[cfcubed]

>  Once it is decided, will there be another separate "group buy" thread started?
 
Yep, so we'd carry this topic (GB, BoM sourcing, etc) over to such a thread.  Good idea.

 

[Mullet]

I did the last group buy. It went well and was not hard to set up as per the mentioned thread. We bought something like 40 boards, which came to something around $7 per board. The more you make the cheaper they are. I think in the US it was $5.30 for flat rate priority shipping. So that's like $12 for one and any extras are around $7 more.
 
Hope that helps and I hope you guys can get another group buy off the ground.
 
Good Luck!

 

[schwallman]

I would  grab a board.

 

[stringgz301]

I'm in for 2 boards.

 

[cfcubed]

OK, guess I'll take on a GB or straight PCB batch purchase, either way the boards would be available to builders at cost (fab, shipping, paypal fees, etc). 
So we'd need no more commits to PCBs in this thread.
 
BUT a quick tour of the pesky parts, at Mouser & Digikey, shows the relay (551-EC2-12NJ) unavailable <<< In stock now 11/5.  So this may be on hold until another source OR perfect sub is found... Anyone interested could try to help with that or I'd get to it over the next several days.
 
ALSO the exact 2.0ma & 4.3ma CRDs seem unavailable but close-enough ones are.  The other past-problem parts, LM2595T-ADJ switcher & inductors are around (e.g. 1.0A  732-1429-ND).

 

[blaken]

 


Quote:

 
 

Where did you source your perforated metal from?  I need a new top for mine and that looks pretty cool.

 

[cfcubed]

Mullet found the perforated sheet where he works, tricky part is cutting it neatly incl tube hole.
 
You can search here for perforated & maybe find some sources like http://www.onlinemetals.com/
 
Another way to go is either scrounging around your local hardware stores for something suitable OR making neat holes (measured/center-punched) & cleaning/beveling their edges w/a deburring bit:
 

 
Quote:

Where did you source your perforated metal from?  I need a new top for mine and that looks pretty cool.

 

 

[Mullet]

One of the original builders of the CTH came up with the idea of using perf board and I saw pics and thus my journey began. Then I found the perf board (pictured above) randomly under a raised floor in our machine room at work. I actually found two and with some trial and error I was able to extract a few smaller pieces for use on the CTH. I used metal cutters to cut smaller pieces and a metal hole punch to make the center hole. We're going through a machine room rebuild so hopefully I'll find more that I'm able to cut out and give to a few lucky head-fiers. In the meantime, I gutted an old spaceheater that had perforated metal. It's thinner than the other perf board, but should still do the trick.

 

[blaken]

 
Thanks guys.  I wish I had access to a drill press.  It would make casing a whole lot easier.  I have a perforated top but the tube hole is just in the wrong spot.  For now I am going to slide the top back to where the tube needs to be and then cut off the back extra with a dremel.  I will fill in the gap at the front with a piece of plexi.  It will look a little ghetto but it should work until I can find something else or get access to a press to cut my metal top. 
 
That online metals place has some good options.  It looks like they do custom cuts too and cheap.

 

[Ikarios]

Quick question regarding the relay - the BOM calls for an NEC 12V relay - the EC2-12NJ. I have a different one that has the same pin structure. Mine is a Shinmei RSB-12-S. Can I use my part in place of the NEC relay?
 
Also, for the specced 100nF 63V film caps (for C3L, C3R, C7L, C3P, C4E), does quality here matter much? The BOM calls for Wima MKS2 caps, but I have a set of Kemet polyesters in the same values. Will it matter much if I swap those in?
 
Did anyone ever find a suitable Mouser alternative for L2H? I like the Kilo International knobs from Digikey so I'll probably make a small order there if I can, but if I don't need the choke from Digikey I can skip that order.
 
I don't really understand the circuit too well, so I'd like to stick as close to the BOM as possible, but these two substitutions would save me a couple bucks in replacement parts. Thanks!

 

[cfcubed]

>  100nF 63V film caps (for C3L, C3R, C7L, C3P, C4E), does quality here matter much?
 
Your proposed subs for those should be fine as would any 100nF 50V+ film caps that fit.  Only C4L & C4R are directly in the signal path.
 
>  Mine is a Shinmei RSB-12-S. Can I use my part in place of the NEC relay?
 
OK pin-out/latch type/voltage but not OK size/pin spacing (but could try to hack/solid-core air wire).  This can be seen by comparing the datasheets, see below.  Finding a EC2-12NJ sub or alternative source was one thing holding up the prospect of another small batch of PCBs.  I see Mouser now has them in stock so I can re-ping runeight about the possibility.
 

 

[sharkz]

I have a problem with my CTH and hope someone here can help me out. After swaping some tubes around the other day, I am having problems with my amp cutting out on and off. In the middle of playing, I can hear the relay click and the LED goes from green to red. I then have to wait a minute or two again until the LED goes green. There seems to be no pattern to when it cuts out, but it has only been happening the past week or so. Anyone have any quick ideas? Thanks in advance.

 

[cfcubed]

>  There seems to be no pattern to when it cuts out, but it has only been happening the past week or so.
 
So we'd have to relate the problem to something.  I can think of 2 possibilities; minor damage to the CTH somehow OR an external factor like questionable tube or offset problem in your source (e.g. a different source or source connection).
See if gently nudging to tube while playing causes a cutout, try a known previously-working tube that did not have this problem (w/correct heater switch setting, check if your source has DC offset (DMM mV measure bet its L & G and R & G).

 

[sharkz]

cfcubed, thanks for your response. Here are two additional observations, but keep in mind these are far from scientific.
 
First is that this problem only seemed to pop up when listening to vinyl. For the several months I have had the amp, I have listened music via a DAC from my computer almost exclusively. However my computer went down last week and I switched back to listen to some of my vinyl. The problem seemed to only pop up when listening to vinyl (Philips turntable to a cheap Behringer phono preamp). The other other observation is that using a 12v tube seems to get rid of the problem. I am not sure how stable if I were to listen to music for several hours, but using a 12AU7 tube I can get through one side of an album with no problem. Switching the three various 6v tubes I have, it seemed like there was always a cutout during the side (say ~20 mins). I am fairly sure the tubes aren't the issue because I don't think all three 6v tubes went bad at once.
 
I do need to play around with this more, but I would appreciate hearing your thoughts. Thanks for your help.

 

[sharkz]

More observations. The issue definitely seems to be with my vinyl system as a source. Even my 12AU7 tube was cutting out tonight. Also, there isn't nearly enough gain when listening to records. Usually I listen from my DAC with my volume knob around 11 o'clock at the most. Getting my albums to a good listenable volume was taking me closer to 2 to 3 o'clock. Hopefully this information helps someone diagnose what is going on here. I am glad that everything is okay with my digital sources, but I like to listen to a good amount of vinyl so I would like to find a solution.