MPX3 SE impressions....

[PFKMan23]

I've recently taken delivery of an MPX3 SE, which is to say that the voltage has been raised to take advantage of the more powerful output tubes, namely the 6BL7GT/As, 6BX7GTs, the 5687sw and the like. If you've got a low impedence and/or low sensitivity can (K701, Grado, etc..) then you definitely need to take this into consideration if you're getting a Singlepower.

And given that this is Headcase, I'd also like to mention that this is the second/third trnasformation my amp has taken on

For me the SE deals with the increased voltage and current bias. I have 2 voltage settings on my amp, one which is 300V and one which is 375. For me it allows me to take full advantege of my 6BL7GT/As. As they are a tube that is transformed when run at the higher votlage/bias. The amount of bass that is yeilded by my two leading combos right now RCA 12sn7GT/6BL7GTA and the 14n7/BL7GTA is phenominal. Point of reference I also have some 5687s on hand and the amount of bass impact, SLAM, whatever you want to cal it is definitely very comparable, if not even greater than the 5687s. It is worthy of note however that the 5687s do have more intimate presentation, being a smaller soundstage and slighter tighter bass. However the 6BL7GT/As crush the 5687s in terms of soundstage, almost to the point where if it is any bigger I fear that it would sound diffuse. The GTAs bass isn't flabby or loose/uncontrolled by any means.

NOTE: At 300V the BL7GTAs sound horrible, they are harsh and just plain out nasty sounding.

For example with the Narnia Soundtrack Track 12: The battle, the ampount of bass thatis felt/heard by the frums can get downright scary at some points. The people who say that the K701s have no bass have low frequncy hearing loss However the amp/tube combo also retains the inherent smioothness of the 6sn7s, which for someone like me, who is a pop/classical listener A large soundstage is what i crave, (you could call me a soundstage freak) and with this combo I get that.

Summary:

If you guys are loking to get Singlepowers or sending thme back or whatever this is something you need to consider. The BL7GT/A and the BX7s are definitely tubes to be reckoned with when they are run at the higher voltages.

It even satisfies power freaks like 5687

[909]

Are you going to give us some visual stimulation? Or does it look like a regular MPX3, except the different tubes?

What does SE mean? Special edition?

[PFKMan23]

Are you going to give us some visual stimulation? Or does it look like a regular MPX3, except the different tubes?

What does SE mean? Special edition?

Most of what makes an MPX3 SE what is is goes on one the inside (wiring it and such so that the tubes are biased higher voltage and current wise). The tubes used are essneitally the same tubes that can be used in a regular MPX3, but after hearing them in a "regular MPX3" I must say with the higher bias they sound alot better which is what we're going for, I think. Nothing really special to look at but here are 2 pics I took just quickly:

The second pic shoes the votlage switch which is the key to where all the majic hapens and how I can transform my amp

[Gabe Logan]

There it is!! That's my amp right there baby!

Now RFKMan23 on that second pic is a smaller knob,now does that allow the voltage switch?

edit:just realized what you wrote under the pic.

[909]

I like the look of the black Singlepower chassis. It does look like a stock MPX3. I think the finish and streamline look is really tight. But based on pics and then how it actually felt when I picked it up it was somewhat deceptive to me because I was expecting it to weigh a lot more. All the weight is in the power supply and the rest of the chassis feels so light.

That tube in front looks like a Sylvania 6SN7 metal base tall bottle from WWII. If it is I got one of those in my EC2A3. Great tube.

When I had the MPX3, I thought the right NOS tubes made all the difference in the world. I really didn?t like the stock electro harmonix tubes at all. I thought it extremely limited the amps full potential to such a degree that it wasn?t even worth using them.

Congrats! That's a really nice set-up.

[Rob N]

When the 6BL7's are run at higher voltages is the soundstage greater than with 6SN7's?

[Guest sacd lover]

When the 6BL7's are run at higher voltages is the soundstage greater than with 6SN7's?

I think so. I have only tried them in my Supra 392 so far though. The 6bx7gt is maybe even more open sounding because the 6bx7gt has a leaner tonal quality. Rob you sent me a pm and I have some extra 6bx7gt's. I need to go through my 5687's and see what non Raytheon's I have in any kind of quantity.

[Rob N]

It it essential to run the 6BL7 at the higher voltage?

What does it sound like at lower voltages?

[tkam]

Don't feel like starting my own thread yet so heres a pic of my slightly different than stock Slam PPX3 that arrived on saturday:

[aerius]

When the 6BL7's are run at higher voltages is the soundstage greater than with 6SN7's?

