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Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread. - Page 44

post #646 of 672
2/15/12 at 4:46am
Thread Starter 

You need not worry about components that are <= 75C.  Only your ICP reading is cause for concern. 

BTW my bet is many CTH's ICPs are running up to 80C & have been doing so for years.

Please let us know the input voltage to ICP (pins 1 & 2), perhaps your A/C adapter is supplying > 27 VAC under load.

You can also search my posts about ICP's heatsinking, e.g. you don't want to snug it all the way down on the PCB.   You want ICP & its heatsink up off the PCB. 

If you still have temp problems consider doubling up its heatsink, since its tab = ground you need not worry about its contact w/case or lid.


Edited by cfcubed - 2/15/12 at 4:48am
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post #647 of 672
2/16/12 at 4:39am

Houston, I've listen to the radio on the CTH!

 

I had the same problem with the 332C, and I reduced it with a gridstopper. The CTH already has a 300 Ohm R. Should I increase it to 1k?

 

With the 332C there was radio with any position of the pot, but with the CTH there is no radio from 0% to 60% of the 50k pot.

 

My other creatures, like the G3, XM6 or FF400 do not suffer from radio interferences.

 

 

CTH + G3

Note: the 6F8G grid cable increases the interference, but there is also interference with the 9 pin tubes.


Edited by Pingfloid - 2/16/12 at 4:41am
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post #648 of 672
2/16/12 at 5:15am

I would think it has to do with your power source. I've two CTHs and noticed a similar phenomenon when I'm using my work CTH and have the volume at 80 to 100%, which I would never do anyways. I swapped CTHs and noticed the same thing. When I took them home the interference went away. I work in a facility that has a rats nest of old video and audio cables all over the place and my nook is in the midst of all of it. In my situation I think the old cable is introducing RF interference. On the brighter side of things I'm currently ripping out all the old infrastructure and puttting in a brand new machine room with newer modern cable. It would be interesting to see if it goes away. In your case maybe a better power conditioner would solve the problem.

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post #649 of 672
2/16/12 at 8:36am
Thread Starter 

Very, very cool photo.  Man you are not wasting any time before going as far as you can with your CTH:) 

I'd a 6F8G (forget brand) + adapter which I thought made my HD650s(?) sound their best w/CTH.   Looks nice & crazy too w/that giant tube + wire on top of the tiny CTH:)

Traded 6F8G + adapter away because I still prefer HD600s & like "chrome" plate best w/them.

 

Guess you drilled some holes in case, consider back & side ones as well + creative heatsinking when pushing the limits.

 

BTW IIRC never had audible interference w/my CTHs, so can't help there.
 

Quote:
Originally Posted by Pingfloid View Post

Houston, I've listen to the radio on the CTH!

<snip>

CTH + G3

Note: the 6F8G grid cable increases the interference, but there is also interference with the 9 pin tubes.



 

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post #650 of 672
2/16/12 at 10:03pm

That picture was purely accidental. I didn't notice that the exposure was on manual and I moved the camera before it was finished cool.gif

 

The CTH do not receive interferences at my office, so it may come from a giant group of antennas that is about 500m from my apartment, and the absence of control over RFI regulations in Thailand.

 

Like with the 332C, there are 2 simultaneous radio stations: one with news an other with music. And the intensity is higher at night.

 

I have inserted ferrite beams in all the cables. Moving the supply cable makes no change, but moving the headphone or signal cable makes huge differences. Rising both the headphones and signal cables makes the sound from the radio louder than the music.

 

I have already tried different signal cables and sources.

 

 


Edited by Pingfloid - 2/16/12 at 10:15pm
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post #651 of 672
2/20/12 at 10:10pm

Beside the Radio Interference at the CTH, the 6F8G cap cable creates a lot of microphony and some ground noise. Do you also have that problem?
 
My adapter came with a very thin and quite flexible cable. Do you think that replacing this cable for a special one would reduce the microphony? I do not think that the microphony comes from the tube itself, because it only happens at the channel with the grid connection on the cap. Also, I have 3 different 6F8G's (1 Raytheon and 2 RCA) and they all show exactly the same result.

 

The ground noise disappears when I touch the case. This is one disadvantage of using a wall transformer: there is no ground connection.

 

It is a pity, because the 6F8G is the only tube that I have tried so far that gets closer to the warmth and fatigue-free of the Sense G3. Some of the other tubes that I’ve tried are 12AU7/6DJ8 Amperex BB, 12AU7 RCA, 12AU7 GE Long Plates, ECC88 Telefunken...  But I will keep on experimenting. I will also try rolling C4 cap. Otherwise the CTH will not be able to substitute the dead quiet and warmly sweetie Sense G3. (for my personal taste)


Edited by Pingfloid - 2/20/12 at 10:21pm
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post #652 of 672
2/20/12 at 11:58pm

Could someone confirm for me real fast that these tubes would work OK in my CTH?  I searched for 5965 in the spreadsheet but didn't see it listed, and haven't done a lot of tube rolling so wanted to make sure before I pulled the trigger on them.  The eBay ad says the following.  Thanks in advance!!!

