Hoffman blues jr modified HELP ME!!

[ClippIn4tae]

So i took a hoffman blues jr build and removed the master volume when i seen how much volume it takws away from the total output and now it breaks up at three and  its so thick its not pleasing break up.

So i removed the gain stage right before the phase inverter and it worked but the volume was way way less than it was before

But the break  up was great.

I wonder why the volume loss? There are tons of circuits with two gain stages that are loud ,plus the volume should be from the power tubes anyway right?

So this leaves me with a issue.

I would love a classic fender circuit  (ab763/5f6/6g2) lite  version of course.  No reverb no trem.

Can yall help me?

There has got to be a way to either fix the blues jr circuit .
I dont want the master volume but i want a pleasing breakup.

 I would love for some of yall experienced guys to help me.
I used the hoffman schematics for this build. I used 6v6 tubes.

The only mods i done was to remove the master volume totally from board.


So now i want to put a classic style CIRCUIT.

Maybe a princton 6g2 no trem.

So blues jr trannys chassis and cab, ss rec.

So maybe yall can help.

Either help fix the issue or help with a new circuit

Either will be great!!!!

Thanks

[jim]

The PCBs are cheap and extremely fragile--a throw away really and problematic to mod.  Some techs (like Gerald Weber) believe that MV is a tone thief but it is challenging in a small tweed chassis with factory boards.. so...... what you need to do is install the Hoffman hand wired turret board available on this site which is an excellent mod platform.  The crappy reverb is replaced with a resonance control. You reuse your transformers so its not really that expensive.  Jim

[ClippIn4tae]

As i wrote in the message

I have a hoffman blues jr

[ClippIn4tae]

I took out the master volume and i need the proper resistors and caps that go to the next part of the circuit.

I have the physical caps and resistors i just need the vaules and order to  the amp function normaly with out the master volume pot.

It works as is.

Just breaks up too soon.

I put a 12ay7 in the v2 and that cleans it up but its still breaking up early.

As it should be it has 3 gain stages before pi.

I will redo my post to make it clear.

[ClippIn4tae]

Yes three gain stages.

And its breaking up alot soon.

But its loud as hell!!!

I put a cap/resistor to ground and resistor/ cap to phase inverter but its still breaking up alot

So put just the 250k pot in line?

[ClippIn4tae]

Slucky?

How do i hook that up?
And why would i want that?
Thats just another master volume isnt it?

Please explain.

Do i put coupling cap before and after the pot?

[dude]

He's telling you to put the MV back as it was but use a 250K pot.


al

[ClippIn4tae]

Okay!!im gonna do it right now!!be right back with result! Thanks so much

[ClippIn4tae]

Jee whiz thanks sluckey!!!
So its a quick fix and got me playing agin

But i must build a bigger better amp.

Since i cant afford to buy vintage i will buy a Hammond chassis/amp off ebay and build a better amp.

Thanks so much

Im not pleased with blues jr a awhole.its just not what i prefer.

But its got me playing!

[ClippIn4tae]

Im gonna check voltages when i get off work today.

I had considerably lower on the plates of power tubes.
I removed the meat control.
I just removed the 22uf cap and pot.

Its probably all wrong
Bcuz the tone should be better
No howl
 It works fine.kinda dark and sounds voxy (i guess bcuz the nfb is wrong)

Thank god i came on here to get your help.

The 6v6 added alot of bass so i removed the meat control

I just like it with out it. Would rather a presence.

Cant wait to get home from welding all day to come fire up my soldering iron!

Im so happy your helping slucky!

Plate voltage on the power tubes was 301 amd aross the pin 8 was .0065
Thats how i biased it anyway.

Talk this afternoon!!

[ClippIn4tae]

Im sorry there .065

I used the calculators and its like 9.5 watts each

[ClippIn4tae]

I will come home after work and give a correct voltage reading.

I must go put in these 8hours of work

The amp  functions . But i think there are some issues also.

I changed the tube sockets and they seemed to bias right
 U know there is a 50k pot in dougs board.

I was sure it wouldnt work but it did and it has more room to turn.

