[tomb]

Harbor Freight - most of the time, they're $2.99 - all I ever use ...

P.S. Thanks for your comments on the site, mb3k - that's high praise coming from you.

 

[mb3k]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Harbor Freight - most of the time, they're $2.99 - all I ever use ... P.S. Thanks for your comments on the site, mb3k - that's high praise coming from you.

Excellent, but I just found out HarborFreight does not ship to Canada

Anyone up to helping a fellow DIYer?

 

[splaz]

Maybe try some electronics/hardware shops if you have any around. Most should carry cheap multimeters with hfe, maybe not at such a low price but still pocket change.

 

[NeilR]

Quote:

Originally Posted by threEchelon /img/forum/go_quote.gif Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound?

I initially planned on socketing all the buffer parts necessary to make a "convertible" buffer. I got hung up over how to socket the output transistor positions. I bought some nice transistor sockets that accept either the smaller TO-92 leads or the big fat TO-220 leads. The problem is that the sockets are offset from the pin position. Although I think I could physically place the sockets on the board, the transistors would have sat out from the heat sink and I was concerned that I would not get good thermal contact with the sinks. Also, the RB8 pad would have been at least partially underneath the sockets.

Edit: In addition, you would have to figure out how to set up the elevation of the output transistors such that they either fit one of the available pre-drilled holes on the heat sink or you would have to drill new holes. This would have to be done with at least 8 trannies and sinks, potentially a great deal of effort.

With a lot of care it might be possible to bend the transistor leads to set up that offset.

I was able to use those transistor sockets in the QB2/QB3 positions, and I did so, mainly to experiment with the signal drivers in or out, both of which are viable build options. I'm not sure if, for example, the JFET position could be socketed with that part. Can't be sure now without an empty spare board, but it doesn't look good.

You would also have to socket the JFET (QB1) and almost certainly the two trim pots. I socketed the trim pots because I didn't have 1K trimmers handy (I had not done my breadboard trials before placing my order) and I planned on swapping out my 2K trimmers (which I did thanks to Tomb's help with the needed parts). I know that Steinchen successfully socketed TO-92 parts on the dDB boards and has an image on his web site. I grabbed a couple TO-92 parts at random and tried plugging them into some SIP pins. I wasn't comfortable with the fit. The leads were a little too loose for my comfort factor.

I was in a hurry to get my build completed because the MOSFET configuration and BOM was dependent on my work, and decided that all the above didn't fit my schedule and time available.

In summary, though, electrically it is very easy to socket the board such that it can be configured either way and I hope someone does this some day. The problem is with the mechanics of the socketing. If you can get past that hurdle, I can help you with some configuration ideas. Given your casing skills, you could probably figure out these mechanics.

Although I have a Millett with dDB boards in addition to the Max Millett I have not compared them. I'm probably the wrong person to do that anyway because I don't hear a lot of differences between minor part changes such as transistor swapping and I don't have a good way to quickly A-B two amps (something I have been mulling over for quite some time but haven't built the rig).

Neil

 

[vixr]

WOW! tomb... that site is amazing. Thank you for the awesome support.

 

[tomb]

Quote:

Originally Posted by threEchelon /img/forum/go_quote.gif Will anyone be selling matched transistors or even entire kits?

You should do your own transistor matching. Seriously, it's discussed in pretty good detail on the site. Moreover, I was just checking 2n5087/2n5088 prices on Mouser today:
http://www.mouser.com/search/Product...ey512-2N5087BU
http://www.mouser.com/search/Product...ey512-2N5088BU

There are multiple listings just this cheap: $2.90 per 100

Combine that with a $2.99 DMM from Harbor Freight that measures HFE (also available at many other places for $10 max), and there's no excuse for anyone not to match their own. Buy a hundred of each - you'll never worry about not having enough, stepping on a few, or losing them under the sofa cushion. You will have more than enough for sufficient matching for perhaps a half dozen to a dozen MAX's.

Quote:

Also, do you have to choose between the diamond buffers or MOSFETs? If so, what are the differences in sound?

Neil detailed the issues with switching back and forth. The short answer is YES, you must choose. For now, the diamond buffer has been vetted for years with ample support on Steinchen's site, Tangent with the PPA, etc. It is the default choice, but does not short on performance. Keep in mind that you can easily bias up to 50ma or more, perhaps. The PPA is limited to 30ma, not that I'm comparing the two amps - just relative biasing.

The MOSFET version has been built by two people: NeilR and Bperboy. Along with its huge current demand, it should be considered the more challenging of the two options and may potentially have more teething/troubleshooting issues.

 

[tomb]

Quote:

Originally Posted by vixr /img/forum/go_quote.gif WOW! tomb... that site is amazing. Thank you for the awesome support.

