FYI: Dynaco ST 400 (A reveiw of sorts)

The Donk!

Member
2008-02-24 4:48 am
I just rebuilt a Dynaco 400 and I wouldn't recommend it. I wouldn't recommend it to anyone who considers them self a beginner, and I sure as hell wouldn't recommend it to anyone who works on gear for a living, or regularly; you'll be very mad at yourself for the time you spend. you will waist your life on this unit.

It just isn't worth it.

These amps are horribly designed.

Electrically, and mechanically.

Electrical speaks for its self. (Why are people always replacing finals and driver boards? Crappy design from the get go!

Mechanicals.

Well, honestly, I think the patent office should prohibit such horrible designs.

You will spend literally hours just disassembling and reassembling the amp, let alone time spent on the electrical aspects.


this amp was probably the 1000th piece of gear I worked. And it doesn't work. No matter what. It just doesn't work.

I give this piece of gear a F for every applicable reason to grade it.

It's POS.


Imagine using new parts for everything. And everything is assembled correctly. And it doesn't work!

Somethings wrong!

And it ain't me babe. It ain't me.


I'm sure, allot of people love this amp, and for those of you that do. I'm sorry.

Good luck........
 

wg_ski

Member
2007-10-10 5:21 pm
+1. The best use I've found for Dyna 400 is to reuse the dead carcass. I like the huge heat sink. Drilled for four extra power trannies, and built a more conventional circuit (resembling a PL400, using 3xMJ15024&025 per channel) into it. Sounds way better than the original.
 
wg_ski said:
+1. The best use I've found for Dyna 400 is to reuse the dead carcass. I like the huge heat sink. Drilled for four extra power trannies, and built a more conventional circuit (resembling a PL400, using 3xMJ15024&025 per channel) into it. Sounds way better than the original.


It has a great power transformer; if you're into transformers.

Mike.
 

d3imlay

Member
2004-09-09 11:34 pm
Ohio
I never liked the totem pole output design, but it was reliable. By cutting the voltage across the transistors in half the power dissipation was decreased by 4X and allowed them to stay well within their SOA. In the late 80's/early 90's I did contract work for a company that reintroduced the 410 in kit form which is a stripped down 400. I tested all of the driver boards and I know I tested at least a 1000. Very few kits came back and it was always due to assembly errors/poor soldering. I hated to work on them, but they didn't fail.
 

maqm

Member
2010-03-11 11:18 pm
Dynaco ST-400 bias adjustment

I never liked the totem pole output design, but it was reliable. By cutting the voltage across the transistors in half the power dissipation was decreased by 4X and allowed them to stay well within their SOA. In the late 80's/early 90's I did contract work for a company that reintroduced the 410 in kit form which is a stripped down 400. I tested all of the driver boards and I know I tested at least a 1000. Very few kits came back and it was always due to assembly errors/poor soldering. I hated to work on them, but they didn't fail.

Taken into consideration your experience with the 400 series of Dynaco amplifiers, Could you tell me if 150 mA. is the correct value to calibrate properly the bias in the ST-400 ?:)

Thanks