[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif EDIT: Note that the Gold Chromate finish is not ROHS-compatible. Get 'em while you can.

How did you know I was eye'ing those? I'll be grabbing the gold screw mount 2-1/2" Aavid for the DBs and the larger 2-1/2" Wakefield for the LM338T. Would the 2-1/2" Aavid gold heatsink work for the LM338T also? They are rated for 9W so I think it should be fine. Although, Purdue colors are Black & Gold, so maybe I'll just stick with the black Wakefield for the LM338.

I'm going to keep them on separate transformers. I just don't want the amps sucking all the juice and dropping the voltage down on the MAX board. I have little DIN rail mounted terminal blocks and IEC circuit breakers, so I can get pretty crazy with the power supply wiring if I wanted too, but I'll just use the terminal blocks to make it easy. I might be putting the PSUs in a separate chassis too so I can install a couple of isolation trafos I pulled from bad UPS units.

 

[bperboy]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Although, Purdue colors are Black & Gold, so maybe I'll just stick with the black Wakefield for the LM338.

Uh oh.... I'll be going to Rose-Hulman in the fall; when I was at the bookstore last summer, I saw a tshirt that said "Friends don't let friends go to Purdue"!

 

[BoilermakerFan]

Quote:

Originally Posted by bperboy /img/forum/go_quote.gif Uh oh.... I'll be going to Rose-Hulman in the fall; when I was at the bookstore last summer, I saw a tshirt that said "Friends don't let friends go to Purdue"!

LOL! Rose is a very good school, but it wasn't co-ed when I started college. They came after me and offered a little scholarship, but I had additional priorities besides an education, so I went to Purdue instead. I forget when Rose went co-ed, but it was in the mid-to-late '90's. I actually ended up switching over to the School of Technology (now College of Technology) at Purdue and dropped Chem. E. when I realized Purdue's engineering was all theoretical paper-pushing. The Industrial Technology program at Purdue was lots of hands-on lab work and perfect for me. I still use at least 80% of my degree 12 years later. Not many Purdue engineers I know can say that. I am becoming more interested in pursuing a Masters in applied mathematics though, with a heavy focus on algorithms.

 

[pinkfloyd4ever]

Quote:

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

what are you powering your Optivols with? I've been thinking about ordering one for my Max but I don't know what to power it with(and desoldering the Alps that's in there now does NOT look like fun). Anyway, for those who don't know, the optivol requires a +/- 15vdc supply, but uses only 13 mA

EDIT: does the optivol have its LEDs & LDRs encapsulated in something light-proof? If not that's gonna be another hurdle since my Max is topless and of course it also has tube lights which would mess with the LDRs obviously

 

[djbob]

I'd like to start by sending a BIG thanks to TomB for his professionalism, dedication, guidance and wonderful support of a great project. Of course, many thanks also go to Colin for a fantastic design and his generosity in sharing the Max with us. This was a fun build and I learned alot. Thank you Gentlemen! I look forward to building more of your designs.

As for my Max, well....It is simply Fantastic. I basically chose Boutique build #2 and it sounds wonderful. I now know what the "slam" is that TomB writes about. I'm currently running 12FK6's. I've tested with Senn HD25s, AKG 240s, and AD-A700. All of them sound incredible. I've also tested with different sources and my favorite so far is my Alien Dac with Muse ES's on output.

I'm in the process of building a custom case to house the Max/Alien together. I used to build custom furniture and have some skills as a PC case modder, so I hope to produce a case that will compliment this great Amp.

Since I'd rather spend money on Audio equip.(not photo) please excuse the low quality of these shots:

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Once again, Thank you Colin and TomB.

 

[BoilermakerFan]

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif what are you powering your Optivols with? I've been thinking about ordering one for my Max but I don't know what to power it with(and desoldering the Alps that's in there now does NOT look like fun). Anyway, for those who don't know, the optivol requires a +/- 15vdc supply, but uses only 13 mA EDIT: does the optivol have its LEDs & LDRs encapsulated in something light-proof? If not that's gonna be another hurdle since my Max is topless and of course it also has tube lights which would mess with the LDRs obviously

I was planning on using either a wall wart or dropping the 18VDC in my NABU case down to 15VDC. I have an email into Greg to see which is the best way to power it. Worst case scenario, I'll have to build a little dual rail PSU. Looking at his picture on the site, the LDR are encapsuated, but they are also polarized to eliminate ambient light "noise" so the open case won't be an issue.

EDIT: There is an on-board resistor (2.2K for +/-15VDC) so you should be able to change the resistor to a higher value for a higher or lower incoming voltage. I don't see why we couldn't use the center LED points from the MAX board since they are at 24VDC without the resistor for the LED. I'll just have to talk to Greg and confirm the new value of the R4 resistor on the OptiVol board. From Greg in the SKA forum: "They're very dynamic... you only need 1 for stereo but a good source of reg DC ~ 30V @ 15mA+." So it looks like the resistor value will drop slightly.

Between the MAX board, a phono stage, Darwin, OptiVol, and gainclone amps, I'm going to need 3x24V, 2x15V, and 1x8.5V secondaries on the PSU trafos. I'll need at least two more secondary voltages if I add a DAC in the future too.

I'll be calling Victoria Magnetics for the toroids as soon as I hear back from Greg at SKA and I know which way I have to go to feed the OptiVol.

 

[BoilermakerFan]

Greg replied about the supply voltage for the OptiVol:

"The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor."

I know tomb posted the info earlier, but I have forgotten, is the center LED mount on the MAX board seeing 24VDC or 27VDC if the resistor is left out and jumpered? This center "tap" would be a great way for those interested to power the OptiVol, but realize it may not attenuate low enough on the MAX with 12AE6A tubes and high sensitivity headphones without bumping up the output resistors on the OptiVol. I'm planning to use mine on my console with the 12FK6 tubes feeding the gainclone amps and old console speakers and will order a pair of 30K resistors to drop the output more if it's needed. The kit's current supplied resistors allow for a max attenuation of -54dB and it would be -55dB with the 30K resistors.