Thanks, Vixr. Your tube photographs really add some class to the page on Millett tubes.

 

[cfcubed]

Quote:

Originally Posted by threEchelon /img/forum/go_quote.gif Will anyone be selling matched transistors or even entire kits?<snip>

Looks like jrossel (glassjaraudio) over @ headwize is considering putting together a kit for this... If it's anything like his deal on his Level 1 SOHA (but more $$$ of course) it'd be nice. Even tho I only finished the SOHA a week or so ago, I don't see myself resisting this Millett Max

 

[abcheng]

I have a couple questions about the MH max. 1. Can I use a 24VDC wallwart instead of 24VAC wallwart? 2. Can only the amp portion of the MH max be built, or does the E12 delay circuit, and DB circuit have to be populated?

 

[tomb]

Quote:

Originally Posted by abcheng /img/forum/go_quote.gif I have a couple questions about the MH max. 1. Can I use a 24VDC wallwart instead of 24VAC wallwart?

Hmm ... not recommeded. You can connect the DC walwart and it will work - just dropping a volt or so through the rectifier. Or, you can bypass/jumper the rectifier string completely. However, there's not much of a way to avoid the regulator and expect to have decent performance. The regulator will lose you another 3V. By that time, you'll only have about 19-1/2V, which is substandard for even the regular Millett.

There are some AC walwarts that are quite powerful and cheap - the kind that have screw terminals and a little screw tab on the top to screw in the center hole of a wall outlet. Those typically range 0.8 - 1.5A, and cost about $6-$9.

on the web has a good example:<br />
<br />
[URL="http://www.allelectronics.com/matrix/AC_Wall_Transformers.html]http://www.allelectronics.com/matrix/AC_Wall_Transformers.html
The Type "D" ACTX2420 is 830ma and only $6.50, the ACTX2440 is 1.6A and still only $8.50.

You should be able to find these in an HVAC supply store, Graingers or McMaster if you don't want to order from All Electronics. Jameco has the 830ma version, too.

You gain voltage with an AC walwart going through rectification and filtering stage - (1.4 x 24V) - 1.4 - 3 = 29.2VDC

Quote:

2. Can only the amp portion of the MH max be built, or does the E12 delay circuit, and DB circuit have to be populated?

No. The MAX's output stage is the DB circuit. There are no BUF634's or DIP-8 sockets for monolithic buffers/opamps. It's possible that the e12 can be jumpered out, but it's there to protect your headphones from driver-destroying DC spikes upon power-on and power-off.

 

[bperboy]

The main benefits of the redesigned Millett is that the buffer and the e12 circuit are built in on the board, as well as the power supply regulation. Thats what makes it a great little amp; only one board needed for all the different features!

 

[abcheng]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Hmm ... not recommeded. You can connect the DC walwart and it will work - just dropping a volt or so through the rectifier. Or, you can bypass/jumper the rectifier string completely. However, there's not much of a way to avoid the regulator and expect to have decent performance. The regulator will lose you another 3V. By that time, you'll only have about 19-1/2V, which is substandard for even the regular Millett. There are some AC walwarts that are quite powerful and cheap - the kind that have screw terminals and a little screw tap on the top to screw in the center hole of a wall outlet. Those typically range 0.8 - 1.5A, and cost about $6. on the web has a good example:<br /> <br /> [URL="http://www.allelectronics.com/matrix/AC_Wall_Transformers.html]http://www.allelectronics.com/matrix/AC_Wall_Transformers.html The Type "D" ACTX2420 is 830ma and only $6.50, the ACTX2440 is 1.6A and still only $8.50. You should be able to find these in an HVAC supply store, Graingers or McMaster if you don't want to order from All Electronics. Jameco has the 830ma version, too. You gain voltage with an AC walwart going through rectification and filtering stage - (1.4 x 24V) - 1.4 - 3 = 29.2VDC No. The MAX's output stage is the DB circuit. There are no BUF634's or DIP-8 sockets for monolithic buffers/opamps. It's possible that the e12 can be jumpered out, but it's there to protect your headphones from driver-destroying DC spikes upon power-on and power-off.

Awesome, thanks for answering my questions. This is off topic, but I just noticed that you live in Atlanta.

I haven't seen many people from Atlanta in here.

 

[vixr]

woo hoo!!! got all my parts ordered...my credit card melted into a puddle but I can still make out the numbers!!! I still cant get over how great the MAX site is...

 

[bperboy]

Quote:

Originally Posted by vixr /img/forum/go_quote.gif I still cant get over how great the MAX site is...

QFT! TomB, very nice work! Even though I've already done my Max, this would be an invaluable resource!

 

[fordgtlover]

Big cheers for all those invloved. I join the chorus of praise for the new site. It is excellent.