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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
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Old 16th April 2018, 05:24 PM   #2921
takitaj is offline takitaj  United States
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Awesome, thanks! So according to that calculator at 333k a 1uf will have a cut off of about 0.48Hz. That should work. The Audyn+ are pricey but I have experience with them in speaker and amp builds, they sound excellent. Fortunately I have extra room!

I'll post some show & tell in a little bit after my phone charges some more.
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Old 16th April 2018, 05:50 PM   #2922
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Up that to near 5Hz by choosing a 0.1uF cap instead I would say. So to avoid cutting below the servo reaction time cycle and to decrease the size & cost of the cap. Less foil and smaller dimensions are for the better anyway.
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Old 16th April 2018, 07:33 PM   #2923
takitaj is offline takitaj  United States
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The lowest value available is 0.47uf. That would give a cut off of a hair over 1Hz. Would that still be ok?

I ran the numbers on the Velman and a 1uf before the 50k pot is about 3.2Hz. Higher than I thought.
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Old 16th April 2018, 10:38 PM   #2924
Salas is offline Salas  Greece
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0.47u is good too. Still saves some size and price.
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Old 16th April 2018, 10:53 PM   #2925
takitaj is offline takitaj  United States
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I apologize for the poor pics but my phone hates darkness, even with the flash.

I did the cnc work on the front panel. The meters are getting blue LEDs inside once it's sorted. The 3rd power supply is 12v for the relays and the meter board. The Velman pre steals it's +/- from the rear DCSTB. The unconnected switch is going to be a tone defeat, someday. I plan on also adding a headphone jack in there too.
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File Type: jpg top.jpg (932.9 KB, 246 views)
File Type: jpg system.jpg (951.5 KB, 239 views)

Last edited by takitaj; 16th April 2018 at 10:55 PM.
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Old 16th April 2018, 11:05 PM   #2926
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
An interesting mix and sharing of components in a box and you managed it noiseless as a whole. Congratulations for that. Nice panel work reminding of recording studio racked tube gear...
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Old 16th April 2018, 11:08 PM   #2927
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Do you have some headphones already? If not, what will be your budget for those?
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Old 17th April 2018, 12:11 AM   #2928
takitaj is offline takitaj  United States
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No phones yet and it may be a while for those...unless I win the lottery. The speakers in the system pic are decent but they're temporary. Some 20 year old Polk Audio R50s. Next will be a 12" SB Acoustics 3way (or 4way) that I already have drivers stashed away for. Almost there!
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Old 17th April 2018, 09:47 AM   #2929
Salas is offline Salas  Greece
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What about $40 ?

Amazon.com: Koss Porta Pro On Ear Headphones with Case, Black / Silver: Home Audio & Theater
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Old 17th April 2018, 11:10 PM   #2930
takitaj is offline takitaj  United States
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Pretty cheap! I prefer an around ear type though. When the time comes there's quite a few places nearby that I can go to and listen. I may hit you up for some advice then if it's ok.

Sorry I missed where you mentioned a "quiet set up". Surprisingly it's super quiet. I can barely hear some hiss with the volume at max but only if I put my ear right up to the tweeter. Absolutely no hum at all either. Very nice!

But...I did notice something curious. I powered it up after the meter LED mod (no other mods) and I could hear a faint sizzling noise. I used a long piece of 1/2" shrink tubing up to my ear and moved it around until I located the noise. It was coming from the DCG3 around the relay. It was strongest over the transistor that drives the relay. When powered off the pitch swept up in frequency and stopped. When powered on again there was no noise until the relay clicked on. It gets quieter after left on for a while but still there. Nothing comes through on the audio, just physically from the board. I've heard similar sounds coming from the outputs devices of power amps singing while doing high power testing on dummy a load. Any idea what it could be?
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