prototype preamplifier

[jonstanza]

hello hags!

my choice to not choose the 2sk170, I had many problems with it, changed its features with temperature, had to buy 20 units to have two identical (I use a differential input), was a sweet sound and slow. And many counterfeit units.

The 2N5566 is very stable with temperature, the sound is very natural, low noise ... the best we've tested to date. amazing, no comparison to 2sk170.

best regards

[jonstanza]

hello BowtoEd

my choice to increase the capacity of power transformer, was to have greatly improved the low frequencies in audio and .... thanks for your opinion

regards

jon

[jonstanza]

I'm now developing unit riaa (phono stage), if possible I'll put here a topic about my new project.

Here is some pictures of that unit.
-riaa passive correction, with capacitor dynamicap,
-mother board, supply rails with a copper OFC 6N.

-power suplly identical to the preamplifier
-and one module of amplification right or left.

note: the boards do not have all the components and after all the components are placed. is cleaned resin of solder.

best regards

[hags]

Originally Posted by jonstanza

hello hags!

my choice to not choose the 2sk170, I had many problems with it, changed its features with temperature, had to buy 20 units to have two identical (I use a differential input), was a sweet sound and slow. And many counterfeit units.

The 2N5566 is very stable with temperature, the sound is very natural, low noise ... the best we've tested to date. amazing, no comparison to 2sk170.

best regards

I would use the same words to describe the SK170.

In a differential input they sound a little slow and I'll also add somewhat rolled off. This has been well documented by Borbely. You can cascode the input but at a higher parts count and more matching.

The Linear Systems LSK170s are a step up but a real, current production alternative doesn't exist. I've searched high and low for a few 2N5566 that you used but unless I want over 100pc @~$200USD there are none available.

[jonstanza]

if you need 2n5566, I recommend utsource. Send an email to Mr.. Davis. sales@utsource.net The price ranges between 8 to $ 10

best regards
jon

[BowtoEd]

my choice to increase the capacity of power transformer, was to have greatly improved the low frequencies in audio and .... thanks for your opinion

I've often wondered why designers use large (300 VA range) power transformers for pre-amplifiers. The preamp I am designing may use 10 mA or less. The main need for current I can see in a preamp would be the output stage, where the final stage sometimes needs to be a mini-power amp to drive heavily capacitive cable or power amps with a low-impedance inputs.

If my preamp had bass problems my first instinct wouldn't be increasing the PT capacity. I'd look at each amplifier and probably change out coupling or bypass capacitors. If there were an NFB loop then I would redesign it. If none of that worked I'd get bigger power supply capacitors.

I'm not criticizing you for your PT choice. Your amp, your parts, your decisions. What method did you use to find the right PT? Was it just trial-and-error or did you calculate it by using the inductance of the pri/sec?

Ed

[carlomar]

Hi John,

Excellent project

Congratulations and best wishes.

[anakgading3]

Wow John, Two Thumbs up for your project. Truly combination of art and engineering!