X100/101 and 105 Plate Voltage's

I had the opportunity to play and scope out a IIC+ with an Export transformer.

With no load the plates see 460V with the X100/X101 (Same Tranny) and 500V with the 105.
Under load using a quad of medium plate current 5881's in both amps the X100/X101 was at
447V and the 105 was 493V.

The difference in tone was noticeable. With the same pre's and power tube in the same position on
both amps, the Export had cleaner cleans and a less pronounced high end. It's tended to have a pleasant, but minimal
sag at higher volumes. Compared to the 105 the biggest difference I noticed was power, by which I mean volume.
The 105 is endless and very loud. The master volume does effect the overall tone as the louder, the fatter. To my
ears you could get into the range of the Export, but it was easily at twice the volume. The Export sweet spot is lower on the
dial, but it only gets better for both as the Master increases. I could see how the Export could excel at different genres a bit
easier than the 105. It has a really wonderful clean breakup like Keef, but with excellent note articulation. The 105 although louder,
seemed a bit more urgent and stiffer, but still very pleasing. For the ultra high gain fans, the differences were not as dramatic as I expected.
They both sing, but the Export does sag a bit differently in a pleasing way. The high end is slightly subdued, which is not such a bad thing.
The amp with the Export had enough gain for three amps, gobs, shall I say. EQ'ing the 105 differently gets you in the ball park, but there is no denying the headroom.
It just does not squish like the Export. A nod to those with a more aggressive nature. It's amazing what 40 or volts can do. Both great amps with slightly different
manners. All in all, one of the best sounding IIC+'s I have ever heard. Thanks to Frank/Dodger916 for allowing me to play the amp and give the review.
It is one sweet amp !!! And a gain monster.....

Both amps in the comparison are SimulClass, right?
Regards

Correct. Both Simul-Class with the tone sucking EQ.

Awesome post, Ed! Thanks for doing this great bit of legwork! You've answered many of the questions I'm sure a lot of us C+ nerds had.

The Export's and the 100 put out the same voltage, around 460V so the sag should be about the same.
Funny you brought that up about the 60W George. The plate voltage on my old 60W C+ was 443 and it had
an early sweet spot. You can get sweet tone's from the Simul, but I've always had to get the Master above 5 and leave the
Lead Master at 1.5. It's a seriously fat full singing lead tone, but you can't switch to the cleans without fear of ear damage.
The Simul's other nature at lower volumes is a brighter, more cutting lead tone. Frank's Export has almost a perfect balance
between channels and an early sweet spot that gets better with more volume.

One thing that is not mentioned is the hotter bias of the Export model vs. the 105 or the 100 domestic models. This could also be part of the tone equation. Was the tone-sucking graphic EQ turned on or off? :roll: :roll: :lol: :lol: :lol: Good work, Ed.

Boogiebabies said:

Thanks to Frank/Dodger916 for allowing me to play the amp and give the review.
It is one sweet amp !!! And a gain monster.....

Click to expand...

Thanks belong to you Ed for your "labor of love" blueprinting my C+.

One more thing to add: it's an upgraded IIA.

dodger916 said:

Boogiebabies said:

Thanks to Frank/Dodger916 for allowing me to play the amp and give the review.
It is one sweet amp !!! And a gain monster.....

Click to expand...

Thanks belong to you Ed for your "labor of love" blueprinting my C+.

One more thing to add: it's an upgraded IIA.

Click to expand...

That amp no longer even resembles a IIA. It's all grade A+ IIC+ !!!

JOEY B. said:

One thing that is not mentioned is the hotter bias of the Export model vs. the 105 or the 100 domestic models. This could also be part of the tone equation. Was the tone-sucking graphic EQ turned on or off? :roll: :roll: :lol: :lol: :lol: Good work, Ed.

Click to expand...

Hey JB. The bias is no hotter than with the 105. The negative voltage is lower because the plate voltage is lower as well.
It takes more negative voltage to bias these amps with 40V or so less plate volts, they only appear hotter on paper.
On a bias meter, they drew relatively close to the same 20-25ma in the inner and outer sockets in both amps.
I had always wanted to figure that one out, but I could not make it a correct assumption due to never seeing an Export.
On the schematic, it gives no clue to what the plate voltage is. At 483V, like on the schematic it would be much hotter,
but in reality it's pretty much the same.

gts said:

And the IIC's modded to C+ with the 100 PT would have even a touch more sag than those with the export PT, don't ya think!?

Maybe that's why I keep going to and using the 60/100 C->C+ (not a Simul). Just seems to suit what I'm doing a touch better these days.
Maybe it's also because I can turn it up and get to it's sweet spot earlier, where as you say BB, the Simul might be blowing some heads off before it hits honey.
Not that I have any problem turning one up! :lol:

Cool you got to try one with an export tranny and compare it with the 105. Great bit of info.
And we all benefit from your insight(s) once again!


Thanks!

Click to expand...

I plugged in my 60/100 C->C+ the other day for the first time in awhile, been using the simul C+, and I have to say it definitely gets me 'there' at a lower volume than the simul. I forgot how good the amp really was. It'd be tough to choose between the two but I'm glad I don't have to

An there is the rub. With the 60/100 in 60W mode you get the outer two 6L6's. With the Simul, you can get the 6CA7/EL34's.
Even with 6L6's in the Simul you don't get that full 60W feel, but what you do get is quite amazing in it's own right.
I think I need to mod my Simul switch to Simul/60W/15W. That would be the balls.

Boogiebabies said:

I think I need to mod my Simul switch to Simul/60W/15W. That would be the balls.

Click to expand...

Now we're talking!

I wonder what the plate voltage is on Ethel ?

Boogiebabies said:

I wonder what the plate voltage is on Ethel ?

Click to expand...

"lesterpaul's" C+ Coliseum measured 520-ish volts on the plates, if I remember correctly. This is right in line with the MkIII Coliseum amps that I have owned. 8)

I have my 105 in my c+ with a 240 to 110 volt transformer on it. I have to say that the 105 has such a tightness/ fastness about it.even at high volumes.Such a good amp. Amazing.Great little write um ed.

Could someone help please with X101 PT?
What are the AC values of Bias and HV secondaries (Standby OFF)?

Need a replacement with similar specs in Europe
Thank you