Stagefright13

NewYorkDave Mila Dual Tube Preamp Help Thread
« on: October 26, 2007, 06:09:27 AM »
I would like to start an official project help thread if I may. This is for New York Daves Mila tube preamp. Info is here:


http://www.twin-x.com/groupdiy/thumbnails.php?album=44

And additional info is here:

http://musiciansgig.com/mila/

http://www.twin-x.com/groupdiy/displayimage.php?album=87&pos=5

http://www.groupdiy.com/index.php?topic=22886&highlight=

OK I will ask the first question lol. How do I rig in 48 volt phantom power? Also anyone know a good source for a Hamptone style chassis for it? And one more. Can I use 12AT7 or 12ax7 tubes cause I have a stock pile of them.

Thanks
« Last Edit: March 28, 2009, 07:22:32 PM by Stagefright13 »
Amateur experimenter


madriaanse

Mila Dual Tube Preamp Help Thread
« Reply #1 on: October 26, 2007, 12:13:43 PM »
I love my MILA!! :thumb:

48V:
You'll want to build/buy a small 48V power supply and run 48V to an on/off switch. From the switch, connect to a 6.8K resistor, and from this resistor connect to input XLR pin 2. Then do the same thing for XLR pin 3. That's basically it. If you want to get fancy do a search for "ramped 48v"

The resistors should be closely matched to each other in value, so buy a few extra 6K8's or 6K81's and use an Ohm meter to pick a "matched pair".

The 48V power supply can be very small, but needs to be clean. A simple phantom setup as described above will draw only 14mA per channel and that's with someone driving a nail through your mic cable and shorting Pin 2 and 3 to pin 1 (absolute worst case, how rude). :green:

cases:
check out http://www.par-metal.com/ or perhaps try ebay.

Also, I wouldn't sub a 12AV7 with a 12AX7 etc. They are pretty different animals even though their numbering is only off by one letter. :green:

Hope this helps,

M.

pucho812

Mila Dual Tube Preamp Help Thread
« Reply #2 on: October 26, 2007, 01:19:22 PM »
this is a good idea :thumb:
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

ChrioN

Mila Dual Tube Preamp Help Thread
« Reply #3 on: October 26, 2007, 01:32:58 PM »
Might be time for some P2P with that neat illustration PDF...
"All PCB traces are curved to emulate the electrical response of point-to-point wiring" -Drip

Freddy G

Mila Dual Tube Preamp Help Thread
« Reply #4 on: October 26, 2007, 03:32:25 PM »
Hamptone style case....something like this you mean?
http://www.hammondmfg.com/dwg14c.htm
PRR wrote:
Use #18 wire for rock-n-roll, #16 wire for classical.

Stagefright13

Mila Dual Tube Preamp Help Thread
« Reply #5 on: October 30, 2007, 05:47:53 AM »
Cool thanks for the help. Yeah that case is perfect! I'm starting on this in a couple weeks as a Christmas present for my son. Should be alot of fun. I'm ordering some parts today or tomorrow. Like the turret board and tube sockets.
Knowing me tho I'll prolly have to make one for myself 2.  :thumb:
Amateur experimenter

dmlandrum

Mila Dual Tube Preamp Help Thread
« Reply #6 on: October 30, 2007, 08:39:48 PM »
I have nearly all the stuff to make two of Dave's one-bottle preamps, but it didn't take me long to realize that I could put it all together into a single MILA amp. I think that's what I'll do.

First, I need to find out if the power transformer I have will work for it.
Darren Landrum

Be comforted that in the face of all aridity and disillusionment
And despite the changing fortunes of time,
There is always a big future in computer maintenance.

NewYorkDave

Mila Dual Tube Preamp Help Thread
« Reply #7 on: October 30, 2007, 09:07:37 PM »
Darren, is that the power xfmr I sold you, the Stancor?

If so, it's perfect for one channel of MILA. In fact, that's exactly what I used.

John, neither 12AX7 nor 12AT7 will sub for 12AV7 despite what you may read elsewhere.

dmlandrum

Mila Dual Tube Preamp Help Thread
« Reply #8 on: October 30, 2007, 09:17:07 PM »
Yes, Dave, that's the one I still have. Thanks for the help! Right now, I'm on the lookout for a suitable case. I'm hoping to recycle something, rather than buy new.
Darren Landrum

Be comforted that in the face of all aridity and disillusionment
And despite the changing fortunes of time,
There is always a big future in computer maintenance.

babyhead

Mila Dual Tube Preamp Help Thread
« Reply #9 on: October 31, 2007, 10:21:26 PM »
I love my MILA-

pics:

http://www.groupdiy.com/index.php?topic=24049&highlight=

Relevent build and trouble shooting:

http://www.groupdiy.com/index.php?topic=22886&highlight=

I used 1/2 of a Hammond 270cax for power.

