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Salas DCG3 preamp (line & headphone)
Salas DCG3 preamp (line & headphone)
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Old 6th July 2021, 03:52 AM   #5731
gadut is offline gadut  Indonesia
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@pfarrell

thanks for your concise review, seems Salas already design a very good product. btw Headphone session is only a 2nd system for my WFH desk, nothing serious. I'm using old LG V20 as my source playing Deezer Hifi and headamp, tweaking with EQ software brought different presentation instead of default.
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Old 20th July 2021, 10:15 PM   #5732
stew1234 is offline stew1234  United States
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Salas DCG3 preamp (line & headphone)
I was originally planning to go with two DCG3 boards for a balanced configuration due to my DAC and amp being balanced but am intrigued by the simplicity of the below balanced input pre-amp kit that can use the MUSES volume attenuator.

The DCG3 would replace the line amplification and the volume attenuation would be performed on a single-ended signal and then converted back to balanced.

Does anyone have experience with this kit?

ISB | academyaudio
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Old 21st July 2021, 02:31 AM   #5733
elwood625 is offline elwood625  United States
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I have the VCM and MCU for my DCG3 balanced preamp along with a 4 input relay balanced selector. No experience with the opamp preamplifier, the DCG3 is a class A preamp, so I built two sets of boards. I'll complete it when the weather changes to winter, after listening to a friend's DCG3, I never considered anything else. I'm sure the opamp preamp is nice, but I'm looking for exceptional sound which is why I spent the money for the muse.
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Old 21st July 2021, 08:03 AM   #5734
Despearce is offline Despearce  United Kingdom
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Quote:
Originally Posted by Salas View Post

So the about +/-17.5V PSU should be capable of at least 200mA on the positive and 100mA on the negative to cover the demanding load example. There is little more to add for the input stage and the servo.
If using double mono BIB shunt regulators a 250mA CCS limit for the positives and 150mA CCS limit for the negatives would be the economic choice heatwise. Double that when with common between channels mono regulators. If using the double mono DC stabilizer there is nothing to set. Its just a low noise non amplified voltage reference with a compound current pass transistor (Sziklai) of high enough amperage.

When not planning to use headphones, or at least not below 70 Ohm impedance ones, then 150mA CCS per rail limit for double mono regulators will suffice.

I'd like to build the DCG3 and have just started reading this thread. So if I'n going to use 4 BiB boards to power the preamp, and won't be using headphones, is the calculation for R1 on the BiB build R1 = 600/150 or do I need to add 100mA? I don't want to make assumptions but having read the UltraBiB build guide was left wondering if CCmA is the same as CCS?
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Old 21st July 2021, 09:03 AM   #5735
Salas is online now Salas  Greece
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Salas DCG3 preamp (line & headphone)
You could also target 570/200 to include Vbe bottom tolerance for closest stock value Rset (R1) 2.8Ω and about 200mA total per UBiB unit. Many DCG3 run at 110-120mA when on 10Ω R10 instead of 100mA on the nose.
Due to matched M3 Vgs (off) samples bit stronger than prototype's likelihood. So 200mA UBiB current limit goal allowing little more welcome slack in reserve.
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Old 21st July 2021, 01:14 PM   #5736
stew1234 is offline stew1234  United States
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Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by elwood625 View Post
I have the VCM and MCU for my DCG3 balanced preamp along with a 4 input relay balanced selector. No experience with the opamp preamplifier, the DCG3 is a class A preamp, so I built two sets of boards. I'll complete it when the weather changes to winter, after listening to a friend's DCG3, I never considered anything else. I'm sure the opamp preamp is nice, but I'm looking for exceptional sound which is why I spent the money for the muse.
The idea would be that the DCG3 replaces the opamp preamp line driver but uses the source selection and attention features. How are you using the MUSES for attenuation on two DCG3 boards? Also, what balanced input selector do you have in mind?

I have been trying to settle on the best approach to get balanced input/out as my DAC and amp are fully differential and also in corporate a single-ended turntable into the mix.
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Old 21st July 2021, 09:04 PM   #5737
elwood625 is offline elwood625  United States
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I'm using 2 VCMs stacked to make a balanced volume control, the Academy Audio website has download info to create a balanced control using 2 VCMs. The selector I'm using I found on eBay, cheap relays however so I replaced them with quality relays.
If you decide to build a balanced version using two boards, make sure you let TeaBag know and he will match the transistors for the two kits. Very important! Salas said that only one power supply pcb is needed even with a balanced build.
It's projects like this that make me look forward to winter.
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Old 22nd July 2021, 02:30 AM   #5738
alexkosha is offline alexkosha  United States
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Salas DCG3 preamp (line & headphone)
Guys, can’t source ADA4625-2 JFET OPAMPs. All reputable warehouses are out of stock now. Maybe some of you have an extra and you will be willing to sale some… I need 2 pieces. Please PM me. Thank you. Alex
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Old 22nd July 2021, 02:38 AM   #5739
hpasternack is offline hpasternack
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Can't you use ADA4625-1? Mouser has thousands of them in stock.
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Old 22nd July 2021, 05:56 AM   #5740
alexkosha is offline alexkosha  United States
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Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by hpasternack View Post
Can't you use ADA4625-1? Mouser has thousands of them in stock.

It is for U1. Must be Dual.
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