[tomb]

Brian,

Here is the pic I was talking about this morning. I could be wrong, but it seems like this would make it much easier to keep track of six separate wires.

This is from Minh Luc's MAXes. He built a couple of excellent examples - one with BG's-VitQ's and one with ES's-K42's:

I love those yellow LED's - gonna have to try those next!

 

[tomb]

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif I'm thinking it's probably the change in my house's line voltage, cause I just checked it and it's 117.2 volts, and every other time I remember checking it it's been right around 120. I checked the bias of the DBs, and I've never had the cover on my amp (too lazy to drill all those holes, plus I love being able to see the inside of it). What are the PS smoothing caps, the little yellow ones b/t the 4 diodes behind the 'sink? I don't know why one of the solder joints would have come loose, but I guess it's worth checking...although I just remembered that I stressed one lead of one of em (if they are the PS smoothing caps) a little too much and cracked the casing when I was soldering them. Maybe I'll get a new one of those with my next mouser order.

Nah - the PS smoothing caps are the four big electrolytics. They help to keep the voltage at its highest after rectification.

Yes - I agree about your line voltage. It could be enough to make a difference. Still, if you have your DB's cranked up, you could back off a bit. Overall performance is probably better with the higher voltage than another 10-20ma of Class A bias.

 

[Beefy]

I've noticed some interesting behaviour on my Max......

Firstly, power supply. At idle it is 27V completely stable, while at load with music it raises a touch and oscillates slowly between 27.1-27.2V. Is this normal behaviour?

Secondly, I thought that a good way to match the tube bias exactly would be to set the left tube at 13.5V ground-TA2L, then set TA2L-TA2R to zero volts using a DC MV scale and the right trimpot. It works well initially, but again, I notice some slow oscillation of about 0-25mV between the two points. Now this may be related to small power supply oscillations, but it may also be something different. Any insight?

 

[Beefy]

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif I used to get about 24.85V ac at the terminal blocks, and now I'm reading as low as 24.2 at times.

Just had a thought..... what do you get as the unloaded AC voltage out of the wallwart? This might be a better determinant of your wallwart's health.

For comparison, I get ~28V AC unloaded.

 

[tomb]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I've noticed some interesting behaviour on my Max...... Firstly, power supply. At idle it is 27V completely stable, while at load with music it raises a touch and oscillates slowly between 27.1-27.2V. Is this normal behaviour? Secondly, I thought that a good way to match the tube bias exactly would be to set the left tube at 13.5V ground-TA2L, then set TA2L-TA2R to zero volts using a DC MV scale and the right trimpot. It works well initially, but again, I notice some slow oscillation of about 0-25mV between the two points. Now this may be related to small power supply oscillations, but it may also be something different. Any insight?

On the first one, it may be that you're experiencing a similar issue as pinkfloyd4ever. It could be that the voltage difference is right on the edge for the LM317. Now, why it goes up slightly - would you be perhaps using high-impedance phones? They put less of a current load on the buffers - even compared to idling without a load. If the LM317 is on the edge of regulation, it's conceivable that it could vary slightly upward. Just a guess, of course.

On the second one - I'm not sure the tubes are even capable of maintaining a bias within 25mV - within a tenth of a volt, maybe, but to be honest, I've never measured them with that kind of resolution. They seem too much like mules to ever toe the line that closely.

 

[Beefy]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif would you be perhaps using high-impedance phones?

No, 32 ohm Audio Technica phones.

Quote:

On the first one, it may be that you're experiencing a similar issue as pinkfloyd4ever. It could be that the voltage difference is right on the edge for the LM317.

I doubt that is the case, because the heatsink gets quite warm, so Vreg is obviously burning a fair bit of power to achieve regulation. Nevertheless, maybe I should drop it down to 26V and see if the behaviour changes.

Of course, it might also be the case that it is oscillating between 27.149-27.151V, and the DMM rounding to four significant figures makes it seem worse. In any case, I'm not particularly concerned because the amp sounds great - just interesting behaviour, that's all

 

[pinkfloyd4ever]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif N Of course, it might also be the case that it is oscillating between 27.149-27.151V, and the DMM rounding to four significant figures makes it seem worse

damn dude I don't find that unusual at all, I think you can expect that much drift from this PS, you have to get up into several hundreds of dollar power supplies to get less I'd think

my unloaded voltage is about 27.9v, used to be a little higher, but again I think it's cause of my house's line voltage

 

[fault151]

Hi guys my hook up wire arrived today, its 24AWG. My immediate impressions is it looks a bit on the thin side???