But with my input and your experience we can get this sucker more toneful.

Gotta go to work.

Be home at 4.

So excited.

So tell me.what all you need i will give you voltages from the power tubes.
Anything else  need?

[ClippIn4tae]

The only reason i went with 6v6 is bcuz i read all over that billm said it could handle 6v6 with no issues.

Plenty of power.

And it seems true

But hell i dont know.

We will find out.
Shit imma be late.lol.

So glad your helping.

I want a supro like u build sooo bad btw.

Off to work.

[tubenit]

What about simply changing to cathode biased and using a 250R/10w resistor bypassed with a 47uf/50v or 100uf/100v cathode cap?

http://el34world.com/schematics.htm#Hoffman_Blues_Junior_Conversion

I have found on cathode biased amps that using a larger value cathode cap on power tubes gives more of a "fixed biased" tone, IMO.  In other words, a 100uf would sound more like a fixed biased amp then a 22uf.

Just a thought for consideration. 

With respect, Tubenit

[Ed_Chambley]

So i removed the gain stage right before the phase inverter and it worked but the volume was way way less than it was before

But the break  up was great.

I wonder why the volume loss? There are tons of circuits with two gain stages that are loud ,plus the volume should be from the power tubes anyway right?

Thanks\(Quote)

Yes, there are loads of amps with less gain stages, but the volume increase is dependent upon how much gain is actually at each stage.  For instance, if you add a bypass cap to a stage that is simply biased with a resistor, the voltage will increase.  This increase will hit the PI harder and in turn push the power tubes harder.  More volume.


Also, lower dropping resistors will increase voltages in preamp tubes is the same plate load and bias is not changed.  The result is more headroom from the stage.  This will increase the clean signal and drive the next stage harder which can easily make it clip unless measures are taken to provide more headroom for this stage.  It will get louder is this is done.


Consider the Trainwreck with 2, EL34 and a 12Ax7 LTPI.  Basically the same output section as a Marshall 1987 Plexi.  If you have ever played both you will quickly see the Trainwreck will in volume same speakers will be louder much faster.  Both dimed they are somewhat closer simply because the Marshall is actually cleaner and only distorting the EL34's.  The tube can only saturate so much.

[ClippIn4tae]

Hey thanks guys for everything! Well im at work so this will have to wait a bit.

Look the amp is functional as it.

But slucky says my bias is too hot.

I got the numbers from rob renits  bias calc for andriod.

It said  that 301plate -.065-1ohm resitor-pin8  was like 78% (give or take on the numbers guys im just saying somthing close for sake of convo at work.i will have precise numbers after work.)

So its wrong i guess. But its not red plating and plays.
But tone could be alot better.

So do i need to go with cathode bias?
Why cant i use the hoffman bias set up as is in hoffman blues jr.
Seems like i could just turn it down to proper bias?

Seems like it would work.

So this brings me to another topic.

I want a cooler circuit in there.

What woukd you guys say is a bad ass circuit?
Opinions guys, if yall had this amp setup what would you build in it?

Like the supro slucky made for instance the only thing is too many inputs for me.

I want to keep the same or simular layout of knobs.

Yes!Thanks i been wanting this help

Okay so for now today i will get off work and bias this thing right.

So can you tell me how?
Measure plate voltage then pin 8 cathode?
Then do the math then adjust?

Thanks guys gotta go back to welding!im so excited.

[labb]

JMO but the Fender AB763 pre amp circuit is hard to beat...Mr. Leo thought so too. Look at all of the Fenders that use it. As for the 6V6 tubes. I have better luck with them when the plate voltage is around 350.

[ClippIn4tae]

Slucky,holy crap!i cant believe they weren't red!

I will check em asap this afternoon.

I think and hope that i can turn it down enough.
I seem to remember that  the pot its turned like 3/4 the way open right now.

We will see. Anyway im so happy to get this help. Thanks.

I would love a ab763 entire circuit in there.

I would like to get it working better first then discuss that part.
It will become a more classic style amp.

I also am doing another build very soon
I will document it also.

Thanks guys.

