Dynaco PAS Full Function RCA Jack Kit from Dynakit Parts

Likely the most popular tube amps in existence, Dynaco has many fans both young and old. Given how well they have stood the test of time, I hope they continue to be sought after for many decades to come. There are a number of companies offering kits resembling the originals with modern bits and pieces, but if you want to build or restore a Dynaco as close to the spirit of the original as possible, Dynakit Parts offerings are a great choice. 

Dynakit Parts is a company based in Paramus, New Jersey and has an impressive selection of reproductions of all the most popular Dynaco vacuum tube products. The kits are about as close to the originals as you can get, from the can capacitor to the screw-down terminal strips but have the benefit of using freshly made transformers and other modern parts.

If you are familiar with the older Dynakits from the 60s, you will remember they featured RCA inputs that are a little different than what we typically see today. On the pre-amps and integrated amps, they were spaced very close to one another and it is hard to find RCA cables that fit them now-a-days, not to mention middling quality (though good for the time).

There have been several attempts to reproduce the RCA board on the PAS using higher quality materials, however because of the spacing, not all the RCAs were able to fit in these offerings. Now that we're in 2020 that is not the case. Dynakit Parts has created a very nice-looking solution for those of you looking to feature all the inputs of the original while also providing a high-quality solution. Best of all, you do not have to cut or modify the existing chassis in any way, the kit fits like a glove. 

Above you'll see the items that are included in the kit. You get the handsome brown polyimide board with integrated grounding scheme, nine pair of gold RCAs, two pair of half-watt resistors, a bag of hardware, some detailed instructions, and a nice decal to identify the connections. The cost is a very reasonable $75, especially considering how many gold-plated RCAs are included. Last I checked they run about $6 a pair at PartsExpress, so you can do the math.

Something else that $75 bucks buys you is you don't have to wire up all the ground connections. Just tightening on the RCAs makes electrical connection with the integrated grounding. The image below gives you a better look at the traces.

So what do you have to do to get this puppy ready for install? Simply populate the RCAs onto the board and lightly tighten with a socket tool of your choice. Next you add the resistors and solder in place, and viola! you are done. So simple you can knock it out in 5-10 minutes. You'd then install on your PAS chassis using the provided hardware, or if you prefer a permanent install you can use pop-rivets to fasten the board in place.

Here is the other side of the board when completed.

...and here are a couple of images of the unit installed in a chassis (the nice ground lug is included in the parts):

So what's the verdict? If you are looking for an RCA board that features all the connectivity of the original PAS, this is a no-brainer. It's well made, easy to use and the gold RCAs look like they'll withstand the test of time. You could make a similar board yourself by drilling out a FR4 board, but you'd end up paying the same or more and it probably wouldn't look as nice. 

Now, if you're not a purist and don't need every connection available for the PAS, Dynakit Parts makes a nice kit with a couple less RCAs for a very reasonable $50 (as of this writing). 

If you're interested in the PAS RCA board or other Dynaco-related items, whether building a kit or performing a restoration, Dynakit Parts should be on your short-list. I've ordered quite a few things from Kevin over the years and everything has been superlative.

Hope you enjoyed the write-up. For more PAS related entertainment, you can check out this restoration I did several years ago.


Review disclosure: Dynakit Parts provided a reviewer's sample of the PAS RCA Board to DIYAudioBlog for an honest review. 

The Bottlehead Single Ended Experimenters (S.E.X.) Amplifier

If you've read my other posts, you'd know that I enjoy building Bottlehead gear. I have both a Bottlehead Crack high impedance headphone amp and Seduction phono preamp, both with the obligatory C4S upgrades. The Crack is excellent for high impedance cans (~300 ohms), but can't really handle the low impedance ones. The solution was to build a S.E.X for those more demanding headphones. ;) 

The S.E.X. kit is a stereo integrated single-ended-triode amplifier with 2 watts per channel output and has been available since 2004. From the Bottlehead site: The two stage zero feedback RC coupled circuit uses parallel feed (a.k.a. parafeed) output, a topology championed for use in modern single ended amplifiers by Bottlehead and MagneQuest. Parafeed output assures articulate, musical bass, great high frequency extension and minimizes the influence of the power supply on the sound. 

