[adydula]

Well,

Getting the itch to solder something once again and I saw this simple amp that was selling for $499 and its now in a DIY format.

The PC board is $20 and the case is $40....and about $60 +/- in parts....

So...what a steal and its a real easy amp to build.

I just got the board and the parts have been ordered, some on back order at Mouser, but I will hot wire it to work!

Here is some info and pix from Pete Millett:










Will post as the project progress and see how this works compared to my other amps..

Alex

[Nick77]

Looks like a fun project, thanks for posting.   

[dB Cooper]

Looks like a fun project as long as you don't use really low impedance and/or IEM headphones (3 ohm output impedance and no gain switch). Probably fine for most full size cans. Maybe not for the hungrier varieties of planar though.

Found specs online, nothing jumps out as a concern except DC offset at +/- 5mv (I assume they meant microvolts, not millivolts? 5mv would be equivalent to the output of a MM phono cart)

http://www.apexhifi.com/Butte.htm#Measurements

Should be a fun and easy build with no SMT parts or point-to-point wiring. I understand the soldering bug but without that I'd probably opt for the more powerful Schiit Magni 3. Like to hear more about the build and results.

[randytsuch]

Found specs online, nothing jumps out as a concern except DC offset at +/- 5mv (I assume they meant microvolts, not millivolts? 5mv would be equivalent to the output of a MM phono cart)

Pretty sure that its millivolts.  5 millivolts is kind of normal for a headphone amp that is dc coupled.

Info on the diy version here
http://www.pmillett.com/butte.htm

[dB Cooper]

My agdr booster-board "Franken02" is spec'd at 50 microvolts DC offset and mine bench tested at about half that. That is substantially lover than either the stock O2 or this amp. But with my close range vision at this point, I'd heed a magnifier, board vise etc etc to build it. This thing looks doable even with my eyes.

[adydula]

Just got the parts from Mouser, but 4 parts are on back order until early May...so ths one will probably not play untl early May...

I have so had and still have several Schitt amps...and the magni 3 is indeed a good amp and was and still am tempted to buy one just for grins....

But the DIY thing here has always been inticing etc...this one is so simple and soldering except for the CCS parts is really easy.

Will definitley post the finding for sure.

Alex

[adydula]

Spent an hour and have all the parts in except for 6 100uf/24vdc electrolytics, the headphone jack and a rear input jack....

Pretty strightforward build, the pcb is very well laid out...only the CCS circuit stuff was a little difficult soldering...the QPC3703's for Q1/2 are vey small devices in the CCS circuit which is optional...but they help bias the amp for Class A for small signals.

The amp has a high gain of 11X from what I have gleaned...so this will be an intersting exeriment. It can easily be changed with a resistor manipulation down to 5x....any lower the op amps need to be changed due to stabiity.

Will look around and see if I can get these parts in sooner than 4 weeks +/_...

Alex

[adydula]

Well!

Its playing!!

I found the caps and headphone jack at Newark and got them this am. Put in the last 6 caps and the headphone jack...funny thing I was so much in a hurry to play with this
Millett high gain amp I soldered the caps and thought I soldered the headphone jack, which was a nice tight fit into the pcb holes but didnt!

As I was trying out headphones the jack cam out!! Ha!

So much for being careful!

Back downstairs to the shop and soldered that puppy in....

The op amp used in Pete Millett's design is a OPA552 which are optimized for gains of 5X or higher. The amp is set up with a 11x gain.

I dont ususally like to use anymore gain than is necessary to drive headphones but this was an experiment to see how this amp performs.

WIth low impedance cans like 35 ohms you cant hardly touch the volume control to get a really loud level in these cans!! With 600 ohm T1's the volume congtrol is about 9 oclock...definitely high gain here..

I immediatley went back and soldered some 1K resistors in parallel with the 1K's in the op amp circuit cutting the gain down to 6. I have more range of control and it sounds better to me.

THe 600 ohm cans are now in the 9-11 oclock range...still could stand to lower it more, BUT the op amps are designed to run at these high gains... Pete Millet has stated to run at a lower gain you should use a OPA 551 op amp but doesnt see any real difference in perf between the two.

This is a very inexpensive amp, the parts like the pot is really "cheap" or should I say "inexpensive" and you get what you pay for....I will probably upgrade this to a better alps pot in the future. Its a bit grainy in one position, but its so far away from what the gain allows me to use its not a real issue.

You could also use better caps in certain spots but again probably not going to matter that much..

So how does it sound or not sound?

This amp really liies high impedance headphones..the 600 ohm T1's sound wonderful....open, spacious great soundstage, the sound is slightly warm IMO...Linda Ronstadt's Round Midnight is a melt in your mouth experience!!

One thing with the lower gain the background circuit noise is almost in audible compared to the 11X original gain setup..this is a good thing.

IMO this is a very good pairing for the T1's. Just as good as anything else I have in house at the moment..its amazing how simple can be very good if designed well...and Pete Millett has a nice entry level amp here.

