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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 20th April 2019, 06:34 PM   #3781
jimk04 is offline jimk04  United Kingdom
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So I finally have a fully functional dcg3. Only myself to blame for silly errors but with the incredible help from Ian (IDM on this forum) it is all good.

Ian has been a saviour to this project for me and I am eternally grateful .

So the dcg3 playing this afternoon. Through an incorrect 10k pot labelled up wrong as I asked for a 20k....this to he remedied very soon. Playing as source an Rpi with hifiberry dac+pro.....still standard SMPS for the entire source.

Sounds very good indeed. I had the Rpi set up with the EQ to add some low level boost. I have 3" fullrange speakers that naturally dont go very low .

Well immediately with the dcg3 in place I had to turn the EQ off as the bass boost was now harming the SQ. Only listened to a couple hours but I am very pleased and happy in the knowledge I now have my probable life long pre amp . I just need to implement a proper chassis for it now .

One question I have.....I get some background hiss on some tracks.....FLAC radio on RPi included. Not coming through the music but at quiet movements in the song you get the hiss.

Is this an input impedance thing that can be helped with resistors ....bare in mind I still need to change to the 20k pot.

Tomorrow I shall test different sources to compare.
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Old 20th April 2019, 08:35 PM   #3782
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Congratulations and kudos to IDM of course

If the background hiss is noticeable on some tracks but not on all tracks then it's not primarily the system's background noise itself. With some given audio source gear at least. It's possible you could live with less voltage gain in the power amp if somehow adjustable. So your dynamic range and background blackness become better optimized. An indication of too much system gain is going too loud with too little volume pot turning. Higher impedance pot will not change the gain, only the tonal forwardness aspect.

P.S. We naturally expect the "triumphant return" video after the trouble description video we had once seen.
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Old 20th April 2019, 09:40 PM   #3783
jimk04 is offline jimk04  United Kingdom
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Of course.....triumphant video to follow
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Old 22nd April 2019, 07:13 PM   #3784
killie99 is offline killie99
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Maybe I missed the post with the answer jimk04 but what was the fix for the issue with the dc offset drifting?

I got my DCSTB powered up today and it worked first time, all output voltages within 10mV of each other, +- 17.15V. So glad I double checked all the parts before I powered it up.

Need to get a heatsink for the DCG3, looking for something that will allow me to fit it in a maximum 60mm high case. Anyone sourced one in the UK?

Any recommendations for hook up wire from the iSelect to phono sockets?

Last edited by killie99; 22nd April 2019 at 07:16 PM.
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Old 22nd April 2019, 07:23 PM   #3785
jimk04 is offline jimk04  United Kingdom
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Hi killie.

Well it was all down to a mistake on my part getting 2 resistors values transposed. I had though I'd been showr careful....and I have good eyesight.....measure twice cut once and all that .

And I think Ian found a dry joint around the OP amp.

Had it playing for a good while today and it is doing a lovely job.

Regarding chassis....yes....find loads online and then the shipping is as much.

I bought a couple TEAC separates......tuner and cassette deck.....in their narrow form factor. Suits my rack nicely as I dont have much spare width.

Picked then up for maybe 30gvp shipped for the 2. Separate auctions. Nice sturdy shell and I will make a nice acrylic or wood face plate.

Good luck with the rest of your build
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Old 22nd April 2019, 07:42 PM   #3786
IDM is offline IDM  United Kingdom
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Hi James,
I am delighted that you are pleased with the dcg3 and that I was able to be of some help.
Cheers
Ian
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Old 22nd April 2019, 08:45 PM   #3787
jimk04 is offline jimk04  United Kingdom
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Good man Ian.

Killie.....heatsink from RS components. Less than 10gbp iirc.

Edit

SK85-50-SA | Heatsink, 1.3K/W, 50 x 160 x 40mm | RS Components
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Old 22nd April 2019, 09:13 PM   #3788
killie99 is offline killie99
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thanks James, I'll get one of them ordered.
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