Blues Jr - 6V6 mod

[haknuts]

Hi, anynone here that has done a basic 6V6 mod on the jr and would like to share that project? Have renovated the amp quite thoroughly but still unhappy with its characteristics. Seems lile the more I tweek, the more I lean towards pulling out those EL84's

[Stevem]

There are a ton of mods that can and need to be to these amps to get them great, but with the stock power transformer in them doing much more than changing out the speaker first is a waste of time some what, as the circuit need good stable current and in light off that I would do the Mercury magnetics PT change out and choke mod before doing much more!

[haknuts]

Thanks. What I have done electrically is the tone-stack, bias and filtercap. Then JJ's all over. To save time I just now ordered the Billm octal mod kit. According to his site the Jr nicely handles 6V6's with the onboard PT. I do not need more watts - just want a cleaner headroom and smoother distortion. Keep up posting

[rock_mumbles]

The Fender "drive" is horrible, even in the Hot Rod Deluxe ... you need to use a pedal for that.

I've been able to get nice clean headroom out of EL84's ... you have to limit the signal on the EL84 grid's

[haknuts]

The Fender "drive" is horrible, even in the Hot Rod Deluxe ... you need to use a pedal for that

OK - I mean the amps natural OD/Break-up

[quote="rock

_mumbles"]I've been able to get nice clean headroom out of EL84's ... you have to limit the signal on the EL84 grid's

Like with an 12AY7?

Q: At what volume (master at 12) does the jr normally break up? Mine starts at 3, and it is not nice at all. Reminds me more of an old transistorized amp

[sixstringer]

I'm with stevem, I've modded a number of BJrs and the adjustable bias mod is the gateway to making the amp more usable. I don't really get the 6V6 mod (although with 6L6s might be cool) over the EL-84s. You'll need to change the transformers for that mod anyway and once you've done all the "standard mods" the transformers are next. Billm has new-ish transformers designed as upgrades for the BJr. I haven't tried them but knowing how carefully Billm develops stuff, I bet they are great.

Usually everyone changes the speaker first thing, trying to get away from the closed-in sound of the stock amp. The bias mod fixes that to a great extent but after trying a bunch of speakers, I like the Eminence Cannabis Rex or my new favorite, the Jensen Jet 12 (JC12-50FA) for the BJr.

[Stevem]

Just keep this in mind, with anything audio or video you are listening to and or watching the units power supply when all is said and done, so the better that is the better end result you will have, we just lucky that in most guitar amps we do not need it to be 100% perfect all the time when we push the amp near flat out!

[haknuts]

I'm with stevem, I've modded a number of BJrs and the adjustable bias mod is the gateway to making the amp more usable. I don't really get the 6V6 mod (although with 6L6s might be cool) over the EL-84s. You'll need to change the transformers for that mod anyway and once you've done all the "standard mods" the transformers are next. Billm has new-ish transformers designed as upgrades for the BJr. I haven't tried them but knowing how carefully Billm develops stuff, I bet they are great.

Usually everyone changes the speaker first thing, trying to get away from the closed-in sound of the stock amp. The bias mod fixes that to a great extent but after trying a bunch of speakers, I like the Eminence Cannabis Rex or my new favorite, the Jensen Jet 12 (JC12-50FA) for the BJr.

Thanks! I did the simple bias approach which is a fixed change to the voltage divider to get the bias down towards 75%. Billm says there is no need to replace the P-transforner for a 6V6 mod., as in opposition to a 6L6 mod.It is my understanding that the 6V6's are less power-hungry than the EL84,s. When the parts arrives I will look more closely into the bias-issue before the mod in order to see if the buzz can be resolved. If not, the 6V6's will have a go..

[dorrisant]

I'm with stevem,
Usually everyone changes the speaker first thing, trying to get away from the closed-in sound of the stock amp. The bias mod fixes that to a great extent but after trying a bunch of speakers, I like the Eminence Cannabis Rex or my new favorite, the Jensen Jet 12 (JC12-50FA) for the BJr.

Agreed... Switch out the speaker for a Falcon and you will be surprised. I have done a lot of the BillM mods on several Jrs. Raised a lot of eyebrows with a Falcon in there.

Can you explain the differences between the Falcon and the C-Rex? I might have to go ahead and get one.

Tony

[sixstringer]

Assuming you have the cream board version, the latest version of the Billm adjustable mod kit is super simple to install (much easier than the earlier ones). The biggest task is pulling the top of the PC board out to get access to the back. If you want more horsepower, the Billm "clean boost kit" is great. It makes the amp much louder without increasing distortion. BTW, I never use the Fat button on the BJr, it sounds awful.

[haknuts]

Thanks all.

1. Would you say that Optimizing tone here is a matter of fine-tweaking the bias, or will it be ok at 75%?
2. If bias is the problem here, already reduced to 75%, at what Level would one expext issues like I have (breaks up With a fuzz-like dist at Level 3/12)
3. Onboard drive/boost - I use TC`s MojoMojo OD, HOF Rev and Flashback DL
4. Yes, I have the Stock Eminence Legend 125/8. Just got hold of a 1963 Jensen P12Q in great working condition. Actually it was when testing this speaker I became aware of the Jr. flaws. Had never cranked it beyond livingroom-level until testing the old Jensen - which led me to belive the speaker could not handle the Power. However, today I put it into an empy Jr.cab and hooked it up to my Excelsior. What a treat that was. It will surely be put to use in the Jr once the amp gives up its stubbornness.

[haknuts]

Confession: I recently installed a new matched pair of 84's, after tightening up the untrustwourthy sockets. I guess the amp has run just a few hours since then. However, the building of the new cab may have put some stress to the amp. I just discovered one of the tubes were kinda deadish. Retightened the sockets - and it became alive again. Now wonder it was buzzy. An interesting observation is that there is a difference in glow-intensity between the pair. I question the matching processes as I suspect they are done with lower DC voltages than the real-life working contitions the tubes experiences. To my defence - there is nothing. Except I have just started the journey to Tube Heaven. Now the old Jensen was put to test. Spine-chimmering highs and fullness , a completely different experience than the stock Em. 125/8. To me it is truly amazing what this lightweight alnico
can do. Bias-wise I have 2.95V across the OT and 12,5V at the grid.

[haknuts]

A somewhat sturdier base for the tubes. The ceramic sockets I had could not be used, but I managed to dismantel their steel pipes and attach them to the Jr's stock sockets. Resoldered, cleaned and tightened the sockets once again. They have sign of heat corrosion and I think the heat also has an affect on the tension of the metal. This will do for now. At next break-down the 6V6 mod will be executed. I do not play live, but still hope it will last for a while ..

[haknuts]

Delete - sorry

[haknuts]

As for 2016 that vintage Jensen got replaced with a Eminence Cannabis Rex hamp-coned speaker. Wery nice improvement in tonal characteristics