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Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
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Old 20th February 2018, 06:48 PM   #2601
615498 is offline 615498  Canada
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Join Date: Dec 2004
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Salas DCG3 preamp (line & headphone)
Default Happy camping

Hi Salas,

It's about time I posted a pic of the finished work. I recently reset the DC offset; the music (AWB today) is centered and rock solid. I love this thing!

Thanks again Salas.

Keith
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Old 20th February 2018, 06:49 PM   #2602
Salas is online now Salas  Greece
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Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by beardman View Post
i have heard that discrete opamp not are the best in servo,,,is it something with the use of jfet in normally opamp ?
He tried the OPA1642 also I think. Bipolar is not best here due to high source resistor but some still work well.
All industrial JFET input dual chips of 12nVrtHz or less noise spec that can handle +/-18V rails at least and have low THD at 10K load are technically competent to roll here. Given the resulting offset is low. I have measured and listened with some that met or bested the above criteria during the development, the OPA2604 too. They all passed with no additional noise or extra THD on the preamp's FFT. Except the traditional old TL072 that showed some measurable worsening contribution. Its below than modern average spec naturally allowed that. But the DC offset was fine.
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Old 20th February 2018, 06:52 PM   #2603
Salas is online now Salas  Greece
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Quote:
Originally Posted by 615498 View Post
Hi Salas,

It's about time I posted a pic of the finished work. I recently reset the DC offset; the music (AWB today) is centered and rock solid. I love this thing!

Thanks again Salas.

Keith
Congratulations! Nice low profile box build, Hammond allowing. Tell us a few words about the system it plays in. I see (EL34?) glass bottles there...
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Old 20th February 2018, 10:30 PM   #2604
615498 is offline 615498  Canada
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Salas DCG3 preamp (line & headphone)
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Originally Posted by Salas View Post
Congratulations! Nice low profile box build, Hammond allowing. Tell us a few words about the system it plays in. I see (EL34?) glass bottles there...
Actually, the Hammonds are normally under cover. And yes, you see right...EL34's driven by a 'Dynamutt' noval board. Magnaquest OPT's.
The speakers are from the diyAudio Fast, Fun OB project elsewhere on this site.

The phono pre (and its pricey tubes) is one of Jim Hagerman's original board kits. The sale of its tubes will buy a planned tubed phono stage (diy of course) and a few records. Sumiko arm on the table, Audio Technica 33PGTII, Kelly/Bergeron speed controller (can be searched under Maxon' GB'), Cinemag SUT,.

All good wife-approved fun...what could be better

Keith
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Old 20th February 2018, 11:04 PM   #2605
Salas is online now Salas  Greece
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Nice DIY system. I have an AT33PTGII too, great VFM. Have also listened to a friend's Manzanita OB with TC9 "tweeter" and they are good. Smooth plate Telefunken are fetching a pretty penny indeed.
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Old 21st February 2018, 05:39 AM   #2606
alexkosha is offline alexkosha  United States
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Salas DCG3 preamp (line & headphone)
Guys, I just finished my first listening session after BC327-40 upgrade and I have quite significant and very positive change in sound. Salas, please accept my respect and applause. I do not know what happen to Beardman unit, but my unit is singing. My mids and mid highs are way clearer. Very pleasant extension. It is kind of more round presentation now. I didn't trusted only my ears and asked my wife if I'm not hallucinating. She also has an absolute pitch and she was a musician in the past. Same exactly feeling. Even humbled U2 ripped CD played from my iPhone sounded like hi-end. No doubt, my second unit with LDRs volume control will be upgraded next weekend.

Last edited by alexkosha; 21st February 2018 at 06:03 AM.
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Old 21st February 2018, 06:45 AM   #2607
beardman is online now beardman  Denmark
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Alex.
it is what i will call a different experience with the BC327..

i will say the same with the more round sound,,but i miss the clearness in the sound..

to me it gave a more polite sound

the best sound right now i have ,is whit the opa2134 this is more the sound i like
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Old 21st February 2018, 06:59 AM   #2608
alexkosha is offline alexkosha  United States
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Originally Posted by beardman View Post
Alex.
it is what i will call a different experience with the BC327..

i will say the same with the more round sound,,but i miss the clearness in the sound..

to me it gave a more polite sound

the best sound right now i have ,is whit the opa2134 this is more the sound i like


I agree. We all are bit different in perception. This is a nice thing about humans. Otherwise, all will be the same and boring....
Can you tell what is your Bias set to and what volume attenuator do you use? I did not test op-amps and still use one advised by Salas. Very happy about latest test results.
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Old 21st February 2018, 07:08 AM   #2609
beardman is online now beardman  Denmark
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Yes it is good we all hear different

my volume is a TDK 2500 20kohm

i cant remember just now what my bias is,,will measure later to evening

you should try the opamp change..but i am not sure if the opa2134 will be good with the BC327
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Old 21st February 2018, 07:14 AM   #2610
Oystein is offline Oystein  Netherlands
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I am looking into this design as a future pre-amp.

As I will only use it as a pre-amp (no headphones) I guess with a > 50k load the bias current can be much less maintaining class A operation.

Any suggestions or maybe even some component change in the last amplicifation stage ?
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