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-   -   Salas DCG3 preamp (line & headphone) (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone.html)

Salas 6th April 2020 09:35 PM

Not R9, the R6 in DCG3. 4X=12dB. Judge if enough for you. Next level is R6=2.2K for 15dB.

Oracle1 6th April 2020 09:58 PM

Thank you!!!

JOIMONF 7th April 2020 09:30 PM

1 Attachment(s)
I completed today the internal wiring. The potentiometer is external, arduino based LDR, I took chance this kind has hability to drive output cables and placed on their own box.
DCB3 has further opened up de sound after two days. I feel confident leaving it powered on these days, as the temperature only reach 37'5 C. degrees on all transistors, same DCG3 and Ubib! Placing dissipators bellow turned to be good idea.
I took care also the internal wiring is graphene with cotton isolation. The same wiring I use in my headphones. On front panel, I placed three different headpone shocket wired in series.
A big thanks Salas and Tea Bag keeping this possible, it turned to be great pleasure at many levels.
Now I will move to build ACA amplifier. Another project that I have all parts stored, for too much time waiting for free time.
Jordi.

Salas 8th April 2020 05:21 AM

You are welcome.

A non standard build configuration that works for you nicely. Congratulations for your efforts. You are also much into headphones I assume.

Keep in mind that the LDR concept adds enough THD of its own due to non linearity of its core elements. Mainly second harmonic. I recommend you try some other attenuation solution at a point also, just to know what is best for you. There are affordable decent pots like the Allo 10k ladder for a taste.

Good luck with your ACA project, stay safe, and let us know in case of any future DCG3 parts changes and evaluations will take place in your build.

donhughes111 8th April 2020 05:16 PM

DCSTB DCG3 pre
 
I am building a standard config DCSTB DCG3 pre with BOM parts. Dual mono configured. I have an Antek 05-20 tx. Can I use it with another 05-20 or do I need to drop down to an 05-18 duo? Starting with gain of 3. Will it run hot? Is it a problem if I try to go for 4x gain? I also want to try it with UBiBv1.3. can I do all this with the 05-20's?
Thanks,
Don

JOIMONF 8th April 2020 05:30 PM

1 Attachment(s)
Taked into account, thanks, and good whishes also stay safe.
In pic atch. DCG3 in my system.
Foot base is magnetic levitation, placed asimetrically due to the gravity center towards the transformers on the left.
Before final assembly I took time to compare different fets on J1 J2.
Having disposable only one true Toshiba transistor, I do all test on one channel only.
Four contenders, Toshiba 2sk170, Chineese 2sk170, Upa68h, and Linear System 2sk170.
In first I heard Chinese. Then Toshiba on J1, after some minutes not much, it become clear that Chinese are bad sounding. Switching Toshiba to J2 worsens the sound. Learned J1 is more critical to sound, so left again Chinese at J2, I was trying different IDSS on J2 and preferred above 7mA. Then when switch to uPA, I learned that those chinesse are good quality, changed my mind after notice that uPA actually less dynamic and extension at both extremes. Finally I placed Linear Systems 2sk170 and deceived again, these sound terrible, mid frequencies recessed, highs hurting the ears and lows bloomed without detail.
uPA much better midband, timbre and coherence, not disturbing. Chinese another jump up more extended high and low extremes, more projection and dynamics, mainly above 7mA. IDSS. You may though it misses nothing till heard Japanese Toshiba. I remember perfectly how much carry further the qualities above mentioned of extension, projection and dynamics, maybe thanks better detail rendition, or low noise (exemplary low level resolution).

myleftear 8th April 2020 06:05 PM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post6152889.html#post6152889)
I recommend you try some other attenuation solution at a point also, just to know what is best for you. There are affordable decent pots like the Allo 10k ladder for a taste.

Sorry to interfere, but this could be appropriate.
I just stumbled upon the muses attenuator, there's (almost) only very good things to read about... (and 3 or 4 different products from US, Japan, Germany...)

Do you know of it? What do you think of these?
(for the mesmerize, also...)?

Stay all safe!
david

Salas 9th April 2020 01:08 AM

Muses has been used for DCG3 by a couple of builders in this thread and they reported happy with it. Without having made comparisons with others, but it worked alright to their liking.

Salas 9th April 2020 01:20 AM

Quote:

Originally Posted by donhughes111 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post6153604.html#post6153604)
I am building a standard config DCSTB DCG3 pre with BOM parts. Dual mono configured. I have an Antek 05-20 tx. Can I use it with another 05-20 or do I need to drop down to an 05-18 duo? Starting with gain of 3. Will it run hot? Is it a problem if I try to go for 4x gain? I also want to try it with UBiBv1.3. can I do all this with the 05-20's?
Thanks,
Don

If DCG3 will be run at 100mA output stage bias, the 2V higher than standard Tx it will cause +0.4W extra dissipation to the DCSTB's sinks. It will probably not ruin the day. Depending on the size and ventilation of the box you will evaluate if the heat exchange is still acceptable.

UBiB heats up more with each excessive AC Volt because of its CCS section. But it is externally sinked so you can help the situation. Its not fixed. DCSTB can only take the next tall model same profile board level sinks on the other hand.

4X gain setting is no problem, DCG3 does it with ease, changes nothing in the heat department by the way.

Salas 9th April 2020 01:24 AM

Quote:

Originally Posted by JOIMONF (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post6153622.html#post6153622)
Having disposable only one true Toshiba transistor, I do all test on one channel only.

Wait for stereo evaluation with matched genuine JFET sets, affects the subjective impressions differently in some areas.


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