Hoffman Single Channel AB763

[purpletele]

I didn't know I had a need for a new amp, but I guess I do, so I am going to plan out an amp as precisely as I can prior to building the amp.  Visio will play a part in that.

I think the TDR is the perfect style of amp to fill this Lush Fenderish tone.  I have a few questions that will help me get started.

Info:

Princeton Reverb Chassis and 1 x 12 Combo Cabinet.  That's what I am going to work with.

Questions:

1. The schematic shows a Master, Volume, Treble, Bass, Unmarked, and then Reverb.  The Layout doesn't indicate the MV and the unmarked 110K Pot is RAW.
     Q: What did you end up doing with the MV?

     Q: Dr. Z is implementing a Level Control on his New Amp the Cure.  I have not seen any info on a level control on any of the amps that are discussed on this forum.  How     does a level control work and how is it different to a La Mar MV.   I understand the Master on this schematic to drive the Pre-Amp section.

2. I read that you modified the trannies to MM for this amp.
     Q: Do you feel that it is worth the extra cost to install MM? 

3. Do you have info on the MM xfrmrs that you used for this project?

4. I would utilize 6L6's for this project.

Thanks in advance, this one will take a while to procure a set of transformers and parts.  I am going to start laying out the Chassis in Visio.  The Princeton Chassis looks like there is a lot of Real Estate to allow for a super clean job.

BV

[sluckey]

Princeton Reverb Chassis and 1 x 12 Combo Cabinet.  That's what I am going to work with.

That sounds good when you say it fast. But the Deluxe PT will not fit and if you use 6L6s the PT will be even bigger. Better spend a lot of time researching this!

unmarked 110K Pot

Huh??? All my pots are marked and I've never heard of a 110K pot.

I tried the amp with the raw pot as shown on the layout. Then later changed back to the Master as shown on the schematic. The raw pot gives more tone possibilities than the Master, but I wasn't really looking for any dirty sound back then. If I had to do it over again I'd probably use both pots.

Q: Do you feel that it is worth the extra cost to install MM?

No way!

3. Do you have info on the MM xfrmrs that you used for this project?

The PT is a drop-in replacement for the odd sized DRRI PT. The OT is a little larger than the stock DR OT and required drilling one extra mounting hole. Choke and RT were drop-in replacements. Part numbers and pricing are on the MM site.

4. I would utilize 6L6's for this project.

Then you will also need to carefully choose proper iron.
 

[sluckey]

Oh, one other point... My project was all about squeezing that circuit into a tweed deluxe cab. The cab dictated a narrow tweed style chassis. And the chassis I chose dictated that I use a narrow board. My point is if I had used a wider chassis, my board layout would look much different.

[purpletele]

Oh, one other point... My project was all about squeezing that circuit into a tweed deluxe cab. The cab dictated a narrow tweed style chassis. And the chassis I chose dictated that I use a narrow board. My point is if I had used a wider chassis, my board layout would look much different.

Thanks Steve,

I will start researching transformers.  I also have a Blues Junior Chassis that I had built and it fits into a Mojotone 1 x 12.  that might work as well.


This will be a good project to implement Visio!

[sluckey]

Best way to learn Visio is with a project that you are juiced about. Just jump in and start making all the mistakes I made. You'll get better every time you drag something around.

[Tony Bones]

The Weber Princeton Reverb chassis is cutout for a Deluxe PT. I think they call the Princeton "6A14" Evidently because they don't promise that every detail is an exact copy of the original Princeton Reverb. I don't know for sure if the Weber chassis will fit another makers cab exactly... They do have fairly accurate drawings of the chassis on their website, so one could always get out the tape measure.

However, their Princeton Reverb cab is guaranteed to work with their chassis. What interests me is that they offer a 1x15" Princeton 6A14 cabinet that is about 5" taller than the standard version (the baffle is roughly square.) Someday I'm going to get one of those taller cabs and chassis with the baffle cutout for 12" speaker. I want to think that the slightly larger size cab will sound better. A little narrower and taller than a Deluxe Reverb with more than enough space in the chassis for a single channel 20W 2x6V6 amp.

