Millet Max problem

Quote:

Originally Posted by ryli 

Weirdly enough the problem fixed itself after a while. Im not sure how, maybe the tube had to burn in or there was a weak connection that fixed itself, but the amp is now working.

That's good.  The tube trimmers are quite a compromise, in that they have to provide reasonable adjustment precision for tubes of three different gains.  I'm not really aware of another tube amp that has that kind of flexibility, but in any event, it means that for some tubes, you may be way on one end or the other of the 21-turn trimmers.  So, it may seem like you're not getting any response to the bias, when it's simply that you haven't turned the trimmers enough.

Anyway - glad to hear it's working!!  
 

Quote:

Originally Posted by ryli 

Thanks tomb,

I actually ran into a different problem now that I've biased it. Using the Bantam dac through the amp to a denon d2000, there is a loud buzz and static, and when music is played, it is heavily muted and distorted, as well as staticky and scratchy.

Where should I start with troubleshooting?

I would check the Bantam output - MAX input signal wiring very carefully.  If the ground channels are not well-connected, you may get everything from reduced sound to loug pops and static.  I don't know about you, but the Push-Down connectors that cetoole spec'd for the MAX V1.2 PCB are a brilliant solution, but they're not something with which many of us have had experience.  I've found a number of issues that can be traced to the type of wire, how much insulation is stripped and how the wire is placed in the Push-Down connector.  On one of my MAX's, a couple of the Push-Down posts stay popped up about halfway.  Luckily, the wires are so big relative to the connector block that they still make good contact.  However, it's easy to see how they can get messed up with different wiring.  You might double check that connector and see if that's the source of the issues you describe.
 

Quote:

Originally Posted by ryli 

I double checked the dac connections and they seem to be fine. There is still static.

Interestingly enough, whenever i touch any metal part on the amp, usb connector, volume knob, top of capacitors, etc, there is an audible click and either a increase or decrease in the volume of the buzz/static through the headphones. Does this point to a grounding problem?

Yes.  First question - did you solder in and attach the ground wire to the Alps pot?  If that's OK, then did you scrape the inside of the back plates where the RCA jacks connect?  Regardless of whether you checked the DAC connections, the symptoms you confirm is that there is not enough grounding taking place.  As stated before, the first place to look is the ground input signal wires.  They can look fine in appearance, but they may not be making a good connection.

Well, here's the problem: You've connected the BantamDAC into the terminal block that's meant for the BantamDAC.  Problem is, it's not selected by default.  You have to wire an SPST (at least) into the two-position terminal block and throw the switch for the input relays to pull from that terminal block.

Try one of two things if you don't have a switch ready:

1. Short the terminals on the two-position terminal block, or

2. Connect another source into the un-used terminal block and try your listening tests using that as a source.

Actually, I'm surprised that you're getting anything at all, but this is an extreme case.

That said, I take this as my fault.  The operation of the relays is not very well documented on the website.  So, please accept my apology at your frustration.

P.S. Those are excellent photos, btw and it looks like you've done quality work.  I'm sure things will go very smoothly once you get past this.

Finally, it will help if you connect a second ground wire to that un-used output terminal on the BantamDAC.

Oh - by the way, the ground wire is the small pad to the right rear of the pot.  You need to solder a wire in there and screw the other end into one of the pot screws.

Look at "#5. Volume Pot Ground Wire -" on the MiniMAX website here: http://www.diyforums.org/MiniMAX/MiniMAXwiring.php  All amplifier construction using the Alps RK27 is the same as this.

Tangent also has a pic of this on his PPAV2 website:

Quote:

Originally Posted by ryli 

I tried shorting the 2 position terminal block, but it had no effect on the sound whatsoever.

Also, after grounding the pot, there was less static, and touching metal parts did not click or change the sound. However, the sound coming through is very muted and lacks bass, like its not being amplified at all. Is it possible that we have some component backwards or a short?

Let's take one problem at a time.  Try a separate source that you're familiar with.  Connect it into the unused input terminal block and let us know what you find.