[Iniamyen]

CR4 and CR5 look oriented correctly. I tried to get a close up picture but they're pretty well hidden haha.

 

[tomb]

Quote:

Originally Posted by Iniamyen /img/forum/go_quote.gif CR4 and CR5 look oriented correctly. I tried to get a close up picture but they're pretty well hidden haha.

Their polarity is critical. There should be a tiny red "+" on the yellow blob on the positive side. If not, there's no way to tell once they're soldered in. You'd have to remove them and turn them around to make sure.

Before you go that far, what do you measure in AC Volts at the input terminal block? DC Volts into the regulator? You can measure this with one probe in "Gnd" and by touching one at the front pin on CR3A or CR3D, or the front pin on DR1A or DR1D.

 

[Iniamyen]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Their polarity is critical. There should be a tiny red "+" on the yellow blob on the positive side. If not, there's no way to tell once they're soldered in. You'd have to remove them and turn them around to make sure. Before you go that far, what do you measure in AC Volts at the input terminal block? DC Volts into the regulator? You can measure this with one probe in "Gnd" and by touching one at the front pin on CR3A or CR3D, or the front pin on DR1A or DR1D.

I can see the markings on CR5 even though it's soldered in. There are similar markings on CR4 so I deduced that it was correct without actually seeing the "+". The marking is a line pointing to the + terminal like this:

_______
|
|
|
|
+

Also I just found what may be a bad resistor in RR1. It should be 120, but it says 121K on the resistor, and Ohm's to 3K and slowly climbing.

I'll double check the rest of the resistors in the morning when I'm less likely to make another dumb mistake. Maybe I can find a cheap 120ohm at Fry's or ratshack so I don't have to wait another week

I'll post back when I get this corrected and it hopefully fires right up!

Thanks!

 

[soloz2]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif I didn't realize the Opus only needed 15VA. What about the Buffalo DAC, it's SPDIF and USB our of the box with passive I/V and only like $30-$40 more than the comparable Opus. I think the Buffalo will be in stock before the Opus. I'm patiently waiting for their revised Joshua Tree... The wait is killing me!

I don't think the Opus or Buffalo draw a lot of current. It seems to be the output stages that draw more. But without reading all the pages in the Opus thread I can't be sure and I've sent several emails to TPA over the course of a few weeks and haven't received a response yet so...
The Buffalo will end up being around $80 more. The buffalo and LCDPS runs about $190, where the Opus, USB module and LCDPS runs $185. I think the Opus will be good enough for the Max, and I'm already spending more than $$160 more than intended. I'd like to keep the overage as little as possible right now.
I'm not even entirely sure how often I'll use the USB in as I have a good sound card right now anyway. and for the time being I don't have another digital source in my office.

 

[tomb]

Quote:

Originally Posted by Iniamyen /img/forum/go_quote.gif I can see the markings on CR5 even though it's soldered in. There are similar markings on CR4 so I deduced that it was correct without actually seeing the "+". The marking is a line pointing to the + terminal like this: _______ | | | | + Also I just found what may be a bad resistor in RR1. It should be 120, but it says 121K on the resistor, and Ohm's to 3K and slowly climbing. I'll double check the rest of the resistors in the morning when I'm less likely to make another dumb mistake. Maybe I can find a cheap 120ohm at Fry's or ratshack so I don't have to wait another week I'll post back when I get this corrected and it hopefully fires right up! Thanks!

Yep - the wrong value at RR1 would do it.

Be careful checking the rest of them. You need to visually inspect the rating, if you can. Measuring will be inconclusive for many of them because they are in parallel with other resistors in the circuit.

 

[BoilermakerFan]

OK guys, Off Topic, but I had to share...

The street a few blocks over has a huge yard sale every year. This year we were out at 7:00am right at the start. Spied a set of speakers, but didn't want to lug them around so I stopped on the way back and they were still there.

Marantz HD-55 speakers for $5 for the pair. Tweeters looked great, and the mids/woofers looked too, so what the heck. Figured the L-Pads might be toasted and that's why he was selling them as "broken". Took them home and fired them up. One non-working tweeter and one non-working mid on the other. But when I pushed on the L-Pads, the two drivers in question worked! So I now have a pair of circa 1976/77 Marantz speakers for $5.

