Low Powered Build Recommendations?

[Gibsonman63]

I did a little project for a client last week. The guy had an Epiphone Valve Jr. ($100) and Mercury Magnetics upgrade kit ($300). I was very impressed with the results. At 5 Watts, it sounded absolutely huge through a Marshall 4 x 12 cabinet. Now I am thinking I need to build a couple of lower powered amps for studio amps. I think it may actually be less work to build something from scratch. On the Valve Jr. project, I had to cut traces and drill new holes in the PC board which was a bit of a pain. It would be nice to upgrade the jacks and pot and do something with turret board construction.

Any recommendations for something around 5 Watts with a fair amount of gain that I can build without having to do a design project?

[10thTx]

I built this SoLow Watt amp and like the tone of it real well. It's probably around 3-5 watts. Uses ECL84 tubes which are inexpensive.

http://www.soundclick.com/player/single ... i&newref=1

Here is a picture of the amp:
http://s28.photobucket.com/albums/c216/ ... ampcab.jpg

Pretty easy build to do, IMO.

With respect, 10thtx

[Gibsonman63]

Holy crap, that's a beautiful build!

For the first one, I am looking for something with a bit more gain, for ZZ Top/Skynyrd/Trower type stuff.

If this works out, I may need to build a few different types for the studio and I will need something bluesy like your SoLow Watt. Anybody build an AX84 High Gain?

[10thTx]

For the first one, I am looking for something with a bit more gain, for ZZ Top/Skynyrd/Trower type stuff.

Did you listen all the way thru the sound clip? The sound clip starts clean and then progressively is more pushed into OD.

Listen to the sustain at around 2:04 in the clip.

Then try listening from 3 minutes into it to the end. This is a high gain amp and the sustain is comparable to my Dumblish inspired amps.

I used 12AV7 tubes in both V1 and V2. You could easily increase the gain by using a 5751 or 12AX7 in V1. The 12AV7 is somewhere between a 12AY7 and a 12AU7 so it is pretty low gain.

With respect, 10thtx

[Gibsonman63]

Maybe I am not properly describing it. (ok, nobody ever does!) I would like to build a reasonably priced small amp with some chrunch for the ryhtym and saturated lead tone. I respect what you have done, but I am looking for something a little heaver for the first one.

http://www.youtube.com/watch?v=UscivHCS ... re=related

http://www.youtube.com/watch?v=yEouc2h_SBA

http://www.youtube.com/watch?v=lUeuAnMNDhA

These are just a tad brighter than I want, but with a 4 x 12 cabinet and some heavy palm muting, I can pound out some bottom.

[Phil_S]

OK, heard the clips. Here's an idea for ya. Build a TWX type amp. Crank down the power amp to around 315v, adjust the supply dropping ladder to keep the preamp voltages up. Run it with a pair of 6AQ5's into the MPS 6K6 OT20PP http://www.musicalpowersupplies.com/3.html. OK, you don't want 6AQ5's, use 6V6's or crank down B+ a little more and use EL95's. If you use the EL95's (can be had for silly cheap $) it's going to be tough to get the preamp right unless you put it on a separate supply or branch the B+ ladder at the first node.

You'll need to find a PT that's around 230-0-230 @ ~100mA. It won't split your ears, and you won't need to spend an arm and a leg for it. Iron should set you back less than $100.

Do you drill your own chassis? http://ddawgamps.com/Amp_Chassis.php It's a big money saver. It will cost you time.

Small parts (pots, wire, caps, resistors, whatnot) will run $50-ish unless you insist on musturds and the like. It is possible to get the amp built for under $200. Of course, head box is extra.

[gingertube]

ECL84 (6DX8) are a stunning little tube. I've only used them in Push Pull for a HiFi amp (which was gorgeous) and in Single Ended for a Reverb Driver in a larger amp.

For guidance of the ECL (triode + power output pentode) range.

ECL82 = 6BM8 (modern production available), triode is 12AT7' ish
ECL83 =- ??? I'm aware they existed (used for record players etc., just never seen one).
ECL84 = 6DX8 - great sound, triode is 12AT7'ish
ECL85 = 6GV8 (Assie guys there ar a heap of these around dirt cheap from old television stuff - people are throwing them out, coz no one has ever told them they can be used for audio, Triode is mu of 50)
ECL86 = 6GW8 - great sound, most powerful output pentode of the range, 12AX7 compatible triode (Marshall used them a lot)

Cheers,
Ian

[surfsup]

I built an ax84 HO (you asked about the high gain ax84 designs). It was actually my first amp. Turned out to be quiet and quite a nice amp. It has some gain for sure and can be very crunchy. I like it a lot but it doesn't clean up super niceloy unless you really bring down the gain or you can mod it with a lead/rhythm switch (i have not).

I plan to build a SoLoWatt, or something close, but never got around to it yet. I have all the parts though...so it is a matter of time. But you might want to check the ax84.com forum for opinions as well. There are also a lot of pre and power amp designs there you can download and build, mix, match and mod.

[roberto]

Valve Jr is a nice amp to mod, but it's a nonsense to multiply by 4 its price with a kit mod, while you can make it sound way better with just 10$:

referring to this schematic:
http://www.rawbw.com/~emiller/Euthymia/DIY/VJstock.jpg

R1 to 1M directly on the jack
R2 to 33k
R3 and R4 same value but 1W
R6: put 1n in parallel for more beef or replace with 470k//470p for more bite
R7: remove (use as R1)
R8: to 2k7
R12: to 470R
R15: (optional, try 5k6 if you prefer)

C3: remove
C4: to 680nF 100V
C6: to 47µF 450V

[10thTx]

OK, if you are willing to have the parameters stretched to 7 watts instead of 5 watts or less ............. then here is another option.

HoSo56 developed by DaGeezer on Hoffman forum. My version had reverb and I called it a 56T. I added VVR to mine and could get a really fat tone at only a few watts volume.

Sort of Marshallish topology with a 5879 pentode for a fatter sound & 6BM8 power tubes.

Schematic and layout here: http://www.el34world.com/Forum/index.php?topic=6176.0

Here is a soundclick of it (lead to a backing track):

http://soundclick.com/share.cfm?id=7988948

Just another idea for the mix to consider. I have no agenda for you just trying to offer ideas to consider given the parameters you specified.

With respect, 10thtx

[10thTx]

OR ............. if you're willing to stretch another watt to about 8 watts you can build a Tweed Overdrive Special with 6K6 tubes. However, this may be more of a complicated build than you are wanting? This would be a D-inspired amp.

There is an editable schematic and layout here:
http://www.el34world.com/Forum/index.php?topic=11455.0

Here is a soundclip of a TOS using 6K6 power tubes.

http://soundclick.com/share.cfm?id=11527276

Again, I have no agenda for you, just offering ideas.


With respect, 10thtx

[Structo]

Hey 10thx,

That SoLow looks nice.

On the schematic I only count five pots but in your picture it appears to have seven.

Did you add VVR and reverb to this amp?

[10thTx]

On the schematic I only count five pots but in your picture it appears to have seven.

5 is correct. I eliminated two pots after the picture was taken.

vol, treble, mid, bass, PPIMV

With respect, 10thtx

[Gibsonman63]

Thanks for all of the suggestions, gents. I can see now that I will end up building more than one.

Roberto, I agree with you on the cost factor. It was a project that I did for a friend of a friend and he had everything purchased and in hand before he brought it over to me. I would have never spent that much on that amp, but it did sound really good when it was done and the guy is happy with it. But for my own amp, I think I can get there with much less cost with a construction method that allows easier tweaking.

[chopstuck]

I have to second 10thx on the Hosa 56T.

It really covers a lot of ground. I used the RCA 5879 pentode.
The reverb section needs a little mod to get some surf going on but that's personal taste.
The amps is just magic and not too loud. You can dime it and it holds together. Very flexible. Think Princeton / Cambridge Reverb with a great cleans and a smooth transition to overdrive.

I built Geezers' Little Wing before this one and liked that a lot too. It's limited but does the plexi thing real well. I have to say I like it more than the 6V6 plexi which is still too loud (for me).
I built mine out of leftover and used parts. The circuit seems very forgiving.


To me a really good small amp sounds like a really good loud amp but farther away.