[spritzer]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif For $300 it had better be a better case than the stock 4070/O2 one. Is it the same case though?

I have no idea. I haven't been able to find a picture anywhere.

 

[Duggeh]

My Omega 2 has been unplugged and the SRM-717 turned off for the better end of three weeks. I turned it on and plugged them in about 10 minutes ago but the volume is non-existant. I checked all my wiring and its fine and ive tried changing the interconnect and the power cord. The only way I get any sound is with the volume dial nearly to full.

Anyway, im worried, any reassuring words for me are they just recharging or should I be getting sound out of the box anyway?

 

[spritzer]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif My Omega 2 has been unplugged and the SRM-717 turned off for the better end of three weeks. I turned it on and plugged them in about 10 minutes ago but the volume is non-existant. I checked all my wiring and its fine and ive tried changing the interconnect and the power cord. The only way I get any sound is with the volume dial nearly to full. Anyway, im worried, any reassuring words for me are they just recharging or should I be getting sound out of the box anyway?

They should need some recharging but that is a bit extreme. Try plugging some other amp into the same source to see if the problem is there.

 

[Duggeh]

My diy portable amp and my AMT amp both work fine from the same cinch cable, I dont have the SRM-212 or SR-202 up here to do any troubleshooting that way. I think that i will be making a trip back home tomo to sort out whatever this is.

 

[spritzer]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif My diy portable amp and my AMT amp both work fine from the same cinch cable, I dont have the SRM-212 or SR-202 up here to do any troubleshooting that way. I think that i will be making a trip back home tomo to sort out whatever this is.

Try leaving them plugged in for about an hour playing music. I've not been using mine much for the last months but when I do they need an hour or more to come up to speed.

 

[ericj]

Found something odd/interesting today.

I went to go look at the lm4562 datasheet and clicked on the application notes instead.

I find that their app notes include an RIAA preamplifier and . . . a 'stat amp.

http://www.national.com/an/AN/AN-1651.pdf

This looks very simple, very easy to build.

I know it's just an example circuit in a vendor's app note, but it was an odd find indeed, and i know some of you folks know your way around an electrostatic amplifier schematic.

So I'm curious, what do you make of it?

 

[spritzer]

Looks like a good budget amp though it doesn't swing a lot of voltage. The tube output option is a nice touch and makes this comparable to the Stax amps. Without knowing the Stax circuit off hand this could be pretty similar.

 

[ericj]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif Looks like a good budget amp though it doesn't swing a lot of voltage. The tube output option is a nice touch and makes this comparable to the Stax amps. Without knowing the Stax circuit off hand this could be pretty similar.

I think it's kinda interesting that the schematic shows their latest & greatest opamp driving a discontinued obsolete mosfet. Either it's a circuit they've put in many app notes over the years or the irf72 was just the only high-voltage mosfet symbol they had handy in their schematic drawing library.

Myself, i have a hard time dedicating the time to building a 'stat amp by hand when all I've got to drive with it is some mediocre stax electrets, one rather nice sony electret, and an ESP/9. At least, when looking at stuff like a KGSS.

But this thing looks single-weekend easy.

 

[spritzer]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif I think it's kinda interesting that the schematic shows their latest & greatest opamp driving a discontinued obsolete mosfet. Either it's a circuit they've put in many app notes over the years or the irf72 was just the only high-voltage mosfet symbol they had handy in their schematic drawing library. Myself, i have a hard time dedicating the time to building a 'stat amp by hand when all I've got to drive with it is some mediocre stax electrets, one rather nice sony electret, and an ESP/9. At least, when looking at stuff like a KGSS. But this thing looks single-weekend easy.

It does look like a fun amp to build but I would use 7n7's for outputs since they are very cheap, even NOS.

I guess they used the IRF72 because high voltage mosfets are rare and getting even rarer due to the flat panel insanity and CRT's falling out of favor.

Btw. they are back!

 

[Duggeh]

The O2 has returned from the uncharge-d dead. Thank heavens.

 

[AudioCats]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Found something odd/interesting today. I went to go look at the lm4562 datasheet and clicked on the application notes instead. I find that their app notes include an RIAA preamplifier and . . . a 'stat amp. http://www.national.com/an/AN/AN-1651.pdf This looks very simple, very easy to build. I know it's just an example circuit in a vendor's app note, but it was an odd find indeed, and i know some of you folks know your way around an electrostatic amplifier schematic. So I'm curious, what do you make of it?

Now that circuit uses a LM317 as constant current source.....

 

[luvdunhill]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif Now that circuit uses a LM317 as constant current source.....

heh, I saw a circuit recently that used a LM317 and a single resistor to ... feed a power LED

 

[ericj]

Quote:

Originally Posted by AudioCats /img/forum/go_quote.gif Now that circuit uses a LM317 as constant current source.....

They make reasonably good current sources. There are better current sources, but not for the money or parts count.

Unless I'm confused, it's pulling a tiny amount of current from the source pins of the mosfets.

That bottom power rail should be labeled -15V.

Quote:

Originally Posted by lvdunhill heh, I saw a circuit recently that used a LM317 and a single resistor to ... feed a power LED

What's ironic there is that LEDs themselves are sometimes used as current sources.

I prefer to just measure the LED's voltage drop and do the math vs. the supply voltage - but some people apparently prefer the full belt & suspenders.

 

[Ken B]

Quote:

Originally Posted by audiod /img/forum/go_quote.gif Stax has officially announced a SR-007mk2 coming in October/November!!!!!!!!! Silver for Japan, Black for export.

Good to hear Stax is updating the Omega's. I think it is time for an updated 404 (lambda), don't you think?

 

[audiod]

Quote:

Originally Posted by Ken B /img/forum/go_quote.gif Good to hear Stax is updating the Omega's. I think it is time for an updated 404 (lambda), don't you think?

Most companies use their flagship model as a basis for lower priced models. Stax has surely recouped the engineering costs of the SR-007 and should start using some of it’s technology to come up with a replacement for the aging (almost 30 years old) Lambda series. Could you imagine a replacement for the 404 that is approaching the sound quality of the SR-007. I’m surprised that Stax would upgrade the SR-007 when it is almost unchallenged in the “High-End” arena and not take advantage of a O2 based upgrade for the Lambda series. Come on Stax it's time for you to help us audiophiles on a budget!