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Cavalli Compact Tube Hybrid (CTH) Tube & Tweak thread. - Page 34

post #496 of 672
3/16/10 at 11:02pm
Thread Starter 
> Is there any technical reason (theoretically) why or why not the CTH amp would work well with the Tesla T1

Not that I can see from its specs. AFAIR CTH has been used to good effect w/some of the most difficult to drive dynamic cans around. Yep, the T1 may be better w/different tubes - perhaps those w/"less" bass. And there are always can/amp synergies to consider.
But if one is spending that much on cans they might be inclined to consider upper/high-end amps. Unless such amps have a way to "flavor" them (e.g. tube rolling) be sure you like what you hear before buying the combo.
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post #497 of 672
3/17/10 at 12:50am
Yeah, are not that good for critical listening but they are good for getting a taste of things. I would tend to agree that the T1 deserves a pretty high end amp.

I tried the T1 with a Woo Audio 5 and it sounded fantastic. I tried it with the WA6 and the results were not as impressive. The sound got a little sloppy in the bass. Then I tried it with the CTH and I basically got the same sound as out of the WA6. I would say the CTH may have sounded a bit better, although I'm prejudiced. Still, I don't think fooling around with tubes is going to give the CTH the sound of a WA5.
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post #498 of 672
3/17/10 at 1:21am
There is a long thread over at "the other place" on the T1 being designed around a 120 ohm output impedance on the amp driving it. The idea was put forward that the T1 sound is less than optimum if the dampening factor is too high from amps with too low an output impedance. Sounds goofy to me but the idea had traction with people with more smartz than me, so who knows. I don't have a T1 so the discussion was just a curiosity.

I would guess the output impedance of the CTH is what, 1 or 2 ohms ?
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post #499 of 672
3/21/10 at 8:26pm
Quote:
Originally Posted by bada bing View Post
There is a long thread over at "the other place" on the T1 being designed around a 120 ohm output impedance on the amp driving it. The idea was put forward that the T1 sound is less than optimum if the dampening factor is too high from amps with too low an output impedance. Sounds goofy to me but the idea had traction with people with more smartz than me, so who knows. I don't have a T1 so the discussion was just a curiosity.

I would guess the output impedance of the CTH is what, 1 or 2 ohms ?
I though the output impedance was dependant on R18 which is also used to adjust the gain, and can thus be rather high.

Anyone know the correct answer to this?
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post #500 of 672
3/23/10 at 2:18pm
Quote:
Originally Posted by Henmyr View Post
I though the output impedance was dependant on R18 which is also used to adjust the gain, and can thus be rather high.

Anyone know the correct answer to this?
The raw Zo of the amp is about 4R. Any series resistance simply adds to this number. So R18 of 150R would make the Zo about 154R. Etc.

Sorry for the delayed post.
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post #501 of 672
4/4/10 at 11:59am
I got some Raytheon 6gu7s, and 6cg7s. Weird thing is, the 6gu7 is made in japan with grey plates, while the 6cg7 is made in usa with black plates.



Also got some RCA cleartop 6cg7s. I can't really comment on their sound for now, since i don't have a good source here.
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post #502 of 672
4/4/10 at 3:27pm
I'm still waiting on my 7824's but am looking into amps for some incoming AH-D5000's so
Quote:
Originally Posted by runelight
The raw Zo of the amp is about 4R. Any series resistance simply adds to this number. So R18 of 150R would make the Zo about 154R. Etc.
seems very well timed. I read that Denon's like low output impedance, but I don't really know what would be defined as low? Or for that matter what value I got in the kit, though I guess the 150 default. Not with the amp atm...

My Grado's seem to have a problem (left side much quieter than right, but still measuring the right resistance and crackly at loud volume) so I'll probably only have the K340 and Denon's - any thoughts on what value R18's should be used for these cans?

Glad to hear your CTH is up and running Devast, I'd have answered your question if I could. Those tube pics make me want to start rolling!
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post #503 of 672
4/6/10 at 8:29am
Thread Starter 
Quote:
Originally Posted by suicidal_orange View Post
I'm still waiting on my 7824's but am looking into amps for some incoming AH-D5000's so

<snip> Or for that matter what value I got in the kit, though I guess the 150 default. Not with the amp atm...

<snip> so I'll probably only have the K340 and Denon's - any thoughts on what value R18's should be used for these cans?
Default R18s = 100R & they were incorporated for reducing gain to give more useful range on volume control, not for the purpose of altering output impedance. It may be possible that the R18s could save your OB from errant Line-In/Line-out swaps as well (mines survived that a few times).

