Salas DCG3 preamp (line & headphone)

[Salas]

Originally Posted by Tea-Bag

Listened to Peter Gabriel's Scratch My Back version of Heroes over the DCG-3 the other night.
It's a slowly sung song, seems close mic and it ramps up to a kind of chilling end with strings if you let it.
The lower mids of his voice never sounded so strong. The presence of him in the room was both strong, almost uninvited after a certain point. You may get this emotional reaction when you realize the sound can really have a visceral affect on you like that. This is one of the reasons I like audio - to get this experience from music. Sometimes you can only get that when the equipment is crisp and spot on. Like the low-noise of the folded, this pre allows you to squeeze a little more information out of your gear, and push it at you. It's not even a spectacular recording, but it's well delivered.

I felt like sharing this part of it. That the circuit may kick your butt if you let it.

I am very interested in what VGeorge and Salas have to say with their headphone shoot out.

Hey Mike, George visited yesterday afternoon. He will post at a point I believe but he got tired from the round trip I guess. Me I changed some components from generic to better grade today but not too fancy. Some signal path related dirt cheap generics to RN60 Dales (not even all of them - enough desoldering for one evening) and I also changed C5 MKS2 to MKP2 (it fits alright). Can hear little better smoothness, info, and space. Not a night and day difference but at this level worthwhile. It took an hour of warm up to settle because I changed the random local lytics to fresh Pana FCs too. I am listening to DSD "Any Major Dude Will Tell You" (Steely Dan - Pretzel Logic) in DoP right now. Reminds me of my old vinyl record enough. Here's a photo.

[merlin el mago]

Salas what DAC are you using to stream DSD?

[Salas]

AUNE S16

[vgeorge]

As teabag said, when over to salas two days ago and we had a headphone testing with his new headphone - line amp.
Dacs we used were his old and trusty 0404 EMU and his new Aune s16.
Headphones were my Sony MDRV-6 and AKG712 pro and salas AKG612, Grado SR60 and Sennheiser HD600.
We started with the EMU to get used to the sound of the headphones and continued with the Aune, which proved to be more revealing and better dac overall. I think that the EMU showed his age.
I also listened to the 712 and the HD600 direct from the Aune, as it has a dedicated headphone output. I preferred the Sennheiser, but it was obvious that the Aune could not properly drive the AKGs.
With the DCG3 now, there was a different game! It should be mentioned that it had no problem to drive any of these cans properly and at high level.
All of them sounded better through the DCG3. Everything was much more transparent and more musical.
The Sony and the Grado sounded very nice but the Sony were a little bit hot on the treble. Decent resolution for old designs.
The 612 and the HD600 were very similar in character, very neutral but I think that the 712 got the edge with a bit more musicality.
The DCG3 was powered by salas cap multiplier and used generic cables and components and nothing seems missing.It is really good! Only wonder could happen with dual BIBs and premium components.......

[Salas]

Originally Posted by vgeorge

but it was obvious that the Aune could not properly drive the AKGs.

The Aune is proud of a very potent integral headphone amp. The weird sound thing with its driving the 62 Ohm AKG712 PRO leads me to believe it also has high output impedance though. Maybe 30 Ohm and only properly compatible to 300 Ohm plus models because they always picture it with Sennheisers. Given it drives the HD600 alright it should always give better result with those at least than with sending the signal out to another amp through long wires and a pot. Well, not always

[Salas]

Originally Posted by vgeorge

The 612 and the HD600 were very similar in character, very neutral but I think that the 712 got the edge with a bit more musicality.

The 612 is indeed great value for money and neutral in tone. Being much cheaper is bit coarser in the treble and bit opaque in the mids vs the two more expensive ones. The HD600 gives the impression of better clarity like having a generally faster resonance decay spectrum. The 712 is noticeably cleaner and softer than the 612 covering distance but still more lush than the 600. Both AKG are self adjusting and feeling like wearing a cloud when the Sennheiser clamps me and after a few hours it gives me a mild headache. If I had to have only one model for enjoying sweet but accurate enough music in comfort I would get the 712. The HD600 is more like a test instrument.

[MASantos]

Originally Posted by Tea-Bag

Listened to Peter Gabriel's Scratch My Back version of Heroes over the DCG-3 the other night.
It's a slowly sung song, seems close mic and it ramps up to a kind of chilling end with strings if you let it.
The lower mids of his voice never sounded so strong. The presence of him in the room was both strong, almost uninvited after a certain point. You may get this emotional reaction when you realize the sound can really have a visceral affect on you like that. This is one of the reasons I like audio - to get this experience from music. Sometimes you can only get that when the equipment is crisp and spot on. Like the low-noise of the folded, this pre allows you to squeeze a little more information out of your gear, and push it at you. It's not even a spectacular recording, but it's well delivered.

I felt like sharing this part of it. That the circuit may kick your butt if you let it.

I am very interested in what VGeorge and Salas have to say with their headphone shoot out.

Interesting!!! I ordered a couple dozen jets for this project already!! Never hurts to have extra!!

[Salas]

Originally Posted by MASantos

Interesting!!! I ordered a couple dozen jets for this project already!! Never hurts to have extra!!

Any >3mA idss sample and preferably of no more than 2mA idss difference to use between channels will do fine. The LTP's tail CCS forces the units to bias at about 2.5mA Id per LTP side. There the Yfs is the same for any >idss unit because fixed lower on the curve. So no need to have many for producing careful matches.

[massimo]

Another Salas' interesting design! Thank you for sharing, it definitely deserves a try.

I have a few questions:

1. uPA68H (old, fat) or uPA68HA (new, slim)? You had the chance to test both, any prefrence? Preferred Idss grade should be K or L in this application, shoundn't it?

2. Series or shunt O/P relay: you stated "I avoided (shunt) because in case of strong transient the robust output stage is capable of passing strong current to the ground through the relay contacts." I prefer shunt. If the tiny contacts (1A) of the relay concern you, why not use them in parallel?
Or, maybe better, use two shunting contacts after R15/RZ. Yes, it costs few € more, but using two relays (and associated components) allows to equally load the PS, especially if dual mono. The same applies to U1 when using a single op-amp (see below).

3. DC Servo: a friend of mine (EE) claims that lowering the frequency (he goes down to 0.1Hz! ) it becomes "less audible" (better phase response). Did you try going lower than 2.3Hz?
I read you tested several dual op-amp but the "classic" LF411 very often seen in many designs, including JC's. It's described in the datasheet as "low offset, low drift high speed integrator", it's single and much cheaper. Apparently perfect.
No doubt the AD823 suggested is a good choice from a reputed manufacturer, anyway. BTW, does it exist as "single op-amp" with a different designation?

4. Power supply: you proposed a dedicated series PS. No shunt regs this time (i.e. SSLV1.1)? Does the DCSTB sounds better with this circuit? If I would like to use the SSLV1.1 should I leave out C6/C7 or fit a couple of low value resistors before these caps?

Naste kalà!

[PJN]

I too am very interested in this project. Always on the lookout for SS designs that can compete with valve designs. Count me in for a board when they are ready.

PJN