bonnie & jason

Beta 22 amplifier build

I got a fair amount of work done on my next project the last couple days. This one is a high power, three-channel, active ground amplifier and matching power supply. These also come from AMB labs.

Here’s the power supply board in progress:

And here it is complete:

Here are the three amplifier boards in progress:

More to come… there’s still a lot to do!

Edit: The boards are done… now comes the difficult task of connecting them all up together and running tests to make sure everything works as it should.

In the meantime, here’s the obligatory Ashley and Amanda pic:

Edit 3/8/2009:
Just about done with the amp. I still have to wire in the headphone jacks when I get them, but it works with the speaker jacks already.
Here’s the full amp in all it’s cookie tin goodness:

The front panel:

The back right:

The guts:

Edit 3/17/2009:
I was getting some transformer hum problems despite my best efforts to keep the signal wires on the opposite end of the enclosure, so I ended up moving the toroid into it’s own enclosure while keeping all the wiring, IEC, and on/off switch in the original tin.

As luck would have it, I had a round cookie tin lying around so I put it to good use! As such, I present to you the cookie tin/beta 22 hybrid:

I just need to trim and mount everything to that board (scrap piece of shelf from IKEA) and then it should be completely finished.

More DIY electronics

I built a headphone amp and DAC today. Both are designs from AMB Labs.

Here’s the amp:

Here’s the DAC:

So now, I can get the digital optical signal out of my Mac Pro, convert it to an analog signal, and amplify it with a nice portable but powerful amp. Woohoo! I’m liking this DIY electronics stuff quite a bit at the moment. It’s not quite as brute force a project as the bike building, but it’s not nearly as messy either. One more project to go… details to come.

Millett Minimax headphone amp

This is officially my last project before the arrival of the twins. You may remember I took on a small DIY headphone amp project a couple weeks ago. Although that amp performed pretty well, I still wasn’t really impressed with my new headphones. After doing some research, I thought they might reach their full potential with a higher powered amp. Furthermore, many folks swear by vacuum tube amplification for great sound quality. As is usually the case, I figured I’d try to build my own rather than purchase a retail version of one of these amps.

Lucky for me, a number of enterprising folks have put their heads together and developed the parts list, assembly instructions, and other resources to help you put your own amplifier together. So after some more research and a couple mail order deliveries, I had everything I needed to git ‘er done.

I still need to find a volume knob.

(this image courtesy of www.diyforums.org)

Assembly notes:
As you can see, it’s a fair bit more complex than the little Cmoy amp, but the assembly was actually fairly straight forward. For those of you who are looking to build your own, here are some thoughts (based mostly on my mistakes) that might help supplement that already extensive instructions found on the official website:

1. The standoff kit works great, but pay attention to the instructions to make sure you have the washers in the right place. Otherwise, it won’t fit in the enclosure.

2. Tom (the proprietor of the official site) doesn’t yet have instructions for the final connections for the RCA jacks and such but does have some pictures to show how others have done it. I would probably leave enough slack in those wires to be able to just take the back panel off by no more than 1″. Any more and the slack in the wires gets in the way of bolting the panel to the enclosure.

3. When you first get all the baggies of parts, separate and order them by size (height) so the assembly process simply requires going through the little baggies one at a time.

4. The BOM is confusing in what buffer transistors you really need. At first glance (and second and third for me) it seems like you need eight. This made sense to me since there are eight spots on the PCB for said transistors. As it turns out, you only need four. The extra four spots are used if and only if you use transistors of reversed pinout (in which case you would leave the other four empty.)

5. I followed Tom’s advice of using the 12AE6 vacuum tubes and eliminating the RB14 transistors considering my Sennheiser HD 650′s are 300 Ohm impedance. I also used the “can’t miss boutique” parts listed on the website with 2SC3422/2SA1359 transistors. Although I have nothing to compare against, I’m very happy with the results.

Listening impressions:
1. Wow! Although I’m still relatively new to the high end audio scene, I’m very happy with the results. Whereas before, the headphones seemed a bit tentative and “veiled” as some users have stated, everything opens up with the new amplifier. Soundstage is larger, vocals sound more intimate (both female and male), and bass notes are tight and accurate.

2. The difference in good vs. bad recordings is more evident now. I guess the sound engineers in the booth really do make a contribution behind the scenes!

3. I’m hoping that everything sounds even better as the amp gets broken in. However, even if that doesn’t happen, I’m still very impressed. Unfortunately, I don’t have enough experience to say if it’s the “tube” sound that appeals to me or if it’s just the fact that this amp has more power. Maybe I’ll just have to find a similar power DIY solid state amp to build next!

DIY headphone amplifier – JDS labs CMoy bass boost version 2.02

With the stress of Alissa’s terrible twos and the impending birth of the two terribles, I’ve been taking on little projects here and there. The bike was one of the more ambitious projects. My latest project, though less ambitious, is new territory for me.

It’s new territory because it’s an electronic device which is not intuitive to me at all compared to the mechanical things I’m used to tackling. Anyway, without further ado, here it is:

What is it? It’s a headphone amplifier. Stuffed into an Altoids tin. Much like big speakers need amplification to sound their best, headphones also can sound better with stand alone amplification. It’s based on a simple inexpensive home brew design originally dreamed up by Chu Moy (which is why these are called CMoy amps.). Since the original incarnation, many folks have tweaked it to suit their needs. Some have built and sold them on ebay. Others have started small businesses providing parts and advice.

One of those businesses is JDS Labs. They provide the assembly guide, bill of materials, and the printed circuit board to guide you through the process. John, the man behind JDS was super responsive and really helpful in answering my questions and getting me parts quickly.

After reading the instructions multiple times and picking up some ancillary supplies, it took me about three hours to put the whole thing together. And to my surprise, it worked without having to do any trouble shooting! I probably could have taken my time a bit more on getting the holes in the tin more exact, but it’s not bad.

As for performance, it definitely improves the sound quality of my ipod and even the signal coming out of my Mac Pro. Everything is more detailed and “live” sounding. I will say that different combinations of songs, headphones, and sources provide different levels of improvement. The bass boost is thankfully not boomy or obnoxious at all. As a matter of fact, with the cheapo headphones I’m using now, I’d probably just leave the bass boost on all the time. I might feel differently after my new cans arrive next week though.

Since this is my first headphone amp, I don’t really have anything to compare it to. But as far as DIY projects go, this one was fun, rewarding, and not that expensive. And actually, since the parts were relatively cheap and I figured I would break something along the way, I ended up buying enough parts to make three. So I guess I have to start eating some Altoids!

EDIT: 1/25/09
I ended up finishing the other two amps. One is simpler in that I eliminated the bass boost knob. Here’s a pic before putting it in the peppermint altoids tin.

The other retains the bass boost knob but moves it to the stock location. This one went into a wintergreen altoids tin.