The fate of a Bassman

[SILVERGUN]

I got my hands on a Bassman 100 recently, and decided that it was the perfect platform for a D-style build because of all of the available room inside the chassis, and the perfectly good iron that came along with it.
I was able to fire it up and test everything and it all worked fine as-is, but the tone was nothing special and the rats nest inside was terrible to look at.

So, I commited to gutting it and using it for my new #1 amp.
Part of the allure is to have the 'vintagey' look but with a hot-rod under belly that you wont see coming.

I have proven to be horrible at documenting what I do, so I'll just try to post progress pics, and maybe you guys can stop me from doing anything too stupid.

I will not be cloning any one particular design, but just using all of the information that is available to try to make the best amp for ME. I am very pleased to not have to worry about cosmetics, and the only change I will need to make is to the name on the faceplate as pictured below. Now that that's out of the way I can move forward. 

[DummyLoad]

they sound like $#! £. they make terrible high gain platform. layout and cap locations. turn it into a steel string stinger or twin.

[SILVERGUN]

they sound like $#! £. they make terrible high gain platform. layout and cap locations. turn it into a steel string stinger or twin.

OOoops 
Guess I shoulda asked first!

I'm already at about 69% 

By gutted it I mean GUTTED it....the only thing original is the box, chassis and xfmrs.
Layout will be new and based off what I picked up from lurking at TAG.....doghouse is gone and caps will be mounted and grounded near the circuit sections they serve.........cross your fingers for me 

[SILVERGUN]

And then Bossman label? 

That's my sense of humor shining through there.

The only real modification to the faceplate is the new name I have given it.
I will not be wasting time on cosmetics.

It's meant to be an ugly duckling, sleeper.

[SILVERGUN]

I'll be out in the shop tonight, pressing forward....
I'm working in 'modular' sections,,,and so far I've made some changes on the fly,,,but for the most part, it still looks like this.

I'm trying to not focus on beauty, but still get the wiring looking cleaner.

[HotBluePlates]

Looking a damn sight better than the original!! 

[Willabe]

Looks very nice!

Even put a little bend in a black wire above a bolt that holds the turret board in place so you can get at it if need be.


                    Brad   

[SILVERGUN]

Thanks for having a look guys!....focus on the positives!

First pic below shows a couple mistakes/changes that I made:
- The yellow circle on the left is where I thought I was going to put a relay (on the 2 homemade standoffs)
   ...until I realized that I probably didn't want that coil so close to my PI input cap,
 so I fixed it by adding a couple eyelets and making it a filter cap location,,,which happens to make way more sense.

- The pink circle is where I sized/shaped the turrets into a triangle to attempt to fit a little bias pot as a PI balance pot...
   the problem with it was that I then realized I would be greatly exceeding the voltage rating of those little bias pots...and those turrets were awefully close together.
   ..so I decided to use the full size 10K bias pot that Doug sells and mount it to the back side of the chassis to give me access to that balance control when the amp is buttoned up (pic coming soon)

- The green circle was originally just a solid jumper (red wire), but I wound up inserting a dropping resistor in it's place.

Second pic is where you can clearly see where I tucked the rectifier board right next to the standby switch that I moved to the front panel.....you can also see where I added one of Doug's relay power supply boards.

[TubeGeek]

Looking good....better than original for sure!

[SILVERGUN]

Looking good....better than original for sure!

Since you challenged me to a race  I was trying to sneak it in so it looked like I was moving quick.....reality is I've been chipping away for a couple weeks while working on some other stuff 



Here's a shot of the PI balance pot.
While thinking about this I have realized that I should probably isolate the shaft/body from the chassis for safety.

The b+ goes into the wiper and then each outside leg feeds a plate, with leads going back to the board to meet up with the coupling caps to the output tubes.

The theory is to have a point where you can intentionally balance/unbalance the AC wave coming off of the PI plates,,,,and part of it can be done by ear, so I figured it wouldn't be crazy to have an external adjustment.

[Ritchie200]

And those recently acquired KT88's?  For shame.....  I thought you had actually turned the corner.  You can take the buzzsaw distortion, pinch harmonic, wanna-be out of the pit - but I guess the dark side runs too deep with this one....


