Building Millet SS, need some help
Dec 30, 2008 at 2:16 AM Thread Starter Post #1 of 10

Dr Evil Dan

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Ok, so I have decided to build the Millet Starving Student (mostly due to it being cheap and simple, and apparently awesome), and I need some help with tweaks. I am not a complete newb to electronics or soldering, but we never learned about amps or bypass capacitors in high school electronics, so I have some questions.
1). I would really like to get most of the parts from one place. If I could buy the caps, resistors, PSU, jacks, MOSFETs, and heatsinks from one place, that would be awesome (Tubes I can get separate). I DO plan on using high quality caps (Eyeing the Nichicon Muse series, or Elna RFS Silmic II series) and resistors. Is this possible? Because I've looked on at least 5 websites, and they all seem to carry only a few of what I want.
2). What would the optimal values be for the Electrolytics? I was thinking 470uF. Same question for the Film caps (except those wouldn't be 470uF, most likely .22uF or something).
3). I have read a little bit about bypass caps, but I am not sure how to implement one on the SS. Is it needed? Would it improve sound?
4). Is it possible to have 2 output jacks, one for low impedance 'phones and one for high impedance 'phones? Or would you have to rework the entire circuit?
5). Are there any replacements for the 19J6? It seems to be pretty rare, and I would like to maybe explore other tubes...

As you can see, I want this amp to work with a variety of headphones, because I am a starving student and cant afford different amps for different 'phones
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. The sound I am going for is something with preferably NO sibilance, detailed, deep, smooth, and not overpowering bass, and as neutral as possible mids. I hate hiss, and I listen to my headphones on pretty low volume, so power is not an issue. Right now I am using Grados, but plan to upgrade to a pair of Denons or something.

Thanks for the help, and if you can think of any other tweaks that would improve the amp, by all means state them.
 
Dec 30, 2008 at 5:47 AM Post #2 of 10

bmwpowere36m3

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OP, the Millet "SS" is actually a fairly easy build with casework being typically the most difficult for folks... probably due to the lack of tools. Otherwise it's a great Point-to-Point build. I built it as my second amp after a CMoY and currently just completed a SOHA II.

1). I doubt you'll find everything one stop shop, unless you want to compromise. The PSU is probably strictly found on eBay (~15 shipped) and the resistors, caps*, mosfets, etc... can be had at Mouser, Digi-Key, Newmark, etc...

Caps*, typically you won't find any "boutique" capacitors at those major vendors. You can find decent high-quality, but you wont get Nichicon Muse, Elna, Blackgates, etc...

2). 470uF seems like the best compromise and that's what I any many others have gone with
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3). I would read up on bypassing, but I honestly doubt you'll notice much of a difference on this level of amp. But your choice... I only bypassed the PSU caps w/ Wima's since they were "cheap", I figured it couldn't hurt. For the actual signal portion of the amp, I went with a VitQ .22uF as the cathode bypass cap (C2,C4) and Nichicon Muse KZ 470uF and the output caps (C3,C5).

4). Not sure about this, what are you trying to accomplish? This amp has a high overall gain (~15 or so) and it drives my HD580's (300ohm) really loud at only ~40% volume. I'd ask someone else, since the phones you have might not really work with this amp (too easy to drives phones, Grado's???).

5). Not that I know of, and nobody has mentioned anything. The whole circuit is based around the "unique" operating points of the 19J6 tube.

I'd say stick with a mostly "stock" BOM build and only modify components as you see fit, not just because. Ask more specific questions. I'd say there is only so much you can get out of this amp, so there's no point in getting too "boutiquey" with this amp.

Here's my build: My "SS" Hybrid and attached BOM of it.
 
Dec 30, 2008 at 6:06 AM Post #3 of 10

elliot42

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There's no replacement for the tubes, and you may have trouble finding some left so I'd make sure you have a set of tubes in hand before going and spending money on all the other components.

As for high and low impedance cans, I use my SS with Alessandro MS2i (low impedance) and listen between about 15% - 35% volume. There's certainly plenty of power in this little amp and there's still enough play in the volume to get good levels with low impedance cans.
 
