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In Reply to: RE: DIY'ing posted by jedrider on February 17, 2015 at 14:08:37
Here's my 2 pennies worth. I'm a user of a nice sounding solid state preamplifier featuring a few design factors that are important to me:
A vital aspect is the sonic signature (or lack thereof) of the volume potentiometer, since it has a profound effect on the signal. A volume control is by nature a necessary evil piled on top of a second gain stage which already ruins the Audiophile Holy Grail of "straight wire with gain". Perhaps the best one can hope for is the original signal from the source component is not poorly affected, and the signal output circuit of the preamplifier complements the signal input circuit of the power amplification involved.
Another vital aspect is having a separate outboard power supply unit in order to isolate the power supply from the preamplifier circuit board, as well as potentially better optimize the layout of the preamplifier circuit board when the power supply section is eliminated from the scenario. Make sure to build a high performance DIY DC umbilical to use between the outboard power supply and the preamplifier unit. I reckon the power supply is the heart of a preamplifier, which in turn is the heart of an audio system, for better or worse.
Vibration control, power line filtering, and the choice of AC power cord can make a big impact on the ultimate result, IME.
Follow Ups:
My $0.02 is that it's the design that makes a preamp sound great. Implementation details like volume control used, whether the power supply is in a separate box, the types of cap used, etc, etc, well, these can ruin the sound, but they are not going to make it great.
I simply shared personal interests -- didn't say anything about those factors in and of themselves making a design great.
I am not all that convinced that OUTBOARD power supply is a requirement. However, I am leaning towards BIGGER power supplies and if there is not enough space, then it must go outboard!
H'mm. I'm ready to pull the trigger on a discrete Curl clone from eBay with switching and I would intend to try to put it in one box with a toroidal and it does have it's own power supply so I just need a toroidal.
I don't know, but it is fun and I can afford it!
John Curl on Toroids:
"Toroids are not as good as non-toroids when it comes to preamp transformers. This is because they have higher inter-coil capacitance, than E-I, or the newer R core transformers. We avoid them for even the best preamps."
He must be getting old now, so on 'hemorrhoids'.
Please post a link to the eBay listing. TIA
Most of the battle is knowing the search terms. There was a board with NOS parts that was described like one describes aging wine! Alas, it's gone now, but there remains a completed unit that is still probably a good deal.
Oh, there are still these, though, but I wanted the switching included:
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