Salas DCG3 preamp (line & headphone)

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#2,402
Do that and let me know how the presentation changes with halving the kΩ, inform me the exact pot type also, so I can try grasp the total sound and maybe suggest extra tricks to further subtly system match. There is no DCSTB but a NewClassD UWB regulator and tantalum resistors in your build so some unfamiliar things, you also got big speakers with many woofers, we will have to work on it a little.
 
#2,403
Salas said:
Guys I suggest you stop the subjective fighting thing before it escalates and some moderator takes notice resulting in penalties. I will not intervene as a mod because its a rule we don't moderate in our own threads not to be prejudiced. Each one to his own preferences. Ammel likes very much an apparently class B biased BJT straightforward push pull Schiit pre with an op-amp chip driver. But the guy in the youtube review says Ammel's has glare and compression with a hint of V shaped like quality. Go figure. Others may like the class A SE discrete minimal FET DCG3 because its closer to tubes tone but Alex took out of his rack a real tubes several k$ highly reviewed Japanese preamp and listens with the DCG3. Go figure. In the end science says ABX blind all the properly measuring stuff you got and I guarantee you can't pick them apart. But all people did not just make an O2 and stopped there. Go figure.
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Sorry Salas, I didn't think my comment would've escalated into a subjective fighting thing, but apparently I was wrong.
The last thing I need is a moderator's penalties being quite familiar with them from past posts/comments.🙂

Regardless of what the clown in the YouTube video you watched states about a certain "glare" and a hint of "V shaped EQ quality", I can tell you emphatically that the Magni 3 has no "glare" nor recessed mids. If it did, I would've sent it straight back to Schiit for a refund and wouldn't have purchased 2 more Magni 3 amps from them.
In fact, one thing I can NOT stand in any audio component or speaker is a recessed midrange. My personal preference has always been for a more forward midrange to make vocals stand out, but I certainly don't prefer a more forward treble as I hear in most Class D power amps.
The bass of the Magni 3 is particularly good and may be the first thing most people will notice upon hearing it for the first time.

Though I haven't removed the cover and tried to "reverse engineer" the circuit, I agree with Patrick that the op-amps are probably for servo duty since the design is supposed to be DC-coupled from input to output.

I'm not stating that the Magni 3 is the Holy Grail of HAs, because it isn't.
But...there will always be DIYers who'll believe their amps have to sound better since "they built it themselves".
After all, isn't that what DIY is all about?😀

In this day and time $99 USD isn't much money for a HA, so if anyone on this forum thinks they have something that sounds better than the Magni 3 and they're willing to part with their amp, I'll gladly PayPal you a fair price for your amp plus shipping to compare to the Magni 3 for preamp duty.

Thank you Salas for all your help and for allowing me to post on your thread!
 
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#2,407
I've just build a second DCG3 preamp, everything went smooth.
Set for preamp duty, I have 99ma bias, should I push it little bit to, say, 100ma-110ma

Now since for this one I'm using BIBs (4 for true dual mono), set around 350mA, I'm wondering I should get two 60VA or even 80VA transformers. Mind that it would be a 21VAC whilst the standard calls for 18VAC.
Finally, since this is a class A circuit, should I use the recommended 10mf for the main cap of the BIBs or could (or maybe should) go for 15mf

I will report my findings with this one against the pretty much standard one.
 
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#2,408
It will make no difference to push it just a little. 50VA double mono is still adequate for 350mA set BIBs.
Higher secondary voltage will bring more heat to the BIBs but they also like the higher voltage across their CCS Mosfets.
6800uF to 10000uF is good for the purpose. BIBs will tax reservoirs the same no matter what class they feed. They work in constant current regardless.
We will be happy to know how you will like this new configuration. For what purpose you make a second one by the way?
 
#2,409
It's for a friend of mine who had listened to my DCG3 briefly in comparison with his, in my system. I was going to suggest two 60VA with 10mf but I though it's better to have your opinion before my friend orders his trafos. Currently I have two 22VAC which I happen to have and with 21VAC ones I'm aiming for 10V headroom.
Finally I'm gonna make some comparison with different type and size of transformers and caps just for diy fun.

