em83 questions

jsax420 · 22nd August 2010, 05:41 PM

Hi all, I've been playing around with this em83 schematic, and I can't seem to make it work. Has anyone built this successfully? Also, what is .47n as shown on the schematic? I used .047uf for this as I didn't think they meant .47 nanofarads, so this might be the problem? Sorry if these are dumb questions, I'm a bit of a newb, and there isn't alot of info on the em83, especially if you don't speak German...

Also, is there an easy way to add an em83 to Frank's preamp schematic, or is this not advised for some reason? Any comments or advice will be welcome. Thanks!

hidnplayr · 22nd August 2010, 06:02 PM

The capacitors should be 0,47nF (470pF) otherwise, it will work very slowly, or perhaps even not at all.

jsax420 · 22nd August 2010, 06:14 PM

Ahhh... Thanks! I'll try that first, and I will try not to second-guess schematics in the future.

Arnulf · 22nd August 2010, 08:20 PM

And regarding that pre-amp: your magic eye VU-meter won't cause any problems to the pre-amp, but I don't think you'll be getting the results you're after (pre-amp's output swing probably isn't large enough to drive the magic eye tube to full excursion, these usually come with additional preamplifier triode and even then they require 10+V peak to peak input swing). End result is likely to be next to no action on the magic eye, while you're probably after full swing thumping ...

jsax420 · 22nd August 2010, 09:08 PM

Yes, Arnulf, I was hoping for the display to move

Does it need to be run off a power tube to get the proper voltage then? Where would you want to connect it to get better results? Thanks for all your help!

Arnulf · 22nd August 2010, 09:39 PM

I don't have the datasheet handy but the reference I found mentions it has sensitivity of 3 mm per volt which would imply it doesn't require as much as input as (say) EM84.

If I owned one and wanted to make it work I'd get a lab supply (well, I already have one so check

), apply the suitable anode and target voltage and play with grid voltage until I get the full excursion, then record whatever voltage it was to get it right and proceed from there.

You're likely to need multiple volts worth of input for full swing.

jsax420 · 22nd August 2010, 10:10 PM

Thanks again for your help!

I can probably arrange a power supply to play around with this some more.

22nd August 2010, 06:02 PM	#2
hidnplayr diyAudio Member Join Date: Sep 2008	The capacitors should be 0,47nF (470pF) otherwise, it will work very slowly, or perhaps even not at all. __________________ Real tubes have top-caps

22nd August 2010, 08:20 PM	#4
Arnulf diyAudio Member Join Date: Feb 2009	And regarding that pre-amp: your magic eye VU-meter won't cause any problems to the pre-amp, but I don't think you'll be getting the results you're after (pre-amp's output swing probably isn't large enough to drive the magic eye tube to full excursion, these usually come with additional preamplifier triode and even then they require 10+V peak to peak input swing). End result is likely to be next to no action on the magic eye, while you're probably after full swing thumping ... __________________ mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."

22nd August 2010, 09:39 PM	#6
Arnulf diyAudio Member Join Date: Feb 2009	I don't have the datasheet handy but the reference I found mentions it has sensitivity of 3 mm per volt which would imply it doesn't require as much as input as (say) EM84. If I owned one and wanted to make it work I'd get a lab supply (well, I already have one so check ), apply the suitable anode and target voltage and play with grid voltage until I get the full excursion, then record whatever voltage it was to get it right and proceed from there. You're likely to need multiple volts worth of input for full swing. __________________ mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."

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22nd August 2010, 06:14 PM	#3
jsax420 diyAudio Member Join Date: Nov 2008	Ahhh... Thanks! I'll try that first, and I will try not to second-guess schematics in the future.

22nd August 2010, 09:08 PM	#5
jsax420 diyAudio Member Join Date: Nov 2008	Yes, Arnulf, I was hoping for the display to move Does it need to be run off a power tube to get the proper voltage then? Where would you want to connect it to get better results? Thanks for all your help!

22nd August 2010, 10:10 PM	#7
jsax420 diyAudio Member Join Date: Nov 2008	Thanks again for your help! I can probably arrange a power supply to play around with this some more.

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