Project files: The Muffsy RIAA clone

What is it?
My version of the “Muffsy” RIAA board. As I observed in the first post my version really looks nothing like the original, so here’s a quick rundown of what I have changed:

  • The board is mono and intended to be stacked two channels on top of each other as shown in the pictures because that was what I needed. Side-by-side placement and/or dual-mono configurations are of course possible as well – if maybe a little less practical…
  • The board uses single opamps instead of the duals on the original. This of course increases the cost a bit, but it also offers more flexibility for those that want to experiment with how different opamps change the sound (because the choice of singles is much bigger – especially after this).
  • Because I’ve found myself using the mute button on my amplifier quite a lot when changing records, I got the idea to include a relay-based mute on the output of the RIAA so that mute is available even if your amplifier doesn’t have a mute option.
  • The input cap position has been kept because my usual cartridge expects a slightly higher load capacitance so I need a capacitor in that position (you can of course still leave it out if you want).
  • The output cap position is bigger to make space for a more “audiophile” sized capacitor 🙂
  • The selectable input impedance resistors have been removed. All of the cartridges I am reasonably going to use on my Pro-Ject turntable will be MM-types that need a 47k load impedance so I skipped this option – not that it’s a bad idea though.
  • The selectable gain I have kept, but instead of a DIP-switch I used a header/jumper which doesn’t take up as much space on the board. It’s only marginally less user-friendly than the DIP-switch in my opinion.
  • Otherwise the basic schematic and the component values remain the same as the original Muffsy.

How big are the boards?
The board measures 3.925” x 1.45” (app. 100 x 37 mm.).

What is the status of the boards?
The board file is v1.1 as I’ve fixed some minor niggles with the prototypes. I’ve tested the board and it works but I still don’t have detailed listening impressions, not least because – as the pictures show – I’m missing a couple of fairly important PSU components 😉

Does it use any special/expensive/hard-to-find parts?
Most of these components are standard sizes and it should be easy to find from the usual sources, however note the following:

  • Capacitors in the signal path should be polypropylene** film types and ideally 2% tolerance or less and in packages with 5mm pin spacing. If you can’t find 2% capacitors, buy a few 5% types of each value and match them using a multimeter to at least keep the variance between channels as low as possible (honestly this is worth checking regardless of what you buy).
  • Resistors should be 1% tolerance (or better – so if you want to “splurge” on 0.1% types go right ahead 😀 ). Obviously the resistors for the relay and the LED are exempted from this requirement 🙂
  • The muting relay is a tiny G6K type from Omron and as far as I know there are no substitutes from other manufacturers. Make sure you get the version with even 0.1” pin spacing.
  • I don’t really recommend buying expensive opamps from eBay or aliexpress because it is simply too easy to fake the markings on a standard DIP-package to make a surplus TL071 look like a NOS OPA627 at 10-20 times the price, but only you can decide if you think the risk is worth taking. There are some great offers on eBay, but sometimes you have to go through quite a bit of grief to find them…
  • **No, in actual fact no one is really going to die because you use polyester film caps but you’re an audiophile so you should aim for the best (within reason, if you happen to be both an audiophile and an engineer or just an audiophile that still has a bit of common sense left 😀 )

Anything else I need to know?

