Cap Upgrade - Stereomour II

[amritdesai]

Absolutely love my stereomour unit!

Will going with a 4.7uF 630VDC in place of the stock 3.3uF have any influence on bass? I've read some threads on the subject - curious if the 4.7uF is appropriate. I am driving fullrange coaxial speakers and would like to improve bass extension.  I think I'm going with the ClarityCap MR series. Thoughts?

Amrit

 

[Doc B]

4.7 will be fine and it might or might not create a perceivable difference in the amps LF response. But don't expect making that cap bigger to compensate for your full range speakers' low frequency rolloff. Fullrangers just don't go that low.

 

[amritdesai]

Thanks Doc. I think I'll get both and play around with them. I'll make sure to report back my findings.

Amrit

 

[Doc B]

If you have the right test gear (signal generator and some way to measure frequency response) you could conceivably find a value by trial and error that might create a bump in the LF response of the amp that hits right where the speakers roll off. That could theoretically extend the bass of the speakers a wee bit. But there are a lot of factors to measure and consider when trying to get the best bass response, you  can't usually just throw a cap in and listen to tell if it is working they way you hope it is. The design of the speaker cabinet has a dominant influence on the LF rolloff, and in the end the response in room might negate any advantage gained on paper or by measurement. As long as you keep all of this in mind so that you don't make any inaccurate assumptions about the end result I see little harm in giving it a try.

 

[drewh1]

Nice choice of wood for the base! I love that big knot.

 

[Paul Joppa]

In theory (which assumes an 8 ohm resistive load in the deep bass 10Hz-40Hz) region, the larger cap will improve the extension but reduce the available power in the deep bass region. My nominal optimum, which is my take on the best compromise, would be 2.5uF. But anything from half to twice that is pretty reasonable - the effects are modest enough that listening is a better guide than theory ...

 

[amritdesai]

Drew, Thanks for your kind words. The Steremour II is a beautiful piece of equipment!

I installed the 4.7 uf Calirty MR caps yesterday morning. I wasn't expecting them to be so big! They actually fit quite nicely and the wires were very stiff and thick so no further reinforcement was needed. I also replaced what I understand to be the stock .1 uf coupling capacitor with a .1uf Clarity MR 630Vdc having read about the small sonic benefits in previous posts on the forum.

I replaced also the stock potentiometer with a 100K alps and bypassed the switch and balance control. In the process, I replaced the CAT 5 wire using some audioquest RCA cable from a previous project.

These are the changes I've made to the stock Stereomour II unit after listening to it for around 150 hrs.

 

[amritdesai]

For the past month the Stereomour has brought me so much joy - music has never sounded so good in my living room. But I've been having issues with imaging - the image was always shifted heavily to the right. I've been having to use the balance control more than I would like to center the image. I checked every component of my system, switching my DAC, cables, and speaker position - I even considered my hearing as the source of the issue.

I also noticed when switching sources the left channel would sometimes go out - I would have to toggle the switch slightly to get both channels to work. The connection was kind of sloppy in two of the three positions - maybe the switch was the problem? I don't know.This is the primary reason I decided to re-wire the amp without the switch.

I replaced the volume pot while I was re-wiring the signal path. I'm happy to say it went pretty smoothly and I think the Alps feels well made for $12. While I had everything out I installed the Clarity MR capacitors and was able to resolder and check some connections in those areas. The amp tested well with no issues!

WOW!The sound of this amp has dramatically changed. What I noticed immediately, was the imaging. The music had a rich spatial quality that I was not expecting. Voices were now dead center of the image. The soundstage was incredible - I was absolutely blown away!

I'd like to imagine the switch in my stock unit was the source of all these issues. Or maybe the volume pot wasn't great which is why I was having to adjust the balance controls so much. I'm not sure. I'm grateful though, having the resource of this forum to resolve these questions.

I'll have to report back on the differences made by the Capacitors - Either way, there is some mindblowing music coming out of my speakers and I'm having a blast with this project!

 

[Paul Joppa]

Just a note - sometimes a cap will sound worse at around 10-20 hours, before it starts sounding better. Give it 50-100 hours before making judgements.

 

[amritdesai]

I've had a few days to evaluate the capacitors. Without question there has been a change in sound - in particular the bass which at first was more snappy, punchy, and more resolute in comparison to the stock stereomour unit. After about 15 hours though, the bass has become overwhelmingly boomy, bloated and muddled.

I was also initially very impressed with the extension of the upper end - a level of clarity and brightness I was not expecting with the 4.7uf parafeed cap. But now, the sparkle is gone and all the upper resolution has been removed from the music, overwhelmed by a boomy 60 - 100 hz bass- not exactly a tonal improvement. I did not realize that parafeed cap would have such an influence on the sound output.

I'm still trying to understand this breaking-in phenomena especially as it relates to capacitors. Paul and many others on the forum are spot on when they say ^^ it gets worse - I just hope it gets better. With that said, the soundstage has improved tremendously and any issue I had regarding balance is gone - I'm very happy about this. I'm not sure what is going to happen to the bass as these components settle down but there is LOTS of it. I'll have to reserve judgment about the lack of detail, texture, and precision of the upper end. Currently, it just sounds underwhelming and weird. 

Amrit

 

[amritdesai]

Amateur Hour  8)

I was switching out RCA interconnects last night while music was playing and realized that sound was coming from both speakers having only the left RCA plugged in. In other words, for quite some time I've been listening to my stereo in mono?

The good news - this explains the funky sound.

I'm going to switch back to the stock potentiometer as I triple checked the wiring to the Alps pot and everything looks fine.

I must have a signal bridge somewhere in the wiring. Assuming the pot is not the issue are there any other components that have both signals going to them? Any ideas?

Thanks, Amrit.

 

[Doc B]

Maybe the input selector is miswired.

 

[amritdesai]

Even though it is still attached the aluminum plate, the switch has been bypassed. The signal wire coming from the RCA inputs go directly to the potentiometer.

 

[Doc B]

We can't really make any assumptions if the build instructions were intentionally deviated from. We can only make suggestions based upon the assumption that that the kit is built as we describe.

In this situation the best we can offer is generalization. If the signal is coming out of both channels from only a left channel input you must have signal hot wires of both channels connected together somewhere. The best approach is probably to compare the signal path of schematic with the actual wiring. Start at the inputs and see if you can spot the places where such a mixing of L and R signals could occur. Flipping the ground and the signal hot connections at the volume pot could cause this.

 

[amritdesai]

Thank you Doc. I'll take some time tonight and will look more thoroughly at the signal path and the wiring at the pot - they might be flipped.

 

[amritdesai]

I flipped the connections at the RCA inputs which fixed the issue.

Thank you Doc!

Things are sounding better than ever!

 

[Paul Birkeland]

With the signal carrying wire, it looks like you have black wired to the center post of each RCA jack, and it looks like you've grounded those connections up at the pot.  If this is true, this is backwards. 

 

[amritdesai]

Yes, that was the issue - it was wired backwards. 

Everything sounds great. Really happy so far. Thank you for your help.