[BK_856er]

Just to close the loop on my Dec. 2011 CTH RevA temps with high heater draw 6N6P tube with the proper 6.3V heater setting.
 
Measured with a micro-tip thermocouple snaked into lid holes after ~30min powered up:
 
Room temperature = 23C
Rear of case ambient just under top cover = 37C
Tube surface at top cover height = 67C
ICP at heatsink bolt = 71C
ICH at heatsink bolt = 61C
 
All is well.  

 
BK
 

 

[Misterrogers]

I'm getting parts together for my next CTH build, and I've been shopping for some good cap upgrades. I picked up a pair of Robert Hovland Supercaps .22uF 400V. Anyone have any experience with these?

 

[Mullet]

BK~ smooth move on the heater voltage thing   ...I'm surprised the 6N6P even worked at 12v
 
MR~ I don't have experience with the hovland supercaps. I've heard good things in general about the hovland musicaps, but not in relation to the CTH. One thing to keep in mind is cap size. You might have difficulties with installing those caps because of their size. Auricaps because of their size fit in easily. Wimas are no challenge either. The Sonicap Gen 2s that I've been using are approx. 1 inch long and just barely fit in a V orientation. The bottom of the V is facing towards the tube socket. You might be able to use a similar orientation and have success.
 
By the way I just finished another CTH build for a fellow head-fier. Used .15uF Sonicap Gen 2s with success. I'm curious if the .33uF Gen 2s work as well. Sonic Craft is officially out of .22uF Gen 2s. CF3 mentioned to me in a PM that .1uF to .22uF (and maybe .33uF) would work in the C4 position. I'm just curious if there are sonic differences between .1uF and .22uF.
 
The other thing that was different about this build was that I used 120ohm R18s instead of the BOM 100ohm R18s. The one difference I've noticed is that if I compared the volume dial in relation to "perfect listening level" on this CTH vs. mine I can move the dial up to 2 o'clock vs. 12 o'clock using my AKGK701s.

 

[particleman14]

Finally put together my Rev. A tonight.  I swapped my led orientation so red means good to go, green means bad  other than that I'm enjoying this amp w/ a 6922 tube (looking forward to rolling some more!).  
However, I notice there is a solid amount of hum if I turn the volume up a bit.  the volume knob needs to be turned up to levels I wouldn't dare listen. Connecting the signal ground to the case doesn't seem to kill the hum for me.  any ideas?  otherwise I'm quite happy with this amp!
 
here some pics..
 

 

 

[Mullet]

@particleman14
 
I found that with my first CTH build when I touched the volume knob I'd get a hum. It would go away when I took my hand off the knob. I was told to take the input ground / ground + and tie that to the pot. So for example the RK27 has two screws on the back. I'd partially unscrew one of the screws and tie a wire from that to input ground and ground + on the pots wipers. No more hum. Not sure if this will help but give it a try.
 
Congrats on your build.

 

[cfcubed]

WRT hum - What Mullet said plus check all input jack -> PCB wiring compared to wiring diag on CTH site (use ohmmeter to assure).
Try different tube.   We've no hum issues in this design AFAIK except perhaps barely audible hum between songs w/ultra high efficiency can/IEMs.

 

[particleman14]

quick follow up regarding the massive hum at higher volumes.  turns out its the tubes!  after swapping in some new ones everythings' great!  still undecided on what tubes I should put in this guy... I've got 6922 JAN and russian 6n6p..

 

[proid]

I'm really interested in building a CTH. How does the parts cost (just normal build, nothing fancy)?

 

[BK_856er]

 
Quote:

I'm really interested in building a CTH. How does the parts cost (just normal build, nothing fancy)?

I had a $95 Mouser order, a $10 Digikey order (both excluding shipping) and small orders elsewhere for a tube socket and tube.  And of course the board.
 
I'd say under $150 at the end of the day.
 
Worth every penny!
 
BK
 

 

[cfcubed]

Just another heads-up that there are handful of PCBs left in MisterRodgers IC/GB thread.  Don't know when the next one will happen.

 

[wiatrob]

 
Quote:

Finally put together my Rev. A tonight.  I swapped my led orientation so red means good to go, green means bad  other than that I'm enjoying this amp w/ a 6922 tube (looking forward to rolling some more!).  
However, I notice there is a solid amount of hum if I turn the volume up a bit.  the volume knob needs to be turned up to levels I wouldn't dare listen. Connecting the signal ground to the case doesn't seem to kill the hum for me.  any ideas?  otherwise I'm quite happy with this amp!
 

It was nice to see this at the Bay Area Meet, sorry i didn't get to listen...

 

[particleman14]

Ya it was cool meeting you Wiatrob.  With all the awesome gear there the CTH was definitely overshadowed. I was very impressed with the liquid fire though!

 

[Mullet]

I have a few questions about this amp that I've never seen answered before...
 
What is the output impedance of this amp? Is that directly tied to the R18 resistors?
 
What is the voltage swing provided by this amp?
 
What is the current this amp pushes out?
 
Not sure if these measurements are available. I'm sure there is a way to find this out with a DMM. I can do the measurements with a little guidance. TIA.

 

[Misterrogers]

Ok gang - need some help. Working through setup with a new CTH Build (Belleson Super Regulator in ICP, and Hovland caps used in C4L/R). When I power up (it goes green), I get ~12V between SG/OG and SG/OL. When I go to test SG/OR, I go red and get ~< 12mv readings. If I hold the leads at SG/OR, it'll cycle every 4-5 seconds flip green then back to red. While cycling, my reads reset to ~0mv and tick up to ~12mv; then another cycle. Thoughts?

 

[Misterrogers]

Found it. One of the leads of the super reg was making contact with C2P. It's a bit of a tight fit.