[Ampersand]

forgive me for butting in, but what was the concensus on best moderate-to-low gain tube for the MAX? I remember reading in one of these posts, but i can't remember now if it was the 12Fm6 or 12Fk6. I know the 12fk6 has the higher gain, but is one slightly better than the other for overall sound? I'm currently running the Can't Miss Build #1 through Grados.

Thanks,
mike

 

[fran]

I've just been outside doing some other work and a light bulb lit over my head:

The optivol can easily be made to fit the case. The pot can be mounted as usual on the front panel and then just fly wire it to the optivol PCB. Fully built as stock, it measures 50mm by 25mm (2" x 1").

Wiring it:

1. your power supply: + and PS ground.

2. Left - hot and ground in and out

3. Right - ground in and out

4. Another ground wire which connects the ground plane of the PCB to your main PS ground.

If you are fly wiring it, just a matter of 3 wires to essentially extend the legs of the pot.

Fran

 

[tomb]

Quote:

Originally Posted by Ampersand /img/forum/go_quote.gif forgive me for butting in, but what was the concensus on best moderate-to-low gain tube for the MAX? I remember reading in one of these posts, but i can't remember now if it was the 12Fm6 or 12Fk6. I know the 12fk6 has the higher gain, but is one slightly better than the other for overall sound? I'm currently running the Can't Miss Build #1 through Grados. Thanks, mike

By all means - butt in. It'd be nice to get back to discussing the MAX.

The 12FK6 has the lowest gain of all of the Millett tubes. Chances are you'd want those for Grados. Here's the list:

Tube....Amplification Factor(gain)
12FK6.........7
12FM6........10
12AE6/A......14

Now, the actual results in the MAX are quite a bit lower and depend on the impedance of the load - but that gives you the breakout comparison among the tubes.

As for detail/bass slam, the 12FK6 has the most detail and "air", while the 12AE6/A has the most bass slam. The 12FM6 is sort of inbetween, but probably closer to the 12AE6 in my experience. These are very generalized listening experiences, of course.

 

[fran]

we are discussing the max

 

[Ampersand]

Right, the 12fk6 has the lowest gain - what i meant to type. And in fact, these are my current tubes. Just wasn't sure if people preferred the FM's over the FK's if there wasn't a preference for gain.

 

[tomb]

Quote:

Originally Posted by fran /img/forum/go_quote.gif we are discussing the max

Actually, we've been discussing pots for so long that I've had people PM'ing me for help on their MAX instead of posting in this thread. This was because they didn't think we were providing support anymore.

Ampersand might've been another case of that, since he "apologized for butting in." You'll just have to forgive me if I get a bit concerned when I start seeing comments and PM's like that.

Quote:

Originally Posted by Ampersand Right, the 12fk6 has the lowest gain - what i meant to type. And in fact, these are my current tubes. Just wasn't sure if people preferred the FM's over the FK's if there wasn't a preference for gain.

I think you'll find that MAX builders run the gamut on tubes. Everyone has a favorite. Generally speaking, though, the differences run as I mentioned in the previous post - it just depends on which you prefer and how those tube tendencies match up with your headphones.

 

[Ampersand]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif I think you'll find that MAX builders run the gamut on tubes. Everyone has a favorite. Generally speaking, though, the differences run as I mentioned in the previous post - it just depends on which you prefer and how those tube tendencies match up with your headphones.

Great! I've been really enjoying this MAX build (my 2nd actually). Just wanted to make sure i wasn't missing something profound by using the 12fk6's.

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif By all means - butt in. It'd be nice to get back to discussing the MAX.

LOL!

I don't know, I think this is part of what makes the Millet hybrid and Colin's MAX design in particular so amazing. I haven't built mine yet, but based on all the posts and comments, I think it's safe to say it's a very good sounding amp if built to the standard BOM and it becomes a great sounding amp with relatively low cost upgrades. Then you can add another $100 and take it over the top of headphone amps that cost 3 to 10 times more.

I certainly know that nobody implied the design or BOM as spec'd was flawed and it requires a LDR to "fix" the problem. I'm planning t o build one with the LDR and two with the ALPS pots. I'll decide which volume attenuator I like the best with each individual build and decide if it's worth the $10 difference to add it to all the builds and reallocate the ALPS pots to better uses. It all comes down to my challenge of the best bang for the buck for my personal listening tastes.

The one potential "drawback" to the LDR that I saw was is it potentially limited attenuation that may not be low enough for certain speaker/amp combinations. This could potentially be an issue with easy to drive cans or IEMs like my Denon C700s, so that will be something I'll take into consideration for my office MAX console build. It's a non-issue for me since my gainclone amps will all be built on the LM3886 chip with mute, so I can just flip a switch to ground the mute pin and it will be quiet enough...

And in my case, for at least two of my console builds, the push on volume pot is a benefit and very welcome because my vintage knobs are all push-on types!

But, as Tom pointed out, my builds fall into the "advanced" category and I won't using the stock BOM enclosure for at least 3 of them.

- BMF

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Actually, we've been discussing pots for so long that I've had people PM'ing me for help on their MAX instead of posting in this thread. This was because they didn't think we were providing support anymore. Ampersand might've been another case of that, since he "apologized for butting in." You'll just have to forgive me if I get a bit concerned when I start seeing comments and PM's like that.

Missed your post when I was typing my last one, so I wasn't trying to pull it off topic any more. I am disappointed to hear that peeps thought they couldn't post their requests for help because they were afraid of interrupting a side discussion of the MAX building process.

 

[tomb]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Missed your post when I was typing my last one, so I wasn't trying to pull it off topic any more. I am disappointed to hear that peeps thought they couldn't post their requests for help because they were afraid of interrupting a side discussion of the MAX building process.

Well, in truth - some of it has been the horsing around about John's expensive builds, but the pot discussion entered that, too. Regardless, your post didn't seem out of place to me.

 

[Migroo]

Hi guys.

This has probably been covered before, so apologies. I've read through a great deal of this thread, but I've probably missed parts as its so long!

I have a question on insulating the heatsinks. I've read the page on the MMax site - MAX Heat Sink Mounting but I'm still not too clear.

Must I insulate the parts from the heatsinks, or is it optional? I have some thermal compound, but I guess that isn't the issue...

 

[ruZZ.il]

Quote:

Originally Posted by Migroo /img/forum/go_quote.gif Hi guys. Must I insulate the parts from the heatsinks, or is it optional? I have some thermal compound, but I guess that isn't the issue...

It's optional, but heavily advised! to the point that one could define it as a mandatory precautionary measure. Thermal pads should be put between the transistor and the heatsink and depending on the transistor type, possibly insulating shoulder washers too. What type of transistors are you using?

 

[BoilermakerFan]

Quote:

Originally Posted by Migroo /img/forum/go_quote.gif I have some thermal compound, but I guess that isn't the issue...

I'd be careful there too, as Artic Silver is a very common CPU thermal compound, but it is conductive and could cause problems if you plan to use it or a similar compound.

 

[Migroo]

I got a kit from Jeff Rossel at Glass Jar Audio - so I believe I have:

LM317T for power supply regulator
QB8L/R = MJE243 NPN power transistor
QB9L/R = MJE253 PNP power transistor

Thanks!
Chris

 

[Thomas_K]

Seems like a nice little amp this. I have sent an e-mail to Jeff to inquire about shipping costs.

In the meantime i have been looking for a wall wart to power the thing with, but i can't find anything locally. I do however have a few toroidal transformers lying around. A 230V primary with 2x 24V secondary windings should be good, should it not? Or maybe one with 2x12V secondary windings and couple them in series to get the required 24V. I have both 2x12V and 2x24V available. Both are 20VA. Can i use one of these, or do i need something more powerful?