Confused again.

[Mike_J]

Hoping someone will help out an old man having a senior moment and tell me which of these caps is the bass cap. Is it the one attached to the 56K resistor or the other one?

[Mike_J]

I know they are both attached to the resistor but I mean the one that the termination of the resistor points to or not in the picture.

[Mike_J]

While I am milking the confused old man angle I need help in picking the correct diode for my 5f6a. Have an IN4001 rated at 50V. Let’s see we are using 100V ecaps so that isn’t the answer I don’t think. Then I have IN caps in 400, 600 and 1K range. Starting to think the IN4004 at 400 volts will serve my purposes. Then I am thrown a loop with a 3 amp ultra fast diode. Is there any reason to use an ultra fast diode in the bias section of this amp? Looks like I have a lifetime supply of all of them.

[Bieworm]

First off, the UF diodes are less noisy due to the faster switching nature. But if it's percieveable is food for debate... the higher the voltage rating, the safer?

The caps.. the cap between the 250pf and the outer 22nf is the bass cap in a standard AB763 tone circuit. I'd say you don't show enough of the schematic to be sure. What do the caps connect to at the other side?

[jjasilli]

The bass cap is the one in the middle.  See:  https://robrobinette.com/How_The_TMB_Tone_Stack_Works.htm#:~:text=Band%20pass%20filters%20remove%20frequencies,pass%20through%20the%20tone%20stack.


(FWIW, IMHO the TMV tonestack is so interactive, that other than the treble cap, the other 2 caps part of a large complex filter - so their names are more for identification than a pure description of their function.)

[2deaf]

Hoping someone will help out an old man having a senior moment and tell me which of these caps is the bass cap. Is it the one attached to the 56K resistor or the other one?

It doesn't matter because they are both 0.022uF.

[2deaf]

The caps.. the cap between the 250pf and the outer 22nf is the bass cap in a standard AB763 tone circuit. I'd say you don't show enough of the schematic to be sure. What do the caps connect to at the other side?

The middle capacitor is the midrange cap on AB763 layouts.

[Mike_J]

Hoping someone will help out an old man having a senior moment and tell me which of these caps is the bass cap. Is it the one attached to the 56K resistor or the other one?

It doesn't matter because they are both 0.022uF.

Won’t be for long because I am changing the bass cap to .1uF and the slope resistor to 100K. Again for two reasons. First the reissue used them and was supposedly taken from a good sounding amp and some guy on the web had two and liked that combination better. Can always be switched back. 


The amp was made both ways. Why or when the switch happened I have no idea. Thank you for responding.

[Mike_J]

The caps.. the cap between the 250pf and the outer 22nf is the bass cap in a standard AB763 tone circuit. I'd say you don't show enough of the schematic to be sure. What do the caps connect to at the other side?

The middle capacitor is the midrange cap on AB763 layouts.

It is on the Bassman as well. I was getting tired from populating my board and needed a little help. If I wasn’t so tired that is something I should have figured out myself. Any way thank you for your help.

[Mike_J]

The caps.. the cap between the 250pf and the outer 22nf is the bass cap in a standard AB763 tone circuit. I'd say you don't show enough of the schematic to be sure. What do the caps connect to at the other side?

The middle capacitor is the midrange cap on AB763 layouts.

Looked at the 5f6a schematic and the wire feeding the left lug of the treble pot (maybe ccw if my memory is correct) over to the wiper of the bass pot is from the bass cap. Thanks, think I may be getting a second wind.

[Mike_J]

The bass cap is the one in the middle.  See:  https://robrobinette.com/How_The_TMB_Tone_Stack_Works.htm#:~:text=Band%20pass%20filters%20remove%20frequencies,pass%20through%20the%20tone%20stack.


(FWIW, IMHO the TMV tonestack is so interactive, that other than the treble cap, the other 2 caps part of a large complex filter - so their names are more for identification than a pure description of their function.)

Appeciate the information. Thank you.

