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Crack;Bottlehead OTL - Page 246

post #3676 of 5900
Quote:
Originally Posted by audiowize View Post
 

 

I'm going to disagree here.  Both draw the same filament current at the same voltage.  In the Crack circuit, both draw the same current from the high voltage supply. 

 

If the plate/heater voltages go up with a 6080, then the 6AS7 would in fact run hotter. 

 

In any case, they carry the same ratings and often have the same guts, just in different glass envelopes. 

That's exactly what I had in mind at the very start but upon power up I noticed the 6080 got hotter faster and measuring the different pins shows a large difference almost double. I think it might be a shorted tube unsure at the moment because I've been using this pair of 6080 for every 6AS7 amp (not 6SN7 if I mentioned it typo) to test with. But the odd thing is it sounds fine and I get no arc's upon power up. What's the max voltage for the plate of the 6080? 300volts or something 6as7 is 250v max, there is a regulated cap that feeds pin 5 of the socket rated at 250v when using 6as7's plate voltage is 126v but as soon as the 6080 goes in 276vdc, or is the voltage doubled off the positive lead of the cap feeding back to pin 5 on the socket? Otherwise I'd expect the 250v cap to start smoking since it's 26vdc over it's rating. This is not the Crack btw.

post #3677 of 5900
The envelope of the 6080 is tighter, less surface area than a 6AS7. So the radiated flux will be a little more dense through the envelope, and it has a little less surface area by which to conduct/convect that heat into the environment. The glass will probably measure a little hotter because of this. But the internals are essentially the same and total power radiated into the room by the 6080 will be the same as the heat radiated by the 6AS7 if the tubes are operating at their design spec. P=VI.
post #3678 of 5900
Quote:
Originally Posted by Doc B. View Post

The envelope of the 6080 is tighter, less surface area than a 6AS7. So the radiated flux will be a little more dense through the envelope, and it has a little less surface area by which to conduct/convect that heat into the environment. The glass will probably measure a little hotter because of this. But the internals are essentially the same and total power radiated into the room by the 6080 will be the same as the heat radiated by the 6AS7 if the tubes are operating at their design spec. P=VI.


Some times you sound almost too smart :) No wonder that mainline sounds soooo good!

post #3679 of 5900
Quote:
Originally Posted by Doc B. View Post

The envelope of the 6080 is tighter, less surface area than a 6AS7. So the radiated flux will be a little more dense through the envelope, and it has a little less surface area by which to conduct/convect that heat into the environment. The glass will probably measure a little hotter because of this. But the internals are essentially the same and total power radiated into the room by the 6080 will be the same as the heat radiated by the 6AS7 if the tubes are operating at their design spec. P=VI.

True but what could you about vdc being almost doubled when measuring the plate pins substituting a 6AS7 for a 6080, unless this Raytheon 6080 is shorted? I'm at lost now even it produces sound, no arcs on power-up.  

post #3680 of 5900

I want to share THE GREATEST CRACK MOD.  Ever.

 

I can't over hype this enough.  It's better than the Speedball, tube rolling or caps/pot upgrade...  Combined.

 

Now, I think the Crack is great amp, but I always found it to be a bit noisy.  So I started reading about tube amps and interference.  I live downtown Toronto, so there is plenty of radio/electrical noise in my condo.  I read about magnetic chokes, and wire cages.  Then I read about a different method of reducing noise...

 

I moved my amp 3" to the right.

 

Oh.  

 

My.  

 

Gosh.

 

What a difference.  It's the best upgrade I've ever done to my amp.

 

I'm floored.

 

Anyway, I just thought I would share :D 

post #3681 of 5900

lol somebody's trippin from the Crack.

post #3682 of 5900

A 6080 should hit the same numbers as a 6AS7 in a Crack amp. If you are having problems with an amp from another manufacturer I suggest you talk to them as we have no clue what the circuit is and can't offer any useful insights because of that.

post #3683 of 5900
Quote:
Originally Posted by DefQon View Post
 

True but what could you about vdc being almost doubled when measuring the plate pins substituting a 6AS7 for a 6080, unless this Raytheon 6080 is shorted? I'm at lost now even it produces sound, no arcs on power-up.  


Buy 5 6080's and 5 6AS7G's that are tested good.  Perform your experiment several times, draw appropriate conclusions. 

post #3684 of 5900
Yep leaning towards that need more 6080 got too many 6AS7's.


Is pin 7 heater ground reference and pin 8 6-7vac/dc heater supply?
post #3685 of 5900

6V AC or DC needs to be supplied between pins 7 and 8. 

 

Ground references are up to the designer, and will vary widely depending on other design parameters. 

post #3686 of 5900
Quote:
Originally Posted by audiowize View Post

6V AC or DC needs to be supplied between pins 7 and 8. 

Ground references are up to the designer, and will vary widely depending on other design parameters. 

So either of the two heater supply pins will be supplying the 6vac/vdc? But not both..
post #3687 of 5900

Current requires a loop to flow.  If you have 6V on pin 7, and nothing connected to pin 8, no current will flow though the heaters.

 

If you measure the voltage between the two pins, it will be 6V AC or 6V DC. 

post #3688 of 5900

Cheers man got it been working on this amp project for a while finally got it working and sounds nice. The Raytheon 6080 turned out fine had my wiring bit mixed up and the double voltage for the plates I was reporting was VAC using my other fluke DMM. Currently have the amp direct coupled, no cap between the output stages, for the heaters I did trafo to filaments then bridged from pin 7 and 8 to the 6SN7's octal sockets, using one of the pin's as a heater ground reference, 6vac on the heater I might go further regulate it to dc to avoid any hum issues guess it's time to change the schematic, similar fashion to my modded DV 336SE.

 

Any idea how easy it is to re-wire or even if possible from 6AS7 to 6BQ5's, in this case for the Crack? I really want to put them to use as I have heaps of quads and pairs, quad EL84's are nice as power tubes in another amp I have, these tubes can take lot more voltage abuse and euphonically coloured - in a pleasing way.

post #3689 of 5900
Quote:
Originally Posted by DefQon View Post
 

Any idea how easy it is to re-wire or even if possible from 6AS7 to 6BQ5's, in this case for the Crack? I really want to put them to use as I have heaps of quads and pairs, quad EL84's are nice as power tubes in another amp I have, these tubes can take lot more voltage abuse and euphonically coloured - in a pleasing way.

The 6BQ5 doesn't have some of the luxuries available in the 6080 - mainly the +/-300V heater-cathode insulation rating.  Triode strapped, you can get decent transconductance out of a 6BQ5, but you'll need to carefully consider the operating point. 

post #3690 of 5900

Processed By eBay with ImageMagick, z1.1.0. ||B2

Processed By eBay with ImageMagick, z1.1.0. ||B2
Hey guys,

Someone is offering me this tube. It looks a lot like the GEC straight brown base tube. Can any expert confirm that it is indeed that tube? The owner said that it is from a company CVC but he claims that it is made by GEC and rebranded by CVC. Please let me know as it will be a pretty big investment for me! ><

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