[purpletele]

The Weber Princeton Reverb chassis is cutout for a Deluxe PT. I think they call the Princeton "6E14" Evidently because they don't promise that every detail is an exact copy of the original Princeton Reverb. I don't know for sure if the Weber chassis will fit another makers cab exactly... They do have fairly accurate drawings of the chassis on their website, so one could always get out the tape measure.

However, their Princeton Reverb cab is guaranteed to work with their chassis. What interests me is that they offer a 1x15" Princeton 6E14 cabinet that is about 5" taller than the standard version (the baffle is roughly square.) Someday I'm going to get one of those taller cabs and chassis with the baffle cutout for 12" speaker. I want to think that the slightly larger size cab will sound better. A little narrower and taller than a Deluxe Reverb with more than enough space in the chassis for a single channel 20W 2x6V6 amp.

Thanks TB,

Now I am going to start looking at what I have and what I need.  The Princeton Tall Boy cabinet that I have will take a 12" speaker.  I told to use the Mojotone chassis due to the original collaboration.  Time to start measuring and drafting.

I bought the cab from Jim at Lil'Dog Amps in Lincoln, CA.  He has an incredible on-line business of building really nice Fender Clones.

But for now its all about the chassis and the transformer size.

Thanks,

BV

[SILVERGUN]

I've done two similar amps running push pull 6L6 is in a Princeton chassis and both times used Hammond 290cx power transformer. I had to enlarge the PT hole and from what I remember I was able to use the inside corners of the mounting holes for the original size transformer as a template to fit the 290 CX.


I also built my own cabinet and wound up with a perfect square that was about 20"x20", open back.
So, it's a tall Princeton and you dont have to worry about the transformer or power tubes hitting the speaker frame. Player comments were "its a perfect size 1x12 combo"
I thought so too.


IMHO, sluckey's TDR with 6L6 is a perfect amp, and following his design makes for a sure win.

[SILVERGUN]

OK, so I lied a little...
When I went to find you a pic of the cab I built I noticed that it was taller than it is wide, and I now remember that the baffle board was square at approx. 18.25" x 18.25". (more like what Tony Bones was talking about)
So when you add the height of the chassis to that, it was more like 21.75" high x 19.75" wide approx., overall
 
EDIT - Had to fix dimensions - kept thinking the Princeton Reverb chassis was 17" wide

[Tony Bones]

One thing I've noticed about the 60's style Weber cabinets is that they're not tapered top to bottom like the original Fender cabs.

I have a tall 1x15 Deluxe Reverb style cab on order - it should be here tomorrow. I'll let you know if it looks weird with the baffle being perfectly vertical.

[purpletele]

Here are some photos of the Mather Princeton Tall Boy that I am considering.

I ordered the Princeton Chassis from Mojotone but I am going to wait until I get the chassis before I determine what transformer.

I want to get as close to the secondary voltage of 330 V similar to what Steve used.

David Allen suggests his TP25 as a perfect fit in the chassis and that has 310V on the secondary.  I would like to use the TP40D, but that will require chassis modification(Hacking)

I looked at the Hammond 290CX and that will work with hacking. 

BV

[HotBluePlates]

This will be a good project to implement Visio!

I checked back at some notes from the first time I used Visio to plan an amp build.  I realized I spent 4-5 months on the planning/drawing, but only about 1 month on the actual build.  And that build-time included getting 2 custom chassis, a custom-engraved faceplate, a custom cabinet (Thanks again Tubenit!!), and painting the chassis & transformer endbells.

Most of the planning time was learning Visio and creating shapes, to be sure the diagram-parts were scaled/dimensioned as the physical parts would be to answer, "Will it fit?"

[purpletele]

This will be a good project to implement Visio!

I checked back at some notes from the first time I used Visio to plan an amp build.  I realized I spent 4-5 months on the planning/drawing, but only about 1 month on the actual build.  And that build-time included getting 2 custom chassis, a custom-engraved faceplate, a custom cabinet (Thanks again Tubenit!!), and painting the chassis & transformer endbells.

Most of the planning time was learning Visio and creating shapes, to be sure the diagram-parts were scaled/dimensioned as the physical parts would be to answer, "Will it fit?"

I know I am in for a learning curve, which is good.  Visio is a great tool and is helping me with my Commercial Real Estate Construction with details and such.

[purpletele]

Looking at transformers and clearances.

With the clearances that I have I don't know why I couldn't mount an upright transformer. 

