• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Gold plated Dynaco ST-70 for $3k

No mention of compensation for the higher B+ due to (1) higher ac line voltage today, (2) removal of the 5AR4 rectifier heater load, and (2) the fact that he removed the valve rectifier and replaced it with SS rectifiers which have lower voltage drop.

I've not been a fan of Sprague Atom capacitors. The quality just hasn't been there in the past 20 years, but that is personal preference. In the 70s and 80s I would have recommended them.
 
Removing that rectifier tube function but leaving the heater connected was a master stroke of tackiness.
If you study the picture of the wiring very closely, it lools to me like the rectifier tube is still connected (both plates & filament) and the SS diodes are in parallel with the tube. You can just see the blue wires on pins 4 & 6. Make your own decisions about the quality of that type of work.
 

kmaier

Member
2007-07-12 1:42 am
Well, some thoughts:

Sprague Atoms - newer ones aren't that great, but the ones in the amp were made in the latter 80's, does this change your view? The new issue Mallory quad cap is pretty much junk and won't last very long (it will pop and sizzle and might even spew out). The rest of the components are average, nothing more.

Gold plating and silk screening - having had some ST-70 chassis chrome plated over the years, I seriously doubt you get that done for anywhere near $400... likely more than double that. EPA regulations make it very expensive to do this kind of work nowadays.

Tubes/Sockets - sockets look cheap... tubes are nothing special and one of the output tubes has a broken locating stem. Also the rectifier doesn't look to be lit, so either it could be bad or the transformer winding is open, hence the SS rectifiers.

Overall, nothing special in any way, sans the chassis work which does look nice in the pics. It's also showing free shipping. Ebay is nothing but a service... if the guy put it in the local newspaper classifieds, would you now hate your local newspaper? The world is full of greedy people, always has been, they have access to the same tools and services as everyone else. Do some homework first, then avoid the low class people that are simply looking to rip-off the general public. Dare someone actually say, "buyer beware"?

Regards, KM