Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread.
New Posts  All Forums:Forum Nav:

Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread. - Page 29

post #421 of 680
Quote:
Originally Posted by regal View Post
I see people using 6n6p's and 6h30's, these tubes require alot of plate to cathode current, I thought the CTH was only a 1 mA HV powersupply? I'm not talking heater current.
The plates are at 2mA at 80 volts.
post #422 of 680
Quote:
Originally Posted by sachu View Post
The plates are at 2mA at 80 volts.
Amazing that the 6n6p and 6h30 are even listenable at this current.
post #423 of 680
Thread Starter 
Quote:
Originally Posted by regal View Post
Amazing that the 6n6p and 6h30 are even listenable at this current.
Guess it's just an amazing little amp

Think smeggy might have been 1st to use 6n6ps but others e.g.barleyguy and I have as well.

Maybe tubes unexpected to sound well do so because of their light loading / high impedance typical of Alex's designs. And decent plate voltage.

You have one of these around yet?

Funny story - During my 1st PCB build my bench must have been too messy because I had to take a few moments to find the partially populated PCB on my bench... I'd actually "lost" it due to its size
post #424 of 680
Quote:
Originally Posted by regal View Post
Amazing that the 6n6p and 6h30 are even listenable at this current.
Quote:
Originally Posted by cfcubed View Post
Guess it's just an amazing little amp

Maybe tubes unexpected to sound well do so because of their light loading / high impedance typical of Alex's designs. And decent plate voltage.

You have one of these around yet?
Regal you should really build one of these if you haven't already.

I haven't built that many amps being new to the DIY thing, but I can say this truly is an amazing amp. I haven't come across any amp that reveals a tube's characteristics as well as this one. This is a tube rollers dream come true.

Thanks Alex.
post #425 of 680
Quote:
Originally Posted by TimJo View Post
Regal you should really build one of these if you haven't already.

I haven't built that many amps being new to the DIY thing, but I can say this truly is an amazing amp. I haven't come across any amp that reveals a tube's characteristics as well as this one. This is a tube rollers dream come true.

Thanks Alex.
Actually spent some time with RCA 6AU7 and 7AU7 Clear Tops last night

Listened to all my dynamic cans to see which were going on the block - the CTH has become my reference (er, would if I could stick to one tube, which would probably be the Raytheon 6GU7). Quite nice driving JH-13 pros, which is my new work rig.


I agree it's an amazing amp, perhaps the hidden jewel amongst all of Alex (and Chris'!) MANY contributions to the DIY community.
post #426 of 680
Quote:
Originally Posted by wiatrob View Post
Actually spent some time with RCA 6AU7 and 7AU7 Clear Tops last night

Listened to all my dynamic cans to see which were going on the block - the CTH has become my reference (er, would if I could stick to one tube, which would probably be the Raytheon 6GU7). Quite nice driving JH-13 pros, which is my new work rig.


I agree it's an amazing amp, perhaps the hidden jewel amongst all of Alex (and Chris'!) MANY contributions to the DIY community.
I have the same problem,,,so many tubes and really relatively inexpensive too. Latest is the Russian 6n23p which are really clear, solid state like, but i also keep coming back to the Raytheon 6gu7 which just seems to do everything right.
post #427 of 680
Thread Starter 

6F8G -> 12au7/9-pin mini adapter heads-up

Quote:
Originally Posted by dpmiller View Post
Stock Spruce Canyon kit build with 40's/early 50's RCA 6F8G; I like it. This amp is fun.
Couldn't resist trying this and ordered one of those $25 6F8G -> 12AU7/mini adapters off the bay. They are no good for the CTH. Edit: dpmiller found the 6F8G to 6CG7 one is the one to get.

CTH uses pins 4 & 5 for (serial) heater supply. Center-tap pin #9 is unused in CTH and it looks like that adapter relies on is use... Note circled mini heater pins 4 & 5 are shorted in this adapter:



Just before powering up a CTH of mine using this adapter I thought "Hey, I better check this thing out w/an ohmmeter." Glad I did. CTH's heater circuit would not have been happy.
So a bit of re-wiring of the adapter & she'll be good to go.
post #428 of 680
Has anyone tried using different power supplies with their CTH? I'm using the one from Spruce Canyon (24 VAC - .83amp) and was curious if anyone has found that the supply made any difference in performance.
post #429 of 680
Thread Starter 
Think it depends on your tube's (series) heater draw... Most target tubes draw up to 350ma or so & IIRC the full draw of the amp with that was about 550ma (?). So going > 750ma WW should not yield a benefit then (.833ma being fine in most cases - it's what I use).