  • The muting relay is powered by the positive supply rail (via a resistor if the voltage is higher than 12V) with the switch in series, so any latching switch will be usable as the mute switch.
  • As standard, the muting relay switches both signal and ground. Not sure if this is always a good idea, but if not then it’s quite easy to bridge the GND-connection on the back of the board so only the signal is switched.
  • If you don’t want the mute option at all just bridge both of the positions marked on the back the board and you can skip the relay, the resistor, the diode across the relay and of course the connector and switch.
  • As is my custom for PCB layouts this is quite tight (ok, make that “cramped”), so a couple of tips: 1) remember the decoupling caps on top and 2) measure the voltage on the opamp sockets to ensure that everything is OK before mounting the opamps becasuse the decoupling electrolytics make it a bit difficult to remove the IC afterwards. If you want to experiment with different opamps, consider stacking two sockets on top of each other. This should lift the actual opamp above the electrolytics making it easier to remove.
  • Again: Note the two SMD decoupling caps on the top of the board. They need to be mounted before you solder the opamp sockets!!. They also mean that you have to use a socket and you can’t mount the opamp directly to the board.
  • I’ve used a basic LM317/LM337 power supply for mine (this one to be specific), but there might be something to gain by using more sophisticated low-noise types. It is also possible to power the circuit from a couple of 12V SLA batteries, but if it is worth the trouble I’m not sure (probably not though – if you want to put that much effort into a RIAA you should maybe consider starting from a more advanced circuit instead 😀 ).
  • Regarding the opamps, the “default” option is the LME49710, but there are lots of other DIP-options as well that could potentially be used (LT1363, LT1028, AD797, OPA627 etc. are all common choices for RIAA-circuits) as well as of course several others in SO-8 packages that can be used with suitable adapters. Unless you already have a favourite IC, my advice would be to start from the default (which should be among the best “value-for-money” options anyway) and then change once you’ve tried it so you can more easily identify changes.

Downloads:
Download design files here

Related information:
As this is effectively a clone of the Muffsy board, you should read the Muffsy website for additional information (and if you really want the background, the original Audiokarma CNC thread as well).

Note: Always read the “intro post” for additional important information about my designs.

Oh, and remember I did this because I wanted to experiment and tailor an existing design to my own requirements and preferences. If you just want to build a board and get sound out of it, don’t bother with this but buy boards/kits of the original Muffsy instead 😀

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The Muffsy RIAA clone (teaser…)

It’s been a while and I’ve got no time to do a big writeup right now (it’s Christmas eve!!) but it’s here, it’s working and no, it looks nothing like the original. More in a few days but a very merry Christmas to everyone for now 😀

Phew!

Been very busy lately, with both life in general and (especially) a job change. So, finally it’s been a (relatively) free weekend and a chance to relax with some solder fumes. Haven’t build anything that’s worth showing off at the moment, but it was nice to have some time to build again 😀

Apart from a bit of soldering I also managed to finish some PCB files as well. Most important was the PCB for my version of the Audiokarma CNC RIAA (or, actually the “Muffsy” evolution version of it). I’ve been listening to a lot of vinyl lately and this looks like a very interesting (and simple) RIAA, so I had to give it a try – albeit with a few changes over the original. Boards should be here in a couple of weeks 🙂

Going “retro”….

For the past few months I have noticed something: Most of my everyday listening is with a portable rig, either at my desk at work or during the daily commute. When I am at home, while I have my entire 800+ CD-collection ripped to lossless files and a whole dedicated setup for listening to it (dedicated Mac Mini with Audiolab M-DAC etc.) I was actually not using it a lot. It’s not that I don’t like the sound, but it is a bit of a faff having to turn everything on, wait for the computer to start up and then having to either turn on the TV to navigate or get out an iPad/iPod/iPhone to use the remote app etc.

After this (slow) realisation, I started thinking back to when I started playing music on my own. My first “real” system was a simple Harman/Kardon CD-player and integrated amp and I lived happily with that for nearly ten years. There was nothing to wait for, just two on-switches and a play-button and then there was music, and there was a bit more “tactility” to the process overall (if not much). I don’t think I’ll ever really go back to the CDs, but I have actually – slowly but surely – started playing a lot more vinyl at home.

