Arrgggh... MPX3 SLAM transformer configuration compatibility?
Jun 25, 2008 at 1:38 AM Thread Starter Post #1 of 19

moredes

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I'm driving a set of Denon AH-D5000 cans (the infamous "low impedance" hurdle). Just when I settled on a Mullard ECC32 and two Tung Sol-D 5687's, I got bit; I gotta stop reading this forum...

I'm ready to try acquiring a 2C51 adapter and pairing it with a couple of 6BL7GTA's. However, I'm unclear on the transformer requirements for my amp.

Is it safe to run a 2C51 / 6BL7GTA combination in an MPX3 SLAM, or does it need the SE upgrade for that? (somebody say,"no, it ain't safe" and save me from myself)

Here's another question---can anyone compare their experiences with these specific combinations (Mullard ECC32 - TSd 5687 vs. 2C51 - 6BL7GTA) in an MPX3 SLAM? That is to ask, is there a good chance that there'll be an improvement with the 2C51 combination?

Thank you.

I should pro'lly just call Mikhail. But then I'd open a real can of worms... what, I can upgrade?? sure, where's the credit card?
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Jun 25, 2008 at 2:51 AM Post #2 of 19

nikongod

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It MIGHT be safe to run the 6bl7, but probably not. the heater current is what kills the option, not fun.

IME, the 6bl7 is better at almost EVERYTHING than the 5687. The 5687 might have a SLIGHT edge for grados depending what kind of sonic mood you are in, but the denons being BOTH current and quality dependent do better with the 6bl7. I dont always like the denons with the 2c51 though: too bright for me. A good 6sn7 & 6bl7 rocks the party.

I would call mikhail, or just wait for amp with the bigger transformer to come up for sale used.

edited: It IS safe to run a 2c51/5687 in the amp you have, no doubts there.
 
Jun 27, 2008 at 12:12 PM Post #4 of 19

nikongod

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Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif
Would someone please explain what is the Slam and the SE upgrades? Thanks.


slam means that the amp has the adapters for 5687, or in rare cases that it ONLY has 5687 as output tube. the ppx3 slam is a sweeeet option although rare. MPX3 with 5687 as the only output tube is also an option, but even less common than the ppx3-slam. most "slam" amps use the adapters.

5687 tubes give a little more power than 6sn7 or 6cg7. the upgrade allows the use of the stock MPX3/PPX3 transformers, so is quite an easy addition.

SE means any number of things depending who is saying it. Originally it meant that the mpx3 had the supra transformer, and was later applied as well to a supra with the high voltage switch. I have seen it used to refer to an MPX3 with stock transformer but stepped attenuator (What?) but I dont think that is correct at all.

the SE upgrade to an MPX3 allows the running of 6bl7/6bx7 tubes. very nice. the HV switch allows for a slightly different sound and some more power still when running 6bl7/6bx7. i have posted elsewhere that the ONLY advantage to the supra transformer was in the heater power, but on firther thought i dont think this is correct. the supra transformer allows for the use of an even less efficent high-voltage supply (as if to think you could get less efficent than an amp that sucks 100W from the wall to only put less than 1/4W into the load in average use...) that has some solid sonic benefits.

Someone should think of a cute name for adjustable bias.

adjustable bias allows for smaller adjustments to the texture of the amp. on my amp at least it changes the texture from fairly hard to fairly soft. its pretty cool, and accomplishes some of the goals of the "texture knob" without feedback.

the texture knob is so named because of tis most major function: adjsuting the "texture" of the amp. It takes a PPX3 from tis standard somwewhat stereotypical tubyness to a much harder and crisper sound at the spin of a knob.
 
Jun 27, 2008 at 5:33 PM Post #5 of 19

mrarroyo

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
slam means that the amp has the adapters for 5687, or in rare cases that it ONLY has 5687 as output tube. the ppx3 slam is a sweeeet option although rare. MPX3 with 5687 as the only output tube is also an option, but even less common than the ppx3-slam. most "slam" amps use the adapters.

5687 tubes give a little more power than 6sn7 or 6cg7. the upgrade allows the use of the stock MPX3/PPX3 transformers, so is quite an easy addition.

SE means any number of things depending who is saying it. Originally it meant that the mpx3 had the supra transformer, and was later applied as well to a supra with the high voltage switch. I have seen it used to refer to an MPX3 with stock transformer but stepped attenuator (What?) but I dont think that is correct at all.

the SE upgrade to an MPX3 allows the running of 6bl7/6bx7 tubes. very nice. the HV switch allows for a slightly different sound and some more power still when running 6bl7/6bx7. i have posted elsewhere that the ONLY advantage to the supra transformer was in the heater power, but on firther thought i dont think this is correct. the supra transformer allows for the use of an even less efficent high-voltage supply (as if to think you could get less efficent than an amp that sucks 100W from the wall to only put less than 1/4W into the load in average use...) that has some solid sonic benefits.

Someone should think of a cute name for adjustable bias.

adjustable bias allows for smaller adjustments to the texture of the amp. on my amp at least it changes the texture from fairly hard to fairly soft. its pretty cool, and accomplishes some of the goals of the "texture knob" without feedback.

the texture knob is so named because of tis most major function: adjsuting the "texture" of the amp. It takes a PPX3 from tis standard somwewhat stereotypical tubyness to a much harder and crisper sound at the spin of a knob.



