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post #736 of 10363

The 5998 has to be run with the proper bias to get the most out of it. So it's cathode resistor has to be 1/2 the value of the resistor that would be

used for a 6AS7. Then the transformer and rectifier has to be able to handle over 250ma. That leaves only a few rectifiers that can handle the current

The 3DG4 the old original 5AU4 or the 5U8C. No 5U4 type can handle this current not even the 596 or 5U4GB at 270ma. Add the 16 ma for the 6SN7

and it is 266ma that would be drawing over the 270ma to recharge the filter capacitors.

 

Silent One I will take a PIX but I have to dust it off first.

post #737 of 10363
Thread Starter 

Thanks for the 5998/cathode resistor explanation. When I get modded, I'll get mindful. And take the '596' out before flipping the switch!

post #738 of 10363
Quote:
Originally Posted by Clayton SF View Post


Thanks. Here's some pictures. I also use a Zalytron. Any info on the Zalytron?

 


Indeed, that is a Hytron GT.  Great sounding tube, especially in midrange resolution.  I think they are underrated.

 

I think the second tube is a Raytheon GTB.  If the getter is attached to one of the plates and fired onto the side of the glass then it definitely is.  It's on the back side so I can't see it in this photo.

post #739 of 10363
Quote:
Originally Posted by 2359glenn View Post

The 5998 has to be run with the proper bias to get the most out of it. So it's cathode resistor has to be 1/2 the value of the resistor that would be

used for a 6AS7. Then the transformer and rectifier has to be able to handle over 250ma. That leaves only a few rectifiers that can handle the current

The 3DG4 the old original 5AU4 or the 5U8C. No 5U4 type can handle this current not even the 596 or 5U4GB at 270ma. Add the 16 ma for the 6SN7

and it is 266ma that would be drawing over the 270ma to recharge the filter capacitors.

 

Silent One I will take a PIX but I have to dust it off first.


This was very informative Glenn.  For some reason I was under the impression that the 5998 still drew less current overall than a 6AS7.  I'm glad I never tried the GZ33 in the amp again after the mod, it might have arced even though it seems to be barely within specs.

 

The 6AS7s can't touch it for clarity, the 5998 is just so much more transparent and controlled post mod.  I do wish they were a little better behaved in terms of noise but you can't win 'em all I guess.

post #740 of 10363

^ You are the 6SN7 god!

The all knowing.

The all seeing.

The all spending! biggrin.gif

 

I thank your expert eyes.

post #741 of 10363

Those #26 tubes surely have large plates. Do they glow much? What is PITA about them?

Quote:
Originally Posted by 2359glenn View Post

I really don't use it as a preamp I have a stand alone preamp that uses #26 tubes I feel the #26 direct heated triode sounds better then any 6SN7.

Now All my amps are all direct heated triodes I just love the sound of these tubes. They are a PITA to work with but it is worth the hassle.

post #742 of 10363

A direct heated triode has to have DC power to the filaments especially if used as a preamp or driver. Each tube has to have a separate power supply and winding

from the transformer and I usually have a separate choke in each power supply. This is what makes them a PITA to work with and they tend to be micro phonic. I

went through many 26 tubes before I found a pair that was quiet. The only ones that are quiet are GE and Westinghouse that had the modern getter I think they

are both made by GE.

      Really you can barley see them light up they have a 1.5 volt at 1.1 amp filament this low voltage high current filament makes them less micro phonic then

say a type 01A. That sounds better but is terribly micro phonic it's thin low current filament will easily vibrate and make them micro phonic. they were made for

battery radios in the 1920s when most of the country had no power and the low power filament gave longer battery life. Now the driver in my 300B amp a #10 that

has the same size plate and a thorated tungsten filament lights up like a light bulb you can just about read the paper by the light from the filament.

post #743 of 10363
Quote:
Originally Posted by Xcalibur255 View Post


This was very informative Glenn.  For some reason I was under the impression that the 5998 still drew less current overall than a 6AS7.  I'm glad I never tried the GZ33 in the amp again after the mod, it might have arced even though it seems to be barely within specs.

 

The 6AS7s can't touch it for clarity, the 5998 is just so much more transparent and controlled post mod.  I do wish they were a little better behaved in terms of noise but you can't win 'em all I guess.

 

You can use the GZ33 the amp is choke input and the GZ33 can handle 300ma with choke input

post #744 of 10363
Quote:
Originally Posted by Clayton SF View Post

^ You are the 6SN7 god!

The all knowing.

The all seeing.

The all spending! biggrin.gif

 

I thank your expert eyes.


Every once in a while you'll see people auctioning a collection of multiple non-pair 6SN7 tubes.  These are the ones to go for, they almost always end cheap and sometimes there are good treasures in them.  It's a great way to experiment for cheap.  I bought 6 single tubes for $30 a while back and it was the best $30 I've ever spent.  I got my Hytron in that lot, and that tube alone is worth more than $30 by itself.  At this point I would say I've heard everything I want to hear though, with a couple of exceptions.  Some tubes I just cannot afford.


Edited by Xcalibur255 - 9/1/12 at 2:28pm
post #745 of 10363
Thread Starter 

Holy ship! eek.gif I just discovered my amp is sitting in a rising tide...

 

Yesterday, I completed bill payments for the month. And only realized a moment ago, that I have enough funds to return the amp back to the studio to meet its maker.wink.gif Awaiting the OTL amp is the "X"- mod; "Step" and new Black face-plate and control knob. Okay, maybe not the last one tongue_smile.gif I got a bit excited there, Glenn!

post #746 of 10363

Nice, very nice.

Don't forget to post a photo when you get it back. 

post #747 of 10363
Thread Starter 

Well, you know how dicey shipping heavy amps can be...across a great distance. Glenn packs very well; his gear is secure. But, whatever some of these shipping carriers do in between time, can raise both eyebrows. eek.gif

 

Of course, if I chose to spend the extra money, I could have baby returned by courier...and pampered. I'll take the chance and save that extra dough for tubes! biggrin.gif

post #748 of 10363
Thread Starter 

It's a wrap! No, really. Wrapped up the OTL and sent it back to the studio today for further enhancements. During the amp's time away, rather than listen to other amps, I'm going to take a break. And each night...remain silent...while dancing romantically...with Debbie in the dark.wink.gif

 

 

 

 

For Debbie's real name:

 

Warning: Spoiler! (Click to show)

"Debrox"

post #749 of 10363

Dancing romantically without music?

 

No way, you're hiding something.............

 

What mods are you going for?


Edited by rosgr63 - 9/4/12 at 11:56pm
post #750 of 10363
Thread Starter 

dt880smile.png wink_face.gif Tell me, you "clicked" to learn her true identity! YES, the cathode resistor mod to run the plates hotter on the 5998's. I know Xcalibur255 is being mellow (modest) about the mod he thought up and encouraged. But, I like affectionately referring to it as the "X" mod in his honor. biggrin.gif

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