5E3 with Baxandall pre?

[zydeco papa]

I've got a guy that's going to build me a guitar amp. He was going to do a slightly modded 5E3 circuit with a simple passive tone control. What do you all think of putting the Baxandall EQ in place of the passive front end?

[phsyconoodler]

Do you have a 5E3?Why would you want something different than the venerable 5E3?
But,on the other hand,a modified 5E3 would be cool too.A baxandal is more hi-fi sounding and it may require some tweaking to get it right.
The 5E3 is hard to beat stock.....IMHO

[Nolatone Ampworks]

I once wired up an Baxendall in a 5E3 and it didn't sound good, but I didn't put any effort into finding out why. If done right, it might sound great.

5E3 IS a classic, but I've always thought it would be nice to have more tone shaping control. It just won't likely act like a 5E3 any more once you get a tone stack right.

[skipm45]

I
5E3 IS a classic, but I've always thought it would be nice to have more tone shaping control. It just won't likely act like a 5E3 any more once you get a tone stack right.

+1 The 5E3 is at it's best as a 5E3. IMHO it's the tone that makes a 5E3 what it is. Don't mess with success.

my .02


Skip
www.skipzcircuits.com (http://www.skipzcircuits.com)

[Trout]

I once wired up an Baxendall in a 5E3 and it didn't sound good, but I didn't put any effort into finding out why. If done right, it might sound great.

5E3 IS a classic, but I've always thought it would be nice to have more tone shaping control. It just won't likely act like a 5E3 any more once you get a tone stack right.


Id like to find a way to put a bass trim pot in one. Seems like after flipping coupling caps around, it helps, but it also seems like it effects more than just the lower bottom end. It seems like its trimming off to much low/mids with .022's

[zydeco papa]

I hear what you guys are saying. We were talking about what to do, and my only firm specification was that I want to do one single ended triode and one push pull triode (we're doing the PP first). 6V6 made sense, and last time we got together he brought some ideas on the 5E3. I had just been doing some reading on the Baxendall circuit to research the Linden EQ, and I've been playing bass through a B15 ever since I didn't know any better.

I guess a better way to pose the question would have been to ask about mating the Bax preamp with a pair of 6V6 or other triodes. I appreciate the simplicity of a passive tone control and haven't ruled that out either, but a well implemented preamp has its advantages. I think something could be done like the Audere bass preamps (plug-in caps to change the frequencies of the tone controls) that would be a lot of fun.

I'm thinking octal preamp tubes, even though I have a mess of good 12AX7...

[ontariomaximus]

A Bax tonestack will cause quite a bit of gain loss so you'd probably have to have a recovery stage. It's a filter and can only cut. I wonder what one would sound like in a 'wreck express with 6V6's. Try it!

[epluribus]

A Bax tonestack will cause quite a bit of gain loss so you'd probably have to have a recovery stage. It's a filter and can only cut.

Greater gain loss than a TMB? Hm...

Interesting point. In my limited understanding thus far, there's two reasons you use a recovery stage after a tone stack. One is for gain loss, as you point out. The other has to do with impedances, which I understand is why people sometimes use cathode followers in front of the stack as an alternative to a recovery stage. Should we presume that a cathode follower would not be effective in this case? Not suggesting one way or the other, just an intriguing point here, as it's always struck me that the two approaches do vastly different things to a given circuit to achieve the "same" thing. Not sure it's actually the "same."

BTW, Bax stacks on guitar amps. I can only say that I've read in totally undocumented places that they can sound strange in guitar amps, for what reason I don't know. But hedging that possibility, you might take a look at the freq response curves with Tone Stack Calculator (http://www.duncanamps.com/tsc/) to try to visualize the impact of using a Bax. I've found it very handy once I got used to reading it.

--Ray

Ed. note: In all my Franken-wiring, I haven't gotten around to doing much with tone stacks yet beyond tweaking a few R/C values, and certainly not a Bax/James. Someday... :rolleyes:

[ontariomaximus]

A Bax CAN have more loss than a TMB depending on the values chosen (I am very familiar with Duncan's TSC).

