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the CTH (Compact Tube Hybrid) Rev A thread...
Dec 19, 2011 at 12:44 AM Post #301 of 607
I have some local yocal hardware stores I can go to along with a Home Depot. Perhaps, one of them will have something. I'm also going to try and contact Hammond directly to see if they are willing to part with 8 screws. Wish me luck. :/
 
Dec 19, 2011 at 2:24 AM Post #302 of 607
Damn. I missed this one again, I assume that all the boards are gone?
If someone has an extra board they're willing to sell, I'd be happy to take it off their hands. If not, then I guess I'll just wait for the next batch.
 
Dec 19, 2011 at 9:17 AM Post #303 of 607


Quote:
mullet said:
I have some local yocal hardware stores I can go to along with a Home Depot. Perhaps, one of them will have something. I'm also going to try and contact Hammond directly to see if they are willing to part with 8 screws. Wish me luck. :/
Click to expand...



I'm telling ya, you need to hunt down an Ace Hardware store. There appears to be a couple in Brooklyn. The still excel at basic hardware and have a selection and variety unmatched for a B&M store. Home Depot only has volume, although to be fair, while they have started introducing some specialty hardware, they have a long way to go to match an Ace store.
 
It's worth the trip.
 
 
 
Dec 19, 2011 at 12:46 PM Post #304 of 607
Good news! Hammond has been very helpful in helping to procure 8 screws. I emailed them and got a quick response. I love dealing with companies that are willing to help without an attitude.
 
Dec 21, 2011 at 9:31 PM Post #305 of 607
Having a bit of a time finding a decent small 50K pot.  Ended up with an Alps 20K pot which is backorderd at Mouser until mid-January.
 
In order to broaden our choice of substitutions I was wondering what, if any, audible difference is there between a 50K pot Vs 10K, 20K and 100K pots?
 
 
Dec 21, 2011 at 10:54 PM Post #306 of 607
I'd say go for 100k. If I remember correctly, I'd say there is no audible difference. I suspect a low ohm pot would get louder quicker and a high ohm pot would take longer to get louder. 50k is nice middle ground.
 
Dec 22, 2011 at 7:39 AM Post #307 of 607
Dec 22, 2011 at 8:38 AM Post #308 of 607
My goal in this build is to limit experimenting to rolling tubes and R18 to tweak for my Grados.  Although I have plenty experience soldering PCBs (try 1980s 386 PC motherboards - component by component - nutz) I don't want to solder anything and then get the itch to replace it later. BTW, I already have my AuriCaps for C4L/R.
 
It isn't a stretch for me to move up to a $40 TKD 2CP-601 pot but 50K isn't in stock anywhere.  But going up above that model? No way I'm going to spend $100 for a pot in this build.
 
By the way I have corresponded with both Percy Audio and PartsConnexion.  Both say 60 days for the 50K TKD 2CP-601.  So, for the benefit of future builds you may want to send them an encouraging email to stock these.  IMO, the 50K TKD 2CP-601 would be the ideal "affordable" pot upgrade.
 
Addendum:
Mugdecoffee replaced a 50K Alps RK27 pot with a 100K TKD 2CP-2508 and praised it with his Grados here: http://www.head-fi.org/t/417322/cavalli-compact-tube-hybrid-cth-tube-tweak-thread/525
 
Although I'm not too excited about his statement: "One interesting effect is that the soundstage seems a little farther back which feels different especially with Grados."  But then he goes on to say in his next post that he is using a 6DJ8 which has an amplification factor (mu) of 33.  Too hot for Grados.  Which may explain why he's stuck in "the bottom 15 degrees" with poor channel matching.  Or, is the 100K pot the culprit? 
 
 
 
Dec 22, 2011 at 3:43 PM Post #309 of 607
Gents, in general it is better to use a lower resistance pot. This is because the resistance of the pot is a factor in the frequency response of the amp. However, as you know, using too small of a pot can potentially load the source. Most SS sources have very low Zo, but there are a few sources with higher Zo.
 
As a rule, MHO is that if you have to sub, go to 10k instead of 100k providing that your source has a Zo less than 1k.
 
Dec 22, 2011 at 9:51 PM Post #311 of 607
Got my mouser CTH order today.  Once again, I'm flabbergasted at the giant mountain of parts that need to go on that tiny board!  Need to remember to bring my A game for this build.  Will be fun.
 
BK
 
 
 
Dec 23, 2011 at 10:28 AM Post #312 of 607
Gents, you all may have discussed this already, but one practice that will help you if there is a problem will be to mount the resistors so that the value text on the resistor faces up so that you can read it. It's much easier to solve a problem if you can see the values. I know, because I've forgotten to do this and figuring what's wrong when you can't even determine if the right resistors are in the right places is more than a challenge.
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Dec 30, 2011 at 10:13 AM Post #313 of 607
Help! 
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 Firstly, I'm a fairly novice building (2 02 builds under my belt). I assembled my CTH off of cfcubed's bom. When I powered it up, I didn't get any sort of pop or smoke, but the LED stayed yellow/red (sorry - color blind) and didn't go to green. Started checking readings, and here's what I got:
 
 
SG -> OG 2.8V
SG -> OL ~6mv
SG -> OR ~6mv
 
Pin 1: 100.8v
Pin 2: 0v
Pin 3: 4.2v
Pin 4: 0v
Pin 5: 12.6v
Pin 6: 100.8v
Pin 7: 0v
Pin 8: 4.2v
Pin 9: ~6mv
 
TB+: 101.6v
 
ICP: Center -> 0: 5.7v
ICP: Center -> 1: 7.1v
 
SG -> R1P: 32v/18v
 
Q1P and Q2P both pass the Diode test
 
Reading past threads, this pattern seems to indicate I could have a bad LM2595. How would I go about testing this IC on board? Also any/all question or questions are appreciated. Thanks in advance gang.
 
Dec 30, 2011 at 10:24 AM Post #314 of 607
Nope. yourLM2595 is fine.
 
Something's up with your ICP readings.
 
This is throwing off the output readings as well.
 
Tube readings are good which means heaters and HV is working fine. Just the LV and splitter section is not right.
 
Remove ICP and measure at the pad of pin1 of ICP wrt SG. You should see about 32volts.
 
Dec 30, 2011 at 10:34 AM Post #315 of 607
Thanks for jumping in sachu. A couple of noob questions:
 
To clarify, I'm trying to get ICP out of the circuit and just measure voltage at the pad? This implies it's safe to power up without ICP in?
 
Quote:
sachu said:
Nope. yourLM2595 is fine.
 
Something's up with your ICP readings.
 
This is throwing off the output readings as well.
 
Tube readings are good which means heaters and HV is working fine. Just the LV and splitter section is not right.
 
Remove ICP and measure at the pad of pin1 of ICP wrt SG. You should see about 32volts.
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