[heliosphann]

Tungsten say what???

 

[UsoppNoKami]

+1: Gen 2 MC glass / gold would be cool...

 

[LCMusicLover]

Hey gents, I've been getting questions about using 12AX7s or 12AU7s in the Platinum. I highly recommend that you do not do this. These tubes do not fall within any operating region that the Platinum is designed to handle.

Please keep in mind that the LP expects to see 6922s or equivalents (meaning very close operating points). It isn't reasonable to expect that it can take an arbitrary tube type and make it work. While it is not visible to you, what the LP has to do to bring some of these tubes into operation is outside of its safe operating area. As long as you stick to properly operating 6922s it will remain well within its safe operating regime.

Near arbitrary tube rolling is what the Liquid Glass was designed to do.

Just to be clear, all of these:

6922
ECC88
E88CC
E188CC
CCa
PCC88
7308
CV2492
6DJ8

are OK, correct?

 

[Wes S]

Just to be clear, all of these:

6922
ECC88
E88CC
E188CC
CCa
PCC88
7308
CV2492
6DJ8

are OK, correct?

All but the PCC88/7dj8 are good. My next post has Dr. Cavalli's response to pcc88/7dj8.

CV2493/E88CC-01 is another ok one.

 

[Wes S]

7DJ8 will be running 1V low on its heaters which will cause the cathode to run cooler which will reduce its emission. It may not give a good result. I'm not sure how this sub can be used in other products without significantly affecting the sound unless there is some internal compensation built in to the product. But I know that people are doing it.

I can only recommend that you all stay with 6922 or exact equivalents.

I found post about pcc88/7dj8.

 

[Wes S]

You must be a Texas boy if you have a gift certificate to Luby's. There is one not too far from me.

As for new stuff, just hang in...............

I am saving my pennies, starting now. . .

 

[Serge Bernamej]

That sucks, if it happend to me i'd be real tempted to sell my replacement unit after verifying everything worked. Bummer man, as stated it should not be an issue getting a replacement unit. Monoprice is a big company with a decent track record.

I have to say that they see to be having a great service right now. Offering a refund. But I love the amp !!! Tempted to try A THIRD TIME. But very hesitant as you might guess.

 

[Serge Bernamej]

Have any of the MP customer service people tried to diagnose the problem with you? It is extraordinarily unlikely that two amps in a row would fail like this. When you say they are not starting, what exactly are they doing?

I suspect they did not send me a full replacement unit but repared it or something (change the power brick?) because it’s the same problem that came up. The amp is just not starting up, no light nothing. With or without tubes. And when I start it up the brick flashes the green light on and off...it blinks.
Any recommendation for a similar sounding amp (even if SS) in that price range? violetric?

 

[TK16]

Just to be clear, all of these:

6922
ECC88
E88CC
E188CC
CCa
PCC88
7308
CV2492
6DJ8

are OK, correct?

PCC88 tubes work at 6.3v and Brent Jessee mentions they will last longer running at 6.3 spec 7v. vs ECC88.

 

[runeight]

PCC88 tubes work at 6.3v and Brent Jessee mentions they will last longer running at 6.3 spec 7v. vs ECC88.

Even though the pcc88s will operate at 6.3V (because their cathodes do heat up) does NOT mean that they can be biased properly by the LP. In order to get the cathode current it needs to see from a cooler cathode the LP will have to increase the plate voltage. The servo can do this but will max out at some point and could be out of its safe regime.

Remember that the LP is an embedded hybrid. It is DC coupled so there is no blocking capacitor to separate the tube's operating point from the rest of the SS circuitry. If the tube's op point is far from 6922 it will skew the rest of the circuit, possibly too much. It is not the same as many other tube hybrids and you cannot make the same assumptions about swapping tubes.

MHO is that it is risky to do this without actually measuring what's going on inside the LP with this tube. It maybe be ok, it may not. And, no, not me, I've got other amps to design.

 

[LCMusicLover]

...And, no, not me, I've got other amps to design.

Yes you DO sir!

Thanks for the response.

 

[jb77]

@runeight What about 6n23p tubes? Can they be used safely in the LP?

 

[Odin412]

I've got other amps to design.

Excellent - many of us are waiting to see what comes next!

 

[jb77]

@runeight What about 6n23p tubes? Can they be used safely in the LP?

Just wanted to make sure @runeight sees this

 

[Luckbad]

Just wanted to make sure @runeight sees this

No need to quote yourself from earlier in the day. Do a few minutes of research and you will find that they are exact equivalents.