Hard to say, but in general I think they do. I've only heard a couple types of 6BL7's and I haven't heard the super-duper 6SN7's (eg. TS roundplate, '52 Sylvania) yet so I can't make a definitive statement.

If run at lower power levels, they don't really open up and end up sounding more like a GE 6SN7GTA than anything else. Not bad, but not great.

[Guest sacd lover]

Don't feel like starting my own thread yet so heres a pic of my slightly different than stock Slam PPX3 that arrived on saturday:

WOW! .... nice. I always wanted a Singlepower with a plitron transformer. Maybe someday?

[tkam]

Hehe . I'm sure you'll get one someday. I should get my octal adapters today or tomorow then I'll give a pair of 6bl7gta's a shot as the output tubes. The voltage is set higher than the stock 300V on my amp, doesn't seem to affect the 5687s much although it wouldn't surprise me if it'll knock some hours off their lifetime. The increased voltage should be great for the bl7gta's though

[Guest sacd lover]

Hehe . I'm sure you'll get one someday. I should get my octal adapters today or tomorow then I'll give a pair of 6bl7gta's a shot as the output tubes. The voltage is set higher than the stock 300V on my amp, doesn't seem to affect the 5687s much although it wouldn't surprise me if it'll knock some hours off their lifetime. The increased voltage should be great for the bl7gta's though

He is running my 5687's at 350 volts on my SLAM SE. He told me they should bias fine in my Supra 392 but I like the 6bl7gta's so well I never put them in. You are fine as long as the plates dont turn red.

[tkam]

Yeah they have been fine so far, the amp was on about 8-10 hours every day over the weekend with no problems at all.

[hirsch]

It it essential to run the 6BL7 at the higher voltage?

What does it sound like at lower voltages?

I haven't upped the voltage of my single-ended SDS, but am able to run 6BL7GT's just fine on the outputs. However, Mikhail altered the bias so that the tubes are being pushed hard. Also, I use an adapter to put a 5687 in the driver position. This seems to bring out the low end of the R10 a bit better than 6SN7's with no loss of detail or space that I can hear.

[909]

I completely missed/didn?t realize the different tube selection going on with this amp. :'(

Does the higher voltage result in a shorter tube lifespan because it is being driven harder and hotter? I remember the stock MPX3 ran so cold except for the tubes. It was surprising to me at the time being the second amp I'd ever listened to especially in comparison to my time with the Raptor.

[PFKMan23]

ok to address a few things...

No it isn't essential to run the output tubes at the higher bias and voltage. HOWEVER... IMO they do sound alot better when run at the higher voltage. In the case of the BL7GTA, they actually make the tube sound good because running at the standard/lower voltage, they are absolutely horrible. In the case of the BX7GT and the B L7GTA, they warm up quitea bit and do come alive.

And yes it does decrease the life of the tubes, but we're talking like 8k hours vs. 10k hours so...

[tkam]

Voltage and current bias need to be bumped up a bit . Oh yeah and some 5687-octal socket adapters so you can pop in some 6bl7's.

[PFKMan23]

would my regular transformer be able to handle the higher bias?

Probably not. I'd get atleast a MPX3 transformer just to be safe.

[KenW]

$%*&^#@......another temptation to upgrade! These sites are killing me! My slam is just a baby. Someone tell me it's not worth the trouble to send it back for this upgrade.

[909]

$%*&^#@......another temptation to upgrade! These sites are killing me! My slam is just a baby. Someone tell me it's not worth the trouble to send it back for this upgrade.

The upgrade option is a hauntingly good idea....

[Gabe Logan]

$%*&^#@......another temptation to upgrade! These sites are killing me! My slam is just a baby. Someone tell me it's not worth the trouble to send it back for this upgrade.

No i wont tell you to send it back for an upgrade.But what i WILL tell you is keep the SLAM as is and get this newer one on top of it

[tkam]

And you guys thought the slam looked funny with just the plitron.....

Those are the 9-pin to octal socket adapters with GE 6bl7gta's.

[Guest sacd lover]

And you guys thought the slam looked funny with just the plitron.....

Those are the 9-pin to octal socket adapters with GE 6bl7gta's.

I like the plitron look. Those socket adapters atleast look like they grip the socket well. Anytime you go small to large the appearance can look unusual. Now how does the amp sound with the 6bl7gta's? 9 pin mini to 9 pin mini would likely look

[tkam]

Well the soundstage is larger compared to the 5687s but that was expected. So far they sound pretty nice . Btw I'll take some close-up shots of the adapters later today as I know you wanted some detailed pics of them.