I'm always here for guidance if you so desire.



Jim

[SILVERGUN]

And those recently acquired KT88's?

Funny you mention those 'cause I got myself in a pinch..
I wired up the output tube sockets so that pin 1 is a tie off point for my grid stoppers,,,and if I wanted to try the 88's I'd have to rewire accordingly.....unfortunate lack of foresight

But I was considering running 2 of 'em with a 8 ohm cab to 4 ohm tap mismatch...
UNTIL, I was reading up about how they don't like the screen V too close to the plates....or they don't tolerate that condition as well as 6L6

 
Rookie

For shame.....  I thought you had actually turned the corner.  You can take the buzzsaw distortion, pinch harmonic, wanna-be out of the pit - but I guess the dark side runs too deep with this one....

Nah man,,
This is gonna be my soft-soul-funk unit.........I'm done with that high gain stuff....I grew up 
Now I just gotta find the right Tele 

[Mike_J]

Does anyone know how many volts the 10K Fender style pots are rated for?  A lot of the Dumble's seem to run around 290 to 300 volts on the PI.  Presuming your tube is pretty well balanced usually optimal setting is where there is a six to seven volt difference between the two.

Mouser has a part 858-93PR10KLF for what is supposed to be a one watt trimmer.  However, the data sheet shows a maximum dc input voltage of 200 volts.  How can that trimmer be rated for one watt then?  If it was truly a one watt trimmer I would think it should easily handle the 300 volts.

Most Dumble's I have seen documented have two 220uF caps in series minimum for the HT.  Some use 300uF plus caps.  The screen supply cap and the rest of the caps are commonly 20uF.  The 100uF caps may work though.

Have you decided if you are going to go with the 100K plate voltages on the preamp tubes or are you going to go higher.  Another thing you have to decided on is which overdrive circuit to use and whether to put an FET input in it. 

I would use Doug's relay power supply.  Much simpler than the Dumble method.

In my experience having the preamp boost on a footswitch is worthwhile.

The suggestion to make a Steel String Singer out of it is pretty good too because everyone should have one of those.

Thanks
Mike

[2deaf]

That Mouser pot. has a dielectric strength of 900V.  The 200V max. is what it can drop across it up to one watt.  You're going to drop 20V or less across it.

[SILVERGUN]

1) Most Dumble's I have seen documented have two 220uF caps in series minimum for the HT.  Some use 300uF plus caps.  The screen supply cap and the rest of the caps are commonly 20uF.  The 100uF caps may work though.

2) Have you decided if you are going to go with the 100K plate voltages on the preamp tubes or are you going to go higher.  Another thing you have to decided on is which overdrive circuit to use and whether to put an FET input in it. 

3) I would use Doug's relay power supply.  Much simpler than the Dumble method.

4) In my experience having the preamp boost on a footswitch is worthwhile.

5) The suggestion to make a Steel String Singer out of it is pretty good too because everyone should have one of those.

Thanks Mike, I numbered your questions/comments so I could directly address them easier

1) Yes,,most of the D machines out there have 220uf and up, but if you look back at some of the older units, he was using 100s and they will be fine for me....I'm pre-planning that this thing will probably be running on 2- 6L6s cause I just don't need to be 4-6L6 loud.....2-100uf's (which equals 50uf when connected as I have) will suffice, and maybe lend themselves to a slightly less 'stiff' response. I put 50uf on the screens and then 20ufs down the line from there. Should be close enough for rock and roll.

2) I'm guessing you mean 100K plate resistors?....if so, no, I'll have 220K first stage

3) There's one in there, and hopefully it will be sufficient for the 3 relays that i'll be running

4) I'm going a slightly different direction, and will make that feature front panel switchable only

5) The SSS is probably the best clean sound ever,,,,but unfortunately I'm not a good enough player to play clean all night, so I'll have to 'settle'  for an ODS type

 

[Mike_J]

That Mouser pot. has a dielectric strength of 900V.  The 200V max. is what it can drop across it up to one watt.  You're going to drop 20V or less across it.

