[tomb]

Quote:

Originally Posted by Migroo /img/forum/go_quote.gif 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

Yeah, the guys are right on this. The MJE243/253's have a metal back, so they will come into contact with the heat sink. There's anodizing involved, but the screw, lockwasher and nut sort of mess that up in terms of insulating.

In the MAX, the heat sinks sit on the ground plane. So, any slight scratch in the anodizing or in the PCB's green mask (green mask controls solder, it doesn't insulate) could make contact with the heat sink. If the transistor is not insulated from the sink, then you could potentially have a short if anything touches the sinks - like your DMM probe, your biasing screwdriver, the case lid, etc.

 

[tomb]

Quote:

Originally Posted by Thomas_K /img/forum/go_quote.gif 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?

You'd need to wire the 2X12 in series or the 2x24 in parallel, but other than that, 20VA at 24V should be 833ma, enough for most BJT MAXes that top out at 50-60ma buffer bias.

 

[Thomas_K]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif You'd need to wire the 2X12 in series or the 2x24 in parallel, but other than that, 20VA at 24V should be 833ma, enough for most BJT MAXes that top out at 50-60ma buffer bias.

Thanks, tomb.
I guess, since i have everything i need, i'll be ordering a MAX from Jeff tomorrow. Or maybe two..

 

[fran]

Absolutely the last thing I'd want is for anyone to be scared off asking a Q here. Thats what the thread is for!! and may I say, it is absolutely singular in the DIY world IMHO. Nowhere do you get this kind of help and variety of builds. The very fact that there are so many different builds leads to huge levels of info and experience with the max and makes it an even better amp - no easy feat. I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be. Did I mention that its a great amp too!

A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good.


OT: Side discussions can be helpful too - even if they do take up 17 posts out of 4069.

Fran

 

[pinkfloyd4ever]

fran, check ebay

 

[cronic]

Anyone looking for heatsink mounting options, I suggest taking a look at the HiQ Heat Sink Mounting Kit at beezar.com. I used them in my build and they are absolutely top notch. I should also add that everything I have gotten from beezar.com has been incredible.

At this point I have 450 plus hours on the max and 701s. It is unbelievable how great this setup sounds.

 

[tomb]

Quote:

Originally Posted by fran /img/forum/go_quote.gif Absolutely the last thing I'd want is for anyone to be scared off asking a Q here. Thats what the thread is for!! and may I say, it is absolutely singular in the DIY world IMHO. Nowhere do you get this kind of help and variety of builds. The very fact that there are so many different builds leads to huge levels of info and experience with the max and makes it an even better amp - no easy feat. I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be. Did I mention that its a great amp too! A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good. OT: Side discussions can be helpful too - even if they do take up 17 posts out of 4069. Fran

Fran,

Those are very kind words. Thank you very much.

About the 12FM6's - yes, they are getting very rare. They've always been that way, but with the popularity of the Millett and now the MAX, even more so. If you've had a chance to read the thread all the way from the beginning, you'll see that MAX builders personally cleaned out a couple of vendors of 12FM6's. Phil at Radio Daze even sent me a personal e-mail requesting that I tell everyone - among other things (a very nice e-mail, btw).

YGPM.

 

[tomb]

Quote:

Originally Posted by cronic /img/forum/go_quote.gif Anyone looking for heatsink mounting options, I suggest taking a look at the HiQ Heat Sink Mounting Kit at bezzar.com. I used them in my build and they are absolutely top notch. I should also add that everything I have gotten from bezzar.com has been incredible. At this point I have 450 plus hours on the max and 701s. It is unbelievable how great this setup sounds.

Thanks for the plug, cronic! However, it's beezar.com.

Glad you are enjoying your MAX - thanks again!

 

[Migroo]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Yeah, the guys are right on this. The MJE243/253's have a metal back, so they will come into contact with the heat sink. There's anodizing involved, but the screw, lockwasher and nut sort of mess that up in terms of insulating.

Hi Tom (And others who responded) - thanks.

I've ordered some insulating kits.

I'll post up pics when I'm done

 

[jarensberg]

Hi all! I'm been lurking for a while and need some help.

I'm finishing up my second MAX and got everything in and had a gray moment while doing the initial DB bias. I had my meter on AC voltage instead of DC. When I finally noticed that and switched to DC the reading was high (around 200mv or so). i quickly powered everything off and reset the trimmers all the way down. Now I can't get less than 70 mv or so. So, how bad did I fry things?

Thanks in advance

 

[BoilermakerFan]

Quote:

Originally Posted by fran /img/forum/go_quote.gif I know the max is not advertised as a first time build, but with the help here, and primarily from TomB, it could be.

It will be a first time build for me! But, I'll be building three at the same time, so does that make it easier or harder?

Quote:

Originally Posted by fran /img/forum/go_quote.gif A back-on-topic Q: last time I bought some tubes, the 12fm6 were out of stock in my usual places. Is this a harder to find tube do you think or did I just hit a scarce patch? Funny thing is I would like to lay hands on a pair, even though when I built my max I put in the 12FK6 first and have yet to change them out for the 12AE6 even though I said I would at the time. They sound very good. Fran

I found a source in the States that had them, but they wanted over $20 a piece for them. I actually was the one who bought the very last tube from Radio Daze. I ordered 4 and was only shipped 1.

A member here is working to help me out and try to match up a tube with my existing one... Speaking of which, I need to go take a pic of that lone tube!

