Getting a cleaner, louder Blues Junior

[ctcpete]

Whole tone, thanks for the reply. The different tube options sound interesting.
I have tried moving the xformer wires around etc while powered up with no luck (I am comfortable with this stuff, I have a long tech background in the printing industry but am a tube amp novice). In the instructions, Bill recommended re routing the transformer leads so the like colors where wire tied together and routed well off the surface of the pcb. Originally they where all wrapped around each other coming off the xformer. I was sure to put each wire back to it's original terminal on the pcb (labeled them before removing).
Would I be able to better shield these wires somehow? Maybe shrink wrap?
Thanks again for the great information.

Regards, Pete

[Direwolf]

You could try the Eminence Red White and Blues speaker. I believe they recommend it as a replacement for the BJr. Sensitivity is 102db which is about 3-4db higher than the original. It's rated at 120 watts so you probably won't get any speaker distortion with it. I have one in a 5E3 build and love it. I also have a BJr that I did some of the BillM mods on. Tone stack, bias and added a cap in the power rail. I love the tone I get from it. I use the 5E3 and BJr in tandem and get a very unique tone, one I can call my own. I've also hooked the BJr up to the RW&B in the 5E3 and I really like the way it sounds. I may just replace the stock speaker in the BJr with another RW&B.

[Robmosis]

Have you simply tried to max your master volume and start you preamp volume low and turn it up as needed. This usually helps for headroom. When you max your master you are using your power tubes which break up a lot later than your preamp tubes. I you reverse this then your preamp tubes are made to break up early.
Also Have you tried maybe a 12AY7 in you v1 position. This has a lower gain of about 60% if I am correct, compared to the 100% of the 12AX7.
A Lot of people doen't realize but when a lot of classic fenders like Bassmans, Champs, and such first came out they were built around the 12AY7 for more headroom and later breakup. People switched to the 12AX7 when the supplies of 12AY7's started to dry up. Eventually changing the sound people expected from these classic fenders.
Speaker efficiency is another big point also as stated earlier. Other than the stuff people have told you You might have to consider that you just have the wrong tube amp. It happens to most who first convert to tube amp. Myself included. I now use a Vox AC30CC2 and it has massive amounts of clean headroom and fantastic drive. Not to mention the unbelievable Vox tone.
Best amp I have had with just a gright cap mod in the tb channel and tubes.
I will change speakers next.

[thunderfoot]

speaker options

I've owned several modern tube amps(solid state rectifiers with pc board mounted tubes and pots),and I'm telling you,it's one thing to replace the speaker,but if you ever get close enough to a silverface pro reverb,or any other vintage tube amp in the less than 50 watt range,you're gonna be tradin' in the junior!!!! I own a 1999 Blues Junior,jj pre amp tubes,torres bass boost mod,and swapped the speaker for a celestion v30-this amp sounds way bigger than it looks.I've tried it through crate extension cab with a pair of celestion 80's,with my '76 twin with a pair of red coat gov'ners,and in my '73 pro with a pair of v30's.The pro is what sold me for the junior.They're rated at 60 watts each,giving a nice break-up almost perfectly in time with the overdrive of the tubes.The mid spike they are notorious for helps the junior in the low-mid range to the point of vibrating the cabinet enough to rattle!!!! The gov'ners are softer in the middle,which is great for the twin,and the pro reverb is gutsier and darker with the v30's.Just for a giggle,I hooked the junior up to the stock speakers outta the twin....not even funny-v30 all the way( yes,I know the junior is an 8 ohm load,and the pro and twin are 4 ohms with both speakers,but I only used one of each-the crate cab was 4-8-16 ohm selectable)...I have a stock junior to compare the modded one to,and I hope I never hear another stock junior....Like the others say,it's your choice-if you're playing an articulate style of music(blues,jazz,older country),you want that big,fat,but clean note sound.If you're playin' rock,you don't always want the single notes to stick out,more likely,the transition from note to note will be smoother and more important than the note-I can't believe I just said that.
So,it's not just the mod's,speakers,guitar,cord,pedals(if any),or amp that you wanna consider.The musical style,the amount of time you play through the amp,how much you want to spend-very big factors ..
As i said,I had to work my way through some amps to get the sound I wanted...Tube Works Tube Driver,Crate VC50,Crate Vc30,Fender Blues Deville,Blues Junior,Hot Rod Deville,Blues Deluxe,Princeton Reverb II,then eventually my 73 pro,then 76 twin...The junior is very cool,light,and wicked hot with the new speaker and mods,but you hafta walk that path yourself to find what you like.BTW,the v30's need a lotta break in time-warehouse speakers has a clone for half the price.....Good luck

[boyt_bpc]

I tried the JBL D120F from my silverface Twin in my Blues Junior and it was amazing. I'm going to order Webers California speaker, which is very similar.