If the clearances work I am going to consider using the Edcor 178.  330-0-330

I am using an Edcor PT and OT with my mini Bassman soon to be HoSo.  I don't know what would make them special, good or bad, but they seem to be real quiet and they are very attractive with price point first and looks 2nd.

Any feed back on Edcor or using a standup Transformer for the Deluxe?

[sluckey]

I like standup PTs. Less chassis work. Edcor is a popular name. I haven't heard any bad mouth.

[purpletele]

I like standup PTs. Less chassis work. Edcor is a popular name. I haven't heard any bad mouth.

Sluckey,

I have settled on a transformer for the LDR, I have attached the specs on it

Questions:

1. What wattage of OT did you utilize?  25?  30 Watts?
2. Did you have an input impedance value that you utilized on the Output transformer.  I have options for 2.5K, 5K, 6.5K and 10K for input impedance on the OT's.

Thanks,

BV

[sluckey]

This is the OT I used. MM is usually pretty skimpy with details...

     http://www.mercurymagnetics.com/images/transformers/schematics/OT/FBFDR-O.pdf

[SILVERGUN]

That last PT you listed is under rated for your application:
  Edcor XPWR047 330-0-330.pdf   
 
With it, you're already .5 amp over rated current for the filaments (running 6L6GC)...it would possibly be ok, but with Edcor, I'm sure there is a better choice. 120mA secondary for running 2-6L6s is also low   That PT would be an OK choice if you were building a stock DR with 6V6 

[sluckey]

That last PT you listed is under rated for your application:

I agree.

[purpletele]

That last PT you listed is under rated for your application:
  Edcor XPWR047 330-0-330.pdf   
 
With it, you're already .5 amp over rated current for the filaments (running 6L6GC)...it would possibly be ok, but with Edcor, I'm sure there is a better choice. 120mA secondary for running 2-6L6s is also low   That PT would be an OK choice if you were building a stock DR with 6V6

Silvergun,

Can you take a look at the specs from these two transformers.  Let me know if either of these will cover all of my bases.

BV

[SILVERGUN]

I actually thought that the first one you posted earlier in the thread was a better choice (than either of these two)
Edcor 178...for what you are trying to accomplish.

Both of these two new choices 'will work', it's just a matter of how high you're willing to go with your B+
I think the 380-0-380 unit is too high.

[purpletele]

I actually thought that the first one you posted earlier in the thread was a better choice (than either of these two)
Edcor 178...for what you are trying to accomplish.

Both of these two new choices 'will work', it's just a matter of how high you're willing to go with your B+
I think the 380-0-380 unit is too high.

Oh!  Thanks, I appreciate the feedback.

The 178 has 3.15V on each of the HT taps instead of 6.3 Volts.

I'll find one yet. 

[SILVERGUN]

I actually thought that the first one you posted earlier in the thread was a better choice (than either of these two)
Edcor 178...for what you are trying to accomplish.

Both of these two new choices 'will work', it's just a matter of how high you're willing to go with your B+
I think the 380-0-380 unit is too high.

Oh!  Thanks, I appreciate the feedback.

The 178 has 3.15V on each of the HT taps instead of 6.3 Volts.

I'll find one yet.

3.15-0-3.15 gives you 6.3VAC for your heaters, and that's what you want 

The term HT is usually reserved for the high voltage secondary winding...in this case 330-0-330

[sluckey]

This is my choice from Edcor...

     http://www.edcorusa.com/xpwr124

[purpletele]

This is my choice from Edcor...

     http://www.edcorusa.com/xpwr124

All,

I really appreciate the assistance.  Steve, I like the selection of the XPWR124.

I found that the Tone Clone OT that you used from MM had a 6.6K Input Impedance.

I selected an Edcor 30 Watt 6.6K to go with the PT

Please let me know if the OT is within range of what I am trying to procure[/b].

Thank you,  unfortunately Edcor is closed on Friday.   

I have the HoSo to work on this weekend.!

[purpletele]

LDR Update:

I haven't started laying out the chassis, board and components for this Bad Boy on Visio to date,

however, I received my custom Princeton Blanks and I an very pleased.  We verified the angle of the faceplate and ended up at 72 degrees.

I decided to load the speaker and turn over the cabinet to view the clearances of the transformer's

Clear sailing unless I am missing something.

