Tube Amp + Raspberry Pi + DAC build

  1. Marzie
    Hi all!
     
    I used to be fairly active here, but haven't done much with HiFi audio for a few years. I'd like to get back into a DIY project, so I'm looking for some suggestions. Please forgive me for the somewhat unfocused post; like many others, when I become excited about a new project, I have about 10 different paths my mind goes down, quickly switching from one to the next with little thought to those trying to follow me.
     
    My last audio project was to use some Raspberry Pi's around the house for a distributed audio system. But now I'd like to use one as a dedicated listening station. I converted one of my Pi's with a HiFi Berry Digi+ board into a standalone Volumio player. For those unfamilar, Volumio a Linux distro that turns the mini computer board into dedicated audio player with a web interface. The Digi+ board is an add-on board for the music player that outputs the audio stream via optical or coax.
     
    I'm running the Pi into the Digi+ board and out of it's optical port, into a DIYEDEN DAC (had it about 7 years, no idea of the components inside.) From there, it goes into my CK^2III amp and into my HD-600s. Overall, the sound is a little bright/warm for my taste, and I'm not sure which of the components is causing it. I don't remember the CKKIII having that problem (if you want to call it that) in the past, but as I mentioned, I have not been using my hifi headphone setup for quite some time. It could be due to losing my memory of my source material, but I don't know.
     
    Either way, I think I would like to move toward a tube amp, with a different DAC, and the Pi, and all the components integrated cleanly into a single case. I've always feared case development in the past, but I have a little more experience in fabrication under my belt, and my perfectionist streak has mellowed out a little, so I think I am willing to give it a try.
     
    I'm looking at the Bijou amp, as it appears to be an amazing quality amp for the price. I currently have a Millet Max and I love it's sound, plus the build was dead-easy, if I remember correctly. I don't think the Bijou is more difficult at first glance, however there is more risk with the higher voltages, and the more complex circuitry. I'm not sure it would be a good project to start with.
     
    The other factor I am considering is the cost vs. performance/features. I think I would want to make sure I can use the tube amp with other sources if I wish, as that would give me a little more bang for my buck. This would mean either having the digital port (or RCA jacks, see below) from the Pi coming out the back and into an input for the DAC (or amp, see below) or building an input switcher of some kind.
     
    As I said above, I used the Digi+ board from HiFi Berry. This is digital out, necessitating a DAC in between it and the amp. They also offer a DAC+ board, which outputs via RCA jacks. This simplifies the build in one sense, eliminating an entire component in the process. However, the chip on the DAC is the PCM5122, and I don't know the quality of this chip. Also, the circuit seems pretty damn simple, and I think if I go the Bijou route, I will want to have a higher quality circuit for my DAC.
     
    There is another route I could go, that would save a few dollars, and might be a better "starter/reintroduction" project. I was thinking of using the Pi with the the DAC board, and building a Millet amp instead. If I wanted, I could use the Digi+ board instead, and incorporate a DAC in between, but because I am not going "top dollar" on the amp, I wouldn't feel as bad about using a more budget friendly DAC.
     
    That's what my coworkers would call a "mind dump," so I hope you all can make sense of my intentions and help steer me toward a good solution. I'd love to hear what you think, as I would like to start ordering parts and building as soon as possible. Once the DIY bug bites, the fastest remedy is to lighten my wallet. [​IMG]
     
    Thank you all in advance for your help.
     
    Mike
     
  2. DutchGFX
    From what I can tell, you seem capable of building a Bijou, which I have never built, but because there is no instruction manual, you will be mostly on your own and have to pull info from online. As a result, there is a marked difference in difficulty from the crack to the bijou. You will likely need tk troubleshoot, but it seems like you can do it. I have heard great things about the Bijou. Another option is the EHHA, which I have listened to. Mullet built one and it sounds quite nice. It's low voltage so you won't need to worry as much. They make circuit boards for both the EHHA and the Bijou, so it won't be too difficult.
     
  3. Marzie
    I actually decided to build using a Millet Mosfet Max. I am familiar with this amp and love its sound. Plus, there a smaller chance of catastrophic failure, at least that's how it looks to me. And Jeff at Glass Jar Audio has a pretty easy ordering process to get a full kit. One of the biggest pains of the DIY process was price checking your components on the top 2 or 3 sites, then making multiple order forms/carts, changing them when something was out of stock, etc. Maybe now that I'm a little older and more patient, I would see it as an "it's the journey, not the destination" type of thing, and find some pleasure in it. Maybe on my next build...
     
