Hey, just an update, since Nate is getting ready to send out the boards. I've updated the web site with some build instructions. Please feel free to pick 'em apart and make improvements.

-Drew

Hi all,
Looking to gather the parts together for my Millet, so i was wondering can i use WIMA MKP 0.1uf instead of the 0.22uf's. Didn't Pete mention the caps absolute values aren't critical?
btw- i have 2 bags of these so i'm hopin' they're ok to use


evo_lution

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Drew,
Where did you get the tube sockets you used for that build? Thanks.

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Hmm...good question. I got them from a surplus outfit, but I don't remember exactly which one. I don't think that they have anymore of them

[edit] Oops, I guess I lied. I got them from Electronic Surplus. 50 cents each (a bargain!)[/edit]

[edit (again)] I guess I'm getting old. 7 pin sockets are here [edit (again)]

-Drew

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Yes, they'll work perfectly. I get the feeling that when Pete originally built his amplifier he was faced with the same situation

-Drew

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doh! thanks anyway. i have some of the ones from tubedepot that I modified to allow for a center hole but the ones you've got look much nicer.

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Thanks Drew

on the D2L/R the instruction says "Either 1N5291 or J503 must be placed, but NOT both", that means we have to keep consistency right? So we should have to put on both diodes on D2L/R right.

Also a small request, does anyone have extra parts for D2L/R and R2R/L? I need 4 of each. Thanks

It just means that you want to use one type or the other and only populate one of the pairs of positions on the board.

So for each amp you'll either need a pair of 1N5291s or J503s.

Sorry I can't help with the spare parts problem, I just got what I hope to be my last DigiKey and Mouser orders for a long, long time. $500 in parts showing up is fun, but really hard on the wallet. Look for a pretty interesting Millett Hybrid to be built in the near future.

Time to go home and start packing boards.

n

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I've updated that part of the web page to make it a bit more clear:

Locations are provided on the board for the 1N5291 and the J503. Do not populate both diode types! Use either the 1N5291 or the J503, but not both. Also, do not mix and match - use two 1N5291s or two J503s, but not one of each. You've been warned...

If you use one of each, nothing terrible will happen, but the two parts are not identical, just very close. Expect channel imbalance if you mix'n'match.

If you populate both positions, the amplifier's gain will be too high so you won't enjoy the full use of your volume control and you'll hear plenty of distortion.

-Drew

I have been tinkering around with my Millett a bit, and have happened upon a nice, inexpensive, tweak. Pete's article suggests using 22R resistors on the output, but also suggets that their resistance should be about half of the headphones impedence.

I had been using the Dale resistors from Mouser suggested in the article. I replaced them with Kiwame carbon film resistors. This made the sound a bit warmer and more natural, took off a bit of upper mid glare, (I have been replacing signal path metal films with carbon films all over lately) and perhaps made the amp a bit more lush and tubey. I am sure this is not for everyone, but it is for me.

I also lowered the resistance to 15R. I am using Grado RS-1s, and this seems to have brougt out a bit more bass. fwiw, my amp is ceraphines all around except for Nichicon muse 470uF on the output, an alps blue, and 12ae6a tubes.

-d

Post moved to "Group Buy" thread. Thanks.

Several build curiosities:

a) What is the optimal (in your most humble opinion) voltage setting (using a STEPS) for the 12ae6a and the 12fk6 respectively?

b) I am using a wood front panel on a PARS metal case - is steel shielding (an easy option for me) likely to be needed?

c) The PARS metal case has an aluminum divider - does that need to be steel (an easy option) to shield the Millett board from the STEPS?

d) Which tube set is likely better for Senns (HD600 or HD650)?

e) Do I need to adjust any resistor values to boost the gain for Senns (600/650)?

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From what I've read and what I hear the bias setting is not super critical with the exception of not going higher than say 14V. I'm sure someone can clarify this. If it were me I'd just set it at 12V and forget it.
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Sheilding would only be need if you're getting interference. If the amp is going anywhere near stuff like monitors, computers or the like I'd find a way to shield it.

c) I'll leave this to others as I'm not sure.
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With the cost of the tubes being pretty low ($3 of $4 a pop) I'd just get a set of each and try them out yourself. One man's trash is another man's treasure holds just as true for audio. Listen and decide for yourself.
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If the amp is going to be used exclusively for Senns I'd say you could omit R4R/L and just jumper these positions. I've built all my prototypes this way and they work fine. You could also use a 10OHM value if you still wanted some resistance.

HTH,

Nate

How does one connect the toggle switch to the pcb? Thanks!