Crap

LM1038 boards

https://www.yuan-jing.com/integated-preamps/lm1036-audio-tuning-board-delux-version Noisy monsters. Avoid!

Good

NE5532

Not to bad noise wise but i prefer opa2604.

https://www.ebay.co.uk/itm/NE5532-Stereo-Pre-amp-amplifier-board-Moving-Coil-Microphone-Amps-Moudle-P9A2/183031160521 Large capacitance load. causes amp to pop speaker cones fully on power up! not good but it does have good noise floor from what i can hear :).

OPA2604

opa2604 tone board centre front view https://www.ebay.co.uk/itm/preamp-Stereo-OPA2604-Tone-Board-Preamplifier-Volume-Treble-Bass-Super-LM1036/181936831248 Easy to power, I use a 15v linear regulator connected to amps power supply, if amp is powered by 24v like tpa3116. When i had it powered directly from battery i had ground loop noise problems :(.

Some noise floor is heard on better speakers, for the hmm last 1/4 of volume. Snags are on power down gives a pop to amp which then makes loud pop sound from speakers :(. It’s other wise the best, most compact, single dc powered tone board that i could find. Took many days or weeks of searching! My favourite features is that is has mid tone control. when most tone boards have bass, treble, bal, vol. Having mid tone control makes a huge difference!

There is also a ne5532 version of this board but i prefer this opa2604 version :)

My Favourite tone board! :D

https://www.aliexpress.com/item/Updated-OPA2604-AD827JN-OPAMP-Stereo-Preamp-Pre-amplifier-Volume-Tone-Control-Board/32730560110.html Very quite, practically doesn’t add noise. Snags are it needs a DUEL ± +/- DC (or ac) power supply. I found dc-dc ± buck and boost converters from china on ebay and aliexpress but ive blow them all up due to wired deep tech issures i don’t understand when i powered them from amps power supply :( :(. Or from the large capacitive load from the large 1000uf input capacitors!

So i have ordered large Isolated dc-dc ± converters from http://digikey.co.uk/ instead. that can take the capacitative load i hopeful. its rated at 1000uf load for each power line. so i hope that works. I chose isolated as that, means i won’t have ground loop problems because the power for the tone board is disconnected from the input power/batt of the setup.

I have been told that i can use a NTC inrush current limiter to limit the current spike as the caps charge up or a inductor or a more efficient curiect. I have got some ntc limiters that i think i wlll do, to try out. A helpful ntc inrush limiter calculator: https://www.ametherm.com/inrush-current/selecting-an-inrush-current-limiter.html

updates pending when i get my ordered bits :)