[cfcubed]

So as this seems to be related to change in source need to know results of this: check if your source has DC offset (DMM mV measure bet its L & G and R & G)

 

[sharkz]

I'll do this after work. Thanks.

 

[sharkz]

Alright, take this with a grain of salt because I don't totally trust my multi-meter (I know some fluctuation is normal, but I couldn't get more than a second or two of a consistent reading) but the following were the measurements from my sources using the 200mV setting on my meter:
 
Sony SACD Player: L 3-4 R3-4
MUSE DAC: L1.5-3 R1.5-3
Behringer Preamp: L.3-.4 R.2-.3
 
Again, I am not sure how accurate these readings will be. I need a better meter than the $3 Harbor Freight one I have.
 
Hopefully this makes some sense to you.

 

[cfcubed]

Those #s look OK to me, I'd guess DC offset approaching 10mV could cause a problem.
Don't know what the problem is here, but when you say there's a 12v vs 6v heated tube diff it makes me think the gain of the tube is partly responsible for this.
The amp's "design center" is the 12au7 + equivalents and these typically have less gain than many 6v tubes that can be used.
You can check this theory by comparing the gain/mu/amplification factor of the tubes (e.g. google tube type + pdf for datasheets or see the tube ref I posted recently).

 

[sharkz]

Cf, thanks for your input. I will have to play around tonight and see if keeping the volume at a constant value and swapping the tubes seems to make a difference in volume. However the issue still stands that the relay is cutting out with any of my four tubes with the signal from my phono preamp. Which is weird because I haven't had trouble with any other amps I have tried coupled with the preamp.
 
In any case I have a new preamp (Musical Fidelity V-LPS) inbound and I will give this a try when it arrives. Hopefully the step up in source signal will solve the problem. Otherwise I am completely confused, because my other sources seem fine. I listened through my DAC for several hours last night with no issues at all. In any case, I really appreciate your help.

 

[cfcubed]

BTW CTH PCBs will become available & I've created an IC thread with the info here: http://www.head-fi.org/t/581511/ic-cavalli-compact-tube-hybrid-cth-pcbs-rev-1-3-aka-rev-a
 
Those that have posted strong interest in acquiring PCBs should read & re-post that interest in that IC thread.  Let's keep this thread for BoM & build issues & the like.

 

[Ikarios]

Got another small substitution question... for D5H, the BOM calls for a 1N5820 diode. I have a 1N5821 diode, which has slightly differing specs. Would it be a useable substitute? I don't know jack about diodes and don't know enough about the schematic to be sure.
 
 
1N5820
http://www.mouser.com/ProductDetail/Vishay-Semiconductors/1N5820/?qs=sGAEpiMZZMuIUjt4yeP9czzQat3OYqJfDL9E1h5QuUY%3d
 
1N5821
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/1N5821/?qs=sGAEpiMZZMuIUjt4yeP9c77RpzYf92T%252beUmm5gvL3b8%3d
 
TIA!
 
EDIT: never mind, looks like I got the 1N5820 diode after all. Now I just want to know out of curiosity/education.

 

[Mullet]

Can I use these as drop in replacements:
 
Mouser
954-E-202 replacement for D1L, D1R
954-E-452 replacement for D2L, D2R  
 
TIA!

 

[cfcubed]

Those look like good finds to me... I'm in the midst of re-mapping CTHA 2026a BoM part #s to in-stock ones & we may change a couple/few parts values. 
E.g. maybe raising R1E/R2E & R4E to reduce the e12's sensitivity a bit more.  More importantly I'm not sure the very last few corrections got into the Rev A BoM spreadsheet on Alex's site (e.g. stereo pot # correction [size=medium][size=10pt]RK097122...)[/size][/size]
 
Thanks for helping with this, we've at least a couple weeks to get it done so there's no rush

 

[Mullet]

I have no issues with the sensitivity of the e12. I can get to around 12 o'clock on the pot before the e12 really kicks in with transients. I suppose going a little higher won't hurt though.
 
I went through the BoM and mostly everything seems to be available along with my two new substitutes ie D1L/R and D2L/R. The RK097 is on order and won't be available til mid January. If people wanted to allow for a higher current than 800mA then they'd have to wait for 542-4608-RC to be available. DigiKey has the 1A toroid in stock - 732-1429-ND. Also, there are a few parts that are looking to be going obsolete, which means it might be a good time to find replacements at least at Mouser:
 
512-BC560C
512-MPSA14
140-XRL100V22-RC
140-XRL10V10-RC
 
The other main parts that are out of stock have alternatives ie the Wima type caps.
 
So it looks like most people will have to wait for a few parts at least if they're going with the RK097. The RK27 is available on eBay from some vendor in Hong Kong. I think you can also get it from Tangent's Audio shop.

 

[kEn ViP]

I'm having an issue with the initial setup. Powering it up, no smoke; LED turned from green to red after 2 minutes and the relay clicked. OG-SG measured 11.71V. OL 11.68v, OR 11.64v.
 
Putting the tube in, TB+ only reads 68.8V. Pin 1 57v. Pin 6 0V. The E12 keeps stripping randomly. Any idea regarding this?
 
BTW, for D1L, D1R, I'm using 2.2mA CRD instead of 2mA, and for D2L, D2R, 4.7mA CRD instead of 4.3mA. Also haven't wired up the pot to the amp,

 

[cfcubed]

>  e12 sensitivity - I've never had nuisance triggers but a few CTHers have, so runeight suggested we adj things slightly.
 
>  tiny RK097 pot for small BoM case - Most will opt for slightly longer (large) BoM case to make it easier to fit RK27s, 1/4" output jack & RCA ins availability of RK097s should not hold things up.
 
>  gunning for 1A+ coils in heater to support up to 800ma filaments -  The 732-1429-ND 1A L2H is a fine sub in any event & perhaps it should be the default.  There is enough flexibility with the value of L1H as part of the post ripple filter, so that M8276-ND sub would be fine as long as it fits.  Be careful bending leads on these, may even want to order an extra just in case.  And if heater draw > 500/600ma fit LM2595 w/at least part of a heatsink.
 
And yes we should re-map to parts non-obsoleted parts & thanks a bunch Mullet for helping with this!   Looks like we should have a workable BoM before the PCBs are fabbed.
 
ken vip - With tube in please carefully measure & let us know DC volts for TB+ / SG and tube type + heater voltage (DC between tube pins 4 & 5).
 
 

 

[kEn ViP]

Quote:

 
ken vip - With tube in please carefully measure & let us know DC volts for TB+ / SG and tube type + heater voltage (DC between tube pins 4 & 5).
 
 

I'm using the Amperex 6dj8. With tube in, measurements are:
+ TB+/SG 70.8V
+ pin 4 and 5 1.9V
+ pin 1/SG 60.1V
+ pin 6/SG ~0V
Without the tube, the e12 seems pretty stable. Putting the tube in, the LED keeps changing color.
 
 

 

[cfcubed]

All those voltages are low.  Please post these (all under load):  assuming you are using a 24VAC .75A+ A/C adapter, carefully measure it under load - its the 2 A/C jack pins in line (see PCB image), also please measure your 24V LV regulator (ICP) input & output DC voltages - that's its center pin to the right pin measurement then center pin to left pin measurement.
So far this is a mystery to me.

 

[kEn ViP]

I got 25VAC from the jack. However measurement from the ICP seemed weird The readings kept fluctuating on both the input and output; I couldn't get a stable reading.