Thanks, I asked because in my case I have adapters to use the 5687 in my MPX3. I also had Mikhail install the Supra transformer (800 volts versus 600 volst on the stock transformer). At the same time I had him replace the two (2) 650 uF each power caps with two (2) 2,400 uF each caps. So it sounds like I have both the slam and the se mods.
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Jun 27, 2008 at 6:28 PM Post #6 of 19

Frihed89

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Do you have a high-low voltage switch? This feature is not implemented by a heftier power supply or output transformer. These would just make it easier to handle the high voltage...but that needs to be created somewhere to get up around 450-500 V.

I think.
 
Jun 27, 2008 at 7:31 PM Post #7 of 19

mrarroyo

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Quote:

Originally Posted by Frihed89 /img/forum/go_quote.gif
Do you have a high-low voltage switch? This feature is not implemented by a heftier power supply or output transformer. These would just make it easier to handle the high voltage...but that needs to be created somewhere to get up around 450-500 V.

I think.



No, I do not. I believe that it is needed if you plan on using tubes like the 12SN7
confused.gif
which I do not plan on, so did not ask for it.
 
Jun 27, 2008 at 11:21 PM Post #8 of 19

tom hankins

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Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif
No, I do not. I believe that it is needed if you plan on using tubes like the 12SN7
confused.gif
which I do not plan on, so did not ask for it.



If you plan on using the 6bl7 tubes you will have a switch that changes the voltage from 300 to 400. The 6 to 12 volt conversion is different, and would be something seperate.
 
Jun 28, 2008 at 2:55 AM Post #9 of 19

sacd lover

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Quote:

Originally Posted by moredes /img/forum/go_quote.gif
, I'm unclear on the transformer requirements for my amp.

Is it safe to run a 2C51 / 6BL7GTA combination in an MPX3 SLAM, or does it need the SE upgrade for that? (somebody say,"no, it ain't safe" and save me from myself)

Here's another question---can anyone compare their experiences with these specific combinations (Mullard ECC32 - TSd 5687 vs. 2C51 - 6BL7GTA) in an MPX3 SLAM? That is to ask, is there a good chance that there'll be an improvement with the 2C51 combination?



You can definitey use the 2c51/ 6bl7gta combo. Why? The heater current required for the 6bl7gta is 1.5 amps per tube = 3.0 amps, plus the 2c51 at 0.3 amps = 3.3 amps. The standard MPX3 transformer can deliver around 5.2 amps; more than enough. I have personally used this combo and left the amp on for > 24 hours.

I love the 2c51/ 6bl7gta combo with my low impedence Alessandro MS2's. The only problem you might have with the combination is hum if your source has to much gain.
 
Jun 28, 2008 at 2:26 PM Post #10 of 19

mrarroyo

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Quote:

Originally Posted by tom hankins /img/forum/go_quote.gif
If you plan on using the 6bl7 tubes you will have a switch that changes the voltage from 300 to 400. The 6 to 12 volt conversion is different, and would be something seperate.


Now I am confused. When Mikhail returned my MPX3 after doing a bunch of mods he sent me a pair of NOS Silvania 6BL7-GTA. If a switch to go from 300V to 400V is needed (do not have it in my MPX3) why would Mikhail send me a pair of tubes that I could not use?
confused.gif
 
Jun 28, 2008 at 2:42 PM Post #11 of 19

nikongod

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Quote:

Originally Posted by mrarroyo /img/forum/go_quote.gif
Now I am confused. When Mikhail returned my MPX3 after doing a bunch of mods he sent me a pair of NOS Silvania 6BL7-GTA. If a switch to go from 300V to 400V is needed (do not have it in my MPX3) why would Mikhail send me a pair of tubes that I could not use?
confused.gif



you can use the 6bl7 on either setting, it is not mandatory to have the HV switch to run them.
 
Jun 28, 2008 at 4:05 PM Post #13 of 19

moredes

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Thanks *very* much to you, Earl, and Nikon! I've been trying to call Mikhail, but no luck except his recorder, and it doesn't look like he returns calls.

Earl,

Is there a way to figure out beforehand if I should expect "too much" gain from my sources?

Thank you.
 
Jun 28, 2008 at 4:26 PM Post #14 of 19

tom hankins

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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
you can use the 6bl7 on either setting, it is not mandatory to have the HV switch to run them.


I would think he does not have the 400 volt option if he doesnt have a switch. They might work at 300 but i am wondering if they would sound better than the 6sn7s at that (300 volt)
setting?
They do not sound as good at 300 (6bl7s) as they do at 400.
 
Jun 28, 2008 at 4:54 PM Post #15 of 19

nikongod

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Quote:

Originally Posted by tom hankins /img/forum/go_quote.gif
I would think he does not have the 400 volt option if he doesnt have a switch. They might work at 300 but i am wondering if they would sound better than the 6sn7s at that (300 volt)
setting?
They do not sound as good at 300 (6bl7s) as they do at 400.



I agree that the 6BL7 sounds better with more volts on it
smily_headphones1.gif
BUT I think that for most cans it sounds better than a 6SN7 even on the low voltage setting. For most headphones over 150 ohms, I prefer the 6sn7 to the 6bl7 on low voltage though.
Quote:

Originally Posted by moredes /img/forum/go_quote.gif
Thanks *very* much to you, Earl, and Nikon! I've been trying to call Mikhail, but no luck except his recorder, and it doesn't look like he returns calls.

Earl,

Is there a way to figure out beforehand if I should expect "too much" gain from my sources?

Thank you.



It is worth talking to mikhail, he is a cool guy to chat with even though it takes forever to get him on the phone.

This is a VERY subjective question, it gets tough. If you listen at a level similar to average conversation, they may have a little too much gain with a standard CD player output.

There was talk a LONG time ago of mikhail offering a reduced range stepped attenuator which started at a lower level, and ended at a lower level.
 

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