[roseblood11]

Hi,

BillM shows a clean boost module on his site, but unfortunately, he doesnīt explain it. If Iīd live next door to him, Iīd let him do the mod, but I live in Germany , so I gotta find out how to do it on my own.

Can anybody explain, how exactly this mod works? I think I understand the circuit itself, it looks like a simple Booster based on one BS170, just like the SHO. But how does he connect that circuit (and a switch) to the amp?

http://billmaudio.com/wp/?page_id=105

regards, Sue

[WholeToneMusic]

Clean Boost

The Bill M mods page Clean Boost is adding an extra Adjustable gain stage for an extra +9 dB. You can get a boost also by bypassing the tone controls (the adjustable EQ can attenuate the circuit by -30 dB or so. These insertion losses are usually compensated for by adding extra gain stages. There are areas in most common amplifiers that can cause dB loss in the circuit. Such as on an amplifier which has a vibrato, reverb or a Negative feedback loop. I always disconnect the Vibrato and or the feedback loop to open up the amplifiers hidden potential. By doing the above mods (disconnect the - feedback loop and the virbrato circuit.) to a Blackface Super Reverb along with adding a boost you can get the amp sounding close to the volumes of a Twin that has the same insertion losses.

[WholeToneMusic]

Whole tone, thanks for the reply. The different tube options sound interesting.
I have tried moving the xformer wires around etc while powered up with no luck (I am comfortable with this stuff, I have a long tech background in the printing industry but am a tube amp novice). In the instructions, Bill recommended re routing the transformer leads so the like colors where wire tied together and routed well off the surface of the pcb. Originally they where all wrapped around each other coming off the xformer. I was sure to put each wire back to it's original terminal on the pcb (labeled them before removing).
Would I be able to better shield these wires somehow? Maybe shrink wrap?
Thanks again for the great information.

Regards, Pete

Shrink wrap won't work very well unless it has a metal casing around it. I would move the wires around with a chopstick with the amp live
to see where they sound the quietest and let the rest there. Some heavy duty foil wrapped around the wires could do the trick to help further isolate the wires.

[roseblood11]

Hi,

I always disconnect (...) the feedback loop to open up the amplifiers hidden potential.

Itīs possible to just open the negative feedback loop? Doesnīt that increase the output impedance? The amp will still work with the same speaker at the same speaker jack/impedance setting as before?

Iīm asking because my Carvin Vintage 33 sounds way too tight and I thought of adding a pot (~1M Ohm) in series with the serial resistor (R33) in the neg. feedback loop. Hereīs the schematics:

http://www.carvinmuseum.com/pdf/amps/VINTAGE33.pdf


~~Sue~~

[Robert M. Martinelli]

Hi,



Itīs possible to just open the negative feedback loop? Doesnīt that increase the output impedance? The amp will still work with the same speaker at the same speaker jack/impedance setting as before?

Iīm asking because my Carvin Vintage 33 sounds way too tight and I thought of adding a pot (~1M Ohm) in series with the serial resistor (R33) in the neg. feedback loop. Hereīs the schematics:

http://www.carvinmuseum.com/pdf/amps/VINTAGE33.pdf


~~Sue~~

The possibility of opening the NFB has little to do with the output impedance, it's a stability-related matter instead.

If you look at the schematic you'll see that your amp's NFB ( neglecting C34 which, if I read the schematic right, is not fitted ) is a fixed voltage divider, formed by R33 and R32 ( Ok....in parallel with R22 and C47 but let's neglect them for a moment to make things easier ), and the resistance to GND of R32-R33 is 242 KOhm. This means that they're negligible as a load, because they're paralleled to the speakers, so the parallel load can always be approximated to the speakers' impedance.

The purpose of an NFB is twofold, it adds stability at the expense of gain, and it can be also used to shape the amp's tonal range. Removing it could bring some amp to oscillate; in your case I would say it could be worth to add an RC NFB, using a pot to find that "sweet spot" you're after. Once you have achieved the tone you want, you could sub the NFB pot with a fixed resistor to "freeze" the "correct" NFB setting.

