Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Stereomour => Topic started by: borism on March 13, 2014, 08:06:58 AM
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Hi,
I have been reading this forum for a few months and have found it to be a great resource as well as fun to read. My kit arrived about a week ago and I have started working on it. Briefly, I have no experience working on electronics, never have used a soldering iron before and have no woodworking skills to speak of.
However, building my own amplifier was so intriguing that I just had to try. Another disclaimer is that I am well aware that I should be building the original kit but I just could not resist making some substitutions that I have seen mentioned frequently on the forum. Clearly, I am not blaming anybody else particularly when, as possible, I come back for troubleshooting help.
So my upgrades include:
goldpoint selector and stepped attenuator
cardas speaker binding posts
Mundorf coupling, parafeed caps
My main issue so far has been, unexpectedly, the finishing of the woodbase. I didn't like the streaky polyurethane finish, so I ended up sanding it down again and starting over.
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I hope the images download correctly. If not, I may need some help.
Boris
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Boris, I built mine with a Goldpoint attenuator and switch, too. If you need help wiring them, (I did) let me know and I can show you how I did mine. They're working fine.
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The one step finishes can end up very splotchy and streaky. I recommend using a separate stain and clear coat.
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Hi Bartguy,
Yes, I think I know the wiring scheme but if you have some pictures or tips it would definitely help.
Doc, I did use a seal coat, then stain followed by polyurethane, but it was just my lack of experience. Now I intend to use shellack spray to see if I can get a smooth finish.
One more photo where things are:
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Sorry, let me try again
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Doc, I did use a seal coat, then stain followed by polyurethane, but it was just my lack of experience. Now I intend to use shellack spray to see if I can get a smooth finish.
The key to poly is multiple thin coats, and sand the finish flat between each coat. The more layers you add the flatter and smoother the finish will become. I used four coats i mine, using finer grade sandpaper between each layer.
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I used wipe-on-poly for wood base. Can't go wrong with this stuff.
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Incrementally adding a little oil based varnish to some wipe on Danish oil or Tung oil gives similar results.
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Thanks for the tips regarding the wood finishing. I was considering a wipe on poly but ended up using the brush. My poor sanding between coats resulted in the corners being stripped of the stain. That's when I ended up sanding it all down to the wood. Has anyone tried a spray on Shellack? Or, maybe going back to some wipe-on finish is safer?
My progress is somewhat slow, in part due to time limitations. Last night I progressed to the first input wire. You'll note that I installed the power board with the 4 resistors replaced by two Mills 270 ohm (seen on this forum for 2A3 tubes) ones. My thought being less must be better. Also, I decided to replace the input wire with a Mogami 2534 quad cable. The ohm-meter was helpful in sorting and marking the wires (there are 2 blue and 2 clear coated ones). Again, I am indebted to this forum for the idea. I only got the input #3 done yesterday.
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I have not tried spraying shellac however I do regularly use automotive clear coat/lacquer on wood and have found it works very well if the wood is dry and well seasoned. You can also use a brush to apply I find if I dip the brush in some thinners first then wipe or spin it out so the bristles are only a little damp from the thinners then dip in the lacquer it flows out nicely.
I did these pieces with the clear earlier in the week.
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Shellac can make a nice finish, but it is actually rather tricky and tedious to do in the best possible way, which is French Polish. It also makes a good filler over which to shoot nitro lacquer as a finish coat - again a whole lot of work.
My suggestion for a relatively easy and foolproof finish is no stain or a good water based stain and then brush or spray coats of a water based clear poly finish, lightly sanding with 220 grit paper between coats.
I don't use a sealer before staining, but I use a water based aniline dye and the penetration characteristics can be different than with oil based stains.
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Here is my suggestion for a finish:
Start at the bare wood. Stain to your liking. Give it a coat of spray Shellac (I have used this often) making a few light coats, 4/0 steel wool in between coats
The shellac seals the wood keeping it from soaking up a varnish. Then spray light coats of polyurethane for shine.
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I did these pieces with the clear earlier in the week.
Sry for going off topic, but what type of wood is the sample on the left?
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Hi Mark it's Spalted Beech and can be tricky to find with consistent patternation running through it, its one of my favourites and a bit different from the norm. You can see wha I am making here as well.
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Thanks for all the suggestions.
Jamie, the wood looks beautiful. Let me know if you do some work on request.
Grainger, since I already bought a can of spray shellack, I might as well give it a try.
Boris
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Shellac can be removed with denatured alcohol. If you mess up use that on 4/0 steel wool again.
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Just to clarify, I think Grainger means grade 0000 steel wool. That's about like 400 grit sandpaper. The potential for confusion is that there is not really "4/0" labeled steel wool but there is a grade 4 steel wool which is about like 30 grit sandpaper, i.e. kinda like using aquarium gravel glued to paper.
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Oooo! I didn't know that! I'll change my responses from here forward.
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I used the shellack spray can and overall it is much smoother. A few areas had to be sanded down and when that didn't work alcohol did the trick. So, hopefully, with a few coats it will smooth out.
The input wiring is complete. It was tedious but also fun to do.
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Hi,
I need some help.
Well I completed my build, checked the solder joints, did the resistance checks and they were all fine.
Then, I put in the tubes, the fuse and powered it up. The tubes were glowing fine, no blown fuses, so I did the measurements. The AC ones were fine. Then, the DC - all are fine except for 2 terminal strip voltages and 2 active load PC board ones:
Terminal: #2 313
#14 290
active load PC board:
OA 317
OB 291
Can someone tell me, what this may mean. The expected voltages in those 4 locations should all read 165-220.
