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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 Today, 08:32 AM   #3791
jimk04 is offline jimk04  United Kingdom
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I have a couple of TEAC separates chassis that are I think 215x270.....snug
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Old Today, 09:04 AM   #3792
Billy Graham is offline Billy Graham
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Join Date: Jul 2017
Location: Bangalore
Hi guys,

My uncle & I assembled a DCG3 preamp with DCSTB DC Power stabilizers. Used two 18 0 18 toroidal transformers for power. I'm using Salas I-Select Mesmerize Type input selector and volume control.

This is then fed into Anaview AMS - 1000-2600 power amp - Imported from Germany.

Power amp, pre-amp, selector, transformers are encased in one chassis.

Output - Jeff Bagby kairos continuum - assembled by us (model - mpbarneyspeakers).

DAC - Grace audio - M9XX


The problem: When I switch on the amplifier - I get an initial buzz. This happens even when the volume is cut off. The buzz lasts for 2 seconds and its gone. Everything is fine after that. The sound is not from the amp - I connected an alternate pre-amp and there is no buzz. I get the buzz when connected through DCG3 preamp.

Can anyone help me out with this please?

Thanks,
Billy
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Old Today, 09:15 AM   #3793
Salas is offline Salas  Greece
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Location: Athens-Greece
Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by jimk04 View Post
Is it REALLY bad idea to have dcstb in a separate chassis to dcg3. Connected by umbilical for the DC. Probably a max length of 6 inches wire between both boards?

Trying to squeeze it all in a small chassis I think is going to give me problems with trafos close by to dcg3 and RCAs etc.. so considering separating trafo and dcg3 in a box on top/underneath.
The main DCG3 board has local decoupling capacitors so it won't oscillate with longer PSU cables. I had tested with lab leads power lines during the project's development and it could oscillate if without C6 C7. If the SQ will go down a bit I don't know, I only know it should work stably, subjectively its for you to evaluate.
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Old Today, 09:19 AM   #3794
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by Billy Graham View Post
Can anyone help me out with this please?

Thanks,
Billy
What's the input impedance of your amp?
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Old Today, 09:36 AM   #3795
Billy Graham is offline Billy Graham
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Input impedance single ended: 2.5 to 14.5 kilohms
Input impedance balanced: 1.37 to 14.5 kilohms
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Old Today, 09:49 AM   #3796
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Does it power up separately or at the same time with the preamp?
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Old Today, 10:00 AM   #3797
Billy Graham is offline Billy Graham
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Same time with the preamp
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Old Today, 10:12 AM   #3798
Salas is offline Salas  Greece
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Salas DCG3 preamp (line & headphone)
Do a couple of experiments. First put 150k resistors at the preamp's line outputs (one per channel hot to ground). If that won't help, modify to can switch the amp later than the preamp.

If one of those tests will work, its about a short period that bothers the amp before the preamp's relay establishes output connection. Else there would be buzz all the time and not only for 2 secs. If it proves so, establish separate power on switches. Unless the resistors are enough.

Useful to can warm up this Class A preamp before listening sessions also. Always switch the preamp first, wait to hear the relay click, switch on the power amp. When powering down do the reverse procedure.

Interesting system that one you described BTW. Does it sound coherent as a whole? Any pictures of the build?
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Old Today, 11:15 AM   #3799
Marra is offline Marra  United Kingdom
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Join Date: Nov 2009
Location: Near Lincoln
Salas DCG3 preamp (line & headphone)
Quote:
Originally Posted by jimk04 View Post
I have a couple of TEAC separates chassis that are I think 215x270.....snug
Cosy but should look good.
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