If using tubes w/heater draw > 500ma or so you could move to a 1A wallwart, but doubt you'd hear a difference. Wallwart would just run cooler. We like to have at least 25% headroom in transformer/wallwart capacity so that they don't get too hot/stressed.
post #430 of 680
cfcubed -
I'm glad you checked.

My adapter says 6CG7 - 6F8G; checking pins 4 and 5, and they are not shorted on this one.
post #431 of 680
Thread Starter 
Quote:
Originally Posted by dpmiller View Post
My adapter says 6CG7 - 6F8G; checking pins 4 and 5, and they are not shorted on this one.
Ack! Yes I should have picked up that one Thanks for clearing this up.

BTW, quick re-wire (split 4/5 pins & moved pin #9 wire to then empty pin #5) and its working but I'm getting some hum w/the 6F8Gs - do you?.
ANY other tubes in this CTH have dead silent/black background.
This is a new, bigger, better CTH build of mine BTW (more room, all runs > 3in are shielded, etc.).
post #432 of 680
Thread Starter 

A good way to build a CTH, 6F8G update

My latest CTH is also my quietest. Perhaps because of the space, shielded runs, 24V reg clearance - who knows but I'm happy.



And no hum issues anymore w/RCA 6F8G. These must have helped: 1) let tube warm up a bit, 2) made cap/grid wire a shielded one (pin #5 of CTH's mini = ground) & 3) moving CTH around or off of Rotel CDP top.



I've tried a few tubes w/my new HF-2s (8416, 6922 PQ, etc) but none really hit me like this RCA 6F8G...

Smeggy & dpmiller know what they are talking about, these 6F8Gs are something special. Thanks for bringing them up
post #433 of 680
might have to try a 6f8G with hf-2, do they mate well with your other phones? Im concerned about noise, the only tubes I have issue with hum are my 6dj8's though I may have three bad ones.
post #434 of 680
Quote:
Originally Posted by cfcubed View Post
My latest CTH is also my quietest. Perhaps because of the space, shielded runs, 24V reg clearance - who knows but I'm happy.
Very nice looking build

What case have you used? Have been considering a HB-360 case from eBay that looks just like it but have not seen one used before.
post #435 of 680
Thread Starter 
Quote:
Originally Posted by keyid View Post
might have to try a 6f8G with hf-2, do they mate well with your other phones?
Not crazy about either of my 6f8Gs w/DT880s & haven't tried w/my D2000s (or HD650s on their way to me from FallenAngel). Liking the RCA in the pic better than Sylvania. Have a NOS RAYTHEON 6F8G VT-99 on the way & they are supposed to be nice.
Stayed up way too late listening to the setup in the pic... 1st time I've done that w/HF-2s. But it's likely other tubes in my stable mate well w/HF-2s - just have to crawl through them.

Quote:
Originally Posted by keyid View Post
Im concerned about noise, the only tubes I have issue with hum are my 6dj8's though I may have three bad ones.
You might. Or perhaps something in your build, but I know you know what you are doing
I'm a big fan of shielded runs. With vol @ 3/4s I could hear the very faintest, hard-to-detect hum w/my most efficient cans between tracks on my other builds. But can't hear any hum or hiss on this one with any of the other tubes I've tried across all my cans.
A very, very tiny bit of hum is detectable in right channel between tracks w/my 6F8Gs that goes away when I grasp the cap/grid lead. Didn't notice it at all after tube was warmed up 1/2hr or so & moved amp away from CDP. Perhaps the nature of having a long grid line to top of tube around. But tube's fun value far outweighs any of this for me.

Quote:
Originally Posted by Forte View Post
Very nice looking build
What case have you used? Have been considering a HB-360 case from eBay that looks just like it but have not seen one used before.
Thanks... Found CTH shines it's very best w/spread out/conventional build like this one. Have a few amps under my belt now & have heard several others @ meets & still come back to CTH goodness

Re: HB-360 - Yep, that's the one. Can't beat the price esp if you combine orders from that guy.
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread.