Tweed type tone control, used with raw control?

[bruno]

So lots of people install a pot in place of the mid resistor in a typical fender blackface tonestack, and I've seen some implementations that take that resistance high enough that the tonestack is virtually out of the circuit, but most of those implementations sound somewhat rought and very low mid heavy to my ears. Have any of you tried adding a tweed style tone control across the volume pot to be used in conjuction with the regular tmb tonestack?

I haven't tried it yet, but I think I might do so...

[jjasilli]

The RAW pot can tweedify the tonestack.  You can verify this with the Duncan Tonestack calculator.  With the RAW pot at about 100K in the Fender circuit, you can duplicate the Tweed (E-series) curve with some T & B dial twistng.  Under 100K you can duplicate the Marshall curve.  Over 100K you can eliminate the mid cut.  So arguably the Fender tonestack with a RAW pot is the most versatile.  2 tonestacks in series will substantially increase insertion loss.  2 tonestacks separated by a gain stage cures the double insertion loss, but is redundant with no benefit.  

To those who strongly prefer the TMB tonesatck, a Tweed amp sounds "raw".  I belive this is why Allen named it the RAW control.

[bruno]

aparently there are some schematic of amps using this...

http://www.vhtamp.com/pdf/VHT_Special_6_Schematic_5-17-10.pdf

[jjasilli]

Well I guess it can't do any harm; and if it feels good do it!  But this looks more to me like a clever one-knob tone control, rather than a choice between TMB or Tweed.

In your example the Tweed pot is being fed by a TMB tonestack with pre-set, hard-wired values (sitting atop a switchable raw control pot).  The steep Fender mid-scoop is already present when the Tweed pot receives it.  So we don't really have a Tweed tone control.  This justifies my guess that two full tonestacks are redundant, which is why the TMB tonestrack is hardwired. Otherwise the user would make himself nuts re-creating the same tones with seemingly different knob settings.  EXCEPT:  the VHT circuit is a different take on a one-knob tone control -- PLUS a pot/sw raw control for a mid boost.  I continue to believe that the same tonal results can be achieved without the existence of the Tweed tone stack (provided that the TMB tonestack has pots, not fixed resistors).  BUT the VHT configuration gives the "convenience" of one knob replacing 2 or 3 tone knobs.

Presumably the extra insertion loss of the VHT configuration is compensated for by the extra gain provide by the 220K (instead of 100K) plate resistors in the gain stages.

[bruno]

my only insterest for the extra tone control is to use when the tmb tonestack is lifted from ground. Which would make it along the lines of a tweed sound. This is nothing new of fancy I just though it would be cool and useful.

I also believe the 65 amps tupelo and lil'elvis use a similar preamp.

Thanks jjasillli, I believe I'm going to try this is a build

[Willabe]

loosechange has a tweed style tone control posted here somewhere. IIRC, he likes it quit a bit.


              Brad           

[jjasilli]

This is nothing new of fancy I just though it would be cool and useful.
Actually I tink it's a clever way to have: a) a one knob TMB-type tone control (Big Muff PI can do that) PLUS b) a mid-boost RAW control for Tweed tone.  That's new, at least to me.

[Fresh_Start]

Wilabe is correct - LooseChange has been using what he calls a "Tweed" control in his Desktop Champ builds:
http://www.el34world.com/Forum/index.php?topic=9594.msg90547#msg90547

I thought you'd need a DP/DT switch which lifted the TMB tone stack for this to work, but LC says not.

Cheers,

Chip

[jojokeo]

I have three basic "Tweed" midrange control / raw control options I've used on various builds:

1) Tone Stack Bypass Switch w/ Filtering: I use something like LCs bypass w/ a DPDT push-pull pot but w/ some low end filtering that helps eliminate bass flubb at high volumes which tone stack bypassing has a tendancy to do. When it does it doesn't sound good and can ruin the affect and your sound.

2)Tone Stack Lift Switch: I've used the tone stack lift w/ a simple SPST switch on one of the pots. Depending on overall amp size & volume a smaller coupling cap prior to this and the tone stack is useful to keep low bass flubb away also.

3)Midrange Bypass Pot: I came up w/ this one after guessing what Gerald Weber calls his "Texas Tea" control on his So-Lo 7 12BH7 amp. A midrange tone stack pot is redundant & therefore not needed. The mid resistor is fairly small on purpose for a basic amount of mid scoop which goes away when adding the bypass control's signal. Adding the "Midrange Bypass" (or more accurately a signal bypass) pot control's signal you're obviously giving plenty of original signal full of mids to the existing Treb/Bass stack until it effectively bypasses it. The 2M pot value is not necessary to go that high as it's listed on my schem. This is the most versitile and controlled of the three and I think maybe better than making a standard midrange pot w/ a high value since it has more of an interaction w/ the tone stack as you add it in to taste and is not just being a part of it as you see w/ Duncan's tone stack program frequency graphs. This also allows the bass to be controlled at high volumes unless full signal is allowed to go through, then adjust or design it as needed for your situation.

Joe