Will it still be ok for use a hook up?

 

[tomb]

Quote:

Originally Posted by fault151 /img/forum/go_quote.gif Hi guys my hook up wire arrived today, its 24AWG. My immediate impressions is it looks a bit on the thin side??? Will it still be ok for use a hook up?

24AWG is good for headphone cable, but 22AWG is all I've ever used for hookup. The 24ga may still be fine if you don't run it too far.

 

[nysulli]

24 awg is good for a few amps, anything past 2 amps though i'd go with something bigger, or just double up on the 24 awg

 

[fault151]

Quote:

Originally Posted by nysulli /img/forum/go_quote.gif just double up on the 24 awg

Yeh thats what i was thinking. Its pretty good stuff, just looks a little thin. Iv compared it to my 22awg shielded cable and there isnt a huge difference, although its obviously thicker. I'll just use it anyway then. Cheers guys.

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Brian, Here is the pic I was talking about this morning. I could be wrong, but it seems like this would make it much easier to keep track of six separate wires. This is from Minh Luc's MAXes. He built a couple of excellent examples - one with BG's-VitQ's and one with ES's-K42's: I love those yellow LED's - gonna have to try those next!

Thanks Tom. Didn't spend anytime online last night, my allergies have been killing me and the meds knock me out.

I have yellow-orange and yellow-green LEDs to try. Not bi-color, just their wavelength is in-between the two standard colors. I'm only going to be tube lighting one of my amps though. The other two will be buried in consoles, so there is no point to drilling out the tube sockets. LEDtronics has some pretty neat color selections too. I have a few other potential projects in the works that require a lot of LEDs, so the minimum quantity requirements won't be a problem for me, so I might pick up a few more unique colors.

 

[BoilermakerFan]

Does anyone make 3" heat sinks that will fit the MAX boards? All I have seen is 2-1/2" or less in Mouser's catalog. I don't even want the solder post style as I would prefer to have threaded heat sinks with screws.

My wife is pushing to get this console finished.

So I "had" to order the TPA Darwin Source Selector kits and the SKA OptiVol kits today. I actually opted to order one of the OptiVols as an assembled and tested unit so I know one will at least work as it should. I'll be ordering the gainclone amp kits from audiosector.com at the end of the week.

The gainclones need about 300VA at 24VAC and I was planning to use a 100VA 24VAC torroid for the MAX, but would it be ok to power both from the same torroid? Each component has it's own rectifier/regulator, but how much headroom should I allow for the gainclone amps if they get a little thirsty? Would 400VA be enough, should I just step up to 500VA, or keep them on separate trafos?

 

[amphead]

It seems that separate xformers, allows you the most versatility, while a combined/central xformer may or may not be cheaper. I'm leaning towards separate, however this is your call BMF.

 

[tomb]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Does anyone make 3" heat sinks that will fit the MAX boards? All I have seen is 2-1/2" or less in Mouser's catalog. I don't even want the solder post style as I would prefer to have threaded heat sinks with screws. My wife is pushing to get this console finished. So I "had" to order the TPA Darwin Source Selector kits and the SKA OptiVol kits today. I actually opted to order one of the OptiVols as an assembled and tested unit so I know one will at least work as it should. I'll be ordering the gainclone amp kits from audiosector.com at the end of the week. The gainclones need about 300VA at 24VAC and I was planning to use a 100VA 24VAC torroid for the MAX, but would it be ok to power both from the same torroid? Each component has it's own rectifier/regulator, but how much headroom should I allow for the gainclone amps if they get a little thirsty? Would 400VA be enough, should I just step up to 500VA, or keep them on separate trafos?

I agree with Amphead on the transformers. You could still combine them all with the same power lead, so it wouldn't get too cumbersome.

As for the heat sinks, I think we are stuck with 2-1/2" maximum. I did some research last night and that appears to be the limit of the offerings from both Aavid and Wakefield. Both of their catalogs are a little much to go through in one sitting, but Allied's Catalog Page 748 shows the pertinent Aavid line pretty clearly:
https://www.alliedelec.com/Catalog/p...df&pageNum=748

The "531 ..." series are what are used on the MAX for the output transistors.


EDIT: Note that the Gold Chromate finish is not ROHS-compatible. Get 'em while you can.