anything i should know before starting a CTH rev A build?
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kchapdaily

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hey guys
 
so i was going to build a soha II, but ive decided to go with a CTH rev A instead ( i have to buy books for classes
).
 
im under the impression that there are no more pcb's available, so im thinking im going to just use a radioshack style protoboard like i did with my starving student. is this going to present any problems with the CTH? the starving student was much simpler, but i shouldnt have a problem figuring out a working layout.
 
does anyone have any advice before i order parts for the build?
 
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>  does anyone have any advice before i order parts for the build?
 
Yes, not to do it:)   I'd not envy someone protoboarding an amp w/150+ parts (over 400 holes in the PCB IIRC).  But I'm sure there are examples of such determination & skill:)
I guess if you've really studied all the schematics, the PCB image:
http://www.cavalliaudio.com/diy/cth/main.php?page=boards
etc & still want to go for it, have fun & good luck. 
BTW its possible if there was enough call for it runeight may consider another GB for CTH boards in the coming months.  If it was me & I could not source a CTH PCB I'd look at other projects, but maybe I'm just a wuss from having had trouble protoboarding things with a dozen or two parts:)
 
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kchapdaily

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yeah i was kind of hesitant about it at first, but i figured i might as well go for it. plus i think working out my own layout is more fun than using a pre made pcb. much more difficult in this situation though.
 
although if anyone has an extra board laying around id be happy to take it off your hands 

 
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cfcubed

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>  i figured i might as well go for it. plus i think working out my own layout is more fun than using a pre made pcb.
 
Actually there were some that asked for a larger PCB version CTH to make stuffing/soldering easier, at least you'd not have that problem.
 
Suggest reading the CTH PCB Group Buy & CTH Rev A threads for parts info, think all the later/last changes made it to the BoM (e.g. R1H/R2H swap correction, A/C adapt jack/plug matchup & stereo pot correction for small builds (RK097122...)).  The tricky parts are the CRDs, LM2595, chokes/coils & possibly the relay IIRC, and think no one vendor has it all so probably need 2 parts orders.
 
Edit:  Of course I'd use good quality protoboard w/plated-through holes, and build it in modules w/screw terminals.  This let's you build & test in stages and, as you'd not have the benefit of a ground plane, get the input stage farther away from the PS.  I did this for the orig proto you can see by clicking the thumbnail in my post below:
http://www.head-fi.org/forum/thread/398839/a-very-compact-hybrid-amp
Note: that proto had the original SOHA frontend e.g. pots, not the more advanced CTH frontend.  Not that big a compromise if you want a bit easier build IMO, e.g. less impact than compromising rail-splitter or output buffer.
 
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kchapdaily

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thanks for the advice! im actually having a hard time finding the 1N5305, 1N5315, and this seems to be out of stock at digikey and mouser. are there any suitable replacements for these parts or should i order from somewhere else?
 
also i just have a few questions about the schematic.
 
on the input stage, where does B+ go? is it to the e12?
 
also im a bit confused on the power supply. it appears to have 2 different output sections. im assuming these are V+, but their output voltages should be different. which ones should be connected where?
 
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Think this is looking problematic & you should consider a different project...  E.g. B+ is the tube's HV, about 80V+ in the CTH (plate -> 0.22 blocking cap -> output buffer -> e12 relay), and the CTH e12 runs off the LV 24V + virtual ground & we've posted CRD/1N5* subs in the threads I referenced.  These are things you should be familiar with prior to attempting this. 
 
BTW the SOHA II has Cavalli's imprint on it, is in the same league sound- & cost-wise and I think Jeff @ glassjaraudio.com may have boards and/or kits (can try contacting him).  I've used/built several GJA kits & have been pleased all-around with them & Jeff's service.
 
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Quote:
Think this is looking problematic & you should consider a different project...  E.g. B+ is the tube's HV, about 80V+ in the CTH (plate -> 0.22 blocking cap -> output buffer -> e12 relay), and the CTH e12 runs off the LV 24V + virtual ground & we've posted CRD/1N5* subs in the threads I referenced.  These are things you should be familiar with prior to attempting this. 
 
BTW the SOHA II has Cavalli's imprint on it, is in the same league sound- & cost-wise and I think Jeff @ glassjaraudio.com may have boards and/or kits (can try contacting him).  I've used/built several GJA kits & have been pleased all-around with them & Jeff's service.
probably a good idea. i was considering the soha II also. 
 
the schematics are a bit confusing, im still learning most of this stuff. maybe ill come back to this after i get some more experience
 
 
 
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