Thanks 2deaf

That means it is a very good trimmer to balance the PI and would fit easily on the main board.  Thank you for straightening up my confusion.

Thanks
Mike

[Mike_J]

1) Most Dumble's I have seen documented have two 220uF caps in series minimum for the HT.  Some use 300uF plus caps.  The screen supply cap and the rest of the caps are commonly 20uF.  The 100uF caps may work though.

2) Have you decided if you are going to go with the 100K plate voltages on the preamp tubes or are you going to go higher.  Another thing you have to decided on is which overdrive circuit to use and whether to put an FET input in it. 

3) I would use Doug's relay power supply.  Much simpler than the Dumble method.

4) In my experience having the preamp boost on a footswitch is worthwhile.

5) The suggestion to make a Steel String Singer out of it is pretty good too because everyone should have one of those.

Thanks Mike, I numbered your questions/comments so I could directly address them easier

1) Yes,,most of the D machines out there have 220uf and up, but if you look back at some of the older units, he was using 100s and they will be fine for me....I'm pre-planning that this thing will probably be running on 2- 6L6s cause I just don't need to be 4-6L6 loud.....2-100uf's (which equals 50uf when connected as I have) will suffice, and maybe lend themselves to a slightly less 'stiff' response. I put 50uf on the screens and then 20ufs down the line from there. Should be close enough for rock and roll.

2) I'm guessing you mean 100K plate resistors?....if so, no, I'll have 220K first stage

3) There's one in there, and hopefully it will be sufficient for the 3 relays that i'll be running

4) I'm going a slightly different direction, and will make that feature front panel switchable only

5) The SSS is probably the best clean sound ever,,,,but unfortunately I'm not a good enough player to play clean all night, so I'll have to 'settle'  for an ODS type

Should be very nice.  My favorite ODS build has the 220K plate resistor on the first stage.  I think a SSS build would make you sound like SRV.  They take pedals well and the clean is so very good.  However, you will enjoy your ODS very much too.  If I could only build one it would be an ODS.  Should hold three relays since the system is a 1 amp system and the relays and leds shouldn't require that much.

Thanks
Mike

[kagliostro]

Ciao SILVERGUN

Nice tread 

do you remember Professor Fate ? 



K

[SILVERGUN]

Nice tread 

do you remember Professor Fate ? 

Thanks K!

I just barely remember Prof. Fate.
"Push the button MAX!"

I rushed myself into this one because I just formed a band and gotta have great tone...sooner than later
Now that I know ODS's exist, and that I'll never see a real one, I'll take the next best thing!   

I'd like to see the Great TubeGeek try THAT one!   (another prof. fate quote)

[Platefire]

So this is the Big Fish you are Frying  Carry on! The Band is waiting 

[DummyLoad]

https://www.youtube.com/watch?v=dzOHq5WbQ8k

[SILVERGUN]

Alright,,,I figured I better come clean with a couple more update pics so at least the thread will have some chronological order to it.
Here's the layout of the additional tube sockets, and my plan for how the different circuits will be laid out internally.

I will be using Tubenit's SCH file for a switchable tube FX loop and switchable tube reverb:

[SILVERGUN]

And here's a shot of the mock'd up relay/ preamp board...

The amp will have 3 foot switchable switchable options;
- Relay 1 - Clean-normally closed --- OD on with energized relay coil
- Relay 2 - FX loop off n.c. --  FX on   
- Relay 3 - Reverb off n.c. -- Rev. on   

I'm thinking that I will be putting LED's in the footswitch, so that is why I arranged the relays to perform this way,,,so that the LEDs will indicate what I want them too (pretty standard stuff)   

The reverb and FX circuits are both self contained on terminal strips right next to the tubes that serve them. you can see them taking shape in the pic.   

[SILVERGUN]

Alright, BIG update....lots of work done this past week.

I got sound out of it on the first try.
Lost the 50/50 OT secondary wire gamble.....how is it that I always get that wrong?

Stil tweaking...removed fourth stage bypass cap,,,etc., etc. (so I won't dare call it a D'ble) 
Working on a schematic,
BUT also already working on another amp.......what is wrong with me?

Relay foot switching isn't wired up yet, but so far I've clipped on power and everything works as planned.