 

[tomb]

Quote:

Originally Posted by djbob /img/forum/go_quote.gif I'd like to start by sending a BIG thanks to TomB for his professionalism, dedication, guidance and wonderful support of a great project. Of course, many thanks also go to Colin for a fantastic design and his generosity in sharing the Max with us. This was a fun build and I learned alot. Thank you Gentlemen! I look forward to building more of your designs. As for my Max, well....It is simply Fantastic. I basically chose Boutique build #2 and it sounds wonderful. I now know what the "slam" is that TomB writes about. I'm currently running 12FK6's. I've tested with Senn HD25s, AKG 240s, and AD-A700. All of them sound incredible. I've also tested with different sources and my favorite so far is my Alien Dac with Muse ES's on output. I'm in the process of building a custom case to house the Max/Alien together. I used to build custom furniture and have some skills as a PC case modder, so I hope to produce a case that will compliment this great Amp. Since I'd rather spend money on Audio equip.(not photo) please excuse the low quality of these shots: EDIT: Camera quality looks fine to me! END EDIT Once again, Thank you Colin and TomB.

Wow - thanks for the kind words, djbob! Your build looks perfect - glad you enjoy the MAX and the SLAM.

 

[tomb]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Greg replied about the supply voltage for the OptiVol: "The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor." I know tomb posted the info earlier, but I have forgotten, is the center LED mount on the MAX board seeing 24VDC or 27VDC if the resistor is left out and jumpered? This center "tap" would be a great way for those interested to power the OptiVol, but realize it may not attenuate low enough on the MAX with 12AE6A tubes and high sensitivity headphones without bumping up the output resistors on the OptiVol. I'm planning to use mine on my console with the 12FK6 tubes feeding the gainclone amps and old console speakers and will order a pair of 30K resistors to drop the output more if it's needed. The kit's current supplied resistors allow for a max attenuation of -54dB and it would be -55dB with the 30K resistors.

We went through this earlier in some of the discussions with Fran about the OptiVol, but I forget what we came up with.

Yes, each LED pad on the MAX will see the full V+ voltage, whatever you have that set at. For 27VDC and using Greg's equation above, you'd have:
(27-5.6)/0.012 = 1783ohms.
Maybe you should send him a note and ask which would be better - 1.5K or 2K. 2K is what we use for the LED's anyway.

 

[pinkfloyd4ever]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Greg replied about the supply voltage for the OptiVol: "The OptiVol is set up to run on 30V DC floating. That can mean +30V or +/-15V. However, internally it is powered from a 5V6 zener through a dropping resistor, so it can be set to run from +18V easily simply by changing the resistor. I can probably supply the changed value if I know the supply. It is a simple calculation. The unit draws about 12 mA so R = ( Vs - 5.6)/ 0.012 . For +24V it would be 1.5K, use a 0.6W or higher resistor."

what exactly is the difference between +30V and +/-15V ?

 

[Beefy]

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif what exactly is the difference between +30V and +/-15V ?

Essentially nothing. Both provide 30V potential difference between + and -.

But a ±15V would normally have a ground at zero volts sitting right in the middle of the +15V and -15V. It gives you more flexibility, because you have can 15V and 30V supplies for different parts of the circuit.

 

[amphead]

Congrats Djbob! Another Max Lives!

Very happy to find your satisfaction with the Max.

Good point Beefy, on the voltage source. Edit:Of course we don't use +/- 15 volts on the Max board.

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif We went through this earlier in some of the discussions with Fran about the OptiVol, but I forget what we came up with. Yes, each LED pad on the MAX will see the full V+ voltage, whatever you have that set at. For 27VDC and using Greg's equation above, you'd have: (27-5.6)/0.012 = 1783ohms. Maybe you should send him a note and ask which would be better - 1.5K or 2K. 2K is what we use for the LED's anyway.

I was going to use a 1.69K or 1.82K from Mouser:

71-RN65D-F-1.69K or 71-RN65D-F-1.82K and they actually have them in stock.

I emailed Greg about which value he thought was better to use.

Thanks Tom.

Note: To all, I'm not trying to imply this OptiVol is a better volume attenuator for the MAX. For my build it will be more convenient because I need to run the volume pot 18" away from the MAX board and the pot in the OptiVol is not in the signal path so induced noise will not be an issue, but I do plan to braid the connecting wires for extra caution. I know others were interested in it too when the discussion took the thread off topic, so I'm sharing the information on how to make it work if anyone else would like to try it. However, on a "standard" MAX build, in the standard Hoffman enclosure, I think the ALPS Blue pot is a lot easier to install and cheaper too.

 

[BoilermakerFan]

Quote:

Originally Posted by pinkfloyd4ever /img/forum/go_quote.gif what exactly is the difference between +30V and +/-15V ?

Greg emailed me back with this information for those interested:

"By floating 30V, I meant that there is no connection to signal ground on the powered circuitry of the OptiVol, only the signal side i.e In / Out / G.

Also the OptiVol is fully ground planed to either signal ground or chassis whichever is convenient, to minimise stray field interference."

And, FWIW, Greg is substituting a 1.8K resistor for my kits, so the 1.82K resistor from Mouser would be the better choice for 27V at the LED pad assuming the PSU is adjusted to 27VDC and the tubes are biased to 13.5VDC.

 

[soloz2]

So after trying numerous combinations of LED/resiters I've come to the solution that the white LED's I originally purchased for a Max build just are bad.

So, can anyone suggest a good source for white LEDs?