The Bottlehead S.E.X. Kit

There are a few special upgrades available for the S.E.X., including the C4S Constant Current upgrade which consists of a pair of small PCBs with mounted MOSFETs, LEDs and resistors (currently $45), and some higher quality MagneQuest transformers and chokes ($300-450 depending on nickel content). And of course you can throw in the nicer caps and such as well.

Building the amp is the typical Bottlehead affair; there's a wooden base to assemble and stain, a top plate made of aluminum you can paint or leave bare, and a nice big instruction manual that makes things easy for beginners. Because my build included the aforementioned upgrades, I had three manuals to look at.

My first concern was the MagneQuest transformers. They may be well made, but they aren't much to look at in my humble opinion. The chokes hide beneath the plate but the outputs would be visible. I sanded down the metal frame, taped off the center with painters tape, and spritzed it with metal primer, copper hammerite paint, a layer of clear coat, then more hammerite paint. It gives it almost a leather looking texture when the clear coat reacts with the hammerite. I then wrapped the center with some thin black leather (Doc's advice). You can see the difference below between the original look (left) and the modded look (right).

Magnequest choke, transformer and stock bell

I got the plate back from the powdercoater with my favorite antique copper finish, so the next step was to begin populating the plate. I had made a few enlarged holes for the Neutrik locking jack, Cardas RCAs and binding posts, Goldpoint attenuator and vintage lamp.

Teflon 8 pin sockets and boards, Goldpoint attenuator

The Goldpoint attenuator required a little bit of work to fit. In the stock hole position, it butted up against the wood frame and the plate couldn't be seated. The hole had to be enlarged vertically to allow clearance. A couple of the little solder strips required mounting to #8 screws to be enlarged. I recommend one takes their time if they use a drill for this, as I broke two of them :P

Further population included a few little tweaks to the stock kit, including rubber washers for the transformers and chokes, shielded Cardas output wire, bypass film caps for the power supply caps, a few nicer Nichicon caps, thicker shielded wire for the power switch, another solder strip for the Neutrik locking plug to keep the installation clean, and some big hulking paper in oil AmpOhm caps, which required the addition of a set of 2" standoffs. Below are a few progress pics of the amp being built. 

Getting Started

Additional solder post used for headphone output

Solen caps placed temporarily for resistance checks

One thing about the build that was a little difficult was soldering the bottom of two of the power supply caps. There were three or so things going into the top hole of terminal 4 with that little solder strip which made it quite difficult to ascertain whether you had a good solder joint or not. With a flashlight a couple minutes of investigation, it could be seen. 

C4S boards fitted

The little C4S boards got in the way of the standoffs for the large caps, so I flipped them 180 degrees and dremmelled into the unused part of the board for clearance. It's almost comical how large the AmpOhm caps are at a mere 2.2uF.

Finished inside - Front

There's a lot of parts shoehorned in here

Finished inside - Back

There's a lot packed into this little chassis, every inch counts ;) I originally had a set of EAR feet on the bottom of the wood frame, but the caps protrude far enough that I had to get larger feet. I initially entertained the idea of some little brass spikes, but the company selling them wanted $80 for a set of four 1" x 1" threaded brass spikes. I picked up a set of 1" black steel spikes and 1" rubber feet (both under a dollar each) from PartsExpress. I ended up liking the black spikes better, so I drilled out the bottom of the wood frame and threaded it for them.

This amp lets it's business hang out ;)

Finished Back

Finished Front

The emblem on the front I had custom made (I had two made in total). I created the logo and sent it off to a promotional company that makes the little metal emblems. 

UPDATE (3/22/11) I got to have a listen to this yesterday, Eileen got me a replacement set of RCA tubes, and I had a pair of Sylvania coin-bases arrive from another supplier. Sound is really excellent, even before burn-in. No lack in the bass department, a nice powerful sound with just enough detail.

I'm currently using a very special custom 10-3 right angle power cord with this kit (my own recipe). Take a look at the details here.

Wondering where I got all my parts for this build? Check out a list of my favorite online vendors here.

UPDATE (3/29/11) Replaced the stock sandcast 0.1 ohm 5W resistor with a Vishay Dale wirewound in the power supply. Can't tell if it made a sonic difference, but would likely be a little more reliable over the years.

The Fine Print:

Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind.