New Millett Hybrid MiniMAX (what happened to this thread?)
Feb 26, 2010 at 3:26 PM Post #1,411 of 1,948

iamthecheese

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Just a random thought...Is there something better than a wallwart the minimax can use...kinda like an M3 can use a STEPS or a TREAD?
 
Feb 26, 2010 at 11:23 PM Post #1,413 of 1,948

tomb

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Quote:

Originally Posted by iamthecheese /img/forum/go_quote.gif
Just a random thought...Is there something better than a wallwart the minimax can use...kinda like an M3 can use a STEPS or a TREAD?


Yes - what PScal said. The power supply on the MiniMAX is actually a modification of the STEPS, which itself was a modification of the standard LM317 application notes. The difference being that the MiniMAX was specifically tuned even further to achieve somewhere around a ~45uV ripple, when measured at the V+ and Gnd points, which essentially is the point of separation between the amp and the power supply.

Just think of the walwart as the transformer in the power supply circuit - that's all it is.
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Feb 27, 2010 at 2:57 AM Post #1,414 of 1,948

iamthecheese

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Quote:

Originally Posted by tomb /img/forum/go_quote.gif
Yes - what PScal said. The power supply on the MiniMAX is actually a modification of the STEPS, which itself was a modification of the standard LM317 application notes. The difference being that the MiniMAX was specifically tuned even further to achieve somewhere around a ~45uV ripple, when measured at the V+ and Gnd points, which essentially is the point of separation between the amp and the power supply.

Just think of the walwart as the transformer in the power supply circuit - that's all it is.
smily_headphones1.gif



I was kinda of hoping to get rid of the wallwart...maybe a psu that would use a standard 110v cord like computer PSUs just to free up space on my UPS(its full and I have to keep switching around plugs).

Is it even realistic to have an external transformer that would be in a lansing case with the same length and width to put under the minimax?
Or would it mostly be a waste of time?
 
Feb 27, 2010 at 5:52 AM Post #1,415 of 1,948

tomb

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Quote:

Originally Posted by iamthecheese /img/forum/go_quote.gif
I was kinda of hoping to get rid of the wallwart...maybe a psu that would use a standard 110v cord like computer PSUs just to free up space on my UPS(its full and I have to keep switching around plugs).

Is it even realistic to have an external transformer that would be in a lansing case with the same length and width to put under the minimax?
Or would it mostly be a waste of time?



You're kidding, right?
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The MiniMAX and its case is as small as things can get without going to SMD!! No, there is no room whatsoever for a transformer.

Frankly, the walwart is a feature - not a detriment. There's an entirely different level of skill and accepted danger when dealing with a DIY-ed transformer using line voltage inside a case. Plus, there is assurance that things are always quieter with the transformer outside of the case. I used to build my own walwarts for many designs just for that very reason - to keep from having to worry about transformer noise inside the case.

There are plenty of extension cords or adapters that can be used to physically get the walwart off of your UPS outlet tree. I often do the same with my outlet strips. Any drugstore or grocery store can probably fix you up.
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Feb 27, 2010 at 1:34 PM Post #1,416 of 1,948

BoogieWoogie

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I had the minimax bias at 17v 16v each tube then I tested it with a dac and the sound was great but I changed after to 13,4v and dint turn on until my dac came, now that it came the sound is to much distorted and metalic feeling, I changed back to 17 just to check and this effect was lessier. Is the my multimeter defected or is something wrong with minimax ?
 
Feb 27, 2010 at 2:29 PM Post #1,417 of 1,948

tomb

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Quote:

Originally Posted by BoogieWoogie /img/forum/go_quote.gif
I had the minimax bias at 17v 16v each tube then I tested it with a dac and the sound was great but I changed after to 13,4v and dint turn on until my dac came, now that it came the sound is to much distorted and metalic feeling, I changed back to 17 just to check and this effect was lessier. Is the my multimeter defected or is something wrong with minimax ?


I'm not sure I understand all of that, but if you're asking if a higher bias could make the tubes sound better - yes, that's entirely possible.

However, you need to be careful that final biases are based on a warmed up amp. Bias will drop over the first hour or two. So, if you set it to 13.5 in the first few minutes, it may very well drop to 12 or less several minutes later. That could definitely sound bad. Or, your 17 or 16V bias (which is it?) could have dropped to 14 or 13.5, which means it might have been where it should've been.
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Also, tubes will change over time as the getter burns out remaining gases that may be in the tubes from sitting on the shelf for the last 50 years. So, a recheck is always in order if you want the very best sound.
 
Feb 27, 2010 at 3:15 PM Post #1,418 of 1,948

BoogieWoogie

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Quote:

Originally Posted by tomb /img/forum/go_quote.gif
I'm not sure I understand all of that, but if you're asking if a higher bias could make the tubes sound better - yes, that's entirely possible.

However, you need to be careful that final biases are based on a warmed up amp. Bias will drop over the first hour or two. So, if you set it to 13.5 in the first few minutes, it may very well drop to 12 or less several minutes later. That could definitely sound bad. Or, your 17 or 16V bias (which is it?) could have dropped to 14 or 13.5, which means it might have been where it should've been.
wink.gif


Also, tubes will change over time as the getter burns out remaining gases that may be in the tubes from sitting on the shelf for the last 50 years. So, a recheck is always in order if you want the very best sound.



I don't think thats it ,Its been 3 hours on and I just checked its 13,50 13,68 , whats the max bias recommend so I can tune it be hear ?
 
Feb 27, 2010 at 3:30 PM Post #1,419 of 1,948

tomb

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Quote:

Originally Posted by BoogieWoogie /img/forum/go_quote.gif
I don't think thats it ,Its been 3 hours on and I just checked its 13,50 13,68 , whats the max bias recommend so I can tune it be hear ?


1/2 the supply voltage, as measured and set at V+ and Gnd. However, if it sounds better to you with your particular tubes and setup to adjust the bias to 16 or 17, then do so.
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Mar 1, 2010 at 3:27 PM Post #1,420 of 1,948

tomb

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I finally got around to posting a bunch of pics of the different MiniMAX builds out there. Surprisingly, even with a custom case there are some variations.
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MiniMAX Photo Gallery
 
Mar 2, 2010 at 1:16 AM Post #1,422 of 1,948

tomb

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Quote:

Originally Posted by the_equalizer /img/forum/go_quote.gif
Great! I enjoy galleries a lot. Thanks TomB !

cheers!



Thanks! Now that you mention it, though, I didn't have the latest pics - including yours.
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That's now been remedied.
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Mar 4, 2010 at 1:05 PM Post #1,423 of 1,948

timmyGCSE

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how long do you reckon the latest round of kits will be in stock tom? I'll probably be looking to order a kit beginning of may.
Also whats the shipping cost to the UK like?

and with the wallwart..can I just use a UK equivelent that gives the same output? or just use a travel adapter..
 
Mar 4, 2010 at 3:20 PM Post #1,424 of 1,948

tomb

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Quote:

Originally Posted by timmyGCSE /img/forum/go_quote.gif
how long do you reckon the latest round of kits will be in stock tom? I'll probably be looking to order a kit beginning of may.


Beezar attempts to keep the MiniMAX kit in stock at all times. Quote:

Also whats the shipping cost to the UK like?

and with the wallwart..can I just use a UK equivelent that gives the same output? or just use a travel adapter..


There are answers to both these questions, but I'm afraid you need to send me a PM or e-mail. It's not exactly proper to be conducting business in the thread (I'll get banned.).
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Mar 4, 2010 at 3:27 PM Post #1,425 of 1,948

timmyGCSE

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Quote:

Originally Posted by tomb /img/forum/go_quote.gif
Beezar attempts to keep the MiniMAX kit in stock at all times.There are answers to both these questions, but I'm afraid you need to send me a PM or e-mail. It's not exactly proper to be conducting business in the thread (I'll get banned.).
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ok cool sounds good

and
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yes of course..thats two bad suggestions in one day *slaps forehead*
 

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