Dynaco Based ST-70 Custom CNC Machined Brass Chassis Vacuum Tube Amplifiers (Price Drop)

Up for Sale is a pair of Dynaco ST-70 based Vacuum Tube Amplifiers. These are 100% custom built and CNC machined chassis out of solid brass plate that measures a ¼ in thickness. Each Brass Chassis measures 14” in width, 10.25” in Depth and 3.25 in Height. Both amps are fully upgraded with Joe Curcio Premium modification boards including Premium main driver board, Premium Power supply board and a Quad Cap replacement board and these amps were built as mirror images of each other. The only stock Dynaco items on these amps are the transformers everything else has been completely updated. These transformers were the cloth wired ones from the late 60’s but the cloth wasn’t holding up very well so I had the Input and output wires professionally replaced with top quality wire.

I designed and started building these amps around 1996 and I could only work on them in small time increments and I didn't finish them until 2004. They were in use on and off until 2011 and more or less in storage ever since. They took many years to complete and they look and sound spectacular.

They are larger than the normal chassis to make room for the upgraded boards. There are no bottom or tube covers. How you see them here is how they are used. I engraved the face panels to indicate the Band Pass and the High pass sides if you wanted to hook them up the same way every time but both outputs are the same. I used top quality Bourne pots for the Bias adjustment and Volume for both channels. The pots were machined with a very small hex if you wanted to use and Allen wrench to adjust them but they adjust very easily with your finger tip. If you look closely at the front view I also machined a small arrow on the face of the post to show where they are rotationally.

The output binding plugs are seated in CNC machined Nylatron inserts. They are currently hooked up to the 8 Ohm taps but the 4 and 16 Ohm taps are sitting inside the bell end of the transformer and can be swapped out with the 8 Ohm taps if needed. They are Bi-Amp configured meaning they have only 1 RCA input per amp. 1 RCA input signal feeds both channels of the amplifier. I used this setup for a wonderful sounding pair of Elac 203 speakers. One channel of the amp feeds the tweeter and the other feeds the full range driver. Both channels produce the full frequency spectrum so your speaker’s internal crossover or your own design will have to be used at the speaker end.

I can’t even imagine the amount of hours and costs I have into building this pair of amplifiers. The brass alone is very expensive and the Joe Curcio Premium modification boards are top of the line, please check out Joe Curcio Audio to see all the specs (and costs) for these Premium upgrade boards. Gold input RCA’s and Gold output binding posts are high quality and all the tube sockets are ceramic with gold contacts. All sound stage and electrolytic capacitors have just been replaced. A brand new set of matched output tubes will ship with the amps and the driver board uses superb quality JAN Phillips 6922. The 6922's are original but still test at over 100%. All the tubes are outfitted with silicon tube dampers. All internal board to board wiring is Teflon jacketed 100% pure oxygen free copper/silver plated wire and WBT Silver solder was used for all connections. There are sockets on the face of the amps for setting bias voltage and a digital volt meter with the proper plug will be furnished with the sale. Power cords will also be provided with the sale but they are standard quality wire with domestic high quality plugs.

12” x 18” Granite surface plates with brass machined tip toes with carpet spikes are also included in the auction.

The amps were both shinny and new when finished but I decided to not coat them with anything and let them age naturally and Patina as they will. I have lots of pictures during the building of these amps that will be included with the purchase.

This sale includes both amps with brand new output tubes with receipt, granite surface plates, 2 power cords and the voltmeter with the adapter for setting the bias voltage.

They are currently hooked up and available for audition in the N.W corner of Washington State. Here’s the zip code 98284 if you desire to look it up. If they are not sold locally they will be packaged up perfectly for shipping and fully insured for a safe journey to their new owner. Fixed shipping costs/fully insured to the lower 48. The amps are guaranteed to not be DOA but no other warranty is implied. They power up fine, hold bias very stable and sound amazing. These amps are not in brand new condition but they are in very excellent condition and fully operational.

I understand that $3,250.00 + Shipping sounds like a lot of money but these are 1 of a kind amps, not another pair like them or even close in the world. I just spent time and money to upgrade all the capacitors and purchase new Electro Harmonics (6CA7) output tubes which sound fantastic in these amps so the new owner will enjoy many years of use without them needing anything. On eBay a fairly well updated ST-70 sells for over $1,200 and still uses the original quad cap… Really! And that’s for one amp. No Brass chassis and no Joe Curcio upgrades ($1,734 for both amps). I understand this purchase isn’t for everyone out there but I’m hopeful that someone will see the quality and appreciate the uniqueness of these amps and will purchase them because they want to own the very best in the Dynaco family. I do intend to sell them so please make an offer and eventually I will take what the market will pay.

I reserved the right to close listing early for sale on another site or local sale. If you live within 100 miles or so from me I will deliver them to you for free to save shipping costs. ALSO: I will be out of town the first week of March. Response time will be slow while I am away.

Thanks