When I first fire up a build I'm inclined to let the novelty factor influence the review, So after further testing, I Put 'Very' in the subject line.
It's really quite impresse HDGoode the little amp sounds for low volume everything', but I especially like the clean ringing chords, and chunky single note attacks [think B. Marley "Could you be loved?"]...single coils get a 'better' spank than I get from the big tube units, after dialing the knobs on the Tube and Transistor input helpers [ Dual Mosfet into 12ax7>Tone Control], I was getting a cleaner [sounds more recordable] spankiness...it is glorious! ! ! Oh of course Echo really helps. Chords ring with every note sounding very true.
The DIST+ and DS-1 builds sound more like the big amp set high than the big amp set low does, or easier to get great low volume tone.
I'm getting excellent dynamics, and near noisless operation.
N/P getting great Distortion sounds, I haven't even tapped the gain caps [between pins 1 and 8 of OA].
The DS-1 and Dist+ builds sound more like the big amp turned up a bit, than the big amp with the volume turned down does. Big Tube amp and 4 x12'' cab obviously will sound warmer and deeper when turned up enough to be 'turned on'.
It sure is nice to have this thing....GREAT Tone/Low Volume, much easier to move setup and use.
Thanks againagin to the folks at ROG Runoff Groove, For the MkII article.
This is a nice little amp, gets much cleaner than the Little Gem I lent to a friend [his Frontman died], instead of bothering him and driving the 20 min. each way I decided to build a MkII.
I had the board working in about 26 minutes, and "Bill, his workshop and I finished the 1x10'' cabinet in about 25 minutes, except for mounting the [imo] gain switches [I tried the 3 gain settings by twiddling wires across pin 8], and soldering the speakers and mounting the board, it's done ! ! !
I was surprized at how loud, I cshould have mounted the other matching 10''er [magnavox stereo console sps.].
Running at 8ohms, I can't tell if the OA's are going to get hot, can't quite tell but OA 2 may be disssipating a tiny amount of heat.
2 x LM386-1's, may be worth upgrading...[?],
I'm going to Green Party convention in Milwaukee, and this thing is going to come in real handy for jammin' up there. I'll get the 14+V battery/brick all charged and just bring a charger too!!!
Probably going to get a 12ax7 [Shaka Tube section, Thanks Aron] in it tonight also, with bypass so I can run battery only.
With efffects...should be Very nice.
The first note...so CLEAN, really happy with it. It Surprized me... :D
What a great way to use a couple 386's, Very quick to wire, very low parts count/had everything right there for it. Main cost would be the speaker, but I get those for 0 often enough. Great build!!!
I'd be interested in any of the heat dissipation solutions that people have come up with for this design. While it is possible to buy 386-4 chips that can suffer 750mw gladly without any heat sinking, most folks don't seem to have access to them, so 386-1's get used instead. Of course commercially available heatsinks for 8-pin DIPs are not going to be easy to find, so I'm curious about what people might be using to keep a pair of 386-1's alive.
water cooling maybe? 8)
Heh, heh....just in case you want to overclock your L'il Gem. Or one of those big fans. 5-10W power consumption for the fan to cool a 2W amp. :wink:
No, I was thinking more in terms of physical heat-sinking and DIY fins or other passive assemblies. For instance, with two 386's lined up end to end, a small hand-cut aluminum or copper device could sit pressed against the chips (with a dab of thermal compount underneath...naturally) and held in place by a single screw going through the heatsink and board. in between the two chips. Things of that nature.
A design of this sort can be pleasingly powerful when powered by 12v or even more, but those chips were never meant to take large amounts of heat. (the LM386-4 is spec'd to be powerable by as much as 22V though the load has to be reasonable - i.e., no 4ohm deals at that supply voltage). The datasheets provide indications of thermal requirements, but the industry doesn't easily support pushing these chips to the outer regions of their performance by means of commercially available heatsinks. It's homebrew terrain here, folks.
Tone being the goal for me on this one, volume is secondary. Volume seems to be plenty adequate even when it's at very clean settings.
The clean tones purity is what really surprized me, I ran a Ross Comp and a 12AX7 in front, a little echo and WOW...nice pure sounding clean tones...very nice sounding...I sat and played for an hour, smiling :D
I dont think i'll be having heating troubles, no heat could be discernably detected.
At 8ohms it probably doesn't get 'taxxed', or is somewhere just above 'idle'.
Whacky way to heat dissipate...wrap stranded wire around the body [no touchy on the pins], and epoxy that around on the chip, then after leaving enough strands length left protruding to put a heat sink between the ends of the wire strands and the chip, solder on more wire or a small 1.5'' or so copper plate. Heat sink lube probably has enough 'glue' factor in it's surface tension to keep something like a plate in place, if the flat surface of the chip matches the flat surface of a small plate. One could run [presoldered on] tie down wires off the edge of the plate to run through to the bottom of a perfboard to a copper pad to keep the plate clamped on the chip.
The surface area of the heat sink could be increased by cutting tabs, and bending them to 90 degrees so they go up...even adding more surface area by adding another plate or even stranded wires in any direction the physical layout would permit...basically looking at commercial heat sink tech, and using some soldered copper pieces andor wires to mimic that, surface area of the heat sink, and contact area of the heat sink to the chip being the critical dissipation factors.
You can glue a small heatsink on top of the IC by mixing thermal compound with a small drop of "superglue"! Apply thermal compound to the IC, put a drop of the glue on it, and stir it with a toothpick or something similar. That should keep the heatsink in place! 8)