the CTH (Compact Tube Hybrid) Rev A thread... - Page 26

I couldn't find any decent perf, so I decided to hack the hammond top.  OMG, making your own perforated material with a hand drill is labor intensive!  Nearly 300 carefully placed holes later, chamfered on each side, and I think it's looking pretty darn good.  I hope the blisters heal quickly.

Also added a heatsink to ICH today.  Moments later I took delivery of my new Russian 6N6P tube.  It's still early, but I like this tube!  Low amplification, very low microphonics, good sound.  Spectacular tube glow - that's worth the price of admission right there.  Hopefully I'm not stressing the CTH too much...

BK

>  Russian 6N6P  ...  Hopefully I'm not stressing the CTH too much.

Nope, 750ma +/- 50ma is fine w/the new/Dec2011 BoM 1A rated heater coils/chokes & the little ICH heatsink  (<<< BK's ICH temp measurements were too high for comfort - see my post below).  Agree, nice heater glow on that 6N6P.

Looks great!   Man that's some patience doing those holes esp. w/a hand drill!    See the headphone 1/4" jack is clear, is that 3.5mm input below it?

Yep, 3.5mm input is below the 1/4" jack.  Nice and short internal wiring far away from the PS sections.  Sounding really nice with the LCD-2.

Sure is toasty....after 45min my thermocouple is measuring 127C at the surface of the tube and the top rear of the case is 56C.

BK

I also make the rounds looking for inexpensive/free materials for builds, but haven't located nice perf material myself.   And haven't ordered it through say:

http://www.onlinemetals.com/merchant.cfm?id=1002&step=2&top_cat=1

Mullet nicely sent me a couple cut pieces when he'd spares.

BK & I've been exchanging PMs about his CTH & temp readings.  He's reported alarmingly high temps for ICH specifically w/6N6P in his build, so I've edited my post above about this.

We want to see all comps <= 85C, preferably lower.   "Standard" builds running the originally recommended max heater draw (< 600ma) have had temps measured & found to be OK.

And though new BoM heater parts are rated 1A+, with extra draw comes extra heat. 

When reaching for higher-draw tubes consider bottom & back plate 1/4"+ holes w/taller feet to allow cool air to enter (& hot air to exit).  May also have to get creative w/heatsinks on ICP & ICH.

if anyone is looking for a board let me know. I got one in the last group buy and will not have the time to try and build one.

As CF3 mentioned above, with the 6N6P tube my ICH and ICP were running too hot.  I measured the actual component temps with a micro thermocouple.

Project "COOL THE CTH" is now underway.  Supplemental big beefy custom fit heasinks and bunches of holes on the underside should help!

BK

Added a bunch of medium holes on the bottom and several small stealth holes on the sides near ICP and ICH.  Also ten more holes near the tube to help tube ventilation (and add some style).  I'll avoid medium vent holes in the sides if I can help it - too hard to hand drill through the pcb slots with a hand drill and have it look good.  After the additional heatsinks and ventilation I should be done!  Will grab some comparison component temps later.

BK

>  with the 6N6P tube my ICH and ICP were running too hot.

Re-clarifying this, the ICH was especially hot (ICP not beyond acceptable) & its because of use of a low heater voltage (6.3v) tube having high draw (> 500/600ma).   

This is because the heater switcher having to work harder to chop its incoming 38v or so & cut it down to 6.3v while passing more amperage. 

Note: SMPS is far superior efficiency/heat wise then common linear methods of doing this, and CTH could not achieve anything near it's small form-factor, and have single 24VAC supply, without it.

You'd not have to go to these extremes in a "standard" build targeting "recommended" tubes (see CTH tubes in my sig). 

But it's been said many times that even standard CTHs using target tubes benefit from good ventilation.

BK - Being into heat-sinks myself I have to say those are some macho sinks you have there:)   And though isolating thermal pads are recommended, the tabs on ICH & ICP = ground so that's not a concern.

BK, your either a Zen Master or a madman. 

Eitherway, the results are impressive and way cool (pun intended).

I still cannot believe you hand drilled and finished over 300 holes....

Very nice BK!! :)

If someone wants to upgrade their CTH, i'd recommend getting a Belleson Super regulator to replace the 24V 7xxx series one in the amp for powering the LV buffer stage.

Quote:

Originally Posted by cfcubed 

>  with the 6N6P tube my ICH and ICP were running too hot.

 

Re-clarifying this, the ICH was especially hot (ICP not beyond acceptable) & its because of use of a low heater voltage (6.3v) tube having high draw (> 500/600ma).   

This is because the heater switcher having to work harder to chop its incoming 38v or so & cut it down to 6.3v while passing more amperage. 

Note: SMPS is far superior efficiency/heat wise then common linear methods of doing this, and CTH could not achieve anything near it's small form-factor, and have single 24VAC supply, without it.

 

You'd not have to go to these extremes in a "standard" build targeting "recommended" tubes (see CTH tubes in my sig). 

But it's been said many times that even standard CTHs using target tubes benefit from good ventilation.

 

BK - Being into heat-sinks myself I have to say those are some macho sinks you have there:)   And though isolating thermal pads are recommended, the tabs on ICH & ICP = ground so that's not a concern.

Just call me a macho zen master madman.

I'm embarrased to admit that in my excitement I was using 12.6V on the 6N6P tube  

I didn't realize the incorrect heater setting until CF3 mentioned 6.3V.  Oh well, I feel better with a special super-cooled CTH regardless.  Will grab some updated measurements and report back.

BK

Quote:

Originally Posted by BK_856er      I'm embarrased to admit that in my excitement I was using 12.6V on the 6N6P tube  
 

Oops:)  I guess that nice, bright tube glow & 120C+ tube top measurement were trying to tell us something:)

Well the tube was drawing 10W+ and the CTH was holding its own.   Now it will do even better with your mods, e.g. no worries w/800ma draw tubes for you.

BTW I've occasionally used the wrong heater setting for brief periods.  Dead giveaways for that are 1) 6.3v for 12.6v tube - lower-than-normal gain, 2) 12.6v for 6.3v - tube brighter-than-normal filament glow.