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The MYSTERY AMP ! (Read 154225 times)
Steve Deckert
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Re: The MYSTERY AMP !
Reply #60 - 05/10/13 at 17:09:07
 
Well, my thoughts behind creating this thread were to give you a real time glimpse into the design process of a new amplifier.  At this stage, I have the design and how it should sound in my head and am trying to make it happen on the bench.

So step one, yes it's alive!  Sadly it sounds like crap... so let the hunt begin!  How many things did I wire wrong?



another mystery...

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Steve Deckert
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Re: The MYSTERY AMP !
Reply #61 - 05/14/13 at 02:43:22
 
Well, quite a few.  Of course, having nothing to look at, and no schematic / that alone increases the odds of mistakes.  However in my own defense, doing a mirror image amp, upside-down and backwards can be a real mind game when tube sockets can not be mirrored.  Turns out I had one channel output transformers out of phase and a few other minor blunders which more than explained the sounds like shit experience...

Today I got to the bottom of all that and the next step is going to be defining the bias windows to make them work perfectly and be more or less fool proof like on the monos....  Sadly, none of the work done on the monos will apply, since all the values change and have to be discovered through trial and error with a wide range of different brand output tubes.

Anyway, a few more afternoons messing with that, I'll be able to have a first real listen... then the voicing can begin.



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Landmantx
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Re: The MYSTERY AMP !
Reply #62 - 05/14/13 at 23:11:29
 
I love it when you take us behind the curtain and let us see what all goes into the creation of a world-class tube amp. This thing is going to be awesome!  I better start saving my money....
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Longbowbbs
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Re: The MYSTERY AMP !
Reply #63 - 05/15/13 at 01:59:30
 
You mean saving your money....Again!
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Steve Deckert
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Re: The MYSTERY AMP !
Reply #64 - 05/17/13 at 04:34:33
 


After two unexpected / additional sessions with it, I was able to capture the actual moment in time of it's first true playback where I actually listened to it to see where we are... what is the starting point going to be...  thought you would enjoy the pic... in fact, here... I'll let you have the full resolution version here: http://www.decware.com/newsite/images/DSC_0052l.JPG

I believe this picture is worth a thousand words... so I'll keep it short.   What am I hearing... amazing balls, incredibly smooth, perhaps too smooth, incredible potential... the voicing will no doubt be quite a ride - I'm sure.  Can't start the voicing with something that sounds this good out the gate until it has actually broken in....  these giant caps can take some real time.
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ncblue
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Re: The MYSTERY AMP !
Reply #65 - 05/17/13 at 04:53:47
 
Darn it, me want! Looks beautiful.
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Steve Deckert
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Re: The MYSTERY AMP !
Reply #66 - 05/17/13 at 05:07:01
 
3 hours into it, the detail is increasing... it's SO the opposite of solid state... interesting.  When any other amp is having a bad hair day... meaning lots of hash in the power grid causing excessive grain and dryness...  I can already see that with this amplifier that is never going to happen...  It's smooth beyond the ability to screw it up.  Put you power plants in the ground and the decomposing steel will enrich the iron content of the soil which will in turn improve the conductivity of your ground rod that your neutral is tied to... this in turn will create blacker backgrounds and better definition than when you had it in your system.   Just a tip.  I have to say what I'm hearing right now is like battery power.  The speed of the entire amplifier is really going to be effected by the main caps...  I'm going to wait to see where it lands wondering if I'll be bypassing the electrolytic with film caps.  I also have a few other experiments going on, or planned lets say, but tonight marks the starting point, and it doesn't suck.

Fun fun fun....  wait to you hear what it took to get to this point...  I'll save that for my next post.

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Steve Deckert
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Re: The MYSTERY AMP !
Reply #67 - 05/17/13 at 05:28:11
 
Crap, I may as well write it down now, otherwise I might forget it... boy getting old sucks.

Well, when I finished the amplifier and there was nothing left to do but test it, I used a variac to slowly raise the supply voltage and remember getting to the half way point on the dial and only getting a B+ of 63 volts vs. the anticipated 210 volts... so I shut it down before I let any of the smoke out.  The smoke is btw, the most tedious process in the manufacturing of parts...  Getting the smoke in the part is expensive which is why letting smoke out of the part is usually fatal.

I don't even remember what it was, but I found the half short and fixed it.  

