Problems with a Twisted Pear Buffalo dac

S Clark · « **on:** 1 Jul 2011, 06:08 pm »

I've got a T.P. Buffalo dac that has stopped making music. Power supply seems ok. It shows that it is linking, but seems to have no output. Is this most likely in the IVY board? Other dacs work fine in the system.

Scott

richidoo · « **Reply #1 on:** 1 Jul 2011, 06:23 pm »

Make sure your DIP switches are set correctly. Make sure the power supply that powers the analog output is powered on, not just the digital sections. If you have Buffalo2 put a full scale sine wave into it and check the output voltage. Create a test file with Audacity. Peak output voltage is ~3V iirc, so RMS voltage will be about 2.1VAC. If you are using Volumite, make sure it is all the way up, or switch it back to non-volumite configuration to test. Good luck

HAL · « **Reply #2 on:** 1 Jul 2011, 06:52 pm »

Scott,
You should be able to probe the differential output from the Buffalo II to the IVY board with a scope or DMM to see signals if the DAC board is running. Just use one side to ground from the schematic. This will tell if it is the DAC or the IVY with the issue. A full scale sinewave as richidoo suggests is a good place to start.

According to TPA the Buffalo can be used as either current out or voltage out. You might be able to switch it voltage out to check if it is working correctly.

Just some thoughts.

S Clark · « **Reply #3 on:** 1 Jul 2011, 07:26 pm »

Ok. You fellas have convinced me that I am in way over my head. Heck, I even had to get Gary D. to put the kit together for me. He checked out the power supply, said it was good, and basically said "This is digital... I'm an analogue guy". My next question is, would any of the group here at the lab be willing to take a look at this (I would expect to pay for the service)? I was hoping that I could simply buy another IVY and move forward. For $79 from T.P, it seemed like a cheap option. The test you guys recommend sounds a lot like an adult talking to Charlie Brown " Waarhh ooynn harggh oonahh bonfff, Scott. You need to garrrrgh lorgenu arprenaugh with a 3.4 uA kaluumbre..."
Sorry guys, I can build a pretty decent speaker, but electronics leave me in the dust. Is the random $79 IVY purchase and switch my best bet?

Richidoo,
It's a Buffalo I. How would I know if the DIP switches were set wrong?

HAL · « **Reply #4 on:** 1 Jul 2011, 07:45 pm »

Scott,
If you have the schematics for the two boards, I will take a look.

If you have my email address, go ahead and send them.

I think Gary will vouch for me being a digital guy.

S Clark · « **Reply #5 on:** 1 Jul 2011, 07:48 pm »

Rich,
I don't have the schematics, but I'll see if I can find them online.

Thanks,
Scott

S Clark · « **Reply #6 on:** 1 Jul 2011, 07:51 pm »

Here they are. I think.

http://www.twistedpearaudio.com/docs/digital/buffalo_schematic.pdf
http://www.twistedpearaudio.com/docs/linestages/ivy_schematic.pdf

HAL · « **Reply #7 on:** 1 Jul 2011, 08:02 pm »

Scott,
Here is a simple thing you can check.

1) Does the output relay click when you turn it on? That would be one point where a single failure would take out both channels.

Will give your more feedback soon.

HAL · « **Reply #8 on:** 1 Jul 2011, 10:04 pm »

Scott,
Here is the link to the Buffalo DAC users manuals.

Not sure which one is for your board. Let me know which one you have. The three manuals do show the switch positions. I would imagine that since the DAC has been working they are fine.

http://www.twistedpearaudio.com/docs/docs.aspx

richidoo · « **Reply #9 on:** 2 Jul 2011, 12:06 am »

Good idea about the relay HAL! Scott said it syncs so that's another sign that DAC is OK.

Scott, Your Charlie Brown teacher impersonation is FUNNY! I can hear her now.