 

[joneeboi]

I don't know if you necessarily fried anything. The fact that you get a voltage at all is a good sign. Set it to 110mV or so and see if you can get sound at the output.

 

[manaox2]

I'm checking out Beezar.com and working out what to order. I want to build a reasonable quality (high, but don't have a budget for good stepped attenuators) BALANCED Millett Max. I'm planning to order enough extra parts to make an extra SE Millett Max for if or maybe I think when I might mess up.

I don't have much over $900 to spend on this project alone, this seems like an good challenge for a first time amp builder. I am still greedy and want the Bass slam and good highs... I am wondering about blackgates or nicholen muse caps bypassed with a good film cap, and I know the gain is going to be kind of high with even the 12fk6 tubes, but don't want to add resistors that would lower dynamics.

Based on what I think I will also use two rk27 Alps Blue Velvet pots, Neutrik combo xlr jacks, and a standard drop power unit with a switch. I got great advice (thanks pabbi1) on a Nabu casing to separate the transformer from the boards and have enough room.

I'm going to try to start ordering parts on April 2nd and don't want to go too far all over the place for shipping. I'm going to be ordering two 2 toroids - one an OPUS DAC to make my source and the other to power the amp boards. I

I'm going to be deciding next on what transistors to order. I'd appreciate any tips others can give me, this DIY amp has the best community and support which makes me really put my faith it it.

 

[tomb]

Quote:

Originally Posted by joneeboi /img/forum/go_quote.gif Quote: Originally Posted by jarensberg Hi all! I'm been lurking for a while and need some help. I'm finishing up my second MAX and got everything in and had a gray moment while doing the initial DB bias. I had my meter on AC voltage instead of DC. When I finally noticed that and switched to DC the reading was high (around 200mv or so). i quickly powered everything off and reset the trimmers all the way down. Now I can't get less than 70 mv or so. So, how bad did I fry things? Thanks in advance I don't know if you necessarily fried anything. The fact that you get a voltage at all is a good sign. Set it to 110mV or so and see if you can get sound at the output.

Yes - Joneeboi is probably correct. You'll get up to 40mV or more with the trimmers at dead zero. If you only screwed them down 20 turns instead of 25 turns, then 70mV may still be OK.

I'm with Joneeboi - see if you can start adjusting upwards and they change accordingly - go 5-10mV at a time until you get to 90-100mV. Let it sit there for a few hours, checking it every once in awhile and listening to the sound. If all's well, then boost it up to 110mV - you're done!

They should be able to take 200mV for short periods. That's on the low side for MOSFETs, for instance, but we normally recommend 1-1/2" sinks in that case. Still, it's not that bad - assuming you don't find something wrong.

 

[tomb]

Quote:

Originally Posted by manaox2 /img/forum/go_quote.gif I'm checking out Beezar.com and working out what to order. I want to build a reasonable quality (high, but don't have a budget for good stepped attenuators) BALANCED Millett Max. I'm planning to order enough extra parts to make an extra SE Millett Max for if or maybe I think when I might mess up. I don't have much over $900 to spend on this project alone, this seems like an good challenge for a first time amp builder. I am still greedy and want the Bass slam and good highs... I am wondering about blackgates or nicholen muse caps bypassed with a good film cap, and I know the gain is going to be kind of high with even the 12fk6 tubes, but don't want to add resistors that would lower dynamics. Based on what I think I will also use two rk27 Alps Blue Velvet pots, Neutrik combo xlr jacks, and a standard drop power unit with a switch. I got great advice (thanks pabbi1) on a Nabu casing to separate the transformer from the boards and have enough room. I'm going to try to start ordering parts on April 2nd and don't want to go too far all over the place for shipping. I'm going to be ordering two 2 toroids - one an OPUS DAC to make my source and the other to power the amp boards. I I'm going to be deciding next on what transistors to order. I'd appreciate any tips others can give me, this DIY amp has the best community and support which makes me really put my faith it it.

Welcome to the MAX! You're already talking to the best person about a balanced MAX with user pabbi. However, you might also talk to the fella that fixed it for him - Amphead. Between the both of them, you should end up with a fine amp.

Remember that the balanced version will double the gain, so the 12FK6 is definitely your best bet. Other than that, I don't know too much about balanced. Pabbi still owes us that article on how to build a Balanced MAX.

As for Beezar parts, I'll be putting up a 0.18uf 96P-series Vitamin Q shortly that pairs very, very well with Nichicon Muse ES's. It makes them sound very close to Black Gates. Motherone on DIYForums.org also has had great experience with the ES's using Xicon MKP's, of all things. So, the ES's can give great performance with the right bypass. They're pretty good with Wima's, too.

As for transistors, my personal favorites are the Toshiba 2SC3422/2SA1359's. However, the Toshiba 2SC2238/2SA968's win the cult status as the most neutral-detailed/hardest-to-get. So hard, in fact, that I don't have them - neither does anyone else, AFAIK - and counterfeits are rampant, so be careful if you go to another source. I also think that the Sanyo 2SC2344/2SA1011's are very similar, but with a slight emphasis on the high end. That works well with the warmth of the tubes. I hope to have the MOSFET MAX option worked out by then and will be selling parts for those, too.

ES's with those VitQ's in front and Wima's elsewhere, 12FK6's, and 2SC3422/2SA1359's is very hard to beat and not very expensive, either - at least $100 cheaper in parts than using Black Gates. Black Gates are very nice and unbeatable if you have the time for break-in and use them often (they will lose their break-in if you let them sit too long). So, take your pick, I guess.