Dec 30, 2008 at 7:47 AM Post #4 of 10

Dr Evil Dan

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The reason I want to modify it is so that I can get the most out of it, because chances are I won't be moving up to anything better for a while.
Also, I basically know how bypass capacitors work, but the part I am still confused on is where exactly do you put one? I read it is supposed to be in series with whatever you want to bypass, but where exactly would this be? Say I wanted to bypass C6, does that mean I would put a small capacitor before or after C6? What size would be good?
By having 2 outputs, I meant something like this http://hollowstate.netfirms.com/HD2manual.pdf
actually, I looked at the circuit for the HD2, and apparently the LOWZ output is the same as the HIGHZ but with a couple of resistors in series with it... So nevermind about that
Thanks

*edit* so apparently, the Cisco PSU can be noisy, and Germania said that she put some caps across the leads to help smooth out the ripple. Can someone recommend values to put here?
 
Dec 30, 2008 at 8:24 AM Post #6 of 10

Dr Evil Dan

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Quote:

Originally Posted by rds /img/forum/go_quote.gif
Series and Parallel
Where did you read it is supposed to be in series?
It is supposed to be in parallel.



I know the difference between the two, its just that we never learned about bypass capacitors or audio circuits, just basic circuit analysis (ohm's law basically). It is 3 am here though, so maybe I just read something wrong, as I can't find where I read it.
 
Dec 30, 2008 at 8:54 PM Post #9 of 10

bmwpowere36m3

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Quote:

Originally Posted by Dr Evil Dan /img/forum/go_quote.gif
The reason I want to modify it is so that I can get the most out of it, because chances are I won't be moving up to anything better for a while.
Also, I basically know how bypass capacitors work, but the part I am still confused on is where exactly do you put one? I read it is supposed to be in series with whatever you want to bypass, but where exactly would this be? Say I wanted to bypass C6, does that mean I would put a small capacitor before or after C6? What size would be good?
By having 2 outputs, I meant something like this http://hollowstate.netfirms.com/HD2manual.pdf
actually, I looked at the circuit for the HD2, and apparently the LOWZ output is the same as the HIGHZ but with a couple of resistors in series with it... So nevermind about that
Thanks

*edit* so apparently, the Cisco PSU can be noisy, and Germania said that she put some caps across the leads to help smooth out the ripple. Can someone recommend values to put here?



Again, don't really worry about bypassing. If you must then they are installed in parrallel with the cap you are bypassing. (You can clearly see it in my build with the underside shot, the Wima (Big Red Box Cap) is bypassing the PSU Cap (electrolytic) they are located on eitherside of the switch.

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This amp is only so much, lets say a perfect amp is 100% and stock BOM Millet is 60% in terms of SQ (purely example). Bypassing caps and such as a total will only give you maybe 2-5%, maybe not even. So the amp is still on the low end in terms of SQ. I'm not taking anything away from the amp, since I love it. But if you can only afford one amp, maybe save up for a better unit.

I think Germania was one of the only builders who noticed a noisy PSU, I and many others have been satisfied with the Cisco unit. The cap across the PSU was more than just to filter noise... I would first build the unit and then worry if you need a cap there.

Quote:

Originally Posted by rds /img/forum/go_quote.gif
...also the BMW guy said you can't get "boutique" caps at Mouser. Actually you can. Here's a suitable cap from their top of the line audio caps, the Nichicon Muse KZ 470uF, 50V. I would use this for the coupling cap.
You can bypass it if you want, but it's not too critical in my humble opinion.



Thanks, after posting a realized a member saying that you can get certain Nichicon Muse's at Mouser. I'd say entry level "boutique"
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Quote:

Originally Posted by Dr Evil Dan /img/forum/go_quote.gif
50v though? I thought the BOM calls for 63v min. Its ok though, I know where to get all the parts, I just wanted to get them from as few sources as possible.


Yes it does, but technically the most it should ever see is ~48V and that's if there's a complete short or failure in the amp. Typically it'll see a lot less voltage.
 

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