A 5E3 has neither so you could be -20db at that point where the TS is inserted compared to the stock circuit. Another AT, AY, or AX section after the TS, with say a 3.9k unbypassed rK will balance it out (just an educated guess though)

As the TS will offer great tonal variations, lose one of the 5E3 inputs.

You would have 12AY7 section, BAX TS, then another 12AY7 section (with unbypassed cathode), after that a 500k volume control, then pick up the stock amp from there at the 12AX7

I am not a fan of cathode followers.

[hasserl]

I've worked with Bax style stacks in many guitar amps and and very familiar with them and the response they provide. They sound "strange" in guitar amps, because we are accustomed to how the more familiar Fender/Marshal/Vox style tone stack works and sounds. the Bax works very different, so the first thing you need to do is forget trying to set it the same as you would a FMV stack and instead adjust the controls as needed without regard to how it compares to what you would do with an FMV. They have a much more flat response and do not provide thre same scoop you get with a FMV. You vcan work with the resistor/cap values to get a response closer to a FMV, but the differences remain.

Second things is yes, they are more lossy than a FMV stack. A simple preamp w/ input gain stage --> Bax tone stack --> Volume --> recovery gain stage --> LTPI will not provide very much gain or distortion, even if you're just driving a pair of EL84's. Use it to drive a pair of 6V6's and it gets even worse. I haven't tried this arrangement with a 5E3 style cathodyne PI, but that would reduce the drive to the power tubes even further, resulting in an amp with none to very little power tube OD, which is what the 5E3 has in spades.

Note that I've gotten aroiund this by using a Raw control for variable tone stack bypass, allowing the user to set how much tone stack response he wants with the Raw control; dialing in more Raw (less EQ control) results in huge gain increases, lot's of OD. Dialing the Raw down (more EQ control) results in huge gain losses and reduced OD, but flexible tone shaping. It makes for a more versatile amp.

[zydeco papa]

Note that I've gotten aroiund this by using a Raw control for variable tone stack bypass, allowing the user to set how much tone stack response he wants with the Raw control; dialing in more Raw (less EQ control) results in huge gain increases, lot's of OD. Dialing the Raw down (more EQ control) results in huge gain losses and reduced OD, but flexible tone shaping. It makes for a more versatile amp.

I like that concept. I used Hughes & Kettner Puretones for a while and like how that works. Good comments throughout your post as well, thanks.

I'm not opposed to another gain stage if needed. Sounds like it will be.

[GuitarsFromMars]

Baxendall is used by design in most of the Tweed Fenders,I believe.If you check,you'll probably find I am dead wrong-memory is shot from a stroke...I may be wrong I'm wrong.

[epluribus]

Great stuff so far, interesting and useful. Always nice to add some clinical clarity to things I think I understand. Dang...now I gotta go read and solder some more...

If you check,you'll probably find I am dead wrong-memory is shot from a stroke...

Huge bummer, sorry to hear it. Glad to see you're up to hangin' around our collective pinnacle of enlightenment. :D

...I may be wrong I'm wrong.

Geez, sounds like my house! :BEER

[WesKuhnley]

Bax stacks are very cool to play with. Lots of vintage amps used some bastardization of a std Bax stack, including some tweed era Fenders. I've been playing with a Super-inspired amp with Baxandall based tone controls.

As mentioned previously, they cannot be approached the same as FMV stacks, and are not necessarily as lossy, but great tones can be coaxed from them that you can't get from FMV stacks.

One cool way of utilizing both a "raw" control and a less "lossy" Bax stack is to put it into a local feedback loop around a high gain stage. This limits your cut and boost to the dB range of the feedback, but eliminates line loss the passive stack would have caused. The amount of feedback can be varied using the raw control to yield a less effective EQ and practical boost.

[RedMan]

My experience with the Baxandall tonestack in guitar amps is that they work quite well clean or on the verge of breakup (midnite rambler), but not very well overdriven. If that's where you live then there may be a better way to go. It's what's in most hifi amps so if you've ever played thru a tube hifi amp or an Ampeg with one you'll get an idea.