I would have to say that the value of the actual amp is about equal to the knowledge I gained from doing the layout and supplemental design myself. This is where we really learn.

Aside, I have used MILA on my 2 bus with very happy results... 10k:10k of course. My ex picked it 3 out of 4 times over my Evil Twin on a passive bass. I dont know how much the expensive components in my MILA helped on that score, but who cares?

Build it.

Thanks Dave!!!


Stagefright13

Mila Dual Tube Preamp Help Thread
« Reply #10 on: November 04, 2007, 01:24:08 AM »
Hey I found  NOS tubes for 8$ a pop. Things are looking up. I just love old tubes. Not sure if I want a $54 case tho. I think NYDAVE has a good setup with the separate power supply. What is a good supplier of portable enclosures? Like Dave used?

Do you have any hum using all that in one chassis?
Amateur experimenter

Stagefright13

Mila Dual Tube Preamp Help Thread
« Reply #11 on: November 04, 2007, 01:32:47 AM »
And one more stupid question ---> can't I use a voltage doubler or tripler to get phantom power supply? And to make my question stupider how do I do that?
Amateur experimenter

louder

Mila Dual Tube Preamp Help Thread
« Reply #12 on: November 23, 2007, 08:06:29 PM »
Hi
one question after reading all the posts about the mila:
the psu sch asks for a 250vct tranny(125-0-125).
the hammond tranny some are using(369jx),its 250V-0-250v.
which one is correct?
regards
pedro

khstudio

Mila Dual Tube Preamp Help Thread
« Reply #13 on: November 23, 2007, 08:23:23 PM »
I would bet = 250V-0-250v is correct.
Kevin ~ KHStudio

NewYorkDave

Mila Dual Tube Preamp Help Thread
« Reply #14 on: November 23, 2007, 08:51:49 PM »
Ummm, don't you trust my schematic? I did design the thing, after all  :wink:

You CAN use a 250-0-250V transformer; you just need to change the rectifier to fullwave (two diodes, transformer secondary's centertap grounded). In the original, I used a 125-0-125V with a fullwave bridge (four diodes, transformer centertap not grounded) just because that's what I happened to have on hand.

Essentially, it's two different routes to the same destination.

khstudio

Mila Dual Tube Preamp Help Thread
« Reply #15 on: November 25, 2007, 02:31:17 AM »
Sorry.

It's been a while since I saw the schematic.
I just remembered the higher voltages (250v) on the schematic, on the plates.
Kevin ~ KHStudio

Stagefright13

Mila Dual Tube Preamp Help Thread
« Reply #16 on: November 27, 2007, 04:37:51 AM »
Hey KHstudio you my neighbor!

Anyways I have to get this thing rolling. I had 2 week project that slowed me down. Need to order parts and get this done by Christmas for a present for my son.

Any help in sourcing will be appreciated. Gonna order what I can find right now. I know some of my other projects took months to sort parts. But I intend to build this by Christmas!! Thanks Dave for the schematic you rule!
Amateur experimenter

Stagefright13

Mila Dual Tube Preamp Help Thread
« Reply #17 on: November 27, 2007, 05:57:58 AM »
OK I got 2 of everything lol! Is on the way. Still didn't decide on cases tho and the 1000uf caps were out of stock at Digikey. But I have tons of them at a higher voltage. Just need to order turret boards tubes and cases. Still need help on cases...
Amateur experimenter

NewYorkDave

Mila Dual Tube Preamp Help Thread
« Reply #18 on: November 27, 2007, 09:52:56 AM »
This is the MILA, right? There are no 1000uF caps in that circuit.

MasonAtom

Mila Dual Tube Preamp Help Thread
« Reply #19 on: November 27, 2007, 11:02:08 AM »
Hey Stagefright, I just got all my pieces for MILA a few days ago, so I might be able to help you source things. Let me know if you have any questions.

BTW - I'm also using 1000 uF caps in the PSU in mine (DC filtered supply for the tube heaters).

Mason


 

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