[2deaf]

Won’t be for long because I am changing the bass cap to .1uF and the slope resistor to 100K.

Saimon.  Just how old are you, son?

[thetragichero]

why not tack solder caps in parallel to see if you'll like it before cutting the leads and committing?
i see no reason to keep anything besides 1n4007 (okay, maybe the UF type) on hand since they're all basically the same price

[Mike_J]

Won’t be for long because I am changing the bass cap to .1uF and the slope resistor to 100K.

Saimon.  Just how old are you, son?

It isn’t usually the age on the tires it is the miles on the tires. Let’s just say I have been rode hard and put up wet a few too many times.

[Mike_J]

why not tack solder caps in parallel to see if you'll like it before cutting the leads and committing?
i see no reason to keep anything besides 1n4007 (okay, maybe the UF type) on hand since they're all basically the same price

Sound advice as I would expect from you. Have attached a picture of the IN4007 and the UF type as well. The UF also has a 1K value. I will let the picture below make the decision. Which one shouts out growler?

[thetragichero]

<doesn't make much sense now with the previous post deleted>

[Mike_J]

only if you've got low oxygen copper mixed with fairy dust for the audiophool set
not sure if it's a fortune as you'd likely do much better selling lits of cheap stuff vs little bit of expensive stuff (who's doing better right now, walmart or wegman's?)

However, that sounds like work. Something I am trying to avoid. You are probably right though. Guitar amp market may not be the place to go with this plan. Probably lucky if I get my $3 back for the part. Guess I am going to have to fight another stress relief, maybe not the right name, thing to get my AC cord secured back to the chassis. Would rather take a pretty severe beating than tackle that job again.

[thetragichero]

no more/less annoying than drilling and filing a cutout for an iec socket

[HotBluePlates]

... which of these caps is the bass cap. ...

I'm gonna disagree with others and say, "both 0.022µF caps are 'bass' caps."

     -  The 0.022µF caps are connected together on one end.
     -  The Bass control is a variable resistor.
     -  One end of the Bass control's range keeps one end of each cap apart.
          -  This isolates one cap from the other with 1MΩ (the 5F6-A's Bass pot resistance)
     -  The other end of the Bass control's range connects the ends of the caps, placing them in parallel.
          -  This turns the 0.022µF connected to the Middle pot into a 0.044µF cap (or adds whichever values you used).

But the Simple Answer is the "Mid Cap" is the one with a wire to the Middle control, and the "Bass Cap" is the one connected to the Treble control (and from there to the other end of the Bass pot).

... See:  https://robrobinette.com/How_The_TMB_Tone_Stack_Works.htm#:~:text=Band%20pass%20filters%20remove%20frequencies,pass%20through%20the%20tone%20stack.

That link makes everything needlessly complex.  The tone stack could be explained much more simply; it boils down to a low-pass filter, a high-pass filter, and a scoop (hopefully near midrange) where the two cross.

[Mike_J]

That link makes everything needlessly complex.  The tone stack could be explained much more simply; it boils down to a low-pass filter, a high-pass filter, and a scoop (hopefully near midrange) where the two cross.

I understand what you said about the additive nature of the mid and bass caps and your explanation of the tone stack being a high and low pass filter. Not at nearly the level you do. Why do you think the guy with a few original Bassman amps and the reissue schematic used a .1uF cap for the bass cap and a 100K slope resistor? Would like to understand this better because it is certainly an area that can be modified to get closer to what I would consider an ideal tone. Realize it is subjective and what is ideal for one person may not be so for someone else.


Have created a box with caps and a pot to adjust cathode caps and resistor values to find the values that made my 5E3 sound good to me. Suppose I could slap one together with a 10K resistor and 100K pot in series and caps of .018, .022, .033, .047, .066, .1 and .22uF to see what I like. Marshall amp I like has a 33K slope resistor if my memory serves me. Don’t know why I think it would be a good idea to add the 10K resistor but don’t see how it would hurt.