[ckunstadt]

(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.

 

[Silent One]

Quote:

(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.

 
You're making some great moves! Bravo on cutting the power leg in the USB - W4S is one of those DACs that can power its own internal USB receiving unit. I may try this...
 
I got my firewire enclosure and 8GB RAM from OWC - great group over there! Currently running a 60GB internal SSD but now thinking about 120GB or 240GB... love my SSD! I'm running Amarra (Full) but on Snow Leopard - was put off by Lion, although Mountain Lion awaits...
 

 

[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. 

 

[Xcalibur255]

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.

 

[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.

 

[wotts]

Quote:

 
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:

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.

 

 

[Silent One]

Quote:

Quote:

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.

 
 

 

 

  This sounds very exciting.

 

I'm paying for being an early adopter - the cost of the mod + shipping could have been NOS 5998's. 

 And I'm still looking for NOS 5998's. 

 Searched over the weekend - wrongly checking eBay... I should have been checking people's closets & basements! 

 
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!

 

[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!

 

[Silent One]

Quote:

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!

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!
 

 

[wotts]

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:

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!
 

 

 

[Xcalibur255]

Quote:

 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.
 

 

[Xcalibur255]

Quote:

 
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.

 

[Xcalibur255]

Quote:

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.
 

 

[Silent One]

Quote:

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.

No issues with Bass control to report. What I can report is the ITT (Japan) 6SN7GTB's sounded better in the Woo, as opposed to doing work in the OTL amp in single mode. The TS-BGRP sounds so much better... even the Ray's. 
 
I currently have a pair of recabled Senn HD600's in-house. They sound good. Though, I have preferred the sound of the Denon's to date. This leads me to believe that the OTL pairing with a low impedance phone like Denon performs better than expected. Three weeks back, I went round-n-round with the HD600-K702-D7000. Eight hours later, I still preferred the D7000. I know that's not really enough time, but I did extended runs from the 30 to 60 minutes at a time. After my brain seasoned, reasoned and settled after each switch, my order of preference did not change from the first round.
 
Additionally, though the D7000 is performing better inside the listening room than on paper, lowering the output impedance will make for a better dance partner - my D7000's can't wait! 

 More current, more happiness...
 
I'd like to hear 600 ohm Beyers and may have the chance when I visit Clayton SF in about 10 days. No need to drag the OTL amp to his apartment... he's got one! Also, as I approached 126 hours (estimated) last night on the amp, I'm hearing my first subtle hints of mellowing. 
 

 

[Silent One]

Quote:

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.
 

Now that I'm committed to getting the "X" mod, I'm taking your advice and seeking a pair of NOS 5998's (hopefully silent 

 ). I have now begun to search high and low 

, maybe sellers don't know I'm out there...