Parts Just Arrived For 5F6A

[Ed_Chambley]

I have heard soooooooooooo much about tweed bassman's I thought it was time to build one.   Supposed to be greater than than turtle soup.  I would like to put the most common mods in-place during the build.  Anyone ever added a separate voicing to v1 pin 7 like the marshall lead?  Does the "Rich Mod" master work well using a 500ka pot.  It is crazy nice on my JTM-45.  Anyone added switchable Silver Mica to the Bright Volume?  What are the votes on the Rectifier Tube and power tubes 5881 or 6L6?  Preamp tubes, gotem all NOS. Which ones, where?  Caps, SoZo Vintage Mustard, Solen, Mallory, Xicon or Orange Drops or combo?  Metal Film or Carbon Comp or a combo of both?
Got a 4, 10's cab with 2 Weber 10A125 20 Watt Alnico on the top and 2 10F125 Ceramic 30 watt on the bottom.  Will this work well, or should I go with the Alnico in all 4 positions.

Any additional input is welcomed.

[sluckey]

I would like to put the most common mods in-place during the build.

You may want to consider building the amp 'straight up' before adding mods. Doing so will give you a baseline to compare the mods.

[tubeswell]

I vote for building it vintage stock (12AY7 in V1, and 5881s) with the weber speakers

[worth]

Yes... how are you going to know what a "Bassman" sounds like , if you build mods into it ?!

[Ed_Chambley]

2 votes for stock.  Stock it is.  What are the closest caps to those old astrons.  I do have a couple 3 old tung-sol 5881 and some 12Ay7 that test real good.  RCA's.  Didn't they have 12AY7 in V1 and 12AX7 in 2 and 3.  Who is making a good current production 5881 I could get to fire it up?  I've got a couple of GZ-34 Sovtek I got from Doug that seem to bulletproof.

I can tell you this, I have never seen a turret board like the ones Doug sells.  Man that thing is durable feeling.  I can't wait to get started.

[Ed_Chambley]

Yes... how are you going to know what a "Bassman" sounds like , if you build mods into it ?!

I always make mods switchable.  Like adding a MV, it is switchable.  Like in 100p on the volume, I add switchable caps.  But you guys have convinced me already.  Build it stock.  That is what I will do.

I just get excited every time I get new build parts in.  I can already smell the flux burning.

[sluckey]

I highly recommend printing Doug's layout AND the schematic. Get familiar with both. Get proficient with finding a part on the layout and the corresponding part on the schematic and visa versa.

And don't clutter your mind with all those other amp ideas while you're building this one.   

[Ed_Chambley]

I highly recommend printing Doug's layout AND the schematic. Get familiar with both. Get proficient with finding a part on the layout and the corresponding part on the schematic and visa versa.

And don't clutter your mind with all those other amp ideas while you're building this one.  

I already have.  Found some discrepancies.  No big deal tho.  Like the filter caps I received are Illinois 22uf/500v and the layout calls for 20uf.  I ordered from his public parts list, just removed everything I already had.  I have the PT.  I did get the 40 watt 2-4-8 ohm OT.  He has obviously replaced the atom 20 with the Illinois as they are way less money.  I have some F&T's in 20uf/475, but I will probably use the Illinois.
The fender schematic has a 8uf/450 cap, have not figured that out yet.  It looks like the screen grid on v2 pin 6 connects direct to the B+ rail with the 100K resistor returning to pin 1 plate and jumped to pin 7 grid.  What happened to the need for the ecap 8uf/450?  Are you just using a 20uf/500 instead?

[Ed_Chambley]

Looks like comparing fender schematics to Hoffman, Doug has through series and parallel of resistors and caps simplified the parts count as well as wiring.  That is what the Hoffman Board is all about.  It looks like it is much simpler.  I guess I will find out.

[HotBluePlates]

...  Found some discrepancies.  ...  Like the filter caps I received are Illinois 22uf/500v and the layout calls for 20uf.  ...

Almost all caps moved from the old value numbering scheme of 10, 15, 20, 25, 50, etc to 10, 22, 33, 47, 68, etc. The exception that proves the rule is the Atom series of caps, which are expressly for the purpose of replacing caps in old equipment. But seriously, 22uF is fine for this point.

... What happened to the need for the ecap 8uf/450?  Are you just using a 20uf/500 instead?

As you note, 8uF is authentic for the preamp filter, so you could swap for the original value on that. Doug does stock that value.

Doug's boards were originally built to drop into the reissue amps of the same model. I don't recall offhand, but it seems the reissue Bassman from Fender has a 20uF preamp filter instead of 8uF. As filter caps were not part of the kit, you reused what was existing in the amp.

Looks like comparing fender schematics to Hoffman, Doug has through series and parallel of resistors and caps simplified the parts count as well as wiring.  That is what the Hoffman Board is all about.  It looks like it is much simpler.  I guess I will find out.