[gldtp99]

Guitar amp with Bax-type tonestack, Split load PI, Push-Pull output and has a very impressive OD tone:
http://www.schematicheaven.com/newamps/orange_mkii1973.pdf

Also has the rotary tone switch (F.A.C. control) that reminds me of rotary selectors on some tube Hi-fi amps.
I built a clone of my '74 Orange OR80 and i used the Duncan TSC to re-shape the curve of the tonestack to get a touch of mid-scoop.
Lots of players have used my clone and liked it but most say it's just too loud when cranked up to get great hard rock distortion. I'm thinking of adding a pentode/triode switch at some point to this one.
A lower wattage version would be an interesting, and probably much more useful, build.
Oranges use big iron---- the 80 watters use the same OT as the 120 watters, the OT secondaries are connected to the speaker ohm switch to give the right plate load for the 80 watters----my orig OR80 has only 8 and 16 ohm speaker load options (orig 4 and 8 ohm taps for the 120 watters).
An oversized OT for 6v6 use (@6.6k-8k primary and 4/8/16 ohm secondary) in an amp like this can be found here: http://www.edcorusa.com/products/transformers/cxpp/cxpp25-ms-7_6k.html
I used an Edcor OT in my 80 watt clone and it is working very well. I'm sure there are other OT's that would be fine but i think the Edcor OT is a good choice for an amp like this---- mine sounds very good..............................gldtp99

[Junction]

I built exactly what you are talking about, the bax stack is strange, I am not sure if I like it, still tweaking, I guess that is the common thread here, that it may require lots of tweaking to get you desired tone. I took a purely theoretical approach to the design, I was thinking of lots of boost (relative to mid freq's) at 150Hz and boost at 2KHz, well sounds like it does that but I haven't yet fallen in love with the sound.

I recall though when I compared the Bax stack to the Marshall type TMB stack, using Duncans calculator, the Bax had significantly lower loss. I am certainly getting loads more gain than I expected, it turns itself into a heavily overdriven amp if I crank it.

You should experiment, you never know, you might just find your sweet spot.

Michael

[WesKuhnley]

My experience with the Baxandall tonestack in guitar amps is that they work quite well clean or on the verge of breakup (midnite rambler), but not very well overdriven. If that's where you live then there may be a better way to go. It's what's in most hifi amps so if you've ever played thru a tube hifi amp or an Ampeg with one you'll get an idea.

Most hi-fi stacks are centered around 1k, the nominal mid-range frequency for hi-fi and pro audio stuff. I've found bax tone controls work best centered on lower frequencies. The duncan tsc works great for finding resistor and cap values that will work.

[RedMan]

Guitar amp with Bax-type tonestack, Split load PI, Push-Pull output and has a very impressive OD tone:
http://www.schematicheaven.com/newamps/orange_mkii1973.pdf

Also has the rotary tone switch (F.A.C. control) that reminds me of rotary selectors on some tube Hi-fi amps.
I built a clone of my '74 Orange OR80 and i used the Duncan TSC to re-shape the curve of the tonestack to get a touch of mid-scoop.
Lots of players have used my clone and liked it but most say it's just too loud when cranked up to get great hard rock distortion. I'm thinking of adding a pentode/triode switch at some point to this one.
A lower wattage version would be an interesting, and probably much more useful, build.
Oranges use big iron---- the 80 watters use the same OT as the 120 watters, the OT secondaries are connected to the speaker ohm switch to give the right plate load for the 80 watters----my orig OR80 has only 8 and 16 ohm speaker load options (orig 4 and 8 ohm taps for the 120 watters).
An oversized OT for 6v6 use (@6.6k-8k primary and 4/8/16 ohm secondary) in an amp like this can be found here: http://www.edcorusa.com/products/transformers/cxpp/cxpp25-ms-7_6k.html
I used an Edcor OT in my 80 watt clone and it is working very well. I'm sure there are other OT's that would be fine but i think the Edcor OT is a good choice for an amp like this---- mine sounds very good..............................gldtp99


I'm not a big fan of the way those amps overdrive either, but that would be another good example.