[tomb]

Quote:

Originally Posted by MASantos /img/forum/go_quote.gif Speakers? How much power can this new MAX deliver?

Should be similar to a basic M3, but will be limited by the heat sinks. It should be superior to the Starving Student doing this, too, and dsavitsk successfully ran small speakers with that. It's not enough for something big, but certainly for some desktop flea speakers or similar. To be honest, I haven't tried it yet myself, but I'm looking forward to it. Cetoole uses his as the primary source for a pair of desktop speakers - for a couple of years now, I believe. That was just the BJT version, though. The MOSFET version is more capable.

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Should be similar to a basic M3, but will be limited by the heat sinks. It should be superior to the Starving Student doing this, too, and dsavitsk successfully ran small speakers with that. It's not enough for something big, but certainly for some desktop flea speakers or similar. To be honest, I haven't tried it yet myself, but I'm looking forward to it. Cetoole uses his as the primary source for a pair of desktop speakers - for a couple of years now, I believe. That was just the BJT version, though. The MOSFET version is more capable.

On the 2-1/2" heatsinks biased around 250mA with a bigger supply, PF, and upgraded LM338 V-Reg, it was calculated to be right around 1W. At 250mA bias, the DBs are dissipating almost 7W and that was really "MAXing" out the biggest heat sinks available.

I forget where the critical bias level is, over 180mA-190mA IIRC, but at a point over 150mA, the stock 5087/5088 small signal transistors will leave their linear range or simply see too much current. I don't have time to search through hundreds of emails to find the exact value, but just know that you can't keep cranking up the bias even if you run the 338T, larger PF, and 2-1/2" sinks.

 

[hedmaster]

Hi guys, I bought a Millet Max second hand and need some help. The inputs in the back are not the usual RCAs, rather it is 1/4" phone plug.

How much will this degrade the sound, if any? Also, there are no holes for biasing. Is that a big deal? According to the builder (have to look up for name), this amp was built about 2 yrs ago.

Would upgrading the power supply to the one on Beezar help with sound quality as well?

I plan on taking some pics of the amp, so that I can get some pointers on some potential improvements, and to get a basic understanding of the build. ie whether or not any boutique items were used or not.

I believe the tubes are the originals (12AE6s). I plan on replacing them. That means that I should buy one of those biasing tools and bias it to match the new tubes, right?

Also, do you lose much low end punch with the 12FM6 vs the AE6? What do you gain, higher resolution on the top end, or ?

Thanks for any help you can give me,
Matt

 

[tomb]

Quote:

Originally Posted by hedmaster /img/forum/go_quote.gif Hi guys, I bought a Millet Max second hand and need some help. The inputs in the back are not the usual RCAs, rather it is 1/4" phone plug. How much will this degrade the sound, if any?

It won't, but it's not very convienient.
Quote:

Also, there are no holes for biasing. Is that a big deal? According to the builder (have to look up for name), this amp was built about 2 yrs ago.

It just means you have to take the back plate off and slide out the lid to get to the adjustments. the only one you really need to worry about is the tube bias.

EDIT: But you have to have a DMM to measure the bias while you're adjusting.

Quote:

Would upgrading the power supply to the one on Beezar help with sound quality as well?

No, the only power supplies on Beezar are high-current Class II 24VAC walwarts. Sound quality is unaffected unless your present walwart is under-rated.
Quote:

I plan on taking some pics of the amp, so that I can get some pointers on some potential improvements, and to get a basic understanding of the build. ie whether or not any boutique items were used or not. I believe the tubes are the originals (12AE6s). I plan on replacing them. That means that I should buy one of those biasing tools and bias it to match the new tubes, right?

A small screwdriver will work fine as long as you don't touch anything else but the adjusting screws. Refer to this page on the MAX website for details:
MAX Setup and Bias Settings
Quote:

Also, do you lose much low end punch with the 12FM6 vs the AE6? What do you gain, higher resolution on the top end, or ?

No, you probably won't notice it unless going all the way to a 12FK6. The 12FK6 is generally regarded as having a bit more resolution on the top end, while the 12AE6 has more punch. The 12FM6 is kind've a combination of both. The primary reason for switching tubes is gain. While the 12AE6 has a lot of low-end punch, its high gain may be way too much for many headphones. The 12FK6 has the least gain and the 12FM6 is inbetween.

Note that any change in tubes will require re-biasing. The sound quality will be directly affected if you don't do this.

It's a very simple procedure, though.
Quote:

Thanks for any help you can give me, Matt

Anytime ...

 

[redfish-bluefish]

I thought I would finally say hi, as I have lurked on and off since 2005

This seemed like the best place to do it, as I have really been thinking hard on building one of Millett Max amps. I built a cmoy back in '05 and then went Lo-fi with my electronics (obsessed with building guitar pedals). At any rate, I am back on my headphones kick and wanted to ask a couple of related questions as I research the various options on the Milletts.

First, I see a lot of posts where people talk about this or that matching well with Grados. When this statement is made, are they speaking of the entire Grado lineup (if I remember correctly, they are all the same or similar impedance) or only the high-end. I ask because of my second question...

A few pages back on the thread I read that Grados would pair very well with the MOSFET build, so this is the direction I am thinking of going. Does this sound reasonable for a pair of SR 80's?

