Low Watt Build Ideas

[dpm309]

I have someone who wants me to build him a single ended (5 +/- watts) "marshally" or "voxy" type head with a simple one knob tone control.  He tried out my High Octane (AX84) and Tramp (Trinity Amps) but it was not what he was looking for.  I'm thinking something along the lines of an AC4HW or Marshall Class 5.  In the past there have been several posts on this forum for a wide variety of amp ideas and was wondering if anyone has something that would fit the bill.

Thanks,

Dan

[TIMBO]

Hi dan, i bought a Epi VJ combo and modded into a hot rod and was pretty happy with its outcome (got some nice cleans and can be cranked into a NASTY little amp).It doesn't have a tone control but i think you would not have any trouble finding a one knob TS that would do the job. Good luck 

[tubenit]

Given that criteria ....................

I'd build Geezer's  HoSo56 using 6BM8 tubes and simply add a VVR to dial it down to 5 watts.  The 6BM8 tubes give about 7-9 watts in push/pull and they are great sounding tubes.   The SoLow Watt with ECL84 tubes are 3-4 watts & that would be another choice, IMO. 

As far as the one tone knob, you can use a 5E3 tube tone knob.  Or you can use a dual gang pot and use a James tone stack or a Vox/Marshallish tone stack on the dual gang pots.

with respect, Tubenit

[HotBluePlates]

What about the original Vox AC4?

You can omit the tremolo circuit using the 12AX7 if he doesn't want that. Simple volume control and 1-knob tone control. It's very much like a tweed Princeton with an EF86 preamp tube and EL84 output tube.

[phsyconoodler]

I just built a single ended trainwreck express with an EL84. Yummy tones!

[jojokeo]

What about the original Vox AC4?

You can omit the tremolo circuit using the 12AX7 if he doesn't want that. Simple volume control and 1-knob tone control. It's very much like a tweed Princeton with an EF86 preamp tube and EL84 output tube.

One of my first amp builds! But w/ Treb & Bass & switched filtered ground lift, switched CF, switched bypass caps, and gain pot for the ef86 and can be pentode/triode switched too. It's got a lot of switched options but that's what happens w/ one of your first builds. Very nice little (loud) amp for it's size capable of a mulititude of tones. It's got a ramrod speaker that pumps and tames the brighness beautifully while giving great midrange & tight bass response.

[Boots Deville]

I just built a single ended trainwreck express with an EL84. Yummy tones!

Did you include a triode in the PI position as a "fake PI"? 

I've read of others doing that in SE Express builds with good results, so I'm curious...

[phsyconoodler]

No triode.Just the wreck preamp attenuated into a single EL84. Kicks serious marshall 5 ass!

[seedlings]

You might have to do something other than a single tone knob so the mids are scooped at least some.  This may be why he doesn't like your other builds - he's not used to hearing 'flat' midrange.  I have a champ build with no tone, and some other single-ended with TMB and always end up preferring the TMB even if all the controls are 'maxed'.

CHAD

[thelonious]

You might have to do something other than a single tone knob so the mids are scooped at least some.

And if there's not room for another pot, adding a switchable mid scoop/fixed bandpass circuit might work. Could even wire it to a push-pull pot.

[seedlings]

You might have to do something other than a single tone knob so the mids are scooped at least some.

And if there's not room for another pot, adding a switchable mid scoop/fixed bandpass circuit might work. Could even wire it to a push-pull pot.

You could give him set mids and a push-pull treble/bass.  Or I hear the Dr. Z Carmen Ghia tone control is a different take, though I haven't built one.  You could alternatively try the Big Muff tone control.  If you don't have Duncan's Tone Stack Calculator, it's worth downloading to try different component values.  You can decide where to omit control knobs.

This concept was just a thought I had.  Could be the standard one-knob tone is exactly what he'll like 

CHAD

[Tyrannocaster]

You could also do a switchable Bridged-T filter. I had an old Epiphone amp with one in it (though it wasn't switched in that amp) and it was surprisingly effective at getting a bit of Blackface into the sound.

[dpm309]

Thanks for all of the feedback.  Have not been able to respond earlier due to my AC going out (4 days in Phoenix w/out AC is not fun) and then a pipe burst flooding out a portion of my work room.  Anyway, I will digest all of this and get back with my friend to decide what to build him.

Dan

[HotBluePlates]

You could also do a switchable Bridged-T filter. I had an old Epiphone amp with one in it (though it wasn't switched in that amp) and it was surprisingly effective at getting a bit of Blackface into the sound.

Or, you could forget the switch, and add a 1M audio pot between the 0.0033uF cap of your schematic and ground.

With the new pot, you can get deeply scooped mids or nearly-flat or anything in between.

[DummyLoad]

twin T notch - semi parametric, level control, and bypass.

https://www.circuitlab.com/circuit/5y3czd/twin-t-rc-notch/

--DL

[lowatter]

I'm in the process of a version of this build following Sluckey's wonderful layout design he whipped up(if I can find the time to finish it). This single-ended circuit may be of interest to you...

[kagliostro]

Very nice layout (Sluckey your layout are always GREAT)

any indication about the PS voltages ?

K

[sluckey]

Voltages are on the schematic in the Kalamazoo thread back in August.

[kagliostro]

Thanks, I missed that tread

I've some 6aq5 tubes, seems that Kalamazoo voltages are compatible with this tube

please someone can give a council about cathode resistor value for the 6aq5 tube ?

may be 330ohm or it will be better 270ohm ?

K

[printer2]

Thanks, I missed that tread

I've some 6aq5 tubes, seems that Kalamazoo voltages are compatible with this tube

please someone can give a council about cathode resistor value for the 6aq5 tube ?

may be 330ohm or it will be better 270ohm ?

K

I usually use a 330 and add some resistance in parallel if I want to adjust the bias/current.

[kagliostro]

Thanks for the info Printer2

as all people know the tube is very close to a 6v6 but not exactly the same

also there are some examples of schematic for PP use and only few for SE

I'm a plagiarizer not engineer and still now in confusion with load curves and math

so

Thanks again

K

[jojokeo]

Measure 6aq5 cathode resistor & write down. Turn on amp & warm up for 5 mins.
Measure voltages plate to cathode, then cathode to ground. Divide cathode voltage by measured resistance. - (if using two tubes divide in half). This is your cathode current. Multiply this by plate - cathode voltage. This is your tube(s) dissipation. Keep at or below whatever tube's rating that you're using. Also use cathode measurements to calculate power rating of resistor (double this or higher for safety / reliability). If necessary and you're over Pdiss use larger value resistor and do all over again.

[kagliostro]

Hi Jojokeo

thanks for your summary of the necessary calculations

I've read this procedure also in the past but my brain refuse to remember

Maybe a tattoo could solve my problem 

Really, I'll try to remember

thanks again

K

[jojokeo]

Lol, it's always a memory exercise for me too.