Stereomour capacitor uf upgrade question

[Sh7eleven]

I have 15 or so hours in the stereomour driving coincident triumphs, bookshelves rated at 91db, and I have immediately noticed a strange sound that I haven't heard out of these speakers before - bass.  It's not setting off car alarms in the neighborhood, but I can feel it in the couch and I am surprised by the clear presentation of bass that I couldn't previously hear with the Asl wave 8's. I can't wait till the caps break in some more.

At around 100 hours or so after all the components are mostly broken in, I'd like to try some upgraded caps.  As far as the values are concerned, I have read that a smaller uf value, say moving from the Parafeed 3.3 to 2.7, there would be a greater bass roll off but that it should sound cleaner and/or crisper? And larger values, moving from the 3.3 to 4.7 should have the effect of better extension? Am i correct? If that's so, what is the better match for me considering that I am using a bookshelves with no sub at the moment. I was thinking bigger is better but maybe not in the case of bookshelves that have a limited range anyway.

I'd also like to after a period of break in try bypassing the upgraded caps.

(P.s. thinking about the obbligato gold premium or Jantzen Z-Superior, they are my candidates because they seem to be in line with budget for the time being for replacing both parafeed and coupling cap and bypassing them.)

 

[2wo]

I suspect that for your situation, you want to go larger.

But consider, you could get 2 pair of the Obbligato film in oil, in both 2,2 and 4,7 for the price of one gold.

the oils are pretty good caps BTW, plenty good enough to see where you want to go Bass wise...John 

 

[Sh7eleven]

2wo - great advice - got two pair film in oil, 2.0 and 4.7 for the price of one gold. Just gotta get some more hours on the stereomour so I can

Grainger, the formula is a leap for me. I've seen it written out elsewhere on the forum, but I'm not sure how to use it.  Teach me to fish - what does the formula help me determine - the ideal capacitance for my application? What is the cross-over frequency produced by a certain cap value? (I have a limited understanding of what crossover frequency means so I realize that my last question might be non-sense. I only know it in the context of building a crossover to send different frequencies to a sub, woofer or tweeter.)

I assume I'm looking to determine C -capacitance, so I go find the crossover frequency specs for the coincidents, and the resistance, primary impedance of the output transformer of the stereomour, and then using those values I ---- scene missing, math happens ---- getting the optimal value of the capacitor for my for my application. 

If there is Too much to explain to bring me up to speed for a posting here, then if you could kindly point me in The direction of a source of self education, I'd be much obliged.

 

[Grainger49]

Sean,

I removed the above formula as it was not taking into account the plate choke and output transformer.  Sorry, I don't want misinformation to remain out there.

 

[Sh7eleven]

I put in the 4.7 uf obbligato film-oils caps this morning, replacing the 3.3 Solens. Still have the stock .1 uf electrolytics in place - they will be replaced shortly. In the right channel tweeter I hear a hiss with a kind ripple sound. In the left channel, I hear absolutely nothing from the tweeter. The hum from both woofers remains unchanged from original build. I can hear it if my ear is about two inches or less from the woofer. 

The hiss ripple from the right channel tweeter is new since I installed the new caps and is at times audible during music, usually louder or busier sections of music.  The hiss ripple sound is continuous when no music is playing, and is audible only if my ear is around the same two inches or less from the tweeter.

The stereomour has about 75 hours of music on it and the tubes have probably 85-90 hours with power.

So is what I'm hearing:

        - the cathode forming that couldn't hear before with the Solens but I can hear now with a better cap? (Though I think I'm close to the 100 hour break mark for the 2A3's)

        - typical noise from a cap breaking in? I put about 12 or so hours on them today, should I expect this noise to subside with further break in? I know I should give them about 100 hours to break in from other posts.

 

[2wo]

Well, you could just wait and see if it improves.

I would inspect and re-wet the cap connections. Also check the nearby connections. Going in to work on something, can make an iffy connection even iffy'er.

Next I'd swap the caps...John 

 

[Paul Joppa]

Grainger's formula is for acircuit with one resistor and one capacitor. The parafeed output has a plate choke (inductance) and an output transformer as well.

My calculation for a "good" value of pareafeed capacitor is C=2*L/(R*R) where L is the plate choke in henries, R is the transformer primary impedance in kOhms, and C is capacitance in uF. (That's 2.5uF in a 2A3 Stereomour.) There is no way to define, much less calculate, a true optimum without involving much more complicated models, including the impedance and response of the speaker - that's why I say anything from half to twice the value in my formula is a reasonable candidate.

It's a tradeoff between maximum clean power and deepest bass extension at lower powers, so the music you use and the speaker efficiency are involved. By far the best approach is to try a few values in your system with your music. I'd get a few Solens like the one that comes in the kit, so that only the cap value is varied, and spring for a boutique cap after you have chosen a value.

 

[Dr. Toobz]

I'm about at the same place with upgrading my Stereomour capacitors, so I appreciate the formula. The wrinkle here is that unlike the OP, I'm using 45's as my output tube, which uses the same transformer primary impedance as the 2A3 (since there's only one!), 4k, but L increases to 40H. That calculates out to 5uF. Does this explain why the 45's seemed just a bit bass shy when I hooked up headphones to do some testing? I'd be amazed if 1.7uF really made that much of a difference in bass extension, but what do I know? Maybe its just the 45's themselves.

Are the Solens really that bad compared to other products where there will be a big difference when going to say, an Obbligato?

 

[galyons]

I recently upgraded to my Paramour 45's w/PT2 to MQ EXO-45 and BCP-15.  After a bit of swapping and listening, I put in 2.65uF Vitamin Q PIO's.  No issues with bass on my Electro-Voice Sentry IV's. (they don't have much extension below 50Hz, but the quality and definition is wonderful.)    I am a PIO cap guy, and these Vitamin Q's strongly reinforce that bias!!  Also tried 3.3, 4.4. 4.7 uf.  The 2.65uF caps were best overall and really fine in terms of bass quality, not necessarily extension.  I really heard no difference in bass extension between the values.  IMO, this is a testament to PJ's  "1/2 to 2X" range on the caps.

I am simply amazed at the huge improvement from the MQ iron.  I know it is  more than just the iron with choke on PS, etc.  But I am truly thrilled with the amps!!!

Cheers,
Geary

 

[Paul Birkeland]

Are the Solens really that bad compared to other products where there will be a big difference when going to say, an Obbligato?

Solen makes some capacitors for Obbligato...

 

[srhombeus]

Hi,i dont wanted to open a new topic.i am using my stereomour with mundorf supreme at coupling caps and parafeed caps.Now i want to make an upgrade with rike audio s cap.Which place would be more improvement,coupling caps or parafeed caps ?  i think you can say both,but for now it would be really expensive to change them all at the same time.  Thanks.