New Dynaco ST-70 by Bob Latino. Upgraded caps + NOS Mullards

Welcome. My late Spring cleaning continues. On offer is a remake of the famous Dynaco ST-70 updated by Bob Latino and labeled the VTA ST-70. Now you can that classic ST-70 presentation matched with modern day reliability. I built it last December and while it sounds fantastic it has seen only light usage. 

This "new" model differs from the original in the following ways:

1. The new STAINLESS STEEL chassis is identical in size, shape and markings to the older original nickel plated steel frame. This upgraded chassis is NON-MAGNETIC and removes any magnetic interference effects of a steel chassis on the audio circuitry.

2. The new USA made power transformer has a higher stack lamination than the original Dynaco power transformer and is rated for 120 volts instead of 115 like the old design. The two tube heater legs are rated for 5 amps each instead of 3 amps each like the old design. This beefed up transformer (which has a bottom plate like the original PA-060 to prevent EMI from the transformer from reaching the audio circuitry) allows the use of KT88 and 6550 output tubes in place of the EL34 tubes for a slightly different tonal presentation. Four heavy duty neoprene isolation mounts are used to attach the transformer to the chassis.

3. The A-470 output transformers are brand new USA made custom production transformers. They use the same interleaved/layer winding technique as the original cloth lead A-470's and incorporate the same high quality M-6 grain oriented laminations. They are dimensionally accurate to the original design and have a durable heat resistant black epoxy finish.

4. The old stock 30, 20, 20, 20 electrolytic quad cap which had marginal storage capacity for this amp has been replaced by a 80, 40, 30, 20 quad cap for almost double the power storage capacity.

5. The upgraded VTA driver board uses three new 12AU7 or 12BH7 triodes in place of the two mediocre sounding 7199 pentode/triode tubes. Dynaco saved money using a two tube 7199 board design but made some serious compromises in sound quality. The older ST-70 design had one bias control for each channel whereas the VTA board has a separate bias control for each of the four output tubes. This design allows for individual adjustment of each output tube bias. Matched pairs or quads of output tubes are not necessary with this design. Eight quality Sprague 716P "orange drop" coupling caps are included with the board.

6. The input jacks are gold plated and have a wider spacing to allow for newer design thicker interconnects.

7. The output jacks are modern gold plated 5 way binding posts.

8. The 7 octal tube sockets are modern high quality Celanex sockets with cadmium plated pins. These sockets are very durable and more reliable than the older stock phenolic tube sockets found in the original amps.

9. Includes two triode/pentode switches to allow switching between these two modes of operation. The switching may be done while the amp is running to compare the two sonic presentations.

More info at:

http://www.tubes4hifi.com/bob.htm

Additionally, I purchased the upgraded caps: 4 Power supply and 4 hand matched Russian K42-Y PIO coupling caps. I also upgraded the input tube with a Platinum Grade NOS Brimar/Mullard from Upscale Audio. The EL34s are vintage UK-made Mullards that have all tested strong on a friend's tester. 

This was a kit that I hand built. I am a very experienced builder so the "construction" and soldering are top notch. Amp works perfectly. And while I never had a single problem with the amp I understand the nervousness some of you may have at purchasing something not assembled in a union factory so the price reflects that, but one lucky person is going to get a hell of a bargain!   

 
No trades. Local Bay Area pickup welcome. Otherwise will be shipped very well packed insured UPS Ground.  

   
Cordially,   

John