Some would say that I have just succumbed to the first “wave” of accumulated nostalgia when you reach your mid-thirties, but it’s not as if I have a long history of actually using vinyl records. Of course I am old enough to know how they work ( 😉 ) and I can remember playing records when I was younger on my parents’ stereo. But when I started buying my own music in the early nineties, CD was already the format of choice (and cassettes were still common as well, mainly for exchanging music with friends). The only friends that bought vinyl were a couple with older siblings that had turntables and even they switched to CDs very quickly. As a result, I’ve never really had that much affection for the vinyl format so I do challenge the notion that this is just misty-eyed nostalgia at work 🙂

To add to that, the turntable obviously has its share of downsides – I had for instance mostly forgotten just how short the side of a record seems when you are working on something and just playing music in the background. I had also forgotten just how much dust a record is capable of attracting and how annoying scratches can be. My turntable is nothing special (a simple Project Debut Carbon albeit with an upgraded cartridge and an aftermarket plexiglass platter), but even so – it sounds very good and it is definitely more of an “experience” or “occasion” to put on a record, lower the stylus and wait for music to come out of the speakers.

So, there we go – I said it: For me this hobby isn’t really about sound quality (at least not only) but also about the experience. Blasphemy to some audiophiles, but a revelation to others maybe? If nothing else, I guess it provides an explanation (or excuse…) for why I continue to design, build and buy a lot of gear that I may never really get to use 😀

vinylaction

Happy 2015!!

Another year gone, another time to make a quick status 🙂

As I have written about a couple of times during the year, I am still a bit overwhelmed with the number of people clicking their way here. The number of page views passed 64k a few days ago which is quite a big step up from the 15k at the end of last year. The download count for the project files is now well over 1300 as well and I really hope to continue this trend in 2015 – workload and bank manager permitting of course 😀

Now, things are probably going to be a bit quiet here for the next couple of weeks as I head to China on Friday. Mostly just a sightseeing holiday, but hopefully with a chance to do some audio-related shopping as well. Fortunately my X-mas break did give me a chance to (nearly) finish some builds that I will be showing over the next weeks/months. A big milestone was reached when I finally managed to case one of my RIAAs, which means I go into 2015 with a working vinyl rig – very nice!

In other news I received my first custom-machined Modushop front panels from Schaeffer/FPX last week. They turned out very well, so it seems my favourite hobby has found yet another way of ruining me which I will show soon. Also, as you have probably noticed from the last few month’s updates I still have plenty of half-finished projects to carry on into 2015, so in case you were worried there’s no real shortage of content for the blog 🙂

For now, thanks a lot for reading and all the best for 2015 to everyone of you 🙂

A real Ba****d – Part 2

Second part of my “rework” of the old “The Bastard” – the RIAA-stage. The first was the tube-based line stage which you can see in one of my previous posts and there you can also find a link to the original article from a (long gone) Danish magazine.

This is a discrete solid-state RIAA stage based on fairly standard BC5xx-transistors. I know virtually nothing about RIAA-designs, toplogies, correction curves etc. so I will not comment on that and all I have done is to lay out a new PCB in Eagle. My enclosure parts for this build are currently on order, so I have only managed to listen very briefly to the board but it does sound promising I have to say :). Once it is built I will be listening further and comparing it against the Retro as well (in an “old-versus-new-technology” shootout :D).

The “Retro” balanced RIAA stage

Since I got my Pro-Ject turntable about two months ago I have been looking for a decent RIAA-design. I have an old Vincent, but it isn’t really good enough. Almost at the same time, I realized that Brian and Russ at Twisted Pear Audio were just finishing up a balanced RIAA design using differential opamps which they called the Retro. It looked like it might be worth a try, so I ordered some PCBs and the few parts that I were missing – sometimes it is nice to have a big cache of parts that can be used 😀

The build is dual-mono including power supply boards (the LCBPS also from Twisted Pear) and separate PCB-mounted transformers for each channel. It is a bit overkill with two transformers, but hey, they were just laying around anyway 😉 The observant reader will notice from the pictures that my ground wiring isn’t 100% correct – I am still trying to get my head around grounding in differential systems but for now it works fine with only a little hum in the speakers.

I haven’t spent two much time listening yet, but even with short tests it is obvious that this design is at least a few steps up from the Vincent, so although I have a few more RIAA-designs I would like to try as well, the Retro is definitely making the Pro-Ject (and the vinyl collection) sing 🙂