SS Phono Amplifier Development
Back in 2017, we looked at doing a phono amplifier product that would be very low noise, universal MM and MC cartridge compatible, and that would of course use our discrete op amps and voltage regulators inside. We went so far as to build a prototype that worked well, but it just wasn't the right time or place to bring such a product to market.
We sure did learn a lot from the exercise, and we then leveraged the knowledge that we gained from this - things like PIC microcontroller programming, TFT touch screen display control, transformer shielding, and power supply design into the Aires Headphone Amplifier.
Unlike this phono amp, the Aires is a real thing.
So here it is - the Sparkos Labs Phono Amplifier. Perhaps to be resurrected someday - but for now it will be filed under "Things That Never Were"
Some local storm troopers stopped by for a listening session and to take some photos of the unit. Their reflections can be seen in the dull metallic sheen of this fully armed and operational Phono Amplifier.
No, but, seriously, here is what it looks like in the prototype enclosure. This won’t be anything close to what the final enclosure will look like, but for testing and shielding purposes, and for evaluating the thermal characteristics of the enclosure, this $80 dollar Digikey thing will do just fine. The logo on the side is gold plated PCB material. Board art. Also not part of the final design.
This is how firmware updates get loaded into the microcontroller. 4 wires – Clock, Data, Reset, and Ground are required, and the rainbow cable does the trick. The blue cable is USB which goes back to the computer. The green board on the top is the dsPIC evaluation board. Programming is being done in this manner through the Eval board because I have yet to flog the PIC KIT 3 programmer into submission. For now it's mostly about working out small operational bugs and creating the graphical content. All of the functionality has been in place and working for a month or so now.
Here is a view under the hood of the prototype enclosure. The Toroidal transformer is covered by Giron material, which shields everything in the box from the transformer magnetic fields. That, and a dissipative bridge rectifier network with softening resistors coupled with a Giron divider between the power supply and amplifier sections (not pictured) should render all of the magnetic fields from the transformer completely harmless. Without these precautions, pickup from the transformer’s magnetic fields would both dominate and destroy the noise performance.
This is the raw unpopulated Phono Amplifier board which was fabricated by Circuits West (Sparkos Labs preferred PCB manufacturer) in Longmont, CO. We were able to take a tour of the factory lead by the president of Circuits West, Chuck Anderson, to witness the PCB fabrication process. To visit the Circuits West website click the link below
Stage one…. Bringing up the power and testing of the raw power supply, AC input section, and the Toroidal Power Transformer. No smoke was observed, nor were any explosions had. Great Success!
The SS Phono amplifier will make use of the finest active devices available on planet earth – Sparkos Labs Discrete Op Amps and Discrete Voltage regulators. These discrete devices will be used in all of the Audio stages throughout the Phono Amp. Here is a close up of an SS3601 Single Discrete Op Amp used in the first stage.
And here we have a lone Sparkos Labs SS783.3 discrete voltage regulator used for powering the Microcontroller and digital section of the Phono Amp.
A close up of a couple of the Sparkos Labs SS3602 Dual Discrete Op Amps which are used in the 2nd and 3rd stages of the Phono Amp. These stages also implement the RIAA correction and use precision 1% tolerance Polypropylene Film capacitors (the large aqua colored caps) and precision 0.1% thin film resistors to achieve an RIAA accuracy of <0.1dB .
An overall view of the main board, fully assembled. Mostly.
A close up of the dsPIC33EP512 Microcontroller. The Microcontroller is responsible for controlling the front panel display, remembering the user settings, and driving the relays that are used to set various cartridge R and C loading, Gain, LF cutoff points, etc…
The Microcontroller is a 100 pin Thin Quad Flat Pack (TQFP), which exceeds Sparko’s hand soldering ability. As such, we called in the the experts at our preferred Electronic Assembly House, TRACER PCBA of Golden Colorado. A big thank you goes out to Cole of TRACER for helping with the installation and soldering of the Microcontroller onto the PCB. Sparko could have never done it without you. Tracer PCBA’s website can be found here –
The SS Phono amp will have 2 sets of RCA inputs to allow 2 turn tables (and a microphone!) to be plugged in simultaneously. Each input (Input 1 and Input 2) can have unique settings that will automatically get recalled upon changing the active turn table input. The output of the Phono Amp will be both RCA and XLR for maximum flexibility.
Testing the front panel Thin Film Transistor (TFT) Color display. Both the display background and the text on screen can have a user controlled 16 bit color assigned to it, yielding 4,294,967,296 (4.29 Billion, or 2^32) possible user adjustable display color schemes. Note that this count includes color schemes that are completely useless, like black text on black background.
The front panel touch screen allows the user to adjust all of the settings for both Input 1 and Input 2. All that is left to do now is to spruce up the graphics of the display, like putting a back arrow icon for the Back Button rather than simply having a button that reads “Back”.
The First Order Ominously oversees prototype construction.
And finally we have Lutz. Sparkos Labs President and CEO. Quietly running the show, calling the shots, and protecting everyone from the evils in the world; the things that geek. What ever would we do without him?
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