@ work I use partial markl-modded D2000s w/Siemens tube & 100R R18s to good effect. Erikzen's CTH is set up similarly & he's used / enjoyed his modded D5000s w/this.
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post #504 of 672
4/6/10 at 1:29pm
Quote:
Originally Posted by cfcubed View Post
@ work I use partial markl-modded D2000s w/Siemens tube & 100R R18s to good effect. Erikzen's CTH is set up similarly & he's used / enjoyed his modded D5000s w/this.

I will vouch for that. The MD5000 DE is my main headphone and I have been using it almost exclusively with the CTH for the past 6 months with very few thoughts of upgrading.
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post #505 of 672
4/6/10 at 2:35pm
Sounds promising, guess I don't need different resistors unless the K340's are too quiet

I now have the D5000's (which are sounding rather good out of the CKKIII, for now) and the 7824's, but still no joy with the CTH. I airwired pin 1 and 2 of the 7824 and measured the voltages, both pin 1 to SG and 3 to SG were 3.7V just like with the old one! Take it out and pin 1 returns to a healthy 37V. What am I missing
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post #506 of 672
4/6/10 at 6:42pm
Thread Starter 
I forget the history of your build, so can just suggest:
* dbl check orientation of 7824 against PCB silkscreen. Its 180 rotated from what one might expect (metal tab to inside).
* w/7824 out check its output pin (#3) PCB location to ground (SG) resistance. I posted mine once, don't recall but it should more than a few ohms IIRC.
* if those are OK, then I'd think something upstream is toast (e.g. Q1P, Q2P) & thus unable to support the load. You could pop new ones in and/or check current going to 7824 input pin (#1) under load & post what you find here.
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post #507 of 672
4/6/10 at 8:07pm
Thanks cfcubed, the orientation is definitely correct and this was the second time powering it on with a new Q1P and Q2P (tried once with the old 7824). I hoped by not connecting pin 3 there would be no load, so it should have coped and read 24V indicating a problem further on (I don't really do electronics but this made sense in my mind ) Am I right in thinking the 7824 must be fully attached to be under load to measure the current?

I've just measured 515 (2000ohm scale) from pin 3 to SG, will look for your measurement tomorrow (or should that be later as it's midnight...) and see if that's healthy. At least it's not shorted but at least that would be something identifiable!
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post #508 of 672
4/8/10 at 4:04pm
I've attached the 7824 to the pcb and it measures 368 at pin 1 (assumed to SG...) on the 2000uA scale, but searching this thread for current just yields lots of discussion on tubes and a bit about peaking at 34V unloaded, so a 50V cap being better.

Can anyone confirm my reading is unhealthily low? This is with no tube in. If so any suggestions what could be wrong would be greatly appreciated
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post #509 of 672
4/8/10 at 11:23pm
Thread Starter 
Tube in/out should not affect the LV circuit much if at all.

So think you replaced popped Q1P (& Q2P) & using new 7824 (after reversed C10P). Something caused your Q1P to blow & we are still unsure what.

I was driving out finding out if A) 7824 is not getting the voltage/current it should be getting, or B) its load is over spec & its falling down trying to supply it.
IOW clarifying if the problem is upstream of reg or downstream.
7824's center pin goes to ground (SG).
Can you tell me (again?) what the LV circuit is doing when everything is attached/soldered, e.g. input V (pin #1) & output V (pin #3) to SG?

If bad, you could then measure 7824's current draw between pin #1 & its pad on PCB (by lifting it, measuring amp across) & let us know that (leaving center pin attached (SG) & pin #3 to load/PCB).
You could then re-attach pin #1, lift pin #3 & introduce an artificial load between it & ground/SG (e.g. 5W 100R -> 300R resistor, 24V lightbulb) and see if it can drive the load to 24V.
If your 7824 cannot drive something like a 220R resistor to 24V (getting it warm) then the problem is upstream/feeding or 7824 itself.
If it can drive such a load then your 24V supply is working (at least through to output of reg) & the problem is downstream in CTH.

Please see if you can do all the measurements & tests above & post back results.
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post #510 of 672
4/11/10 at 7:20am
Thanks cfcubed, I'll try and answer most of these now. The only thing you got slightly wrong was the death of Q1P - it didn't pop, but burnt slowly over at least 20 seconds. Not sure if that makes any difference and it and Q2P have been replaced (twice) anyway.

Without 7284
Pin 1 to SG = 37V

With 7824 fully attached
Pin 1 to SG = 3.41V
Pin 3 to SG = 0.1V

Lift leg 1
Pin 1 to leg 1 = 332uA

Lift leg 3, reattach leg 1
Pin 1 to SG = 3.71V
Leg 3 to SG = 3.11V

Even if I had an artificial 24V load to add I have a feeling it wouldn't do much on 3V! From reading above it's not getting enough current?
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