Try two, turned into a bias issue...  first of all I spent a day getting the bias voltages to work right... this involved a separate  bias supply for each tube operating though a ganged level control feeding a ganged balance control.   The tedium of this is getting the windows of adjust defined....  For example, if you don't want the tube to bias up beyond 80 mills as the absolute max, you have to find the voltage (26.9 volts) that gets it there.  Then you have to define the window for the balance control.  Ideally at least 10 mills minimum, more is better but dangerous in the hands of the ignorant.  So you add the initial window and the balance window together to determine the max and minimum values...  Sadly it's so touchy that even a half a volt can through everything off.  Then when you get it perfect for one band tube, it's less than perfect for another...  It took me over two weeks to get it right on the Zen Torii Mono's...  over 50 hours of testing.

So, after getting it roughed in I was able to play the amp and found I had the right channel out of phase.  In fixing that I wired the ultra linear tap to the wrong pin and connected it directly the negative bias supply.   Upon slowly raising the voltage on the vairac to the half way point, and my face right down in it to see the meters in the mirror under the amp... fireworks as a resistor exploded into shrapnel...  

After fixing that, I ran into an issue with the bias meters on the right channel not acting right... the same channel I almost blew up...  

So I fixed that, but the wired behavior continued on the right channel bias meters...

I then figured The near melt down had compromised the pots used to adjust the bias voltage and balance.  So I replaced them both.    

I then fought with the imbalance on the right channel which was still there despite being identical to the left channel that worked absolutely perfect...  

So for two more days I refined the bias windows and got them closer to a production spec, which is pretty narrow making it hard to damage the amp.  I then found that with less adjustment in balance the imbalance problem between the current draw of the two outputs tubes on the right channel got so bad I couldn't even fire up the amp without burning out one of the tubes and meter, and having the other not even conduct current....

At this stage I realize it's just the same recipe as always.... more pain and suffering = more fidelity and satisfaction.

Tonight I wasted at least two hours calibrating the finicky side just to see if I could make it work again...  getting so ridiculous... tedious... father murphius...

Determined to hear it, I clipped the carefully installed resistors on the the balance controls so that my window increased 10 fold on the right channel, just so I could listen to it tonight.

So  the answer to all this friken problems is clearly seen in tonight's photograph.  Can anyone tell me why one of the meters is overly sensitive and prone to not balance properly?


I'll continue tomorrow...

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« Last Edit: 05/17/13 at 05:41:18 by Steve Deckert »  
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Steve Deckert
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Re: The MYSTERY AMP !
Reply #68 - 05/17/13 at 05:43:05
 
4 hours into it and the power transformers are barely warm.... Impressive.  Starting to really open up too.  Rock and Roll lovers.... this may be your amp.
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« Last Edit: 05/17/13 at 05:43:43 by Steve Deckert »  
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will
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Re: The MYSTERY AMP !
Reply #69 - 05/17/13 at 06:24:16
 
You have my attention!
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Longbowbbs
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Re: The MYSTERY AMP !
Reply #70 - 05/17/13 at 12:48:30
 
Will this new family member end up between the Torii and the Mono's?
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Landmantx
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Re: The MYSTERY AMP !
Reply #71 - 05/17/13 at 18:09:53
 
I am starting to wonder if Steve ever sleeps???
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T Jacobsen
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Re: The MYSTERY AMP !
Reply #72 - 05/18/13 at 13:54:14
 
Hi Steve,

How much power did you measure with this amp so far?
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T Jacobsen
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Re: The MYSTERY AMP !
Reply #73 - 05/18/13 at 13:55:28
 
Are those KT88's you are using as the output tubes?
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Steve Deckert
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Re: The MYSTERY AMP !
Reply #74 - 05/20/13 at 04:00:11
 
Time for another update...

I have never had so much trouble getting bias meters to work properly!  I've had one meter give me fits since the beginning.  In fact the very first thing I did when I first fired this amp with output tubes installed, is peg one of the meters so hard I had to replace it.  

Please take a look here at how much fun it is to replace a meter in this amp!



Each meter has two green oval stickers on it (to help you locate them)  

Wouldn't have been a problem except I had the idea to make the meters even cooler than they are.  To that effect I spent a night drilling holes in the casing after taking the meters completely apart and installing just the exact right LEDs.  That's all find and dandy until you blow a meter...  

Since all ideas actually come from our higher consciousness, and or other entities in that same dimension, it's not hard to figure out that this particular idea was not from the group of dead audio gurus from ancient times that sit around their mirror pool and watch me work...no this idea was from father murphy.  Notice I won't capitalize his name out of disrespect.   In any case, the idea is.

Time out.... before I continue, can anyone guess why I spent literally 10 hours or more trying to get the action of one of the meters balanced with the rest... not to mention the value it read.   The answer is in the last photograph I posted.  If you look at the original size high res version of the photo, it is unmistakable...



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