Planning to convert one of my 5f4 to a 5f6a Bassman

[Ed_Chambley]

I am going to build my first turrent board and convert a 5f4 to a bassman 5f6a.  I have a custom faceplate which has no middle.  I was thinking of using the presence hole for the middle and maybe put the presence on the back.  Is the presence on a bassman very effective and not like the 5f4 which does not make much change?  Could a resistor be used in place of the pot or would that be taking too much away from the bassman?  Also, the PT I have in the 5f4 is the same as the bassman.  Any suggestions for an OT.  Will the same choke work?

[HotBluePlates]

Is the presence on a bassman very effective and not like the 5f4 which does not make much change? 

That's odd... the presence pot on my 5F4 copy stays near-off most of the time, as cranking it up results in a LOT of highs. Maybe you don't have good continuity between the presence pot's ground and the speaker jack ground. Or too high of a series feedback resistor value.

[HotBluePlates]

Could a resistor be used in place of the pot or would that be taking too much away from the bassman?  ...  Will the same choke work?

You could use a fixed resistor instead of a pot, if you know what resistance value will result in the amount of highs you want.

The same choke will work fine.

OT can really be any 2x6L6 with a 2 ohm tap, unless you plan on using the amp with the same speaker setup you have now for the 5F4. In that case, you could probably use the exact same OT.

[Ed_Chambley]

Could a resistor be used in place of the pot or would that be taking too much away from the bassman?  ...  Will the same choke work?

You could use a fixed resistor instead of a pot, if you know what resistance value will result in the amount of highs you want.

The same choke will work fine.

OT can really be any 2x6L6 with a 2 ohm tap, unless you plan on using the amp with the same speaker setup you have now for the 5F4. In that case, you could probably use the exact same OT.

I went ahead and ordered the muti-tap transformer doug has listed.  The listing is junny tho.  It says in the title, 40 watts, but in the description it states 50 watte.  The combo cab I have for this is 8 ohms plus I just like the flexibility of the multi-taps as I have various 2 speaker combo cabinets.
Also, you are correct about the resistor, I have a different value in there for some reason but now I cannot remember why.  I am sure it was something I was monkeying around with.

[HotBluePlates]

Maybe you were experimenting with suggestions that are out there to get a "more raw sound" by reducing the amount of feedback.

The logic is that a presence control typically works by controlling how much high frequency signals are fed back; less feedback at highs than for the rest of the signal makes those frequencies seem louder by comparison. So you get a treble boost. If you reduce the amount of feedback for the "other signals" then you also reduce the amount of apparent treble boost. At that point, the presence control seems less effective (or even non-functioning if there is effectively "no feedback" for all other signals).

[Ed_Chambley]

Maybe you were experimenting with suggestions that are out there to get a "more raw sound" by reducing the amount of feedback.

The logic is that a presence control typically works by controlling how much high frequency signals are fed back; less feedback at highs than for the rest of the signal makes those frequencies seem louder by comparison. So you get a treble boost. If you reduce the amount of feedback for the "other signals" then you also reduce the amount of apparent treble boost. At that point, the presence control seems less effective (or even non-functioning if there is effectively "no feedback" for all other signals).

I have now 3, 5f4's  One is stock with 2,10"s.  Has correct transformers.  All Mallery caps and a ceramic cap .005 on the bass.  I looked inside and changed the resistor back and it does make quite a bit of difference.  The other 2 I have, one is a head and has 2 rectifier tubes and an extra gain stage with a Mercury Magnetics Fat Stack Bassman OT.  I had NOS RCA 6L6's in it, but changed them back to Winged "C"s.  I just like them better.  It too had a different Resistor in it.  I changed it back to stock and it is better as well.  The last one is the one I recently put in the master volume.  You had a hand in that one.  The master is working, but there is something about this amp and I can't put my finger on it.  The best way to describe it is it has no soul.  It is my zombie amp.

[HotBluePlates]

Do you mean it sounds "too hi-fi"?

If you want the best in clean tones, a bigger-core OT is the way to go. Sometimes however, there is mojo in an undersized-OT (power-wise). What happens is the OT starts to saturate, and the bandwidth of the output to the speakers becomes restricted. I mean, there's a bit more roll-off on the lows and highs, pushing everything towards midrange.

Sometimes, you might have "character" in an undersize OT if you like distortion sounds, and putting in an OT great for cleans takes away some soul factor.

The problem is, this is subjective stuff too, and swapping OTs is very expensive (unless you happen to have a bunch hanging around for some reason).

That's a long way to say, "I wonder if the Fat-Stack OT is 'too good' for what you're trying to accomplish?"

[stingray_65]

  The listing is junny tho.  It says in the title, 40 watts, but in the description it states 50 watte.

40 or 50 watts, really not any different.

2 6L6's in P-P can deliver a big variety in output power.

Bias and B+ will change that lots.

Aurally you would be hard pressed to tell which is "louder"

For sheer volume's sake, you can get the most SPL from a high sensitivity speaker such as an Eminence Wizard (103dB 1M /1W)

for fun with numbers check this link to see how speaker efficiency translates into SPL

http://www.sengpielaudio.com/calculator-efficiency.htm

[Ed_Chambley]

  The listing is junny tho.  It says in the title, 40 watts, but in the description it states 50 watte.

40 or 50 watts, really not any different.

2 6L6's in P-P can deliver a big variety in output power.

Bias and B+ will change that lots.

Aurally you would be hard pressed to tell which is "louder"

For sheer volume's sake, you can get the most SPL from a high sensitivity speaker such as an Eminence Wizard (103dB 1M /1W)

for fun with numbers check this link to see how speaker efficiency translates into SPL

http://www.sengpielaudio.com/calculator-efficiency.htm

Cool website.  Yea, I am not one of those that equate watts with volume of Sound Pressure Level as you suggest.  I use heads and cabinets mostly.  I built a footswitchable box to select different cabinets to show a friend of mine that wattage is not the only variable in volume.  I like 2, 12's cabinets and have 3 of them.  One has celestion vintage 30, one has a weber alnico and ceramic, I forget which ones but they are very inefficient and the third has a weber blud dog and silver bell AlNico (this is my favorite)  Setting a 50 watt amp volume first to the inefficient set at a nice volume and start switching.  When you switch on the dog/bell set it will actually hurt the volume increases that much.

I just thought it was funny to advertise an OT at 2 different wattage's.