HTH

Best regards

Bob

[WholeToneMusic]

Hi,



Itīs possible to just open the negative feedback loop? Doesnīt that increase the output impedance? The amp will still work with the same speaker at the same speaker jack/impedance setting as before?

Iīm asking because my Carvin Vintage 33 sounds way too tight and I thought of adding a pot (~1M Ohm) in series with the serial resistor (R33) in the neg. feedback loop. Hereīs the schematics:

http://www.carvinmuseum.com/pdf/amps/VINTAGE33.pdf


~~Sue~~

The negative feedback loops feeds some of the signal from the secondary OT back into the amplifiers Phase Inverter stage in reverse polarity. It does not change your output impedance. You can disconnect it most of the time without issues. If you disconnect it and the amp squeals then reverse the primary ot wires on the power tubes. That should take care of the oscillation. You could replace R33(220k) with a 250K 2 watt mil spec pot for added protection and extended sweep. Tightness in an amp is usually in the power supply. The amps choice of rectification and amount of filtering can determine the amps stiffness. The vintage 33 uses a fullwave rectifier using 4 1N4007 solid state rectifiers and a first filtering cap of 44 uF's. (two 22 uF's in parallel) I would suggest changing out the 1N4007's for HEXFRED diodes. This will give you a softer recovery.

[jrfrond]

After repairing and modding countless BJ's, it has occured to me that retrofitting the amp with 6V6's is a reality that can be accomplished with some work. 6V6's have it WAY over EL84's in the "clean" department, as is usually the case with beam tetrodes vs. power pentodes in most guitar amps. I haven't crunched any numbers for current draw, but there IS a possibility that the PT would need to be upgraded. The stock BJ PT is barely-capable of delivering the needed current as it is. This is due to the puny design of the PT to use as little copper as possible, and using a full-wave bridge rectifier to maximize available B+ voltage. The VA rating, even though I cannot find the specs on it, is pitifully small, as I have replaced lots of these transformers over the years. It wouldn't be impossible to upgrade it to a Deluxe transformer.

The clarity and harder clipping characteristics of 6V6's would really make the BJ sing, more like a DR than anything else.

[papuanewjimmy]

Wow, I had completely forgotten about this post and just randomly came back across it. Well, in case anyone having the same issue finds this thread on a search, here's how I solved my problem: got a bigger amp! Haha, I know, that sounds like a cop-out, but in the end, I was able to get an american made tweed Blues Deluxe for exactly the price I sold the Blues Junior for! The deluxe is a bit beaten up physically, but I actually prefer that look and feel- for example, the stain from a wet drink on top really lends some authenticity! In the end, no matter what speaker I bought, it would have brought the price of the Blues Jr up quite a bit, and as I grad student, I just couldn't really afford to do much experimenting. Overall, I am very happy with the new found headroom I have, and the clean sound of the amp.

Two notes though, for anyone who might be in my exact situation: Of course, as anyone could have guessed, I miss being able to have some real distortion at a tolerable level those for few times I want it. I think there's probably just nothing you can do about this- no tool works for all jobs (if only they made a hammer-duct tape-WD-40 all-in-one!). Maybe buy one of those powerbrakes? However, the other thing I'd point out is that the distortion of the Deluxe sounds different than that of the Blues Jr- and I liked the BJ's better. This could be due to a lot of factors, like speakers, circuit boards, etc, but judging by what I've read and heard, I think it's the power tubes. The Deluxe (I think) has 6L6's; the BJ uses EL84's I think? At any rate, I've often found myself looking up the skirt of amps that have a great distorted sound, and the power tubes are often EL84s or 34s. Then again, could just be a hunch!

FWIW!

Jimmy

[rockon1]

+1 to speaker efficiency! A speaker rated 3 db more sensitive would be like using the same speaker you have and doubling the wattage! Barring finding a speaker to suit your tastes thats more efficient its the simplest way of increasing headroom. Oh and some EL84M's wont hurt either. Bob

[WholeToneMusic]

Distortion

Good to hear you found an amp that's loud enough for your needs. Most of us have border line tennitis. haha we all would like to save our hearing though.
The amount of and color of distortion is mainly from the amount of gain stages within the amps preamp circuit and the tone stack. The power tubes just amplify the tone that's already present at the phase inverter stage.