The first mod with LDR attenuator went very well, my relay attenuator with Dales sounded somewhat grainy in comparison. The first hours I though : good but no big deal, after a day or two it sounded great but with a relaxed character, now can't really tell. Even with a different dac that doesn't excel in dynamics (an everyday shunt powered 9023) like NTD1, still they are quite acceptable.
I'm gonna blame it on Dales, so if I'm gonna put something against the LDR, relay or shunt / ladder, it must have better quality of resistors.

Almost forgot, thanks for the info Salas, always Johnny at the spot
 
#2,411
An opa627 based one. At the time I had First One and Hypex UCD400 (along with Avondales) and I can't remember with which one of the two we've listened.
Anyway, it had completely different presentation, interesting I though. It was quiet but it lacked high and low frequencies but in a homogeneous way, giving more meat to the music but when it came to listening female voices, I remember Sade's voice having a male tone in it (and I don't mean it was bassy) which I though was unnatural and didn't liked it unlike with DCG3 which sounds natural. It was brief so I can't really put down that good-old 627.

As for DCG3, I've changed some days ago to a 9023 dac and I detect the same character in the sound of this chip I've heard with other setups of mine or my friends. Personally that's what I want from a preamp nowadays, to show each device is connect to, it's sound, not to sound fabulous with a particular one and wost, strangely enough, with another. I must say, I have more humble requirements for the preamp from the past.
 
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#2,412
That's very nice to had found a preamp that satisfies you as neutral but also subtle to all those amps and sources you rotate. What is your current favorite source and power amp? Using big magnetostatic dipoles always or having a secondary smaller speaker system also?
 
#2,413
Always Maggies which were bought in "good old days" as we greeks say . No second system.
Same amp for 8 or more years, the others which I have the pleasure of listening are just for friends I do for free.
God's willing and pocket affording, I will start a new amp project I have postpone for quite some time. I just want to make this final test for DCG3 with BIBs and if I like it, I'll implement it's psu also to mine.
 
#2,415
Maybe its an opportunity as long as the new build is still under construction he does a comparison of BC327-40 vs BC560C in the current mirrors too. Because he has an ear for subtleties and he has access to various amps etc.
 
#2,416
Theodosis, I haven't looked at the psu chips but it's this kind of psu, a hefty one I might say. As I've written, it was brief but it had an obvious different character which for female voices I didn't like. Maybe it was a synergy between pre and power amp, don't know. With DCG3 I can hear the character of each amp as I've heard it with different preamps and in other systems also i.e. it's not a game changer, with it in the system it's more or less the same presentation of music for each amp so it retains the strengths and weaknesses of this particular amp as I've came to know them in mine or other systems.

I've finished all boards (BIBs and DCG3) but since an order at Mouser is gonna be placed, which are the following is more suitable and how many you think are needed for the matching requirements of the circuit ?
Mouser BC327-40
 
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#2,417
Even twenty would be enough to find two 5% HFE pairs between them. But as Mouser pricing goes better a hundred of the first option in the row at 0.07 each I would say. Its a lower noise pin compatible transistor to BC560C so you may use some again in other things in the future. Has more Cob (slower) but its HFE is still good (usually 400+) and shows enough consistency. If it will gel well for your subjective preference in the DCG3 is a question mark for now but expect an objective 4nVrtHz less input referred noise. That may give bit more perceived detail or not. On the other hand if it will spoil the tone just pull it out and stay with the original type. Its an easy & cheap experiment.
 
#2,418
Salas said:
Even twenty would be enough to find two 5% HFE pairs between them. But as Mouser pricing goes better a hundred of the first option in the row at 0.07 each I would say. Its a lower noise pin compatible transistor to BC560C so you may use some again in other things in the future. Has more Cob (slower) but its HFE is still good (usually 400+) and shows enough consistency. If it will gel well for your subjective preference in the DCG3 is a question mark for now but expect an objective 4nVrtHz less input referred noise. That may give bit more perceived detail or not. On the other hand if it will spoil the tone just pull it out and stay with the original type. Its an easy & cheap experiment.
Click to expand...


Is it this?

BC32740TA ON Semiconductor / Fairchild | Mouser

nash
 
#2,420
Hi,

I'm ready to go... just waiting for the transformers and the heatsink (arriving next week).

Hope this one will be beat my LME49610/LME49990 HPA I've build some time ago.

Arnd
JdNlxUn.jpg
 
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