My Buffalo32 and Buff2 have 4 really tiny white DIP switches for various settings. If Buff1 has such DIPs you can just check that they are set correctly to the manual. If it worked fine and you're sure the switches have not changed since it broke then don't worry about it. I was just thinking of low hanging fruit that you can try with little effort. TP stuff is very well built, so it is rare for things on the PCB to break.

IMO, based on your description, and confirmed power to the Buffalo (relay click and sync,) the problem is most likely that the power is interrupted to the IVY. If you have a multimeter, you can set it to DC Voltage and put the black probe on the ground (GND) of the power input of the IVY board. Put the red probe on the + of the IVY power input. You should get a reading in Volts.

Before you try that, make sure any of those green connector screw terminal blocks are all screwed tight, on the power supply PCBs, the Buffalo and the IVY, and that no wires have slipped out. Tighten them all for good measure. You need a small flat screwdriver, and make sure the power is off when you tighten. If they are soldered then you don't have to worry about that.

Any good local tech can help you with this. In what city do you live?

HAL · « **Reply #10 on:** 2 Jul 2011, 12:25 am »

richidoo, that is a very good suggestion as that happened to my Opus DAC that I bought used. An easy fix.

There are actually two single point failure possibilities on the IVY board. Either the Relay or IC3 could be bad and take out both channels.

There is a very easy way to check if Scott has a DVM and Test CD.

There is a second set of outputs on the IVY board. The differential output can be used to check for signal. If you play a 1KHz test tone and measure OUT1 or OUT2, + and G terminal with the DVM, you should read about 2Vrms with a full scale test tone. If both those outputs are active, then it is the IVY board's relay or IC3.

If there is no output on OUT1 or OUT2 then no power is going to the IVY board, or the Buffalo DAC chip is bad. That is the easiest way to diagnose the issue.

richidoo · « **Reply #11 on:** 2 Jul 2011, 02:10 am »

Scott, I will make you a test tone mp3 by email if you PM me.

HAL · « **Reply #12 on:** 2 Jul 2011, 02:26 am »

richidoo,
He should have one in his email account at this point!

S Clark · « **Reply #13 on:** 2 Jul 2011, 04:20 am »

Got it. Thanks Rich.

S Clark · « **Reply #14 on:** 16 Jul 2011, 12:50 am »

Ok, everything from here and also over at the Twisted Pear site indicated something wrong with the IVY, so I picked up an IVY III and put it in place of the older IVY II (no longer available). Whereas before, I had lights indicating Sync, and a very faint signal coming out, now I have nothing. I have put several photos of what I did in my gallery, but there are too many to post here.
However, here is one. Can anyone see if I have made a mistake? There are images of the IVYIII at http://www.twistedpearaudio.com/linestages/ivy.aspx

A

HAL · « **Reply #15 on:** 16 Jul 2011, 02:51 am »

Scott,
The TPA documentation is a bit confusing, but I think the Buffalo board is configured as a current output device, not voltage output. There are four DAC outputs in parallel for each channel.

This means that the Buffalo uses the IVYIII board current inputs. The manual looks like it is setup to support the Buffalo via the pin inputs not the screw terminals. I would ask TPA if that is the case.

HAL · « **Reply #16 on:** 11 Aug 2011, 12:55 am »

Got the Buffalo DAC working and shipped it back to Scott.

The picture above actually shows the broken +6VDC grey power lead to the DAC board from the regulator. Replaced the regulator and everything was fine after rearranging the wiring to make it all fit.

S Clark · « **Reply #17 on:** 11 Aug 2011, 01:25 am »

Glad to have this dac back and working. I have been using a NOS Monica II, that is actually very musical, but the Sabre is hard to beat for musical detail.
I don't know how to thank HAL enough.

Got to go. Got music to listen to.
Scott

HAL · « **Reply #18 on:** 11 Aug 2011, 01:40 am »

jtwrace · « **Reply #19 on:** 11 Aug 2011, 01:55 am »

Great! That's what it's about. I've "helped" him so it all goes around...