Moding Blues Jr... where should I stop..??

[ntasher]

Got an almost brand new (3 months old) BJr today from a guy that was hard pressed for cash... I am tired of hauling the HRD around... too heavy for me. So here I am with this boxy sounding amp, listing possible mods and waiting for opinions. I list mods by the order of importance/complexity. I mostly play rock and need cleans, dirt and hi gain. My HRD is heavily modded (moved the gain stage before the tone stack, more gain... etc etc). I use Boss GT8 so I can use that for the distorted/overdriven parts but I am a tweaker so I might as well go all the way with the BJr... so here is the list:

1. Mod the tone stack - 0.1uF bass cap, mid control mod
2. Add extra gain by bypassing V2 cathode
3. Put on Weber 12F150 (currently in the HRD)
4. Use the spare half of V2 as an extra gain stage (switchable).
5. Turn the amp into a faux dual channel machine by turning the volume into gain control (for the gain channel) and fixing preamp gain in clean mode so that I can't drive the thing into preamp overdrive even with my hottest humbuckers. Add the switchable V2B gain stage and equalize the two channels at the master volume so that I don't get a hugh loudness difference between the channels
6. Add switchable volume boost (via footswitch) so I can jump better into leads once the dual channel is in place.
7. make all the above switching controlled by remote control (easier than using a cable).

Anything I missed?

Feel free to knock me on the head guys - leaving it stock is still an option (albeit not a reasonable one).

Thx,
Nir

[jefrs]

ymmv

3) I reckon they pinched a few pennies with the stock speaker, try swapping it out.

7) Murphy's law applies.

[Billm]

I think the speaker is the last thing to change, to give the amp that final push into the tone you want. The stock speaker is not bad, especially if you can hit it a little harder, with a better signal.

Power supply stiffening, tone stack, including the Twin-style mids jumper, and a presence control are the place to start.

I think that the fake dual channel is more trouble than it's worth. I've done it on some of my experimental Blues Juniors and I've also used the unused half of V2 as a gain stage. Apart from the fun of tinkering and tweaking, it's a lot of work for not that much reward. If you're going to have a pedal underfoot, why not make it a good overdrive/distortion pedal? That way you get tone, level, and output controls--all the advantages of a real two-channel amp. And you get to choose the pedal's basic tone without a lot of in-the-amp switching to control voicing.

I will say that one of the more interesting versions I came up with (still too complicated to be a mod kit) was using the unused half of V2 as a second input, with a tweed-style volume and tone control. In my bench version, I could run it right into V1b or pad it and run it into V1A, like a tube pedal.

The BJr also benefits from a better OT. Not to toot my own horn too loudly, but the one that David Allen and I co-developed is a winner.

[Mike Eskimo]

I've always wondered this in regards to all these "mod" threads:

What is the cheapest amp out there that requires NO mods ?

Great out of the box.

[Billm]

A question like that deserves its own thread... where it's likely to be answered, or at least speculated upon.

But the Blues Junior is such a mod-friendly platform that it's almost a shame to leave it stock.

[ntasher]

I guess I will go fire up that soldering iron soon. Start with the tone stack mods and power supply stiffening. See how it goes from there.
What about moving to octal base tubes (6V6 or even 6L6 provided the transformer can handle the extra heater current)? I have a 76' Princeton Reverb so I kinda have the 6V6 thing covered but a pair of 6V6 may prove to be a little more powerful than EL84s and as this amp is going to be used mainy for band practice (drummer, two other guitar players and bass) I might need that extra power. Then again - a more efficient speaker would do the trick and is less of a hassle to try.
Anybody knows what the efficiency of the 12F150 compared with stock Emi?

Thanks,
Nir

[VerySlowHand]

Originally Posted by Billm

A question like that deserves its own thread... where it's likely to be answered, or at least speculated upon.

But the Blues Junior is such a mod-friendly platform that it's almost a shame to leave it stock.

But I keep asking myself (and all of you, 'cos I'm 'thinking aloud') is it an amp for guitarists or for electricians? Isn't all the tone you're looking for, there in your fingers?

But for those of us who don't care about Ohms Law, it would be good to have a thread on the best amp NOT to modify... you know, just buy one and play your guitar. Is that such an old-fashioned idea?

Okay... wrong thread... I'll shut up!

[ntasher]

I think the best amp NOT to modify would by my little plastic Fender Deluxe transistor amp. This is one amp i'd never care to mess with. Other than that - no amp is tinker proof...

[Big John]

Originally Posted by ntasher

Anything I missed?
Nir

Yeah, you could put all those modes together in a different cab, maybe an attractive hardwood something or other.

[jefrs]

With respect to BillM, the first thing I would try, given a spare speaker handy, is to swap out the stock Eminence jobbie, I was underwhelmed with that one. I noticed a complete change in the character of my BJ. It's not just the efficiency but the frequency response. Maybe run the ExtSpk out to speakers in other combos and cabs to try them out.

Whilst the original BJ did come with 6V6(?) valves, an EL84 18 watter is a useful addition to the camp. Is it possible to dual socket it? Changing the op valve will probably not result in an increase in power unless you also alter the HT and bias, but you may get more headroom, bearing in mind that most folks never crank the amp right up, just to the volume they need. I put 6V6GTS into my 420VDC cathode biased 6L6GC amp and noticed no loss of volume at same settings - conclusion JJ 6V6GTS are 5881 ;-)
I've seen (heard) the BJ cope with full club gigs, with drummer, many times, lift it up and tilt it back if necessary, 17 watts is probably enough.

The small box does give the BJ a boxy sound but it does make it handy and portable.

