Hifi Preamps for your Record Player

By: skrodahl | May 02, 2019

While there are lots of quality kits for preamplifiers, I have never really found a decent way of adding more inputs to a preamp. The existing ones are either of dubious quality, spec'ed like a spaceship, or both.


So I decided to make my own input selector. With relays. And an ESP-32 module! A year, and four revisions later, you can buy it on Tindie for $69.

The entire project is fully open source, no strings attached.

So what is it?


It is a programmable input selector for preamplifiers, the size of a Post-IT note, with:

  • Four stereo inputs
  • One stereo output
  • Mute
  • Mains power on/off through a solid state relay control
  • Break-outs for all ESP-32 pins

It's controlled by a rotational encoder and IR remote, and you get the great build instructions that you've come to expect from a Muffsy kit.

Muffsy Relay Input Selector - Kit
Muffsy Relay Input Selector - Kit Contents

The PCB, all onboard components, ESP-32, rotational encoder and IR receiver are all included in the kit. You also get the fully functional software for it, as well as the Eagle project files for the PCB.

The benefit of using an ESP-32 is that you can program it yourself, and use other functions like touch sensors, Wifi and Bluetooth.

By: skrodahl | June 27, 2018

Behold the new Muffsy Phono Preamp!


It'll be available on Tindie, very soon. Actually, it is available: https://www.tindie.com/products/skrodahl/muffsy-phono-preamp-kit/

The new Muffsy Phono Preamp PP-4

What's New?

These are basically the same circuits as before. The focus has been on making the build experience even easier than before, and improve noise prevention.


  • The op amps are OPA2134 and LM4562
  • SNR improved by 2.9 dB, from 79.4 dB to 82.3 dB
  • No screw terminals facing the side walls of the enclosure
  • The AC power cables do not cross the input
  • The DC power cables do not cross the output
  • The AC and DC power connectors line up on the PP-4 and PSU boards
  • The signal inputs and outputs line up with the RCA connectors on the back panel
  • The grounding scheme is redesigned to avoid ground loops
  • The input impedance switches are grouped together
  • The gain switches are grouped together
  • The back panel has a ground pad in one of the corners, to ground the cabinet
  • The back panel now has gold pads and the golden "M" logo
  • The power supply now has the golden "M" logo
  • There's room for heat sinks on the power supply voltage regulators (if needed)
  • The solder pads for the screw terminals are beefier
  • The mounting holes have been increased from 2.8 to 3.0 mm
  • The board width is approx 0.5 mm narrower for a better fit in the B0905 cabinet
  • The board's corners are even more rounded to make it easier to insert into the B0905 cabinet

Built-in Grounding of the Enclosure

One prime example of the thought that's gone into this new version is the fact that the back panel connects to the enclosure for improved grounding and shielding from noise:

 
Back Panel ground pad
 
Grounding the Muffsy PP-4

Crisp, Clear Pictures

I've put my new lightbox to good use, and produced some really nice pictures for the instructions.


Here's one of the new photos compared to the corresponding old phono. Judge for yourself:

New Power Supply Instructions
Old Power Supply Instructions

Thanks

This new version of the Muffsy Phono Preamp couldn't have been created without the (without exceptions) enjoyably long and fruitful email conversations with so many people. Keep using the contact form.


A special thank you goes to the loyal customers who helped me test the prototypes and provided valuable feedback, you know who you are. ;)

Category: News 

Tags: muffsy, phonostage, vinyl, launch, pp-4 

By: skrodahl | March 26, 2018

While I've been sharing a lot of my work on muffsy.com, I've never really clarified how my view is on people using my work (or derivates of it). This is now changing.

I've decided to release all of my content (barring a few exceptions) under the Creative Commons Attribution 4.0 International license.

What does it mean?

It means that everything on muffsy.com, except where specifically stated, is open source. You have the right to:

 

  • Share — copy and redistribute the material in any medium or format
  • Adapt — remix, transform, and build upon the material for any purpose, even commercially.
  • This license is acceptable for Free Cultural Works. I, as the licensor, cannot revoke these freedoms as long as you follow the license terms.

 

If you're going to use any of the content on muffsy.com, you will have to adhere to these conditions:

  • Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
  • No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.
  • You do not have to comply with the license for elements of the material in the public domain or where your use is permitted by an applicable exception or limitation.
  • No warranties are given. The license may not give you all of the permissions necessary for your intended use. For example, other rights such as publicity, privacy, or moral rights may limit how you use the material.

There are also some conditions for muffsy.com to follow. Most notably is that the shared information must be in an open format. The only possible violation to this are my Autodesk Eagle design files. They can be used, but not always processed, by the free version of Autodesk Eagle. They can also be opened and edited (although not always perfectly) in the open source tool KiCad.

What are the exceptions?

Update, 2019-04-05:

All published designs are open source and can be used freely for fun and profit. If you need to reverse engineer anything, it's probably not open source. By all means, do ask if you're in doubt.

The fact that the schematics are open source will of course allow you to design your own PCBs for any desired use, as long as you comply with the terms of the license.

The only exceptions to the Creative Commons on muffsy.com is for a few of my PCB designs, mainly variants of those that I'm currently selling. They are free for personal or non-commercial use, but you cannot use them commercially without my approval.

At the time of writing these are the only exceptions:

If not stated otherwise, everything is free to use as described above. That's right, text, pictures, schematics, design files. The lot!

Category: News 

Tags: muffsy, open source, website 

By: skrodahl | August 31, 2017

YouTube user Blake G has posted a couple of vinyl-rips using the Muffsy Phono Preamp onto the video site. Although YouTube probably alters the bitrate, you can still get an idea on how the Muffsy Phono Preamp performs in his setup. His setup, btw, is:


    • Turntable: Sony PS-X500
    • Cartridge: Empire 999ve/x
    • Phono Stage: Muffsy PP-3
    • Line In: Behringer UCA202

Muffsy Vinyl-rip on YouTube

Here are the links to Blake G's two rips:

 
 

Category: News 

Tags: muffsy, phonostage, vinyl, youtube, rip 

By: skrodahl | January 19, 2017

This project is freely available, and you can have the boards produced yourself. That's not for everyone though, so I've decided to sell the PCBs for the BSTRD on Tindie.

The Bill of Materials on hackaday.io has been greatly improved, and even contains a Mouser shopping cart for all parts except the tubes, tube sockets, LED resistors and transformers.

 
 
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