager to get the amp sounding the way you want - but killing youself or damaging the amp in the process, or spending large amounts of money "chasing tone" by parts substitutions isn't the way to do it. WIthout any background knowledge, you really should simply find the best tech you can, tell him what you want to achieve and pay the bill. You'll spend far less money in the long run and keep yourself (and your amp) out of danger.

On the other hand, if you really want to do this stuff yourself, you need to do a lot of reading. I'd start with Gerald Weber's Guide to Hip Vintage Guitar Amps (the title is something like that), Kevin O'Connor's books, and start poking around the webervst (tedweber.com) board, the Fender Amp Field Guide, and the alt.guitar.amps newsgroup. All these have weak points, but without some basic working knowledge of how tube amps work you're asking for trouble. If you have never taking an electronics class, plan on it - find an adult school class, a trade school, something. This isn't stuff you can do on the basis of a few posts.

Also, the Blues Jr., while a fairly basic amp, is NOT the easiest in the world to work on due to the use of printed circuit boards. You need to know what heat ranges to use and have excellent soldering skills to even mess around with basic changes that involve soldering. Otherwise, you stand a good chance of cooking a circuit board - not a cheap part.

I'm not trying to discourage you from trying to get the sound you want - but without a basic grounding in tube amp technology (pun intended...) you are chasing your tail.

As usual, lots of great advice from Jim - let me add just one more reading tip:

Dave Hunter - "The Guitar Amp Handbook - Understanding Tube Amplifiers And Getting Great Sounds"

Lots of info can also be found here:

http://paulrubyamps.com/info.html

and in the Tech Info section on this site: http://www.aikenamps.com/

Oh, and I forgot to ask - did you buy a new or a used amp? If it is new, expect some change of tone after a while of playing it, as the speaker hasn't been "broken in" yet - new, unplayed speakers usually sound a bit harsh and stiff, it takes a while to loosen them up and make them sound smoother and more open.

BTW, changing the speaker is another easily accomplished option for changing an amp's tone - the speaker type has LOTS of influence on the sound, eg. for a particularly warm tone with lush, not too spikey treble, an Eminence Cannabis Rex speaker would be a great upgrade.

But before you change anything, try playing the amp for a couple of weeks, to see how the tone changes once the speaker and tubes get broken in, and also to find out what you like and dislike about the amp's tone...

Hi Jim,

Thanks for the input! Yes - it is easy to trace my gradual tube novice learning curve in this thread. Like I wrote - "a new can of worms". I had no idea there were so many factors to consider. Don't worry, I'm not intending to to any amp surgery myself apart from maybe changing the Sovtek tubes for better quality ones of the same type (and I have learnt now basically what the different tubes do - I did a lot of reading yesterday of the links kindly provided by people in this thread) but I'm considering first to have the basic of the suggested mods made - by a local amp tech or by this guy Bill M who specializes in upgrading Blues Juniors (see link above).

Best regards,

Fred

Good Fred - Sounds like you're getting a handle on it now. One caution - I would not suggest even changing output tubes on a Blues Junior yourself until the mod has been done to make the bias adjustable. SImply changing power tubes without being able to adjust the bias to find the "sweet spot" is not going to do you much good. At least have that part done by a tech; then get a bias tool that will handle the EL84 pinout.