It Lives!

[4krow]

Man, I shoulda been reading these Stereomore posts a long time ago. There is a lot of info here. I have been reading the Quickie posts and a few others. I will add this to my lisp,  heh he couldn't resist.

[Paul Birkeland]

Hello Mike,

My first suggestion would be to install all of the factory parts (parallel feed capacitor and 0.1uF interstage coupling capacitor), then let the amp burn in for 100 hours.

At that point, you can have a baseline for the performance of the amplifier.

The bass response differences may have to do with the feedback and damping of the other amplifier, but there isn't a good way to know when the amp isn't stock.

-PB

[Mike B]

I think I'll leave it alone -

I can tell you that I'm not going to remove $80 worth of capacitors so I can solder in 8 bucks.  The sound this amp makes now is the best I have ever heard in my house.

As mentioned, it's no biggie.  I just use a little more "fill", and I really mean a little.  I have a 10 inch Dayton DVC in a 40 liter sealed box.  A little plate amp drives one coil and the other coil I have connected to an LPad wired as a rheostat.  I can vary the loading from open circuit to 3 ohms.  I turn down the load and increase the sub level until I can just hear it.  Then I increase the loading until is becomes seamless.  Works really well.

[Paul Joppa]

Weak or lifeless bass is usually perceived before a cap gets broken in.

Generally speaking, a smaller parafeed cap will result in a higher bass rolloff frequency but greater power handling (gets luder before clipping) in the bass, with the opposite effect for a larger cap. But it does interact strongly with the particular speaker. If you still have the original 3.3uF cap, you can parallel it with the 2.5 to test the effect - but don't make any judgements until the caps are broken in and the performance is stable!

[Mike B]

Cool, sounds like a plan.

It doesn't have a hundred hours on it yet, I would say about 50.

I'll let it go to at least a hundred and then solder some clips to the Solen and parallel the stock cap.  That will be ~6 uF, so I'll make sure to turn the volume down before I power up.

[Mike B]

New Tubes!  A perfectly matched pair of electro-harmonix gold grids.

Yeah Baby!  Has all the detail of the Sovtecs w/o the harshness.  I was using a 2 dB treble cut that I have now removed.

I also tried a gold lion 12AT7, but it wasn't as good as the first replacement an NOS Valvo E180CC.  That tall skinny tube is just so wonderfully clear.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ffarm9.staticflickr.com%2F8400%2F8986852223_53f98ab854_o.jpg&hash=37464621142797f99194fcbff4a8812471eba1eb)

Love those white ceramic bases too -

[Mike B]

I tried a couple of Full Music mesh plates.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ffarm6.staticflickr.com%2F5521%2F9062349487_678fdb27e6_o.jpg&hash=7dff6f0582e6129d6f536bd6dce389d300501270)

Don't they look nice?  Those big bottles.  Those glowing cathodes visable through the plates.

They are back in the box.

Sounded weak.  I put a gold lion 12AT7 in and that helped a bit, but not even close to the glory of the EH golds and the Valvo.

Not everything that is more expensive and looks better sounds better.

[galyons]

For how many hours did you burn in the tubes?  Generally take 50-100 hours to get to the base sonics.

Cheers,
Geary

[Mike B]

I couldn't wait that long.

They actually sounded good the first day after I put in the Gold Lion.  Even better when I turned them off after 5 hours.

The next day they sounded like crap.  About a 2 dB balance problem. 

So I thought I'd do a hum re-balance and found that 1 tube wouldn't go below 6 mV.  Was 3 mV the day before.

That's when they went back to the box.

I don't think these tubes are rated for SM plate voltage.  They test at 250.  They say 300 max and SM is at 380.

Dunno.  They look good, but they do not sound good.  A complete waste of $300.

[earwaxxer]

  A complete waste of $300.

Been there, done that.

[galyons]

I don't think these tubes are rated for SM plate voltage.  They test at 250.  They say 300 max and SM is at 380.

I am not an expert on this, but I think the plates are only seeing closer to 300vdc.  I don't have an SM, I have Paramours, but similar circuit.  The plate gets about 365vdc and the heater is biased with about 60vdc, so the net voltage is approximately 305vdc.  Hopefully the real experts will chime in.

Cheers,
Geary

[Paul Joppa]

Yes, the nominal plate to cathode voltage in Stereomour is 300v.

The specs for most modern versions of old tubes such as the 2A3 are usually exactly the same as the original RCA tube, hence the 250v test point and 300v spec maximum. Some brands will note higher capabilities if they are there, but often outside the formal specs. I believe as an extreme example the JJ 2A3-40 can handle 450v.

[Mike B]

I am sticking with the electro-harmonix 2A3 golds.  Spec is 450V max.  Nice headroom -

I am sticking with everything as is, the sound gives me tingles every nite.

Not messing with the parafeed cap either, it's staying at 2.7 uF.

I did find out what clipping sounds like and it ain't good.  Gonna give myself plenty of headroom there too.

I love my Stereomour and if it works don't fix it -