With very simple circuits like this, the quality of all the active and passive parts is critical.  Indifferent capacitors, resistors, and even switches, wire, solder, will be audible.  On the other hand, the original idea of this amp was a simple and economical build-up using readily available parts; from orphan old-time gear, where possible. I relate my own experience in implementing and modifying this amp.  I'll work from the input to the output.  I'll also heat up my good sources the first time I mention them; and once again at the end.

Input Jacks   RCA, 1 pair per input, chassis mount.  Should be lightly made of copper, gold plated. I used to use Radio Shack ones, but I have found that their gold plating doesn't last very well.  I now use part 091-1120 from Parts Express, which are better made and plated.

Selector Switch   2-pole, with as many positions as you have inputs, plus one (for a mute position).  Should have gold or silver contacts.  I only have two sources (tuner and CD), so I use a nice E-Switch toggle switch that has a center-off position, since a high-quality toggle is far cheaper than an equivalent rotary.  Good switches can be had from Michael Percy, and also the bulk vendors (Allied, etc.), if you know what you're looking for.  The E-Switch is silver contact, hermetically sealed, part EG2417-ND from Digi-Key.

Volume Pot   100Kohm, stereo (2-deck). Several places have nice ones. Michael Percy and Angela Instruments have the Alps black beauty for $35 or so.  I have found that the volume pot is a critical part, so I now use the TKD 2511 from Michael Percy; and in the Mœbius preamp, where there's room, the DACT discrete attenuator.  It makes a difference

5965 Input / Driver Tube   These are pretty common, and also the similar type 6414. Andy Evans at Arts and Media advocates the E180CC as the ultimate example of this type; I haven't found any yet (you there, Andy?) I do not consider the parent type 12AV7 acceptable, although they'll work electrically. I tried some that came my way, and they sounded like dried cat scat turning white in the grass; I actually put them in the circular file, which I almost never do. Angela has RCA 2-mica 5965's at an economical price; about $5, they sound good.  This is a dual triode; the two devices shown are actually one tube.

60K and 62.5K 2W Plate Load Resistors   This is a critical part. I've tried garden-variety metal films here, and the sound suffered. The amp shown has two 120K 2W Kiwames in parallel on one side, and a 120K and 130K on the other.  Rikens are also very good sounding, if you can find them in close enough values.  I get the Kiwames from Michael Percy, Angela has the Rikens.  These resistor composites are dissipating about half a watt each, so they're just over the limit for a 1-watt part; but using series or parallel combinations of two 1-watt parts you can use substantially different values without problem.

27K 3W 'Longtail' Driver Cathode Resistor   This is maybe the least critical part in the circuit.  It's a nice Phoenix metal film from Digi-key, part PPC1KW-3JCT-ND.  I tried better resistors and could hear no difference whatever.  You can use Kiwame 5-watters from Michael Percy at 2 dollars if you want to luxe out. On a developmental note: the value of this resistor depends on the voltage you end up getting from you negative 'tail' supply.  You want to draw about 3mA in each 5965 device, so divide your tail voltage by .006 to get your value.

.33µF Coupling Capacitors   These are another critical part.  I use 630V Jensen copper foil paper-in-oils or Mundorf Silver Supremes, which are very good.  They ought to be; they cost nearly thirty bucks each, and are about the size of a 'C' battery.  Michael Percy has 400V Auricaps, which many people like, for $6.50.  I tried them and thought they sounded harsh.

100K and 100Ω Bias Circuit and Screen Coupling Resistors   Regular 1/2 watt metal films work fine here, and are what's in my amp; although if you're ordering from Angela, Riken 1/2 watters would be superior.  Those cheesy 1/2 watt carbon films that RatShack sells are amazingly good if there's no current in them; but at a signal level approaching 16vac, I think they'll get crunchy and noisy.  I use .6W Phoenix metal films from Digi-Key for all this kind of stuff, they're quiet and clear.

6V6 Output Tubes   These are available all over the place in NOS versions at (usually) reasonable prices. I've never heard a bad 6V6, one of the reasons I chose this device; but evidently some of the early-production Russian types were a little raggedy. I currently use the Electro-Harmonix in all my amps; they're robust, terrific sounding, and nice looking. Don't laugh; a lot of 6V6's are painted black inside, including the fabulous NOS RCA's.  As a detour, this circuit is quite suitable for the very similar (electrically) 6BQ5 / EL84 and 6AQ5 types, which I have heard are also very good sounding devices, and even more available than the 6V6. The only modification to the circuit would be to drop the primary B+ voltage from 315v to 300v, which is the screen max for the EL84, or 275v for the 6AQ5.