[Tony Bones]

That cab looks really nice. Looking forward to watching this build progress!

[purpletele]

Most of the planning time was learning Visio and creating shapes, to be sure the diagram-parts were scaled/dimensioned as the physical parts would be to answer, "Will it fit?"
[/quote]

We'll, most of you guys probably know this, but I had just figured out that JJ 20uF 500 V caps are too big compared to the F & T  22uF 500V, so I have avoided that pitfall by being able to simulate the board with the Visio design.

[purpletele]

I am moving forward with the layout for the Luckey Deluxe Reverb.

I figure it is best to get as much computer work done while the familiarity of each program is fresh.

I have decided that I am going to utilize a Head Cabinet for this project, I have also set up the chassis so that I can turn it over a slip it into a Combo Cabinet.  I am going to have a set of faceplates reversed and printed for the Combo Configuration

Here is a pdf of the faceplates. 

PS., I put a spot on the back of the chassis for a Mojotone FX Loop.  I am testing a unit out on my Gies Audio Dual Watt this week.

I'll be constructing this amp and the HoSo FX on paper very soon.

[MFowler]

Wish I had seen this thread earlier.  Next time go the easy route and order transformers from Allen Amps that drop right into the PR chassis holes and allow you to run EL34 or 6L6.


Mark

[purpletele]

Wish I had seen this thread earlier.  Next time go the easy route and order transformers from Allen Amps that drop right into the PR chassis holes and allow you to run EL34 or 6L6.


Mark

Mark,

Thanks,  I will most likely build more than one, I would like to try that transformer.

I'll hit you up soon.

BV

[purpletele]

Visio Progress; time to study layers in Visio, otherwise coming along.

A couple more sessions and I'll be ready to build, but I am going to get the layout complete on the HoSo 56 as well while I am into layout design mode.

[purpletele]

A little progress on the Deluxe,  things are coming together quite well.

[sluckey]

Lookin' good! Tell me again, what are you building? A schematic would be even better.

[bnwitt]

On of the things some beginning Visio users aren't familiar with is the Size and Position Window.  This is a little pop up window that gives you X,Y coordinates as well as width, height and angle of an object you have highlighted.  For line elements you will get the X beginning and end and the Y beginning and end points too.  You can use this window to type in exact coordinates and dimensions of objects which is very important when drilling chassis holes and face/rear plate holes.

[purpletele]

Lookin' good! Tell me again, what are you building? A schematic would be even better.

This is the single channel Deluxe in a head configuration.

I have a second Deluxe developing that will be in a combo that utilizes a super light frame.  That amp will most likely have traditional transformers as opposed to the stand up Edcor's.

I have a little work to do to complete my layout drawings on Visio.  I also need to determine exactly where I am going to place the Cap Board.

I am thinking I am going to place it above the transformer wires next to the main board.

[purpletele]

On of the things some beginning Visio users aren't familiar with is the Size and Position Window.  This is a little pop up window that gives you X,Y coordinates as well as width, height and angle of an object you have highlighted.  For line elements you will get the X beginning and end and the Y beginning and end points too.  You can use this window to type in exact coordinates and dimensions of objects which is very important when drilling chassis holes and face/rear plate holes.

I may need a phone call consultation Barry.  My accuracy in Visio is less than perfect.

Thanks for the Tip.

[bnwitt]

Which version of Visio are you using PT?

[purpletele]

Which version of Visio are you using PT?

The latest version which I believe is 2016.

[bnwitt]

The latest version which I believe is 2016.

Ackk!  A ribbon version.

Well let's set up a drawing.  With Visio open and in a blank drawing, choose the "Design tab on the ribbon menu and then in the page setup area chose orientation and set it to landscape, then choose size and set it to tabloid 11" x 17" and finally make sure "Auto Size" is not highlighted or is turned off by clicking on it until the shading goes away.

Ok now go to your "View" tab on the ribbon menu and in the "Show" section of the "View" ribbon click on "Task Panes" and then click on size and position in the drop down menu.  That will open up and dock at the bottom left corner of your drawing area a small menu (Size and Position) where you will see X,Y coordinates and other info as I mentioned before whenever you have an object highlighted.  If you don't have an object highlighted you'll see nothing in the bars.   