    The funny thing is, with all the DIY I have done, I was not really aware of the DIYaudio forum. There are multiple builders on this site that have done the same thing I am trying to do. I will go there and try to get some help with my build. I'll still make sure to update this thread with any info I can.
     
    On that note, I bought an IQaudio DAC board to use this time, instead of the HiFi Berry. After I had already purchased it, I became aware (through the DIYAudio thread) that there is another DAC with a built in power circuit that can supply the Pi with clean power. I need to do a little more research, as it isn't advertised as being compatible with he RPi 2B, just the older model B+. Also, it appears that you can/should use the HiFiBerry driver in Volumio with it, but I am not sure that works 100% out of the box. There is an email exchange between what appears to be the board creator and the software developer that says a few strings need to be removed from the default config file. I think the DAC was the Duriosound?
     
    The RPi board arrived, along with the wall wart, memory card, and WiFi adapter. I will probably start looking at build threads and photo albums to get some inspiration on the case design. 
     
    Anyway, that's all I have for now. Thanks for your input!
     
  4. FallenAngel Contributor
    Good choice on using the Millet Max. The Bijou is a MUCH harder build. The casework is all custom, there are three boards and all wiring is custom, and with AC heaters, you gotta know what you're doing. I'm building one right now and can say it's not easy, nor cheap. I paid about $500 just for the casework.
     
  5. Marzie
    WOW! I can see the Bijou as being both mentally and financially exhausting. Maybe I can work my way up to it, as it looks like it is well designed and probably has a great sound. Let me know how yours comes out! I checked out your wiring in the other thread, it looks great!
     
    I have made a little progress. In one of the Raspberry Pi threads on the DIYAudio forum, someone suggested this AC/DC converter/step down transformer from ebay. 
     
    http://www.ebay.com/itm/321472165477
     
    I bought two of those but they are coming slow boat from China. I bought two in case one is DOA, or if there are any other issues. I'm pretty excited to start testing on my build, so I also bought this one off Amazon yesterday. Should be here tomorrow, so I should have some more info to report soon.
     
    http://www.amazon.com/gp/product/B00R5I3VTW
     
    I'm hoping at least one of these works for what I am doing. We will see...
     
    I also got a few old USB cables from a coworker. I plan on using the standard micro USB connector into the pi, instead of soldering directly to the board. It might be less prone to failure with a direct connection, but I like the idea of being able to switch out a failed board easily, or re-purpose this one temporarily if I need to.
     
    I bought the Mosfet Max kit from Glass Jar Audio. I had an extra set of leftover tubes from my Millet build, so I wasn't going to buy tubes. But I brought my Millet to work to test with the current setup, and found my original tubes are trashed as far as I can tell. There is a ton of distortion and noise and it generally sounds bad, compared to what I remember. There was a time I had it on for months, maybe even a year? without realizing it. Shame on me, I know. I am breaking in the 12AE6's now, the other ones were 12FK6s. But I ordered a full set from Beezar, including two pair of 12FM6's that were out of stock when I first built the amp. I also have a local vendor for tubes that I'm going to try out, it would be nice to be able to pick one up locally if needed. Wouldn't hurt to have a few extra, plus he is a lot cheaper. Although I don't know that his tubes have been "cared for" as much as the ones I get from tomb. Who knows what musty basement or outdoor garage the local guy might have pulled them out of.
     
    As I said, I'm starting to look at cases, and I like the HiFi2000 cases, although I will cry when I have to pay the shipping from Italy. It would be great if there were a US vendor for these. If I do go that route, I will probably wind up buying two or three cases, as I'm not sure which one will be just right for the build. Also, I saw some beautiful cases made from wood. I feel a little more comfortable with woodworking, as I can get a new piece locally if I mess one up. Not so with the HiFi2000 front, back and top panels.
     
  6. silvrr
    Be sure to post up your experience with those power supplies.  I am putting together a review/build log for a RuneAudio player which is a Sister/Daughter to Volumio.  Would love any input you have.  
     
  7. Marzie
    Silvrr - will do.

    I bought a piece of 1" x 4" cedar and 1" x 4" cherry. I'm gonna use the cedar to test my woodworking skills and then move up to the cherry. I also bought a 2' x 2' piece of 1/4" MDF for the bottom. I bought a 1' x 1' piece of almuminum for lining the bottom of the case. Some people said that some metal would help guard against noise when making a wooden case. I really don't know if it will be necessary, maybe those more familiar with ground issues can chime in. I also bought an oribtial sander, and I might add a router to help with the casework.

    I started using some cardboard to mock up some case designs. I de-cased my Millet Hybrid Maxed to help with the layout, and it looks pretty darn good to me. I'll add some pics, but fair warning, you might need to use your imagination a little.
     