Output Transformer   8K to 10K primary impedence.  The output tranny is the biggest, most expensive, and arguably most critical component in the circuit. A primary impulse for the original development of this amp was, in fact, the recycling of output and power transformers from 6V6 and EL84 consumer hi-fi amps and receivers from the late tube days. These things are getting rather rare, and I discovered that the 7.2K load most common in them is not optimum for the 6V6; loading it down and making it sound 'tubey'.  There are fortunately a good number of output transformers being currently made specificaly for PP EL84's and 6V6's.  Magnequest makes a nice 8K, Brooklyn; Mikey is the most highly respected winder in the US, and this trans is actually quite economical.  I have just gotten a pair of these in, with 'Silver Vein' powder-coated end bells, and they are certainly a far cry from mass-market components; thin, perfectly stacked lams with nickel pinstripes, flanged end bells that are nice and thick so the mounting tabs don't get bent up, teflon leads. I've gotta get them in a circuit.  The cheapest is the Hammond, in both 8K and 10K, which Angela has.  I tried these very hopefully, but I thought they sounded creamy and lo-rez.  Audio Note Great Britain also has an 8K type, the TRANS-200, and I've had very good results with other models of theirs.  Also in Blighty, Brian Sowter makes good ones, the U064 8K, and U067 9K. Look on these guys' sites for US distributors.
     My current fave output transformer is the Silk P-10-15, hand wound by my man Kittipol Saengomnuayporn, principal of SACThailand in Bankok.  There is a small problem in onsies-twosies of these, since the shipping is a bear, and Kitti has to have a moneygram, which is also expensive; but he's a great guy, winds with care, and ships before deadline.  I'm starting to sound like an (M), aren't  I?

Sockets, Wire, Solder, Etc.   All this stuff is important. Sockets, I use nice ceramic-gold sockets for everything; lots of vendors have them, order when you order the rest. Wire, I use regular 18ga solid core from Radio Shack for nonsignal stuff like heaters and unmodulated DC. I like to use solid-core wire inside the chassis, it dresses better.  My standard signal wire is the conductor from certain types of Cat 5 plenum-rated UTP cable, which is high-purity copper in Teflon. You have to do the research; not all Cat 5P is unplated copper in teflon.   A caution: a lot of otherwise good-ish (for audio) quality wire, like non-plenum cat5, has polyethylene or polypropylene insulation. This is low temperature plastic, and is very unhappy inside a warm chassis in the long term. It will discolor and crack and generally not say good things about your product quality to some tech ten years down the road. I use regular PVC wire for nonsignal, and teflon for signal, Belden hi-temp when replacing grotey old transformer leads. Long signal runs should be shielded; I used to use Radio Shack Gold interconnect with the PVC outer sheath carefully sliced off and replaced with teflon plumber's tape or cloth tubing.  The copper braid protects the poly foam dielectric from the heat well enough, and the stuff sounds good.  Nowadays I use some nice (and small) Teflon shielded I got from Mendelson Electronics, a closeout/buyout place; but they don't have any more.  Solder, I use Cardas from Michael Percy.  Don't use generic solder.  One of the things I learned from my misspent youth taking orphan gear apart was that cheap solder turns crusty and groto down the road, making cold solder joints.  A half pound of Cardas or WBT or Wonder is about $20, and works beautifully, and you'll never have to worry about a solder joint again.

The List   Again, here are the guys I use; in no particular order of preference, but frequency of use.

• Angela Instruments   Tubes, sockets, resistors, capacitors, transformers, chokes, other stuff. Nice folks.
• Michael Percy   Wire, solder, switches and pots, connectors, capacitors, resistors, the fancier stuff.
• Antique Electronic Supply   Tubes, sockets, interesting transformers, capacitors, guitar amp and old radio parts.

• Digi-Key   My fave general vendor.  Lots of stuff, good prices, reasonable shipping.
• Mouser Electronics   Dale resistors, switches, cat5plenum wire, UF diodes. A smaller general vendor.
• Allied Electronics   The biggest of the general vendors. Higher voltage transformers, chokes, lots of groceries.
• Audio Note Great Britain   Nice transformers, also tube kits and other parts.
• Electra-Print   Very good transformers. Jack specializes in custom winding, if you get that far.

I used to promote building this amp on the cheap, as a good experiment for those who want to find out just how much power six watts is economically.  I find that as I build more of them, and get to compare them with the Standards of the audio world, I no longer feel that way.  Given the modest cost increment of using really good parts, the sonic potential of the circuit, and the amount of labor that it takes to build one in either economy or all-out dress, I would say to go for the gold.  I did.

That's all I can think of. If I've left anything out, or you have other questions, give me a hoot at I'm working on making this amp buildable from the page, and I welcome suggestions.

Poinz