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post #121 of 570

What's the timing on production boards?  Thinking of building one with a grubdac in the same case.  Has anyone tried this before?

post #122 of 570
Thread Starter 

This was the last run for the CTH :( There was a recent group buy for this final run. Unfortunately, you missed out on this badass little amp.

post #123 of 570
Thread Starter 

Civilmonkey, can you further explain how you had the bypass wired? I'm interested in doing something similar with my current build. I'm in the beginning stages, stuffing resistors. The only difference is that I'd maybe do 100 and 150 ohm resistors instead.

 

With regard to buzz... Here's an interesting observation... I noticed that with 12v tubes in general I'd get a slightly noticeable hum with my Senn HD650s. If I used 6v tubes... no noticeable hum. Then I pulled the RCA jacks from my CTH and noticed the hum go away with the 12v tubes. Hrrrmmm perhaps it's my Gamma-2 DAC that is causing the issue. The Gamma-2 can either be powered over USB or external power. So I pulled the external power and went with USB power only. Now the CTH/Senn HD650 combo is completely hum free. Either something is up with the Gamma-2 or I have a bad power source. Go figure.

post #124 of 570

I found another problem with the BOM tonight.

 

Got my sweet little TKD volume pot - absoutely perfect fit.  Drilled all my casework holes to perfection.  Coming together very nicely indeed and just about ready for power-up.

 

Test fit my AC adapter to the PCB connector.  No amount of force would make it work.  WTF??  Back to the parts order.  The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead.  ARGH!  I can't believe I didn't check this earlier.

 

I suppose the best solution in my case is to refit the AC adapter with a 2.5mm plug, as opposed to desoldering the PCB connector.

 

BK

post #125 of 570

BK, which TKD pot did you get? the 601 or the 2511? 

post #126 of 570

>   The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead

 

Oops.  I'll forward this correction to runeight.   Do we know if Mullet's shared Mouser BoM is correct?

The 3-pin PCB-mount jacks can be a bear to remove if they are soldered in correctly, but I'd be tempted to swap it (I've done so before).  Seeing that shrink-wrap on your adapt cable could bother you someday:)

 

>  There was a recent group buy for this final run

 

It may be possible there is enough interest (& associated prodding:) someday to get runeight to do another run of these Rev A PCBs.  

Again, incl. BoM vendor parts # revisions, esp where our error rate must be like < 1%, is one more brick in the wall against future GBs.

post #127 of 570

 

Originally Posted by Mullet View Post

Civilmonkey, can you further explain how you had the bypass wired? I'm interested in doing something similar with my current build. I'm in the beginning stages, stuffing resistors. The only difference is that I'd maybe do 100 and 150 ohm resistors instead.

 

- From the topside of the PCB, I wiggled 24 AWG silver plated copper wire from navships (ebay) and a SIP socket into each R18 location, so in total 4 wires / 4 SIP sockets.  I used the SPC because of the teflon coating, I didn't want to lose any insulation from melting when soldering and create any accidential bridges on the top side. 

- It was a pain (very tight fit) getting the SIP and 24 AWG into the PCB.  My technique was put the wire in the PCB location (don't twist or tin the wire), then with a pair of fine needle nose pliers, gently wiggle the SIP into the PCB.  I bent a few SIP pins, so those went into the trash.

- The advantage of the SIP is that you want try different R18 values.  I started with 120, but in the end went to 150 for my IEMs.

- I used 24 AWG because a) it's the only teflon coated wire I had besides from 30AWG which I felt was too small, and b) I liked that it was the biggest I could fit along with a SIP socket.  I didn't know the effect of load leads at R18 would be, and thicker wire should lead to less resistance.  I would have been happier (mechanically) using 26 AWG because I wouldn't have had to force the SIP socket into place.

- Mechanically, because of tight fit and use of slight / moderate force to get the SIP socket in, I wouldn't want to mess around with replacing resistors too many times in the SIPs.  Each time bends the SIP pin bends / moves a little (at least, when I do it).  When I did, I was careful to support the SIP socket while inserting / removing new resistors.

- I started with around 6-8" of wire are each R18 location to make sure I had enough for wherever my DPDT was going to go.

-From there, the 1st test was solder the R18L bypass wires together and R18R bypass wires together for a test (See my 1st post).

-Once I knew it worked, wires were shortened to around 3" as I put the DPDT switch on the front panel.  R18L went to 2 of the 3 poles on one throw of the DPDT switch, and R18L went to the same 2 of 3 poles, but other throw of the switch.  So, when the switch is open, L/R bypass wires are not connected, when closed, R18L / R is bypassed by wires.

post #128 of 570

 

Quote:
Originally Posted by ujamerstand View Post

BK, which TKD pot did you get? the 601 or the 2511? 



I'm using the short case, so it's the small 601 pot, which is exactly 16mm cubed.  There is exactly enough room for it to fit between the front right caps and the bottom of the top groove for the perf top (a few more mm clearance if you use the hammond slide in cover due to its offset design).  I'll try to grab a pic in a day or two.  It's a nice pot.  I had to go with 10k, but 50k is apparently available if you order from asia.

 

BK

 

 

post #129 of 570

I'd be happy to lead-up another group buy.  Any idea how many it takes for an order?

post #130 of 570
Thread Starter 

I think we needed a minimum of 20 boards but ended up getting 40. I'd contact runeight to see if he wants to do another run. alex@cavalliaudio.com You'd pay for the up front cost of 20 or so boards plus shipping. Doing the group buy wasn't hard. The hardest part was going to the post office a few times. There are numerous PMs that you'd have to do with regards to keeping in contact with potential group buyers.

 

Good Luck!

post #131 of 570

 

Quote:
Originally Posted by cfcubed View Post

>   The Excel BOM listing correctly shows a 2.1mm jack, but the "import" page has a 2.5mm jack instead

 

Oops.  I'll forward this correction to runeight.   Do we know if Mullet's shared Mouser BoM is correct?

The 3-pin PCB-mount jacks can be a bear to remove if they are soldered in correctly, but I'd be tempted to swap it (I've done so before).  Seeing that shrink-wrap on your adapt cable could bother you someday:)

 

>  There was a recent group buy for this final run

 

It may be possible there is enough interest (& associated prodding:) someday to get runeight to do another run of these Rev A PCBs.  

Again, incl. BoM vendor parts # revisions, esp where our error rate must be like < 1%, is one more brick in the wall against future GBs.


 

I found 2.1 and 2.5mm PCB-mount power jacks locally today, as well as two different styles of 2.5mm adapters, so I'm covered for various scenarios when I sit down to address the power entry.

 

The BOM was very solid thanks to the hard work of you guys.  The little speedbumps that I encountered were due to my choice of the shorter case and the fact that I apparently did not verify the "ancillary" parts specs until late in the game.  The total parts list is indeed a long one!

 

I'd be up for building another one of these if stringgz can pulll together a GB.

 

BK
 

 

post #132 of 570

I'm in for 3 boards if we get another group buy together.

post #133 of 570
If there is another group buy, I am in for one.
post #134 of 570

Here's the small TKD pot installed.

 

Resolved my PCB-mount power jack.  Needed to desolder it and replace it because I messed up the original one trying to make the 2.1mm AC plug fit last night.

 

BK

 

25kn3ih.jpg

post #135 of 570

BK - That is a nice fit for that pot & a nice pot it is. 

 

As far as a GB I guess I'll ping runeight about what that would take.  He's quite busy right now as you can see from cavalliaudio.com:)

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