 

Lot of 6 Assorted 5965/5965A/12AU7/ECC82 Vacuum Tubes Telefunken/Raytheon/GE"

 

 Telefunken 5965 (Made in Germany) Tubes w/grey ribbed plates (QTY 1)

* Raytheon 5965 Tube w/grey ribbed plates (QTY 1)
* Lewis& Kaufman 5965A Tube w/grey ribbed plates (QTY 1)
* GE 5965 Tube w/grey ribbed plates (QTY 1)
* GE 5965A(poor label)Tube w/grey ribbed plates and clear top (QTY 2)

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post #653 of 672
2/21/12 at 12:13am

I think that the the 5965 is a 12AT7 type, with a mu factor of 60. We need the 12AU7 or 6DJ8 type, with a mu around 19~33

 

Please, someone correct me if I am wrong.

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post #654 of 672
2/21/12 at 3:47am
Thread Starter 
PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (which = tube pin #4). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).

BTW never had ground noise that went away by touching the CTH or it's knob pot because I make sure both are connected to SG (which = IG).
Actually I feel the AC adapter supply is a unique advantage - keeps transformer far away from amp and reduces ground-loop problems.

And PF is correct about tube mu - AT is no good - again please see the CTH tube info link in my sig for CTH compatible tubes.
Edited by cfcubed - 2/21/12 at 4:44am
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post #655 of 672
2/21/12 at 6:26am
Thanks guys for the heads-up on those tubes
Quote:
Originally Posted by cfcubed View Post

PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (which = tube pin #4). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).
BTW never had ground noise that went away by touching the CTH or it's knob pot because I make sure both are connected to SG (which = IG).
Actually I feel the AC adapter supply is a unique advantage - keeps transformer far away from amp and reduces ground-loop problems.
And PF is correct about tube mu - AT is no good - again please see the CTH tube info link in my sig for CTH compatible tubes.
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post #656 of 672
2/21/12 at 8:22pm
Quote:
Originally Posted by cfcubed View Post

PF - Are you saying you only get "ground noise" w/6F8G and it's grid wire? If so consider replacing that long cap wire with a shielded one, connecting the wire's shield to case/input ground (which = tube pin #4). IIRC this is exactly what I had to do to my 6F8G adapter - used a thin shielded cable for the grid/green/cap wire connecting the shield to (heater gnd) pin #4 internally in adapter case).

Yes, the ground noise only comes from the 6F8G grid wire. I will replace it for a shielded one, connected to ground through pin 4, as you say.

 

Don't you have microphonics with the 6F8G? I can listen a "bump" just by fingertapping at the table, far away from the CTH.

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post #657 of 672
2/22/12 at 3:47am
Thread Starter 
Googled and it seems 6F8Gs can be micro phonic, some say tube dampers can help, or very cushy feet under the CTH. I think any given tube can be micro phonic, perhaps try another?

BTW IIRC I used an old PC CD drive audio cable as it was thin and shielded and free. Guess a action of cheap RCA IC cable could work too.
Edited by cfcubed - 2/22/12 at 4:10am
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post #658 of 672
2/22/12 at 12:24pm

That CTH pic is tha bomb.  popcorn.gif
 

Quote:

 

 

CTH + G3

 



 

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post #659 of 672
2/22/12 at 5:32pm

Dealing with radio interference can be a nightmare in tube amps - any trace can behave like an antenna. If I am reading correctly, it is worst with the 6F8G , so most likely a feature of the cable for the cap electrode. You could try screened / shielded wire but this will be a tough thing to address. 

 

While on the subject of the 6F8G, I know a lot of people like this tube. Yes here comes the but... it is an early development of the 6SN7 and as such is less mechanically robust and is not as linear , thus there is probably a good deal of tube distortion ( harmonic ) that comes with this package. The noval equivalents of the 6SN7 are the 6CG7 or 6FQ7 tubes which are truly superb. Stax engineers used these tubes in their stat amps and having sampled a fair number of the various tubes, I can wholeheartedly encourage you to try these tubes. The 12AU7 is a 12v derivative of this tube and thus will have similar tonal characteristics , these you are all familiar with. 

 

Please don't think I am saying that the 6F8G would be a poor tube choice, there is a reason people choose tube amps and in particular avoid "sterile" ss amps which have distortion measurements which are 5 decimal points below zero. 

 

..dB

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post #660 of 672
2/23/12 at 1:17pm

Working on another CTH using the same case that cfcubed did with his 'Fancy' CTH. I'm going to use Hovland SuperCaps, plus a Belleson Super Regulator to replace the 24V reg. I'm pretty excited to see what benefit I'll hear with this very clean, fast regulator. Does anyone have any experience with either of these two parts?

 

 

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