Thanks!
1,2
red-blue

 

[tomb]

Quote:

Originally Posted by redfish-bluefish /img/forum/go_quote.gif I thought I would finally say hi, as I have lurked on and off since 2005 This seemed like the best place to do it, as I have really been thinking hard on building one of Millett Max amps. I built a cmoy back in '05 and then went Lo-fi with my electronics (obsessed with building guitar pedals). At any rate, I am back on my headphones kick and wanted to ask a couple of related questions as I research the various options on the Milletts. First, I see a lot of posts where people talk about this or that matching well with Grados. When this statement is made, are they speaking of the entire Grado lineup (if I remember correctly, they are all the same or similar impedance) or only the high-end. I ask because of my second question...

When you see those statements, they're referring to the fact that the diamond buffers in the MAX/MiniMAX/MOSFET-MAX are able to supply high currents to low impedance phones such as Grados. Further, the tubes used in the gain stage give that well-rounded, warm and lush midrange that seems to "tame" the natural hotnesss and sometimes harshness of Grados. I think this applies to the entire line, but of course, as you move up in Grados, the bass gets stronger, there's less harshness, and everything gets smoother (generally). Note that the high currents also apply to K701/K702's as well. A MOSFET-MAX can supply more than enough current to elicit very strong bass from K701/K702's. The Class A bias on a MOSFET-MAX approaches 2W (not all of that is available to the headphones, though).

One caveat to that is that if you're ever thinking of using high-impedance phones, the MOSFET-MAX will do fine, but the BJT versions may have an advantage. There's a turn-on voltage that the MOSFETs need to burn to operate. This means there's not as much voltage swing available as there is with BJT's. Grados and AKG's will never miss that, though.
Quote:

A few pages back on the thread I read that Grados would pair very well with the MOSFET build, so this is the direction I am thinking of going. Does this sound reasonable for a pair of SR 80's?

I think so. I have 3 Grado's myself - HF-2's, HF-1's, and SR-225's. I've owned a pair of SR-80's in the past, too. You will not want for power if using these with a MOSFET-MAX.

Also, on a slightly different note, remember that one of the nice things about the MAX lineup is that even though they use tubes, they are all low voltage - nothing over 24-27V. That's re-assuring when you're first starting out in DIY. Quote:

Thanks! 1,2 red-blue

Welcome to the posting on Head-Fi! I hope you enjoy it.

 

[redfish-bluefish]

Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future.

And yes, it has not been lost on me that this will be a GREAT intro to tubes. I've only built one other tube circuit, even lower voltage than this, believe it or not.

After I have some time to poke around and generate questions as I attempt to answer others, I'll be tossing them out here.
Thanks!

 

[tomb]

Quote:

Originally Posted by redfish-bluefish /img/forum/go_quote.gif Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future. And yes, it has not been lost on me that this will be a GREAT intro to tubes. I've only built one other tube circuit, even lower voltage than this, believe it or not. After I have some time to poke around and generate questions as I attempt to answer others, I'll be tossing them out here. Thanks!

Good deal! We'll be here when you come back for more questions.

 

[Beefy]

Quote:

Originally Posted by redfish-bluefish /img/forum/go_quote.gif Thanks, Tomb. You Sir, are an enabler! I was waffling on this a little, but now I think I'll be scraping the cash together to do the build. Maybe I'll sell something. MOSFET it shall be. I think I should build for what I have now (I don't have much!) and collect for the future in the future.

Depending on your confidence, skills and funds, you may still be better off going with a BJT MiniMax. Beezar sells a full kit, including a gorgeous pre-machined case.

 

[radicalrev]

Guys, bought a pair of tubes from Beezar. One of tubes lights up brighter than the other, is it normal for this? Will there be an unbalanced sound? I tried listening to it and couldn't hear any difference, but still curious.

 

[Beefy]

The heater brightness is often apparently different, depending on the geometry of the glass. If you can't hear any difference, I certainly wouldn't worry.

 

[redfish-bluefish]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Depending on your confidence, skills and funds, you may still be better off going with a BJT MiniMax. Beezar sells a full kit, including a gorgeous pre-machined case.

That might be an option. tomb made a good sell for the MOSFET build. I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option?

Thanks,
1,2
red-blue

 

[BoilermakerFan]

Quote:

Originally Posted by redfish-bluefish /img/forum/go_quote.gif That might be an option. tomb made a good sell for the MOSFET build. I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option? Thanks, 1,2 red-blue

Because it's a full kit with all the machining/drilling on the case done for you. If you build a MOSFET-MAX, it has to go in a bigger chassis like the spec'ed Hammond and you have to mark and drill all the holes as well as order the parts from a few different places.

 

[tomb]

These guys are right. If you're just starting out, the MiniMAX kit is the way to go with MAXes. With the experience you learn, you can easily tackle a MOSFET-MAX later on.

One caveat to that is that I expect Glass Jar Audio to offer new kits for the MAX soon. Jeff indicated to me that he'd like to carry the new PCB as the MOSFET-MAX. He may still be accumulating all of the parts, though, because his listing still says out-of-stock. Maybe he'll be ready by the time you build a MiniMAX kit?

 

[Beefy]

Quote:

Originally Posted by redfish-bluefish /img/forum/go_quote.gif I've no doubt that I wouldn't go wrong with any of them, but what are your thoughts on why the BJT MiniMax might be a better option?

Only because it comes as a really nice kit, with everything in it. Great way to get back into DIY with less risk