High-end preamp for my GC

[ashok]

Is there a new trend for pigeon curry?

Not new trend...............old trend !
A delicacy !

 

[MBK]

Skmenon,

I see you used those convenient looking mid size proto boards from Sim Lim. Beware the substrate is very soft, must be sort of a cardboard mix, not glass fiber. I once built a circuit with OPA627 on one of those and got oscillation despite usual decoupling. I believe they are so soggy (especially in SG) that parasitic conduction / capacitance can mess things up easily.

 

[Nuuk]

Not new trend...............old trend !

Case solved! Now we know where those pictures have gone

 

[air]

Carlos: What differences have you made in the design between the headphonamp and the preamp? (except the different ops) Other gain? Output impedance?

 

[carlosfm]

I'm back...

To haunt you.
Guys, I'm sorry, I've been out for 3 months, working and without any chance to come here.
Not much time now too, but I'll try to read the thread from where I left.
Note: I've done plenty of things meanwhile, but my pre is still the same.
And that means something.

 

[Nuuk]

Nice to see you back again Carlos! And congrats to Porto

 

[carlosfm]

Hi Nuuk!
Well, I've said to some spanish colleagues of mine here at work that Porto is not Milan...
It's much better.

Curious... you're the only one non-portuguese that I know that doesn't say Oporto...

 

[Nuuk]

Curious... you're the only one non-portuguese that I know that doesn't say Oporto

We used to call them Oporto but now (for some reason) the media always refer to Porto!

I was hoping that my team would play them in the final but it looks like we will have to settle for the new manager instead!

 

[carlosfm]

Ok guys, I'm reading the thread now, give me some time...

My experience is that it sounds better even when driving pwer amps.I am currently using the PPA headphone amp with four paralleled buffers per channel as my preamp.I thought that one buffer would be enough for preamp duty (250ma per buffer) but when I started adding buffers the dynamics went thru the roof - huge difference.Made the gainclone sound like a kilowatt hi-end amp with no smearing or lack of finesse.

Protos, you're challenging me.
Someday I may try it.
That's a macho man pre.

Finally built the second channel and applied the mods-
All I can say is that if the GC was a great DIY discovery, this pre is equal in impact! Soundstage is amazing-This is the best I have heard and considering the small outlay, this is the best bang for buck DIY can provide. Music is simply delicious...You actually listen to a musician communicating now-not just information but emotion.
Carlosfm was right on the 200pF cap-it cures some edginess-Seems it may be worth playing around with.
A strongly recommended upgrade to the GC! Thanks to Pavel Macura and Carlosfm for introducing the delights of this beautiful device.

Rest of system: Proceed PDT3, Theta DAC, NIGC, Royd doublet speakers

Ryan

Hi Ryan!
I'm so glad you made it!
Your words tell me:

1. You've seen the light.
2. I'm not mad, I was not hearing things, your words remind me my enthusiasm after listening to my pre.
3. It shows that you know how to LISTEN.
4. I always said that the GC (be it IGC or not NIGC) works better with a good pre.

It seams that Peter Daniel has found out this too recently, so he has seen the light too.

Yes, this is really a special thing.
One of these days we might join the people that built this pre and drink some beers (including Pavel, of course).


Note: The 200pf cap is the final touch that makes this pre ULTRA-HIGH-END.

 

[carlosfm]

(Not that I am doubting the findings of Carlos FM etc )

Make one and try it, Nuuk.
I'm not mad.
Yet.
Or does this pre have some mind blowing effect?

 

[carlosfm]

Carlos: What differences have you made in the design between the headphonamp and the preamp? (except the different ops) Other gain? Output impedance?

1. Other op-amp (the beautiful OPA2132).
2. More gain (I don't remember, but I think that I set the gain at around 10x).
3. 100 ohm output resistor

 

[KT]

If anyone makes a finalized version of the board, any interest in selling one or two? I think there are a bunch of us who would like to give it a try.

Regards,
KT

 

[TeePee]

I'll take 5

 

[jonclancy]

....perhaps with provision for paralleled output buffers???

Jon

 

[Alcaid]

I've made a PCB layout (continuesly modifying it, though), but I haven't buildt it yet (exams ). Currently discussing it here.

Current status:

 

[skilpad]

Hi Alcaid,

Some comments on your BUF pre,

This is probably splitting hairs but ideally the current charging
the main reservoir caps C11,12 should not be conveyed by tracks passing right underneath the opamp
If however you plan to do a copper pour on say the top layer connected to GND then you might get
away with routing only +15, -15 on the bottom layer below the opamp
This sed I still believe that you could gain from supplying power from the BUF's side of the board and
moving C11,12 to either side of the BUF so as not to increase the distance between the opamp and the BUF

I hope this helped

Regards

 

[Alcaid]

Hi Alcaid,

Some comments on your BUF pre,

This is probably splitting hairs but ideally the current charging
the main reservoir caps C11,12 should not be conveyed by tracks passing right underneath the opamp
If however you plan to do a copper pour on say the top layer connected to GND then you might get
away with routing only +15, -15 on the bottom layer below the opamp
This sed I still believe that you could gain from supplying power from the BUF's side of the board and
moving C11,12 to either side of the BUF so as not to increase the distance between the opamp and the BUF

I hope this helped

Regards

Don't know if I understood you correctly, or you understood me. The red layer is the top layer, and it is a groundplane. The blue is the bottom layer, and it only contains V+, V- and signal routing.

 

[skilpad]

Hi Alcaid,
I was revering to the smaller version of the board without the pot
but I see that the final version is done quite differently and I can't spot any problems there.

Best of luck

Skilpad

 

[jhead]

PCB's

When you should get around to finializing your design and have boards made I would be interested in possible two or more I'm sure others will also have like interest in what your doing

 

[air]

carlosfm:

Thank you,

I built one of these (opa627 + buf634, gain ~10)

I have tested the preamp, and it sounds great. But, it sounds even better without the buf634 Maybe this is because I dont need the buf, when my preamp is close to my poweramp, or some other cause. Also tried it with headphones, and it sounded great too.. havent tried headphones with only opa627 yet, but someday I will..