They need new cabinets, but my wife loved their sound, so they will be integrated into new enclosures that fit into the console I'm refurbishing.

Ok, thanks for listening and now back to our regularly scheduled program.

 

[UglyJoe]

Hey guys, I'm putting in a Mouser order for my Max and the recommended CM1 cap (47uF, 25 V electrolytic) is on backorder. Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement? (I think so. The only thing that is different that I see is the length, and I think that the length reported for the recommended part is incorrect anyway.)

 

[Beefy]

Quote:

Originally Posted by UglyJoe /img/forum/go_quote.gif Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement?

Seems fine. This is the cap I used UPW1E470MDD because I went for the UPW series throughout.

 

[bperboy]

Guys, I'm getting kinda antsy, I want to build another Max!

But I think I should get some K701s first to go along with my HD580s.. what do you guys think I should do?

 

[Beefy]

Quote:

Originally Posted by bperboy /img/forum/go_quote.gif what do you guys think I should do?

Finish your σ22

I'm not sure what Max you have now....... but why not wait just a touch until the MOSFET Max site is finalised, and build yourself a MOSFET Max with BlackGates?

 

[bperboy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Finish your σ22 I'm not sure what Max you have now....... but why not wait just a touch until the MOSFET Max site is finalised, and build yourself a MOSFET Max with BlackGates?

Heh, the o22 is working again, but I'm waiting for my amp boards to get back... hopefully it will all come together!

I've got a Mosfet Max right now, actually the first attempted mosfet max, so its gettin up there in age! If I do end up building another, it'll be mosfets, but with boutique caps.. although I think buying a new pair of headphones would be a better investment right now. I've only ever owned the HD580s as a pair of full-size cans; I've always ended up upgrading the hardware behind them, so maybe a new reference would be good.

 

[Beefy]

Quote:

Originally Posted by bperboy /img/forum/go_quote.gif I've got a Mosfet Max right now, actually the first attempted mosfet max, so its gettin up there in age! If I do end up building another, it'll be mosfets, but with boutique caps..

Ah, of course, I remember now!

Yeah, I think that the new changes for the MOSFET buffer, along with nice caps, will be a really nice piece of kit.

Quote:

although I think buying a new pair of headphones would be a better investment right now

Yeah, I'm at the same point in my 'career'. I really enjoy doing the DIY stuff to pass the time, but really need other gear in order to have more fun with the music.

 

[tomb]

Quote:

Originally Posted by UglyJoe /img/forum/go_quote.gif Hey guys, I'm putting in a Mouser order for my Max and the recommended CM1 cap (47uF, 25 V electrolytic) is on backorder. Will this https://www.mouser.com/Search/Produc...47-UVZ1E470MDD work as a replacement? (I think so. The only thing that is different that I see is the length, and I think that the length reported for the recommended part is incorrect anyway.)

The delay relay electrolytics are not critical. Just make sure they're 105 deg.C. because they're up there near the middle two sinks, which can get pretty warm. Other than that, any cap will do. I use Xicon's which are 8 cents each at Mouser: 140-HTRL25V47-RC. Unfortunately, they're back ordered on those, too. To tell the truth, though, I get mine locally in little 25-packs at GA Audio Lab.

The Nichicon UVZ is just fine, though:
UVZ1E470MDD

That one's 22 cents. The e12 and the original prototype BOM used a 22uf 25V radial tantalum, but those are very expensive ($2+), so Colin changed it. The 47uf electrolytic tested fine, so we stuck with it.


EDIT: There's nothing wrong with the UPW that you and Beefy discussed, either - just wanted you to know that you have a wide choice with CM1 and CM3.

 

[Cankin]

do you guys think the MOSFET Max is a better option for low-impedance headphone than MH Max because of the higher current output?

 

[Beefy]

Quote:

Originally Posted by Cankin /img/forum/go_quote.gif do you guys think the MOSFET Max is a better option for low-impedance headphone than MH Max because of the higher current output?

All other factors equal, I don't think that a MOSFET Max is going to be that much better than a BJT Max. Seriously, with low impedance phones this amp WILL deafen you before it drops out of Class A - even with FK6 tubes - regardless of the output stage.

That being said, I haven't yet seen many opinions of the MOSFET Max with AMB's suggested alterations. I'm really interested to see how it works out!