[rbbert]

Great!  The 6922 offers even more (and much more expensive) options for tube rolling than the 6SN7    Will any of the Cca and ECC88 variants work here?

[SoCalWJS]

OK guys, I have the bread-boarded circuit playing in the music room now!  I am running it direct to the amp to make sure that it is quiet and I am very pleased!

I ha

For Example:

• Analog tuner or other analog device into analog inputs.  The signal will be converted to digital and then decoded, but it will all pass through the DAC and tube analog stage.

[/b]
Pricing is expected to be in line with our other mods, starting at $2500 (mod only) for full tube mod with external PS 9.0 (tube rectified but not regulated - sounds best for this model) supply and Truth umbilical.  Audio Magic Pulse Gen and Bybee rails will be evaluated also.


More to come!

Expect to see the Sonica DAC at Axpona!

Thanks,

Dan

If I am reading this correctly, can it be used strictly as an Analog to Digital Converter for getting vinyl onto a computer?

May have to rethink my strategy... Haven't seen anything yet on the 205 having Analog inputs.[/list]

[modwright]

See you there!

[Ric Schultz]

The analog input on the Sonica is not even specified at what frequency and bit it is converting the analog to digital......even Oppo says right in the manual that it ain't no great preamp.  Just a convenience thrown in to make it more versatile.......and the Oppo has no digital out so cannot be used to send digital signals to a computer or anything.

[modwright]

True, the analog input is just that, a convenience.

I don't really see the need for a digital out, considering it is a DAC?  The Transporter was both transport and DAC, true.

I am really enjoying the sound of this unit now that I have fitted it with a fully differential, transformer coupled analog stage.  No feedback, no op-amps, no electrolytic coupling caps...

Dan

[modwright]

Tube rolling today!

As it works out, this circuit, because of the use of CCS's - Constant Current Sources - allows for the use of different tubes.

So far, 6922/7308/6DJ8 has been the basis of design.  I wanted to evaluate the 6CG7 however, because it is the 9-pin equivalent to the 6SN7. I.e. it IS the same tube, but in a small bottle - check the curves! I also tried the 6H30. All three of these have the same pinout and all require 6V filaments.  The PS 9.0 is capable of providing the higher current needed for the 6H30, so no problem there.

Because CCS's are used, the different tubes settle in at different operating points.  I checked and all operate in a comfortable range on their curve.

First Impressions:

The 6CG7 (same as 6SN7), not surprisingly, has a bit thicker and richer tone than the 6922.
The 6H30 is operating at a bit lower plate voltage than ideal, so is not as fast sounding as it typically sounds, but it sounds good.
I will have to go back to the 6922 again and compare with the same music.

The cool thing however, is that no matter what tube I settle on as Basis of Design and that will ship with the mod, all three of these tubes can certainly be used.

I know that many people love the 6SN7 tube and this has been the Basis of Design for our Oppo 95, 105 and Sony XA-5400ES mods.  However, I used the 5687 tube in a radically different circuit in the Marantz SA8005 and I know that many customers who also previously had both Sony XA-5400ES and Oppo 95 or 105 mods were VERY pleased with the greater level of resolution, detail, dynamics and overall resolution.

I want to achieve the same with the Oppo mods.  The SABRE DAC itself is VERY revealing, to the point that I want to be sure that the final product has the RIGHT sound.

More as I settle on this and fit it also into the compact Sonica DAC enclosure....

Dan Wright

[Syrah]

To whatever extent it's a draw, my vote is for a tube type that's available new as well as NOS - like the 6922.  If nothing else, it's a good hedge against escalating NOS prices not to mention complete disappearance once a tube type really catches on.

[modwright]

I agree and this is why I started with this as the Basis of Design.  I also feel that it sounds the best!

For fans of the 6SN7, the 6CG7 IS the same tube in a 9-pin bottle! You can also use 6N1P, 6H30 and of course 7308/6DJ8/6922.

Final PCB work under way as I neatly tuck the transformers and all circuitry into the compact Sonica enclosure!

Dan

[dminches]

Dan, will the tube opening be big enough to fit a 6CG7>6SN7 adapter?

[modwright]

Yes, it will be the same size opening as our other mods.

[MUstageFan]

Hi Dan,
Have you tried the 6h6p tube, also have you experimented with using two modestly priced diodes instead of one expensively priced diode.
I thought you might find this interesting  http://www.audioasylum.com/forums/tubediy/messages/24/242003.html

[modwright]

I have not tried the 6h6p, but I will check its data sheet to see if it is compatible.

I REALLY appreciate the suggestion RE protection diodes at the 5AR4 rectifier socket!  It is true that due to the way the 5AR4 is made, there is the potential for arcing and failure, especially if the tube is not well made.

We already put series resistors in the AC leads and provide capacitor and choke following, all intended to reduce the stress as much as possible, but I can see the benefit of adding the protection diodes!  Thank you very much for that suggestion!

Dan

[modwright]

Adding to the above post, looking at the suggested change to the 5AR4 rectifier, you do realize that you are essentially pre-rectifying the AC signal, right?  It is still a good idea, but I don't know how it will sound.  The diodes are doing the rectifying and the tube is merely acting as a second series rectifier.  You also need to be sure that the diodes you use are rated for the appropriate AC voltage that they will see - i.e. min. 3x VAC per leg.

In short, it is a good idea, but I would have to listen to it to determine if the sonics are better, same, or not.

Thanks!

Dan

[Mike B.]

Dan, are Michael and Jennifer still involved in helping with design work, or is it all done inhouse?

[modwright]

If you are referring to Jennifer Crock, I have not worked with Jennifer in over 15 years.  I do consult with Alan Kimmel and yes, all design work is done in-house.

Dan

[SoCalWJS]

Adding to the above post, looking at the suggested change to the 5AR4 rectifier, you do realize that you are essentially pre-rectifying the AC signal, right?  It is still a good idea, but I don't know how it will sound.  The diodes are doing the rectifying and the tube is merely acting as a second series rectifier.  You also need to be sure that the diodes you use are rated for the appropriate AC voltage that they will see - i.e. min. 3x VAC per leg.

In short, it is a good idea, but I would have to listen to it to determine if the sonics are better, same, or not.

Thanks!

Dan

Sounds interesting. It would be a fun thing to do, but I usually run into a dilemma in these (usually) subtle differences. I can sometimes tell that they are different, but I have real trouble telling which I like better. Even when I am very familiar with a recording.

 

Time for a serious listening session!

[Syrah]

Anyone know where I can find a 6CG7 to 6SN7 adapter?  I have lots of 6SN7s kicking around, so I wouldn't mind trying them out when I get my modded Sonica.

Thanks.

[JG2]

Anyone know where I can find a 6CG7 to 6SN7 adapter?  I have lots of 6SN7s kicking around, so I wouldn't mind trying them out when I get my modded Sonica.

Thanks.

There are lots of options for these adapters available on E-Bay.

[Syrah]

Ideally, I'd like to avoid ebay and China.

[JG2]

Ideally, I'd like to avoid ebay and China.

There is an amp builder on HeadFi, glenn2359, who may build you a 100% USA built converter. He has made me some allowing the use of 6F8G in place of 6SN7's and USAF 596 in place of 5U4.