So now draw a rectangle and with it highlighted/selected type into the size and position window's width bar 15.375" and in the height bar type 1.75" hitting enter after each input and you will then see your rectangle conform to those dimensions or what you have typed.  You can also type in the X or Y bars where you want the center location of an object horizontally on the page and vertically on the page.  So after you create your rectangle you can position it's left side on an even ruler point like 2" and it's bottom edge on let's say 5" on the page  You have to have your dynamic grid and ruler turned on to see these.  So now we have a rectangle representing a chassis face and it has a left starting point at 2" on the page and a bottom starting point at 5" on the page.

Now, draw a random circle (ellipse) anywhere on the page and afterwards in the size and position window set it's width and height both to 0.375"  It doesn't matter where you draw it on the page for now.  After size is set then we type in where we want it in the X and Y bars.  So since your chassis left edge is on 2" of the page grid type in 2.875" for the X position of the circle and to put it in the middle of the vertical face of the chassis which would be 1.75"/2 or 0.875" above the 5" page location of the bottom edge of the chassis face you type in 5.875" for the Y location in the size and position window.  Now you have an input jack hole 7/8" from the left edge of the chassis and in the middle of the vertical face of the chassis.  First hole done

[bnwitt]

Now that the first hole in the chassis face is in position, each subsequent hole to the right will be placed in relation to the previous hole.  If we have a typical Fender 1-2 input dual jack assembly then the next hole for jack 2 will be 7/8" to the right from hole one.  Here is where we use the Visio Array function:

With the pointer tool, select your first hole and then up on the ribbon there is a search bar (Tell me what you want to do..) where you can type in the word array.  "Array Shapes" will show up and click on that.  The you get the Array window pop up.  Your first hole circle should still be selected but if not use the pointer tool to select it again.  Now we will use the array window to make the next hole.  For Rows in the spacing bar type 0 and in the number bar type 1.  Why, because we only have one row in this array we're making.  Rows are up and down columns are left and right.  Now in the columns spacing bar type 0.875" because that is how far you want the next hole to be centered from the hole you have selected and in the number bar type 2 because that is the number of hole columns you will have counting the original when the array is complete.  Make sure "between shape centers" is selected and not between shape edges and then click OK.  Boom! your second input jack hole is in place.

[bnwitt]

From here you can place the rest of your control holes and their center to center distances will vary with the amp model. The positioning of bolt holes, tube sockets, transformers and other items can be done in a similar fashion.  The size and position window is critical to positioning components exactly on your drawing.  Bare in mind that on many chassis the horizontal positioning of control holes is not always exactly in the vertical center of the chassis face.

[bnwitt]

Attached is a screen grab of Visio 2003.  This is a non ribbon based version which I prefer.  You can see that I have all of my most used tools right where I can get at them.  No poking around looking for them like with the ribbon versions.  I'm pretty sure the ribbon versions can be customized but who has the time.

[purpletele]

Barry, thank you!  I'll work through that later this evening.

I have a new amp to layout, the Princeton in a Champ chassis.  The chassis came in today, so I can start verifying layout issues.

BV

[sluckey]

Which Princeton? Which Champ?

[purpletele]

Which Princeton? Which Champ?

I'll start a new thread called Princeton in a Champ

[purpletele]

I am moving along with the final field layout of components within the chassis.

I had two spots possible for the Cap board.  The best place is on 1" stand offs above the transformer wires.

I do not see any issue with the location, does any have any thoughts that would make that location a poor choice?

Thanks,

BV

[purpletele]

OT Screen Windings.

My Edcor OT came with a Screen winding, I think that is the correct description.  I have not seen this configuration before.

I connected the OT screen wire to pin 4 of each power tube in line with the 470 Ohm 3 watt screen resistor.

Is that the correct logic and position to enter into the circuit at pin 4?

What is the function and why would Edcor add that feature?

Things are coming together quite well so far.

Thanks BV

[sluckey]

Those screen taps are for ultra-linear (UL) operation and are not used for this amp. Just tape the ends and tuck away. Pretend they don't exist. Wire the tube pins 4 according to your schematic/layout.

[purpletele]

Those screen taps are for ultra-linear (UL) operation and are not used for this amp. Just tape the ends and tuck away. Pretend they don't exist. Wire the tube pins 4 according to your schematic/layout.

There I go thinking again.  Thank you!

BV