Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: denti alligator on June 03, 2016, 07:59:52 AM
-
Well, I'm still waiting for it to ship, but I thought I'd start a thread anyway, since I want to ask about ohms. I'm using a pair of Klipsch Forte II horn speakers. I'm assuming I would want to wire the Stereomour for 8 ohms. Is that right?
This will be my first major upgrade since getting the S.E.X. 2.0 back in 2010 or so. I'm pretty excited. I think I will continue to use the S.E.X. as a headphone amp until I get some old B&W speakers set up upstairs, then I'll probably swap it out with my Crack in the main listening room. My plan is to use the Steremour switching capabilities and output to the Crack with a separate set of RCAs.
-
Have you looked up the nominal impedance of the Forte II?
-
Apparently:
99dB sensitivity, 8 ohm nominal impedance, 4 ohm minimum
Then there's this file, which I don't quite know how to read:
https://community.klipsch.com/index.php?app=core&module=attach§ion=attach&attach_id=97104
-
The dip to ~3.8 ohms in the deep bass worries me a little. I suggest you try it at 4 ohms as well as 8 ohms, and compare them.
-
Thanks, Paul. Can you explain why it worries you, and also what differences I should listen for?
-
It's the damping factor. Most speakers are designed to operate best with an amp that has a very high damping factor; SETs usually have a DF between 2 and 4. This makes the response sensitive to variations in speaker impedance. Peaks when the impedance is high are limited, but notches when the impedance is low are unbounded.
In the Forte II graph, the biggest dropout would be in the bass where it drops below half of the nominal 8 ohms. There will be a smaller peak in the upper midrange where the impedance is high. Room acoustics are significant, especially in the bass, so sometimes just moving the speaker around will adequately compensate. That's why I suggested trying both options and listening.
-
Arriving today! Will see about posting pics as I assemble.
-
Good luck! Fun build.
-
I'm terrible with a drill, and even though I marked where I wanted the extra RCA jacks, they ended up elsewhere. Oh well, they'll be mostly hidden anyway.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi63.tinypic.com%2F116nqqu.jpg&hash=b2931359092231d6a2b5941f0f1b84227b3fe7f6)
Made a little more progress. Slowly building. Using Danish Oil on base. More of that later.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi63.tinypic.com%2F21cf7k1.jpg&hash=df98d2400ad806222ec477d6952d65a4a8ce1d4b)
-
What am I allowed to do to the plate chokes? I painted mine on the SEX, but I'd like to keep them simple here. Can I clean them with something?
-
You can burnish the steel channel frames with steel wool. I wouldn't clean or treat any other part of the choke.
-PB
-
Ok, thanks. One more question ... I'm waiting for a replacement of the 3.3uF cap, one of which came damaged. Is there a voltage range that is acceptable if I wanted to use another 3.3uF cap in the meantime?
-
630V or greater.
-
Thanks, and I'm assuming this cap can impact the sound quality, that is, if I go for "boutique" caps I should hear some difference?
-
You will be amazed at how good it sounds with the Solens.The design of the circuit is more important than the parts that go into it.
-
There is nothing wrong with Solen capacitors, i have used them in amps and speaker crossovers and they always work well. Boutique caps can sound different / better, but i would try the Solens first and go from there as it may better inform you of what characteristics you would prefer in a replacement capacitor.
-
Alright, I've used the extra leads (orange/blue) and wired them to an additional pair of RCAs, which I want to use to output to a headphone amp, while still using the inputs and switch of the Stereomour.
right RCA: orange solid (ground tab), orange striped (center lug)
left RCA: blue solid (ground tab), blue striped (center lug)
The other ends of these wires need to go to the center lugs A, B, C, and D of the selector switch, right? My question is: which goes to which? My guess: striped orange to A, solid orange to B, striped blue to D, and solid blue to C. But I'd like confirmation before I do this.
Thanks.
-
There is nothing wrong with Solen capacitors, i have used them in amps and speaker crossovers and they always work well. Boutique caps can sound different / better, but i would try the Solens first and go from there as it may better inform you of what characteristics you would prefer in a replacement capacitor.
I concur. The stock Solen caps in the parafeed position are pretty nice. It is however worthwhile upgrading the stock interstage cap which is also in the signal path. Its the one that is .1uf 630v and is brown in color. You dont have to spend a lot of money either. I've used these with very good results.
http://www.parts-express.com/audiocap-ppt-theta-010uf-600v-film-foil-capacitor--027-710 (http://www.parts-express.com/audiocap-ppt-theta-010uf-600v-film-foil-capacitor--027-710)
-
I was never a fan of those poly gum drop caps, i think they are Panasonics. The russian FT-3's are an interesting cap to try as they are great for detail, and very cheap. Money no object i would highly recommend the Jupiter wax caps, both for inter stage and output as i am yet to find another cap i like better.
-
Alright, I've used the extra leads (orange/blue) and wired them to an additional pair of RCAs, which I want to use to output to a headphone amp, while still using the inputs and switch of the Stereomour.
right RCA: orange solid (ground tab), orange striped (center lug)
left RCA: blue solid (ground tab), blue striped (center lug)
The other ends of these wires need to go to the center lugs A, B, C, and D of the selector switch, right? My question is: which goes to which? My guess: striped orange to A, solid orange to B, striped blue to D, and solid blue to C. But I'd like confirmation before I do this.
