[stringgz301]

Need some debugging help on my new build.  Start it up and get the red LED but it never latches.  Measured voltages at the R1E and R2E and get 12.06v and .712 respectively.  Any suggestions?
 
Other measurements:
 
OG to SG = 12.06
OL & OR are both close to 0 (3-5 mV)
 

 

[cfcubed]

Not to be a PITA but I like to start debugging by getting builders to do the steps in my "CTH debug" link in my sig. 
IOW be sure of *all* general/basic/setup measurements first.  And a pic can help as it just did in spotting a reversed Q1P.

 

[stringgz301]

Thanks cfcubed.  Have checked all the basic measurements short of putting in the tube.  Also, picks attached.  Seems like the problem is somewhere in the right buffer.  All suggestions appreciated.

 

[sachu]

post readings of ICE opamp. And of the dual channel opamp in the buffer.
 
And yes, very likely a buffer problem. 

 

[stringgz301]

ICE Opamp:
 
Pin2: 11.54
Pin3: 12.04
Pin4: 0
Pin6: 22.28
Pin7: 24.11
 
IC1 Opamp:
 
Pin1: 6.72
Pin2: 11.91
Pin3: 12.04
Pin5: .958
Pin6: 11.91
Pin7: 1.188
Pin8: 24.10

 

[stringgz301]

Figured it out.  Replaced the Q's in the right buffer 1 at a time.  It was Q4R.  Now have latch and all voltages check out.

 

[tim_j_thomas]

I moved this post to the "Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread".

 

[BK_856er]

Finally got my tube socket and C4 caps today, which will complete the board assembly!
 
Quick question on the Auricaps.  The black lead indicates the Foil end on Auricaps, which should ideally connect to the tube plate side for best theorectical noise rejection, correct?  In other words, the opposite of how stringgz wired his up in the pics above if I have that right.  Maybe no practical consequence to how it's done, but why not.  Can anyone verify before I warm up the iron?
 
BK
 

 

[Mullet]

I've sort of done it the way stringz has his except mine are reversed for each cap. Thus far I've not heard any noise or had any issues what so ever. I will say after having/listening to a few CTHs I like the CTH best with Sonicap Gen IIs over the Auricaps. I feel the Auricaps are more congested with my Thunderpants, which are a have a limited sound stage to begin with.

 

[BK_856er]

I have auricaps and sonicap genII on hand, but the genII are 400V type and rather long.  Too long for a vertical tombstone in the Hammond enclosure.  I initially thought I would socket C4, but the leads are way too large in diameter for my sockets.  The joys of botique caps.  If I decide to start with genII caps, what's a good mounting technique?
 
BK
 

 

[Mullet]

I have them in a v-shape lying flat. The bottom of the v is towards the base of the socket. They fit in there nice and snug.
 
On another note:
 
I'm doing another build for a fellow head-fier who uses mostly Grado-type phones. I've read in the past that 150ohm R18s were preferred for these types of phones. Would I be fine with 100 ohms for this build and Magnums, Grados, etc.? What would be the caveat in doing so?

 

[cfcubed]

WRT foil C4 caps -  Yes there is a preferred orientation, perhaps you've googled stuff like this:
http://www.aikenamps.com/OutsideFoil.htm
BUT since there is little EMF in the audio range in CTH (no transformers, has DC heater & minimal A/C traces) this is likely something not to sweat.  E.g. I'd not remove installed C4s just to change their orientation.
 
The C4 connections are amongst the most critical in the amp, they should be solid & if sockets are used they should be robust.  And try to secure any big C4 caps, at least to each other.
 
WRT R18 values - We only recommend > 0R here for 2 reasons: 1) to provide some volume pot range and 2) to reduce/eliminate hiss BOTH in the case of more efficient cans (esp when also using higher mu tubes).  So we say 100R as it will cover most cans well, though the optimal value would differ between, say LCD-2s (lower) & Grados/IEMs (higher).   I've made a large related post here:
http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/15#post_7348580
Ideally one could fit a DPDT R18 switch for say 0R & 120R (install 120R R18s & have the DPDT simply short those positions or not).
 
I've MS-1is I got cheap here on the way to me & using them would be the 1st time I could speak 1st hand about Grados & CTH.  Till now been relying on the reports of others.

 

[BK_856er]

Thanks, guys.  Just about wrapped things up with this - fingers crossed.  Made a last-minute change and went with the Sonicap GenII instead of the Auricap.  Noticed the leads on the Sonicap are each different length, but I'm not sure if that indicates anything special.  Put an inquiry in with Sonicraft about that.  Lacking a scope, I tried to mimic CF3's orientation from pg1 based on the printing, fwiw.
 
Drying off from the final IPA bath now.  Might get to wire it up and function test tomorrow.
 
BK
 

 

[Forte]

Its on their website "The shorter lead is Shield"

 

[Mullet]

Nice build! Yes the longer lead means it's the input lead. But it doesn't "really" matter or so I was told by Jeff at Sonic Craft. By the way, they no longer have any .22uF 400v Gen IIs. For my next build, up for consideration is a set of .22uF Gen Is, that have a more neutral sound signature compared to the Gen IIs. The Auricaps are the other affordable option. Another thing to think about is that the .33uF Gen IIs are still available. With the recent adjustments made to the e12 specs, would the .33uF caps work without issues? I can say with the most recent adjustments and normal spec'd C4s I haven't had a trip yet from transients, etc. On my older CTHs I had this issue from time to time.
 
On another note... I like the Gen IIs better than the Auricaps. The Auricaps are too meaty for me. I feel the Sonicaps have better resolution and the highs and lows are less rolled off.
 
One more thing... anyone have any extra .22uF Gen IIs they can spare?