Step 3: Time to wire.

Time to wire. I am assuming that you are capable of reading a schematic and then knowing how to wire it. This circuit is easily made possible point-to-point. I debated with the idea of printing a circuit board or using proto board. However, after I built the circuit on breadboard, I realized how finicky the circuit could be. For instance, if a specific wire were too long or in close proximity with another wire weird stuff would happen. For instance I was able to pickup a radio station! Thankfully it was nice smooth jazz. But more commonly I would get humming in one or both channels. It took some time but I finally found the perfect layout for total silence from the circuit in my enclosure.

Some tips include:
• Braid or twist your input cables off of the RCA inputs. Braiding/twisting helps to eliminate any RF interference.
• Braid your LED runs into the tube sockets. For some reason the negative lead picked up some RF interference when near the tubes. Braiding the leads solved this issue.
• Check for shorts. A couple of times I fired up the amp in the preliminary phases and I would get clicking or dead silence. It was a short every time. One loose strand of braided cooper wire touching a resistor or something stupid. More than likely the error is human, the chances of a failed resistor or MOSFET are incredibly low.
• Use the optional resistors from the Dsavitsk schematic; they help eliminate humming and background noise.
• Lastly, keep your runs as short as possible. Audio circuits are finicky.

So, is the heat sink really necessary? Yes, the MOSFETs melted my plastic breadboard after less than a minute of use. Those guys get hot. You don’t want to melt your MOSFETs and risk destroying your circuit. 

The added LED’s were a must for me. I love the way that they look. The tubes do glow, however they’re hardly noticeable unless you’re looking for the filament. Plus the LED’s allow seeing if the circuit is on/off. I also added an additional switch just to turn the LED’s off and on. If you are wiring in the LED’s, make sure to use a resistor rated for the voltage drop. The power supply is 48v, that’s a big drop down to 3v to power the LED’s. The resistor needs to be able to dissipate that wattage. Use a resistor calculator to calculate the wattage rating needed for your resistor (http://led.linear1.org/led.wiz). I used a resistor rated for 2 watts, well above what should be required.
Would this work with 12ax7 rather than 12au7
<p>i would love to be able to make something like this with el34s to have a tube amp going into my usb mixing board for recording </p>
<p>Looks like a mess. Sound like gods! thanks for great instructable! :)</p>
Hey, love your amp, just want to know how you mounted your tube sockets and did you cut an access slot for the mosfets to mount directly to the heat sink? Thanks.
<p>How hard would it be to increace the power output of this amp, without messing up the audio quality? Would it be a question of adding an additional, larger pair of FETs driven off the first? Additionally, How hard would it be to replace the separate left/right volume pots with a volume/balance type arrangement? Would it be easiest to add in an arrangement similar to the first diagram shown <a href="http://www.angelfire.com/electronic/funwithtubes/images/Amp-Bal.gif" rel="nofollow">here</a> after the doubble-ganged input pot? </p>
Will this work if I try and plug it into my amps cab?
Do you have a schematic?
Do you have the exact model number on the Hammond box? It looks like the larger one, but its hard to tell. 1590XXGR maybe? 154x121mm?
Great project! Try to make the links work in your instructable. It makes looking up the extra info so much easier for us lazy people ;)
Looks like I've found my University 'reading week' project. <br>

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