Thanks.
Bumping this question. Anyone know how to wire these rotary switches?
-
Have you had this amp up and running in completely stock form?
-
Have you had this amp up and running in completely stock form?
Not yet. I attached the wires already. We'll see how it sounds. If I have any troubles it will be easy enough to disconnect the four extra wires from the selector switch.
-
I think I see where you're going with this. Maybe you would be better off including a purpose built preamp in you're system. The way you're going now might degrade the performance of both the
S-II and the headphone amp.But how will you know if you haven't previewed the stock StereomourII?
-
I think I see where you're going with this. Maybe you would be better off including a purpose built preamp in you're system. The way you're going now might degrade the performance of both the
S-II and the headphone amp.But how will you know if you haven't previewed the stock StereomourII?
PB said this was the easiest way to go. I'm basically following his instructions. But he never explicitly said how to wire the new RCAs to the selector switch. I think I've got it, though.
As soon as I get my replacement caps I should be ready to go!
-
OK, I got some ClarityCaps to hold me over till the replacement Solens come. Build is complete. Here are the only resistance inconsistencies:
terminals 21/40 0.5
Note that I swopped out the good Solen cap with one of the CalrityCaps to make sure the caps weren't somehow throwing off resistance, but I get the same reading.
Any clue why these would be off?
-
Sounds like something is miswired. Post pictures, particularly of the areas around these terminals and the output transformers.
-
Here are some. I've wired for 4ohms speakers.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi67.tinypic.com%2Ffc740y.jpg&hash=85c02ceb5146bf854f5b117d2ccd24a564e89de8)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi65.tinypic.com%2F2f07m1l.jpg&hash=b4a9907c12db18ed1bc32fadaa53e69384a5cb34)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi68.tinypic.com%2Fouvea0.jpg&hash=d88d465b27b0d80650a3a585a039005f11c0eba4)
-
I haven't trimmed the leads on the cap here because I just switched it out to see if the ClarityCaps were the culprit.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi64.tinypic.com%2F33upch0.jpg&hash=7285a14f598f1c8a37f8ebb8735b86fe8a8583b8)
-
You have mixed up the primary and secondary wiring on your output transformers.
Refer back to pp 57-59 and pay close attention to the terminal numbers on transformers.
-
Thanks, fixed!
Voltages check out perfectly, except that terminal 7 read 239 (still easily within 10%) and terminal 14 read 200. Does this have something to do with the balance control? I also noticed that I got two different brands of 12AT7 tubes, so maybe that has something to do with it?
I'll send some music through it now to see how it sounds.
-
I'm a total idiot! I had to move the amp from one side of my credenza to the other to have the RCAs in reach, and when I moved it I forgot to re-plug it in! ::)
So it's going... I'm using the mono Pet Sounds to set the balance. It's sounds glorious! FAR, FAR more bass. Richer sound, wider soundstage, more detail. Etc.
-
By the way, I've got the hum down to completely inaudible, even with my ear up to the speaker. Should I cancel my DC filaments order, or are there other benefits to that upgrade, too?
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi68.tinypic.com%2F212tyeb.png&hash=20f54036dd1b70c3e3ea1d1f875a26399356e70a)
-
Listening to Kitajenko conducting Shostakovich's first symphony on SACD now and it's jaw dropping!!
All due respect to the S.E.X. 2.0, even with MQ all-nickel iron upgrade, but this leaves that wonderful amp in the dust. Glad to have it as a headphone amp--that's for sure!
-
All this excitement about the sound of this amp made me forget that I had wired it for 4ohm, and still need to try 8ohm to see what difference I hear. Could it sound better?
-
It's the damping factor. Most speakers are designed to operate best with an amp that has a very high damping factor; SETs usually have a DF between 2 and 4. This makes the response sensitive to variations in speaker impedance. Peaks when the impedance is high are limited, but notches when the impedance is low are unbounded.
In the Forte II graph, the biggest dropout would be in the bass where it drops below half of the nominal 8 ohms. There will be a smaller peak in the upper midrange where the impedance is high. Room acoustics are significant, especially in the bass, so sometimes just moving the speaker around will adequately compensate. That's why I suggested trying both options and listening.
Paul, if I understand you correctly, I am more likely to get better bass at 4ohm, but may lose something in the upper middle, whereas with 8ohm I may lose some bass?
I've got it at 4ohm right now and it sounds pretty nice all around. I'll be away for a week, but when I return I'll re-wire to 8ohm and listen.
-
OK, I've re-wired for 8ohms. The difference is subtle, but so far it seems like there's less rich bass. Whatever strengths this brings me might not be worth the trade-off. Honestly, I'm still so floored by the sound that I have a hard time focusing in on whatever slight drawbacks there might be in the different ohm wiring.
-
How did you like the clarity caps vs solens?
-
How did you like the clarity caps vs solens?
Haven't put the Solens in yet. Will try that later. Thanks for helping me out with those ClarityCaps, though!
-
Went back to 4ohms. I think I like that better.