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The MYSTERY AMP ! (Read 170419 times)
maddog07
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Re: The MYSTERY AMP !
Reply #300 - 11/22/13 at 17:29:20
 
Quote:
Madddog, did you scap up some RCA OA3's from Tube Depot?


Stone... what exactly are you referring to here?
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Lonely Raven
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Re: The MYSTERY AMP !
Reply #301 - 11/22/13 at 19:16:54
 

Funny how I have my own moments of Zen. I was just randomly googling some audio gear, and stumbled into this photo, the style looked familiar as well as the giant caps, and it lead me to this excerpt form the Torii Mono thread. I've never read through this thread, but seeing as how the Mystery Amp appears to be based on lessons from the big Mono's, I guess I should give it a read (also states basically what I thought about the input caps on the previous page - I was right!)



Quote:
With tube rectification, you create a power supply filter with two or more capacitors separated by either a heavy duty resistor or a choke.  The value of the capacitors are between 10 and 50uf typically.  We presently use 47uf caps, which are the small ones in front of the large ones shown in the above picture.  The giant high voltage caps shown behind them are around 55 times larger and cost a small fortune.

Since the purpose of the power supply caps is to reduce the AC ripple effect and noise from the rectifier, having a simply giant capacitor fed by two super fast recovery 3 AMP diodes gives such superior filtering that you don't need, the resistor or choke, nor do you even need the second capacitor!  That means the output transformers are now directly connected to the raw current of the power transformer.  No more resistors to soften the dynamics, or chokes to eliminate hum are needed.
The noise and hash in the power grid that the VR tubes are filtering out, can not escape the black hole effect of such large caps.  Thus the power is ultra clean.

There really isn't anything more zen if you consider the simplicity of it.

The complexity was in evaluating and choosing the right caps.  Just because it's big don't mean it's all that good.  I wanted the best, so many long nights of reading through product datasheets, I found these and compared them to identical size German made Siemens and US made Mallary caps by installing them into the amplifier and listening to it.  I found these to be the best.  They are sure to last a long time because they are configured for 1000 volts and only see 510 volts.
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Lon
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Re: The MYSTERY AMP !
Reply #302 - 11/22/13 at 19:21:18
 
Thanks. That helped me understand something.

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Steve Deckert
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Re: The MYSTERY AMP !
Reply #303 - 11/25/13 at 01:43:42
 
The rough draft of the web page is unofficially online.  I will proof and tweak it next week.

http://www.decware.com/newsite/MYSTERY.html




We're getting there!
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Lonely Raven
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Re: The MYSTERY AMP !
Reply #304 - 11/25/13 at 02:13:00
 

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Lonely Raven
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Re: The MYSTERY AMP !
Reply #305 - 11/25/13 at 02:20:07
 

Steve,

Are you starting the builds on the Mystery Amps soon?
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stone_of_tone
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Re: The MYSTERY AMP !
Reply #306 - 11/25/13 at 05:15:43
 
Maddog??  Reply #219.

Steve, thanks for the unofficial thread....I am going to read it now.  -S
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stellablues
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Re: The MYSTERY AMP !
Reply #307 - 11/25/13 at 06:30:22
 
Well then.. I'm new on the wait list for a Torii MKiV but I am pondering changing my order to the mystery... I currently have low sensitivity speakers, ellis 1801 at 85db  8ohms. I definitely will be changing my speakers in the next year or two after I have my amp and perhaps a new listening room.. I know, doing things in the wrong order.. very interested in the janszens but my current room will not hold them.

I have VPI turntable and MDAC USB via Mac MIni as my sources. Current amp is a Pass labs INT30.5 but i need more magic. life, body.

Anybody want to weigh in who has listened to these two from the decfest?

I am still thinking perhaps at MKIII burned in would be a good first amp and then wait a few years to upgrade... but then I will still be thinking about what could have been... wish I could listen to some of these models.

Anybody in San Diego have a Decware I can listen to? cheers,

Aaron
Carlsbad, ca
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Lord Soth
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Re: The MYSTERY AMP !
Reply #308 - 11/25/13 at 09:18:38
 
Dear Steve,

Thanks for the wonderfully written detailed write up of the new ZMA.

I always enjoy reading about all your other amps e.g. The Mini Torii, super zen etc.

Maybe I wasn't paying enough attention in the past but what was surprising to me was to find out that a Pushpull configuration would be used. I had always assumed that it would be a Single ended design.

Regards,
LS
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Steve Deckert
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Re: The MYSTERY AMP !
Reply #309 - 11/25/13 at 17:04:11
 
You bring up an interesting point.   The Zen Triode amp was an SET with a single gain stage and a single output tube, one cap and two resistors in the signal path.  To get more power requires either a bigger output tube or several output tubes in parallel.  Parallel ruins transparency.  Bigger tubes need more voltage swing to drive them, so basically another stage.  That means one more cap and two more resistors.  Again, transparency suffers.  

The only way I could get more power without loosing transparency was the TORII push pull circuit. It consists of one gain stage (direct coupled to itself to also become the phase inverter), One coupling cap and two resistors.  The two output tubes are in series with each other, not parallel, so you hear only one tube at any one point.  It is essentially the same transparency as the original Zen SET amp.  The trick is of course, the phase inverter must be able to perfectly marry the two halves without a notch.   Personally, I found that easier than trying to bend the rules of physics by somehow getting paralleled tubes to sound as transparent as a single tube does.

Hope that helps

-Steve
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maddog07
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Re: The MYSTERY AMP !
Reply #310 - 11/26/13 at 18:47:18
 

I read in the Mystery Amp webpage preview... that the Decware supplied tubes are Tung-Sol KT66's and OA3's...  but I don't see 0A3's listed as a tube at www.tungsol.com that they currently make... are these NOS tung-sol 0A3's?  Or is the tung-sol site not up to date?  
Where might a person find these?  
Anyone care to elaborate?
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Lon
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Re: The MYSTERY AMP !
Reply #311 - 11/26/13 at 19:43:51
 
I don't believe anyone is making new OA3 tubes. The page could mean that he found a supply of NOS Tungsol OA3 tubes (personally I've never seen this type by Tungsol) or just that there are OA3s in use in the amp and Steve didn't mean to infer they are Tungsol brand.
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Lonely Raven
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Re: The MYSTERY AMP !
Reply #312 - 11/26/13 at 19:53:32
 
I don't think Steve meant to infer the tubes were Tung-Sol.

I'm pretty sure nobody is currently making the OA3, but they are long lasting tubes. Just in case, I'm going to stock up on a couple extra pairs.

Edit to Add: looking at the photos, it looks like this is what Steve has in the Mystery Amp photographed

http://www.ebay.com/itm/RCA-OA3-JAN-CRC-0A3-1768-Vacuum-Tube-/321239775100?pt=Vi...

Since stock is limited to what's "out there", he probably doesn't want to specify what tube the MA will come with as it will probably change with what's available. Doesn't the MK IV use these as well?
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« Last Edit: 11/26/13 at 20:20:20 by Lonely Raven »  
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mark58
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Re: The MYSTERY AMP !
Reply #313 - 11/26/13 at 21:40:18
 
LR, the mystery amp does appear to have OA3's similar in appearance to the RCA OA3s we bought.  They are not the same ones as I got in the Torii MK IV...those were not coke bottle types but rather short and straight sided.  Mark.
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Lonely Raven
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Re: The MYSTERY AMP !
Reply #314 - 11/26/13 at 21:50:10
 

I forgot to add:





Grin
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