I am also surprised that it seems so symmetrical.
Thanks,
Boris
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active load PC board
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The most likely thing is, a 12AT7 that has not been properly burned in at the factory. We are seeing quite a lot of those these days for some reason. Let it run for a while and check again. If it does not come down in 50 hours or running, we can replace it. The amp should be capable of making music right now, so you might as well listen to it for those 50 hours. You may notice some pops, scratches, and/or crackling noises, if as I suspect the cathode was not fully formed, but they should also fade out with time.
Of course if you have a spare 12AT7 and are impatient, you can substitute it to see if that changes the voltages.
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This is pretty unusual, did you end up measuring the Kreg voltage?
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Thanks Paul!
I had another 12AT7 and rechecked the voltages:
Terminal #2 190
#14 198
PC board: OA 190.3
OB 198
So, now everything checks out perfectly. However, my wood base is drying from another shellack coat. So, I'll have to wait a little before I can listen.
Another picture of the completed amplifier.
Boris
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It's alive!
Couldn't wait to finish the base and will have to return to it this week. But music is playing and it sounds wonderful (Paul Simon - Graceland). The selector switch and attenuator, everything is working fine. What a great adventure!
Thanks everybody!
Boris
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Not bad for someone who never soldered before. ;) But seriously, you did an excellent job. I'm very impressed with your first kit success.
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Thanks! The instructions are very clear. I also watched all the soldering videos on youtube.
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Congratulations! Not an easy "first timer" build! If you like it now, just wait until it has a hundred, or so, hours of burn in!!!
Cheers,
Geary
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Man this little amplifier is making some sweet music. It seems even with only a day of burn-in it is getting really good. And it turns out that it is driving my speakers that have a sensitivity of 92 (AudioKinesis Jazz Modules) very well. I rarely seem to turn the volume past 12.
Boris
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Man this little amplifier is making some sweet music. It seems even with only a day of burn-in it is getting really good. And it turns out that it is driving my speakers that have a sensitivity of 92 (AudioKinesis Jazz Modules) very well. I rarely seem to turn the volume past 12.
Boris
Hi Boris.
May I ask where you are from or where you are located.
The reason why I ask, it's because I want to know how hot
does the top plate becomes when you touch it?
As you know already, I live in Vietnam
and these days the thermometer is around 35C or 90F+
I am trying to avoid using my air conditioning in my listening room
to save money to buy the Stereomour. ;D
My Decware SE84C+ is getting very hot after just one CD playing.
I have a small super quiet fan that I would like to use to cool down the amplifier,
but I am too lazy to set it up.
Guy 13
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Slightly off topic sorry re cooling without air conditioning a handy Bahamian method I picked while staying with a local spear-fisherman was to pick up a block of ice from the local fish market or you can freeze it yourself. Before retiring for the evening set the ice in a large bowl across from the bed position a fan to blow across the ice towards you. Results a comfortable nights sleep and on waking a refreshing bowl of cool water to have a wash with, it works really well!
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That's a nice story Jamie.
Guy, I live in Connecticut and we have had a very cold Winter thus far. Having said that, the top plate of the Stereomour only gets barely warm. The power transformer bell also seems only lukewarm after hours of playing. Of course, who knows what it will be like once we get some Summer heat and humidity.
Boris
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the top plate of the Stereomour only gets barely warm. The power transformer bell also seems only lukewarm after hours of playing.
That particular transformer is a little oversized for its duties, hence the unusually low temperature.
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Guy, I live in Connecticut...
Boris
Hi Boris:
There's at least a couple of us here in CT. I'm a little south of Hartford and Boulos is near New Haven. I know there are at least a couple of others.
Unlike you, I have not taken that giant step. However, I know a great product and value when I see one. I bought Paramounts pre-built and Boulos built a BeePre for me.
Your Audio Kenesis Jazz Module speakers (Duke?) are a little off the-beaten-path, how did you end up with them and how are they working out with the Stereomour?
Thanks and congrats on your build!
Gerry
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Gerry,
I live just north of New Haven. Duke's Jazz Modules came about when I decided to move away from solid state amplification and low sensitivity speakers (Thiel 2.4) a few years back. Somehow I stumbled upon AudioKinesis on the AudioCircle forum and the rest is history.
The Stereomour is driving my speakers surprisingly well. I don't think that this match would work well for loud rock or loud, symphonic classical music. However, acoustic, jazz and voices are great.
Boris
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A brief update. The amplifier continues to sound wonderful. However, I was never happy with my poor finish of the wooden base. Then, I happened to see a very nice plank of bubinga wood on ebay. So, to make it short, with the help of a friend, I made a new base. All it needed is some linseed oil and lacquer finish. Now, I am happy with the whole package.
Boris
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That is a beautiful piece of wood and a nice tidy build.
I didn't know you could put lacquer on top of linseed oil. You can spray it on top of oil? I thought it wouldn't take.
You learn something every day.
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Beautiful work on the base Boris.
BTW, did you put anything (lacquer/wax) on the top alum. chassis plate to prevent oxidizing?
Asking, 'cause I'm planning to put clear lacquer on mine, but still can't decide whether I should leave it as is and not be to worry about oxidizing of the top plate or put some clear lacquer, but this would give some yellowish shade over time.
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Thanks!
Grainger, there was a very nice video on finishing bubinga on youtube and this is what they recommended. It is boiled linseed oil and you have to wait a day for it to dry and then use lacquer spray.
Kris, I didn't put anything on the aluminum plate and just left it as is.
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Thanks, Boris!
I'll take a look now as I'm resting from hood polishing.
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Nice job the Bubinga has a real neat look to it.