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Dynaco ST inputs?

Dswankey

Dswankey

Lunatic Member
Re; ST-35, 70 & 120

Having owned an ST-70 I could never understand why the inputs were on the front of the chassis as opposed to the back?

I initially thought it must of been a design limitation back then yet the new kits one can buy today still have inputs on the front.
 
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The new chassis Tubes4HiFi is using has them on the back.
It was maybe due to the shortest distance is better thing to help reduce hum using twisted pairs?
 

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Power amps weren't displayed in 1959 - they were hidden in cabinets. Laid out for easy assembly and minimum hum. Routing the inputs to the back panel would require shielded wire, adding assembly steps and chance of error.
 
Maybe nothing. Just arranging connections like most others did at the time when it came to amplifiers? Monkey see monkey do. :biggrin:
 
an inch of standard wire is cheaper and easier to explain than 8 inches of shielded wire that has to be routed in a particular way to minimize hum issues.

I'm not much for front connections either, but I get the benefits from a technical POV.
 
I was a bit shocked at the price of two conductor shielded mic cable the last time I bought some. A short run of twisted pairs is a lot cheaper.
 
I replaced those sockets in front with some test jacks. I want to make some new ones though with three jacks per side. One for ground. At the time I just used the 4 jacks I had on hand. I wish those digital bias meters that are sold to fit those socket holes didn't stick out so much I would use them. But they look so bad sticking out so far.
 
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Did the same on a minor rework after the original rescue. I used one of the empty bias pot holes for my ground TP with the two TPs each in the old octal socket holes. I was going to do the three TPs each socket, but all of my meter leads have the typical thumb guard flange and it gets to be a tight fit trying to get two leads in that small spot. I have the ST and two mono blocks connected to the same preamp output with RCA "Y" connectors. An interesting and obvious observation once you realize it, system ground is common among them via the RCA ring terminal. I can choose any one of the amp's ground points and test bias at the appropriate spot.
 
Dswankey said:
What was it about shielded wire that they did not want to use it?
Click to expand...

The cost of stocking another item.
The dynaco products I've worked on dont use Retma color coding, which would be nice. Instead they provide one color of wire for the kit builder to assemble every circuit with.
I have seen some with 2 colors but they were used to designate right and left channel.
The entire right channel is red the left, green.
That's totally unconventional.
I try and build my custom amps correctly in observation of retma color codes, and using shielding on all input wiring.
 
The ST-35 kits from Dynakit uses braided hookup wire. Solid core would be better.
I wonder if the other amplifier kits they sell used braided wire as well? Braided is a pain with more than one connection per socket.
 
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