Here is a picture compared to the new Burson FUN amp I recently was overwhelmed at how good it is:




The Butte has about $45 in parts, $15 for a 12VAC 1 Amp adapter....and you can get a case for $40 from Pete Millet that has all the holes drilled out and labled! So for about a hundred bucks your home free...yes there are so many other options like a Schitt Magni 3 ( B stock for $89)....but you dont get the DIY buzz I like so much...

To me its so neat to see the pcb and the parts right there looking at you..lol.

Ok so whats next to build!!

Alex

Oh heres the specs for the Butte:

Max output leven into 150 ohms @ 1kHz: 7.2V RMS / 20V P-P / 340mW
Max output level into 33 ohms @ 1kHz: 5.0V RMS / 14V P-P / 750mW
Peak output current: 200mA
Output impedance: 3 ohms
THD+N 1V 1kHz 150 ohms: 0.003%
THD+N 1V 1kHz 33 ohms: 0.005%
FR: 20-20kHz +/- 0.1dB
FR: -3dB DC - 240kHz
Noise 400Hz - 30kHz: 30uV
Max gain 1kHz: 20dB
Dimensions: 4.3" W x 5.3" D x 2" H

Read more at https://www.innerfidelity.com/content/diy-beauty-pete-milletts-butte-headphone-amp#ym8zPsihIm2vJb56.99

[rmcdennis2201]

Hello....

I see you finally got your Millett Butte amp running. Thanks for the loaner FUN amp..it was nice..how does this comapre to it?

Ron

[adydula]

Its pretty good but the FUN is definitely better all around IMO....Its a great entry level amp and it sold for $499 commercially.

It got a good review at Innerfidelity.com and Pete Millett has been around in the headphone arena for years.

I will be happy to load you this once I get a case for it and put some heatsinks on the voltage regulators...they get hot!

Alex

[adydula]

Here a few pix of the amp running :

T1's and I am trying the Burson Cable + Pro I had lying around not doing anything.



Added the heatsinks on the voltage regulators...really helped cool them down!
Still missing the rear 3.5mm input jack and a case.

[adydula]

I havent used this amp very much and after recommedning it to several other DIY fans, who built and tried different op amps in the circuit.
I finally got out my screwdriver and opened up my working Butte and removed the design op amps, OPA 552'S that are a gih gain op amp (11x).

Which at first is way too high IMO for my useage, but we built it because Pete Millett is a headphone electronics wizard that has designed several really
nice headphone amps.

That said it was pretty good, but i preferred the "sound" with other amps more in my collection.

One of my DIY friends tried some Sparko SS3601's in his Butte and was very happy with the results.

So having many op amps in house, I tried several and settled in on Bursons Vivids.

The amp becomes less "muddled" and is similar to other solid state amps now. Very useable, clear, crisp etc.

The Vivid op amps seem to have a brighter high end to me, and with the right headphone matched its a very pleasant sound.

The new Koss KPH30i's work very well with this combination as do my Senn HD00's so anywhere from 60 ohms to 300 ohms no issues.

Still plenty enough gain and volume to blast your ears out, so please be careful with the volume. 

The only issue with the Vivid op amps is that they are tall, and the case for the Butte is too small to enclose.

I wish they made a smaller package, like the Sparkos, but I often listen to my gear opened up to take measurements and just to look at the parts!

Its the old electrical engineer in my!!

Here is a picture of it opened up with the Vivids installed....highly recommend these op amps, they seem to be able to work in a variety of circuits and
made my Millett Butte even more "Butteful"...

All the best
Alex

[adydula]

My Butte has been sitting here gathering dust so to speak and I havent tried this amp with the Focal Clears...so this am I dusted it off and inserted it into the chain.

Wow, its sounding pretty good, hard to tell the difference between it and other similar SS amps...

The only thing is its high gain of "11" which I reduced to 5+ gain...but still with low impedance headphones the volume control is at 8-9 pm...and this is in that
first part of the mechanical travel of the vol pot...so any tracking issues could affect the playback.

I dont hear that and tested the pot with a test tone and both left and right seem to track well even at this low part of the pot.
Guess I got lucky with the parts selection lottery!

But..I have ordered a set of OP 511PA op ampt to replace the OP 512PA in the original design

Why?

Because the design on the amp precludes going any lower in gain due to the 552's internal design to be used in a high gain circuit...so going any
lower could introduce oscillations (distortion) etc...

So hence the 551, this is based on a suggestion from Pete Millett.

Then I can replace two resistors from 1K to 100 ohms and voila 2x gain...

I guess I just like to play and solder!!

Stay tuned see how this "plays" out!!

Alex

[mcgsxr]

Great work!

I enjoyed the Pete Millet amp (Hybrid Max) I had a few years ago paired with a heavily modded set of Grado's. 



Currently have a Bolder modified Grant Fidelity TubeDAC-11 I use as my home headamp, but only have iems at the moment so don't have much call for a dedicated desktop headamp.

But sometimes pine for the presentation that earphones can deliver!

[adydula]

Is that a Logitech "device" in the picture?

Alex

[mcgsxr]

Indeed it was my Bolder modified Logitech SB3.  It was a great piece!

[adydula]

Ha!

Thought so, I had one in their early days.....neat device.

Alex