by drlowmu » Wed Sep 19, 2018 6:28 am
Hello,
Looking at the Sun SV-2A3 schematic, and Hypertriode's neat execution, causes me to ask a question - and make a few comments.
The main question I ask, and most perplexing to me, is why pay attention, time, and money to such a uninspired and mediocre SE design of a 2A3 amp??
There are a huge number of mistakes to SUN's basic design, modifying it seems fruitless. It will never perform as it should, if it had a better overall SE design.
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I will offer three changes, that will improve hypertriode's execution, and these three apply to any quality SE amplifier. All three improve the SUN SV-2A3, and all three are at essentially ZERO cost.
1) NEVER EVER bundle wires in a SE amplifier, as proudly displayed, in the first photo !!!
It is the kiss of death. Looks neat, sounds worse...always !!! Oh my goodness.
In SE amps, all wires need to float in mid air, and not touch each other, be three-dimensionally positioned. All wires have fields, and to maintain the signal's purity, and best dynamic expression through the SET, the wires need to be separated. IF and when they cross each other, do so at RIGHT ANGLES to each other, so there is as little impact upon the two wires as possible.
2) Never EVER put an RCA input jack on the rear of a SET, and run signal wiring lengthwise all the way across the chassis to the front - end tubes !!!!!
Why? The signal level is the smallest signal level in the entire amp, and so, it is subject to degradation, due to longer-than-needed wire lengths, and any and all fields, acting upon that long wire, that are internal to the amp. Common sense. SUN has needlessly , without forethought, degraded the signal before it even GETS to the Input tube for amplification.
In the SUN amp, the RCA jacks should be re-positioned top-deck, right in front of each 6SN7 Input tube, such that there is LESS than two inches of under-deck wire length, between the RCA jack and the grid of the Input tube. In SETs, this critical short length of input signal wire sounds best ( to me ) when it is 2 paralleled runs of 18 AWG silver, high quality silver, or a close equivalent.
3) Along the same vein of thinking, any Pot on the input of an amplifier, if not needed, should be instantly eliminated and replaced with a HIGH QUALITY ( not a carbon comp ) resistor. A fixed-value, high-quality resistor, RCA jack..... hot to ground.
The input Pot on ANY amp is a HUGE signal degrade, again, at the lowest level of signal in the amp. Additionally, the pot has a diode-like wiper arm to winding mechanical interface, and a pot uses less-than-optimal resistive materials.
IF your audio system is thought out, and you have some means of attenuation prior to the amps, ( a preamp, or in my case, a quality system-attenuator ) NEVER using the Pot on the ( SUN SV-2A3 ) or any amp's input ...... is a easy-to-understand design choice.
Imagine using a Pot on the input, versus a really good sounding single resistor, perhaps something like a 1/2 Watt PRP, or a Roedersein Resista MK3, or a Caddock TF020. No contest there ......at all.
We need to put much more thinking into any SE executions. Have fun building. I sure do .
drlowmu