Whatever you do, don't count the number of pots on the front panel. 

[Ed_Chambley]

Looks good.  Tell me about those blue resistors.  They look mil spec.  Who makes them and are they 1 watters?

[SILVERGUN]

Looks good.  Tell me about those blue resistors.  They look mil spec.  Who makes them and are they 1 watters?

Thanks Buddy.
The little blue ones are Dale CMF-60 1/2 watters. mil-yes

I bought a crapload of resistors when I first started and you'll notice that I rarely stay consistent in my usage.
I use whichever color I pull out of the drawer...it makes me feel like a rebel.

Here's a revised version of Tubenit's reverb + FX loop schematic,,,and another opportunity to thank him for all of his hard work and contributions to the SCH library where I originally found this. (before I chopped it up)

I had to adjust the switching tabs to match the relay switching, so please keep that in mind if anyone is trying to copy this.

[SILVERGUN]

The circuit is basically the D #102 with some stuff carried over from a schematic labeled HRM-101 including the additional tone stack after the OD stage. Some changed dropper values,,, 12AT7 PI with balance pot.

I didn't want to take the liberty of posting any schematics that I didn't draw,,,,,but all of this info. is available.

I used just switchable NFB which is either full on or full off, labeled as 'Accent'

Again, nothing ground breaking here, just the culmination of a lot of information. Some D'Lite, some Tubenit, some TAG, and some me. I didn't want to be a guy who just built another clone....I wanted an amp that I thought out for me.

[SILVERGUN]

Here's a glimpse at how I work....I take pics of the amp in progress, and lighten them up to be able to draw in components to map out the circuit.
By the time I finish an amp I have a stack of papers like this that consists of what seems like 100 pages, of revisions, white-out, etc., etc.
This is the final draft for the signal flow around the relays, incorporating the reverb and fx loop.

[Ed_Chambley]

Here's a glimpse at how I work....I take pics of the amp in progress, and lighten them up to be able to draw in components to map out the circuit.
By the time I finish an amp I have a stack of papers like this that consists of what seems like 100 pages, of revisions, white-out, etc., etc.
This is the final draft for the signal flow around the relays, incorporating the reverb and fx loop.

That chassis gives you some real estate, but I hate to say I am not a fan of the tilt in the face nor tubes down, but it makes a solid foundation.  There are always drawbacks.

I get your method of construction.  Lots of guys, including me, consider it as all components sections connected.  It is hard for me to even fathom building one amp for me.  Then again, I have a ton of effects as well.

Why when people speak of Dumble they spell it weird like D'mHumble?

[SILVERGUN]

Why when people speak of Dumble they spell it weird like D'mHumble?

I think it's cause if you spell it correctly 3 times in one thread he shows up at your house to punch you in the face and pick up a royalty check. 

I do it so as to not clog up internet or forum search results with my fictional representation of a Dr. D creation....and just to play along nicely with the rest of the sheep.

I'd rather this amp be remembered as the BOSSMAN 100

It is hard for me to even fathom building one amp for me.  Then again, I have a ton of effects as well.

That's why I had to force myself to do this NOW
If I didn't just commit to an amp and build it I would be playing out of someone else's amp,,,,and at this point, I refuse to do that.
Or, I'd look awefully funny on stage with a breadboard on top of a 1x12 cab.

I'm gonna go straight in, with just a slight 'fattening' delay with a touch of boost in the loop.....step on the loop foot switch and I'm in boosted sustainy solo land....we'll see.

[TubeGeek]

Very nice work SG.  Your level of detail is incredible.  It makes sense.  There is a lot of work into that project, you should be proud.


 


I have been meaning to start using mil-spec resistors in my projects for a while, I just haven't got around to placing the mouser order yet.  I like the look of those, high quality stuff.

[SILVERGUN]

Hey,, THANKS TG!

I've been playing it for a few weeks now, and still trying to dial it in, but I'm glad I did it this way, because it has given me an inexpensive platform to try out a couple ideas.

I still plan on posting a clip and schematic when I'm sure it's done.....I've had to push it aside for a little while whilst I fill a couple orders.

DONE is a funny word around here.