I think the pot will go down enogh to bias these tubes. If not its just a resistor change to get it closer right. 

Anyway later it will be.just a  few hours

[ClippIn4tae]

Okay i turned the bias pot all the way down .

315 on plates
302 screens
25.5 pin 5

Tell me  setting to use if u need more readings

Im gone shower

Oh yes .019 on the 1ohm resistor pin 8

[ClippIn4tae]

Biased to .028

310 on plate
300on screen

Sounds better.
Not as loud (lol)

Well.

I want somthing with good cleans and a bad ass drive.

Thats why i wanted the supro.
I dont know if that will make me happy?
I know a ab763 will.

I need a layout/schematic for a new build inthis donor.

Like i say i want good cleans  a  and nice drive when loud.
Basic controls.

I was thinking of cathode biased two knob tone stack ss rec

Simple and decent.

Any suggestions?

Please give schematic and layout if possible.

Bridge rec/cathode bias.
I dont care what power tubes. All ideas welcome.

I like the idea of supro bcuz of simple yet great cleans and great drive.
I love fender bcuz simple and good cleans decent drive.

Thanks guys yall are great!

[ClippIn4tae]

I checked several times and readjusted.

Im at 70%.

I put a bright cap that i was missing on also.

Sounds as it should.

i may leave it and buy this organ on ebay i been looking at ao29 tube amp.

I think i will rest on it for a while.

This thing is a Friggin tank i tell ya!

 Hoffman is the truth!i live by his law.



Thanks yall.

I will make a new post for the new build asap.

[cliffs_trip]

Hey everyone, getting to this a little late as I was looking over and taking a few notes from a BJ I gutted and repurposed just a few weeks ago.

I used a 25k pot in place of the 50k and it can get me all the way from 4.1mv to 71mv when measuring across the 1 ohm cathode resistors on my JJ 6V6s.

My plate voltage at 21mv across the cathode resistor is sitting at 352. 

The amp is a Trainwreck Liverpool preamp mated to a 6V6 pp poweramp I found on AX84 with the PI from the Liverpool circuit.
I did use a star type ground scheme in the amp as well, my first attempt.

This thing is a little beast!  All you need is a guitar volume to go from clean and sparkly to raunchy distortion!

I did add a choke from a DRRI I had siting around to it as the AX84 poweramp schematic had a choke and I figured what the heck.

I didn't draw up a schematic, or else I'd share it.  Good luck with gettin the amp to the point you are happy with it!  If you want to know anything about my build just ask.  I can provide whatever information I have.  I'm still learning this hobby, as I suspect will be the case for the rest of my life, so you can't expect expert advice from me just yet, or maybe never! LOl

[ClippIn4tae]

Slucky so i can buy ao43 (i just looked at one for 120and 20shipping)
It has el84 and tube rec already and use those supro power tubes huh?

Im thrilled.  So i have to save my nickels for a couple weeks but thats a plan

Hey does  supro have decent clean headroom?
I bet it does have enough for me.

I will build a deluxe later.

I am happy! Yaay!

[ClippIn4tae]

If i put a 500k pot on the master will it be twice as loud?

[ClippIn4tae]

Sluckey,for curious resasons i put a 1m pot there in the master
And of course it was louder but ,as i know now it was clipping in the pi i guess.

I put the 250k back.

I just need a more powerful amp i see.

So

[ClippIn4tae]

Popped in a 1960s pair of reflectors and plate voltage is 336

Yes its gonna work better now.

And you say about the meat,well i dont want that and i compared to other schematics and it seems right.

And how could i have the nfb wrong ,its going from speaker jack to phase inverter.

[ClippIn4tae]

333 on plate and .026
 69% or so.

Checking nfb now.

[ClippIn4tae]

Nfb verified.

Got louder and grittier.

Putting back 50k pot.

[ClippIn4tae]

As i just found out.

I just was going off your post is all.lol

Putting the 250k back and putting  the back on it.

Thanks.

Still want a Friggin 50watter!!!

[shooter]

Still want a Friggin 50watter!!!

add 2 more 6v6's

[ClippIn4tae]

Just need a bigger pt and ot huh?