  8. Marzie
    As I said above, you need to use your imagination a little. I'm already seeing a beautiful wood case, not cardboard and painters tape.

    Forgive the extra holes in front. I started with one set of motherboard standoffs to raise the board, but the tubes were no where near the top edge of the sides of the "case." In the end I worked up to, I think 4? Still not much tube above the sides, but there are various differences between the cardboard mockup dimensions and what I am planning for the wood case, and I think that issue will go away

    The second hole on the back is for a power switch for the Pi. I may need to add a special board that performs a software shutdown on the Pi instead of just dropping 5V. But I plan to use the same switch as the Millet, at least to start with. I also need to add a switch for changing from the RCA inputs for the Millet, or to the DAC. The Glass Jar kit comes with a plain, simple switch, but I think I might try and find something a little nicer. I also need to add the biasing jacks, however I don't think the kit comes with those, and I don't have any, so I will have to track some down. I will have one light in front for the amp, one for the Pi. You may have noticed the excess jacks on the back, I'm going to have jacks for outputs from the Pi, plus outputs to use the amp as a preamp. In theory, you should be able to use one or the other exclusively.

    I still need to cut down a micro-usb cable and test out the voltage conveter, probably tomorrow. I'm going to buy some new wire for ground and crimp on connectors for the switch, as the stuff I used in the past was not the best.

    I'm also debating a touch screen in front for the Pi. Volumio is designed to run "headless" so that might not be a good choice. I could also just use a simple LCD display, as I believe that is a little easier. I'll be doing some research on both options first.

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  9. tomb
    I haven't seen an original Millett Hybrid MAXed PCB in a while.  Good stuff!
     
  10. Marzie
    Thanks tomb! I love the sound of it, I'm curious to see how it compares to the Glass Jar Mosfet kit. I know the caps are the same as the Maxed can't miss #5, but I'm hoping it still sounds as good as my build, I think it's can't miss #3, the one with the green Russian caps.

    Silvrr- the Amazon converter works. I had a ton of noise on the headphone jack, but to me it sounds like grounding noise because there really isn't any grounding at the moment.

    I did learn a few things, I think I need to use DPDT switches for power. Right now, I have both the negatives, terminated on the board, and then I have the positives split and each going through their own SPST switch. Well the voltage is coming back through the negative side, so the power is on to both if either switch is on. I guess that's AC for you. Oddly enough, they both ran with just one switch on, but I'm guessing that was pretty bad for the one with the switch off.

    With both switches on, I was still getting 27 volts on the amp, which is exactly what I was getting before I hooked up the pi.

    I had the Pi going into the HDMI of my TV and it sounded pretty good, I didn't hear any noise on there. Didn't do any "critical listening" as this was just to verify the concept will work.

    I've got a few things to order to get the case built. RadioShack actually had a few things I was looking for, including a nice toggle for the input selection that matches the power rockers. Plus some navships wiring, volume knob, and some other bits and bobs.

    I'll probably build the case before I assemble the amp. In the past, I would want to listen the moment it is assembled so it will be nice to have that step out of the way.

    That's all for now!

    Mike
     
  11. silvrr
    The headphone jack does sound noisy, it uses a PWM or similar method to play the music and it sounds noisy or scratchy.
     
  12. Marzie
    This is more like a very loud hum, which changes as I touch certain components. To me, sounds like a grounding issue. There is some of the scratchiness too, which does sound like the headphone noise I've heard before, only a little more extreme. We will see when it's all cased up.

    There's something else I could use help with. With my last amp, I found these great looking RCA jacks, I think they were from Australia. The problem I've been having since I got them is that they do not seem to take solder very well. The connections are very brittle and break off, almost cleanly. I don't know what they are made of, but it seems like if I get them very hot, it stays a little better but not much. With the recent de-casing of my Millet Hybrid MAXed, the connections broke free again. See photos below.

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  13. tomb
    You need more ground wires. Preferably, one on each jack.
     
  14. Marzie
    They used to have ground wires until I pulled the chassis apart yesterday. What I was trying to say was that anything soldered to these jacks breaks off very easily, which is what happened to the ground wires. Have you ever experienced a material that just doesn't take solder well? What do you do in that case? Or is it just due to the thickness of the material, so I should try and get my iron hotter? Come to think of it, I don't know if my Weller has a temp adjustment, I will have to check.
     
    What I was trying to show with the photos is how "gloopy" the solder had to be just to get a moderately stable connection, and even that is super brittle.
     
  15. tomb
    That's a lot of metal there. It's probably just sinking the heat. I doubt seriously that anyone would make soldered connection RCA jacks that were not solderable.
     

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