Electricians change light bulbs, amps be electronics. The best results seem to come from electronic engineers who are also musicians (or v.v.) and who experiment to get the sound they want. Always experiment.

[ntasher]

jefrs,
Being an electronics engineer by profession and a guitar player (by no means am I a real musician) I always fiddle with whatever equipment I use. The speaker swap is easy. Actually I did try the BJr via the 12F150 loaded HRD and it's a different amp altogether. I wish I had a way to tell the cab from the speaker but that will require some work and will not be an A/B thing.
The BJr was acquired for its portability first. Tilt back legs sound like a good idea. I need to also measure the cab internal dimensions to see if I can squeeze in a full length reverb tank.
Hope to get to all this today. Will report back.

[Middleman]

Originally Posted by Mike Eskimo

I've always wondered this in regards to all these "mod" threads:

What is the cheapest amp out there that requires NO mods ?

Great out of the box.

The new Princeton Reverb. That amp sounds incredible.

[Billm]

Whilst the original BJ did come with 6V6(?) valves

No Blues Junior was ever equipped by Fender with 6V6s. But it's a nice conversion that I do fairly often. With the JJ, it's brighter, with deeper bass and more clean headroom.

The small box does give the BJ a boxy sound but it does make it handy and portable.

The Tweed Deluxe, in essentially the same size cab, does not sound boxy. The boxy sound is from the tone stack and, to some extent, the output stage and power supply.

conclusion JJ 6V6GTS are 5881 ;-)

They're designated 6V6-S in the US. The plates are still smaller than those in a 5881, but definitely larger than conventional 6V6 tubes. Full power appears to be 18W per tube, above the normal 6V6 rating of 14W, while a 5881 can do 23 watts. More info here:

http://billmaudio.com/wp/?page_id=370

I've done a lot of speaker testing in Blues Juniors, too:

http://billmaudio.com/wp/?page_id=295

I just got one of the Eminence Lil' Texas speakers, with the neodymium magnet. It sure is light! I'm looking forward to hearing how it sounds.

[ntasher]

Well, I'm back. Did the tone stack mod (0.1uF cap, mid control mod and changed the 250pF treble cap to silvered mica while at it). Also beefed up the B+ supply and bypassed V2 cathode resistor with a 25uF capacitor to get more thump out of it. Last (but not least) I added a trimmer to fine tune the tubes bias.
The result? A whole new amp!. Better, fuller bass. Gone is that boxiness. Beefier sound. I like it!!! Just need to see how it fares in Thursday night's band practice... If it behaves, I will buy it a new speaker :-)
Thank you all for you kind advices, especially BillM.
Nir

[Billm]

Gone is that boxiness. Beefier sound. I like it!!!

Me too!

Good work.

[emtjr928]

Not to Hijack, but I have been wondering the same thing. Bought a used Black Tolex Bjr. about a month ago and so far have really enjoyed it. Did BillM basic cream board, cathode follower, audio taper Master volume and new JJ Telsa tubes. While I was not disappointed before, these small changes are a real noticeable improvement. Being a tinkerer by nature, I am now thinking what next. Presence control, High voltage pre-amp mod, Fritz the cat mod, new speaker. To those that have been there done that, where is the point of diminishing returns in sound improvement? But realize that part of my enjoyment is in the tinkering and learning.
Thanks to everyone who has made this a wonderful forum.
Ed

[Billm]

A presence control will give you the biggest payback in terms of tone flexibility. The Fritz voicing has worked well for me on a green board but was inaudibly different on a cream board--go figure. Did you do the TwinStack mod?

A better output transformer wasn't on your list, but apart from the speaker it's the next biggest change.

[emtjr928]

Yes Bill, I did do the TwinStack mod. Have about decided on the presence control, have been listening to sound clips and reading feedback on speakers until I kinda glaze over. I know that it will sound different in mine but based on the differences in the eminence clips I lean toward the swamp thang. At least for now. Still debating on the OT. Don't know if I will someday want to drive a separate cabinet which would dictate which OT to use if I understand correctly.
Ed

[Billm]

Even the stock OT will drive a 4 ohm load without problems. Fender did it on the Two-Tone, which used a BJr chassis and a 10 and a 12 in a big cab. An OT with a 4 ohm tap is more efficient driving two 8 ohm speakers or a 4 ohm cab, and is recommended if you play cranked all the time. But an upgraded 8 ohm OT will sound better than the stock OT when pressed into 4 ohm duty because it doesn't saturate on the low end the way the stock OT does.

[jefrs]

Originally Posted by ntasher

jefrs,
Being an electronics engineer by profession and a guitar player (by no means am I a real musician) I always fiddle with whatever equipment I use. The speaker swap is easy. Actually I did try the BJr via the 12F150 loaded HRD and it's a different amp altogether. I wish I had a way to tell the cab from the speaker but that will require some work and will not be an A/B thing.
The BJr was acquired for its portability first. Tilt back legs sound like a good idea. I need to also measure the cab internal dimensions to see if I can squeeze in a full length reverb tank.
Hope to get to all this today. Will report back.

They are nice and portable and I am not sure I did the right thing in trading mine for a bigger amp. If I had kept my BJ I would have modified it.

The best presentation of a BJ I have heard was on a tall metal stand raising it about 1 metre up and tilting it back, most just stick it on a chair.

Strangely, the BJ tank is driven by the same set of chips as the Laney amps but they don't sound anywhere near the same.

Thanks to BillM re the valves. The JJ-6V6GTS I have do look remarkably like 5881 but then the 6L6WGB(5881)/6L6GC/6L6WXT etc that I have all look different.

Having used one in an AD30, I recently thought to myself that a seriously good 10-in speaker like the Celestion G10-30 Greenback would work really well in the BJ's small cab.