2359glenn | studio - Page 4

(Vibrates). Over any of the other gear... my external HD actually creates a lot of its own vibration. But if it's all isolated, then cool!

I was just thinking that if I was using one of my slightly microphonic tubes, then having my HD (sitting nearby) might be a problem. Why-else isolate?

So, I just got a Mac Mini and put 8GB of RAM in it. As soon as I get the little tool kit from OWC, I will put in my 40GB SSD. Running Amarra. Disabled Spotlight, Bluetooth and Dashboard.

Right now I am using a short, very scrawny USB cable. I'm pretty sure it's not USB 2 rated. As an experiment, I cut and pulled out the power pin from the computer end of the cable. The DAC works just fine without USB power. I might try to find a DIYer to do-it-himself-and-sell-me a USB cable with no power wire and with a sturdy, pure silver signal wire.

Then... I will get into power cables and conditioning.

Down the road... have the WA22 souped up or talk to Glenn about a project amp.

Right-o.  Just to put some numbers to it.....

6AS7G maximum plate current - 120mA

5998 maximum plate current - 140mA

Operating plate current of a 6AS7G in this amp's circuit - 100mA

Operating plate current of a 5998 in this amp's circuit - 60mA

You can see the untapped potential there.  The 5998 draws less current in the same circuit.  It's a similar tube to a 6AS7 but not identical, and a 60mA plate current is less than ideal for the tube.  The second set of cathode resistors just allows the tube to draw more current.  It put the tube closer to its ideal operating curve and makes the resulting output more linear.  I did feel it picked up more drive, but the real win was greater transparency.  A clear step above what any 6AS7 I've ever heard is capable of.

I have no reservations about the mod whatsoever today and am very glad I did it.  Maybe all the ear popping my recent plane ride caused was good for my ears because when I got back earlier this week the amp sounded better than ever.  Darn near perfect.  If I hadn't already set things in motion with the 45 project I would be having serious doubts about the need now because the OTL as it is now leaves very little left on the table.  Heck I don't even have a top tier headphone.  I can't wait for the day I can plug an LCD-2 or Hifiman into this amp.

Quote:

Originally Posted by Silent One 

 

Next up for the 6AS7 based OTL amp? The "X" mod (switchable cathode resistors).  The mod is so named because Xcalibur255 brilliantly conceived the idea for the amp, which now has been expertly implemented into the amp's design. This will allow the 5998 tubes to run at a higher plate current in the 6AS7 slot (please correct any inaccuracies here Glenn; Xcalibur255). 

 

I've long saved up the $$$ for the mod, but shipping the little one (12kg?) round-trip from coast-to-coast, may force the consumption of Lipton tea before long! 

 

But, I understand it'll be worth it. 

Hey! I resemble that remark!

Just a few short weeks until I have my own Glenn designed amp in my possesion. The "X" mod will be installed...just need to find some 5998s now. I'm looking forward to comparing it to the Valhalla and Crack with the T1s. I may hook the W3000ANV up as well, but I'm not sure if that will be a good pairing.

Quote:

Originally Posted by Xcalibur255 

If I hadn't already set things in motion with the 45 project I would be having serious doubts about the need now because the OTL as it is now leaves very little left on the table. 

  This sounds very exciting.

I looked at ePay too. I'm not sure I'm going to spring for tubes just yet. I have 4 NOS 6AS7 on hand to try and maybe 3-4 of the 3DG4 rectifiers. I may call on the cat locally with a horde of tubes to see what all he has. Next weekend is going to be busy!

All four are marked RCA on the base, "6AS7 G" on the glass and two are marked "3-04" one with "209" and the last "2-17". The last one appears to have a loose base....  Three are in "Standard Brand" boxes and one is in an RCA box. I am unsure if the boxes are original. I'll dig out my tube testerafter work and see what I can find, but that may be nothing since I'm sure it needs to be calibrated.

 

Quote:

Originally Posted by Silent One 

What NOS 6AS7's are you sittin' on? Hmmm, since you're gonna be sizing this cat up,  how 'bout keeping an eye out for United Electronics Company USAF-596... thanks!

 

Quote:

Originally Posted by Silent One 

 Outstanding contribution, Xcalibur255!  I have just a few more days of collecting $$$ inside my tea tins - can't wait to ship this bad boy! The HE-6's I have in my custody temporarily, nearly suffocated the OTL amp - simply wasn't enough there there. I knew this before hand but I also knew it was an itch... 

 

When I get the amp back from Glenn, I'll chase my neighbor down the street (shipsupt) so we can listen to his LCD-2's on the amp, HD800's and so on. You do know that if the 45 Project yields no additional stratosphere , I'll likely give you what you paid for it. Something to keep in mind, while I focus on getting side-tracked by Pen-Fi. 

 

In the next 30, will try the ITT/Hitachi 6SN7GTB for the first time in the amp with the 5998's; 3DG4.

So you thought the amp didn't have the drive for the HE-6 then?  Then again few amps really do.  The modification might help that some. 

I'm definitely going forward with the 45.  It's very important to me.  I may have mis-expressed myself, I am just feeling a little guilty about replacing the OTL when it is an outstanding piece of gear that doesn't deserve to be replaced by anything.

Quote:

Originally Posted by Silent One 

 

Glenn said the "X" mod lowers the amp's output impedance by half. So, if my Denon's are doing ok @ 25 ohms now, I should see improvements on two fronts. Blue skies ahead? Also, it must be said, this OTL amp represents extreme value - playing well above its price-point!

If you issues with bass control before the mod should cure that.  I'm at 62 ohms though so I was never really challenging the amp in the first place.  Would love to hear a 300/600 Ohm beyer or senn on it someday, that *is* what OTL is best at after all.

Quote:

Originally Posted by wotts 

I looked at ePay too. I'm not sure I'm going to spring for tubes just yet. I have 4 NOS 6AS7 on hand to try and maybe 3-4 of the 3DG4 rectifiers. I may call on the cat locally with a horde of tubes to see what all he has. Next weekend is going to be busy!

No harm in buying up 3DG4 tubes, but I would say it isn't necessary.  The one tube will last for years.  I have a second for backup and am satisfied with that.

I would caution you about buying 6AS7 in advance though, especially if your window of opportunity to return them closes before you have your amp.  US made 6AS7 are often noisy so its good to be able to check them right away and get a refund if necessary for bad tubes.  I learned this the hard way.