There is no reduction of parts count, except for the lack of the snubber cap across the plate outputs of the phase inverter. The added grid stoppers and good wiring dress should obviate the need for them. There is the appearance of a reduction of parts due to the paralleling between shared turrets, as you noted.

One thing that few people will point out:
Apparently, the schematic shows one set of values for the tone circuit caps, but actual amps were shipped with one of three different sets of values. The most common one was (I am told) 250pF, 0.022uF and 0.1uF. Amps were also shipped with the values shown on the schematic, and typical blackface values of 250pF, 0.047uF and 0.1uF.

I only found this out because I built a kit for a customer who was very familiar with the vintage Bassman amps. He was irate when the kit arrived with the values shown on the schematic, and let me in on this information.

[plexi50]

I would build it stock first. There are only a few minor tweaks you might want to do later.  The 5F6A is a great amp

[Ed_Chambley]

As you note, 8uF is authentic for the preamp filter, so you could swap for the original value on that. Doug does stock that value.
I have that value on hand, but on the layout the resistor is on the board instead of the tube socket.  What difference is the additional filtering going to do anyway?

Also, what type of caps will yield a more traditional sound?  Where would you use metal film resistors?  I know this is subjective, I am asking for your opinion not trying to start that cap argument.  I have a good supply of Sprague Orange, Mallory, Solen, SoZo Vintage Mustard

[sluckey]

..., but on the layout the resistor is on the board instead of the tube socket.

Don't compare Doug's layout to the original layout! Doing so may lead to unnecessary confusion or questions. You bought Doug's board, so build it according to his layout. Doug's layout matches the Fender schematic (mostly).

[Platefire]

I've built a couple of 5F6A's and agree with stock first as baseline for seeing what that famous tone is all about. Of course mine were conversions and not scratch builds. I agree about the switchable mods where you can switch yourself back to original. That's what I like to do. If you build it stock first, be sure to leave room on the front panel for adding switches or a MV for your mods. Sure is hard to make room for mods if you didn't plan for it. Platefire

[six el six]

I'd love to see pictures. I'm building one over the holidays myself.

[HotBluePlates]

Also, what type of caps will yield a more traditional sound?  Where would you use metal film resistors?  I know this is subjective, I am asking for your opinion not trying to start that cap argument.  I have a good supply of Sprague Orange, Mallory, Solen, SoZo Vintage Mustard

If it were my amp, I'd use Vishay Dale RN65D metal films throughout the entire amp; metal films because of the low noise, and the quoted brand/type because the printed values are easier to confirm fast than color bands.

Caps? I'd use whatever e-lytics I had on hand (brand is not a concern to me here). If I had a lot of room and was not using a tweed-style chassis, I would use Solen caps for the filters, only because they'll never need replacing. I would likely use Mallory M150 or similar for coupling caps, as the polyester dielectric should be similar to the sound of the original Astrons.

[LooseChange]

Or you could use Mustard Caps (or copies) and make it like the British copy.

[Ed_Chambley]

..., but on the layout the resistor is on the board instead of the tube socket.

Don't compare Doug's layout to the original layout! Doing so may lead to unnecessary confusion or questions. You bought Doug's board, so build it according to his layout. Doug's layout matches the Fender schematic (mostly).

I am going to use Doug's layout.  I was curious how the board could be so much smaller.  I can see now.

[Ed_Chambley]

I'd love to see pictures. I'm building one over the holidays myself.

I use modular chassis on builds which I am learning on.  I get the box from the container store, cut out the bottom leaving a .5 lip and cut out the face leaving a lip here as well.  Then I can cut sheet metal for the face and make a printed vinyl sticker and laminate it.  If I change to a new amp, I can remove the bottom and face as sometimes I will need to mount the transformers differently.  Revise the faceplate art and put it onto a new piece of sheet metal and bolt it onto the chassis using brass thumbscrews.  Once I am completely pleased with the build, I fit it into a cabinet.  JDesigns makes me some of the cabinets and some I make.  I will get some photos so you can see.   When it is complete, it looks like it was bought from a store.  I call all my amps SuperBolt and then a number.  I get asked, where did you buy that amp.  It is really cool and easy to do.

To change this to a Bassman, all IO have to do is copy and paste the presence, move it right and then change the names to allow of the middle.  Oh-yea, and call it a SuperBolt 440.

[Ed_Chambley]

Also, what type of caps will yield a more traditional sound?  Where would you use metal film resistors?  I know this is subjective, I am asking for your opinion not trying to start that cap argument.  I have a good supply of Sprague Orange, Mallory, Solen, SoZo Vintage Mustard

If it were my amp, I'd use Vishay Dale RN65D metal films throughout the entire amp; metal films because of the low noise, and the quoted brand/type because the printed values are easier to confirm fast than color bands.

I have some of these resistors.  I bought them for the reason you stated.  It makes it much easier as I often have trouble seeing the difference in some of the colors.  Mainly, I just check them with a meter.