Small form factor, budget DACs?

Howdy mates...I also have a non os dac- the Scott Nixon Tube + ...Love it..not bad for $500, seperate power supply-a buck and quarter...Old School :)

congrats Hudsonhawk

Gmood1,
yes, 10K input imp of the next stage vs. the driving stage is not written in stone. Usually the rule of thumb is 5X-8X. However, I've found that is not high enough & that 10X works 99% of the time successfully.

OK, from your 2nd lengthier post I think I understand better where you are coming from. Let me see if I can summarize: Hudsonhawk & I were musing why these non OS DACs based on TDA1543 DACs sounded (really) bad on bad recordings. He & I were hypothesizing that it's the lousy jitter performance from the recovered clock.

NOTE: both Hudsonhawk & I have non OS DACs that use a Burr-Brown opamp buffer that drives the RCA outputs. From the spec sheet of this opamp, it has very low harmonic distortion over 20Hz-20KHz + it can drive large capacitative loads - we are talking 5nF & still have a gain-bandwidth product greater than 1MHz + it has very good settle time. So, it seems that this buffer does the job of the BVAudio SR10 & similar after-mkt buffers. Thus, I see very little advantage in further attaching an after-mkt buffer. If there is an improvement in these 2 specific non OS DACs, I surmise that it is most likely to be very little. I wish I had one on hand to give your theory a try (I would be double buffering).

Now, in your Audio Sector Premium non OS DAC that uses passive buffering, the ball-game is entirely different. As an aside, if you look @ the TDA1543 data sheet, you'll see (in Fig 1) that they have suggested the use of buffer opamps that have some bandwidth limiting (that parallel cap in the feedback). It is not the only way to "terminate" the TDA1543 output i.e. one could also use passive buffering. However, the passive buffering will rely on the TDA1543 to drive the interconnect parasitic C + the preamp input. It'll do the job (as your ears have discovered) but you know that the sound could be better (again, as you have discovered). In your particular case, the BVAudio SR10 & similar products work & show the difference since the passive buffered TDA1543 has to drive 100K & very little parasitic capacitance of the active circuitry, a much easier load. I do not think that it'll be quite the same for my SN DAC or the DAC-AH.
There is nothing magical about the 50Ohms output impedance of the BVAudio SR10. It is a standard impedance used in test & measurement equipment & by the RF engineers. It is low enough where it'll work w/ 99.9% of the equipment in the market-place no questions asked. For that matter, 600 Ohms would have worked just as well (would have been an easier load actually) as it would have been low enough to work w/ all the preamps out there.
So, you have to pay the Piper - now (opamp buffer as part of overall DAC in the same chassis) or later (use after-mkt buffer).
So, in your particular case, it appears you have 2 issues affecting the sound: insufficient drive from the Audio Sector DAC & poor jitter performance from badly recorded CDs. IMHO.

Bombaywalla,
all your theories and hypothesis are great.But you really need to hear it to understand where I'm coming from. The Audio Sector DAC has sufficient drive. Probably more than many players. I've never heard a player or DAC make a garbage recording sound good. It is what it is. I can assure you jitter performance is excellent with this combo. I do use a Superclock 3 in the transport.

There maybe nothing magical about the BVaudio SR10 output impedance but it's better than most players on the market o/p. The output impedance and voltage of the analog outputs do attenuate the signal in interconnects if not sufficient correct?

Maybe we're talking about two different things here. I'm talking about the addition of a buffer for people using passives or changing the preamp to one with a higher input impedance. Also the impedance does matter when driving long interconnects or passives. I would rather have more drive than not enough in any case. I wish you were closer ..I could quickly prove your hypothesis wrong. Anyone that has tried this knows what I'm talking about.

You must ask yourself. Why use a preamp between your Wadia and amplifier? Besides the need for other inputs. After all you are double buffering already. What do you gain when using the preamp/buffer than not using it between the Wadia?
I suspect you use the preamp because it sounds better to you than running the CD player direct to the amplifier...correct. So because you do this the Wadia must not have sufficient drive...correct? Ok I was being sarcastic with that one. :-)

What I'm doing is no different than you using the CAT preamp in the loop. Now do you understand?

There's a reason why APL,RAM and other modders concentrate so much on the output stage of their players. Which includes doing away with the negative feedback opamps in some cases. I noticed most of them use single ended designs with no negative feedback and powerful output transformers in their top players. I added the same thing ..just in a different chassis.LOL

I can imagine handling interconnect interactions is a walk in the park for such players. Never heard the APL..but just from what's used, the output impedance(should be quite low using a tube and output transformers) and high voltage should make one powerful sounding player! There's no denying it, the presence of power in the right place makes one hell of a difference in sound!

Oh yeah..the piper is one happy camper! ;-)

Gmood1,

>> You must ask yourself. Why use a preamp between your
>> Wadia and amplifier?
the answer is very simple: Wadia's digital gain control is the absolute pitts! Sonically, it stinks! I know I'm an owner but I will not prop up this unit just 'cuz I spent money on it. What I do is put the volume control to 100 thereby bypassing it. Now I have totally lost control over adjusting the volume. That is where my preamp comes in. Inside the Wadia they provide a set of DIP switches to adjust the buffer outputs from 4.25V all the way down to 0.25V for each channel separately. I believe that the user adjusts this output depending on the amount of voltage gain in his/her preamp.
Wadia claims to have a patented I-->V conversion technique & I wonder if these buffers are doing double duty of I-->V + buffering? I don't know enough about the Wadia design (& the DAC control PCB is multi-layered thereby making wire tracing nearly impossible) to make a useful comment.

>> There's a reason why APL,RAM and other modders
>> concentrate so much on the output stage of their
>> players. Which includes doing away with the negative
>> feedback opamps.
well, even if I try the BVAudio SR10 external buffer, there's no getting rid of the negative feedback opamps inside the SN DAC.
OK, I can understand negative feedback in the opamp-based output stage is less sonically than those outputs stages not having any.

>> Also the impedance does matter when driving long
>> interconnects or passives.
agree! How long is long tho? Not 1m interconnect! I think long would be in excess of 5m.
I would agree that output impedance is very imp when driving passives. A CDP having an output imp of 3K (as written in your orig post) would likely be an issue when driving a passive preamp. I agree!

>> I can imagine handling interconnect interactions is a
>> walk in the park for such players.
I believe that this would also be a true statement for a DAC using a Burr-Brown OPA627.
When I plug this SN DAC into my preamp, I have so much gain from this DAC that I have to crank down the volume knob atleast 3 clicks from where I listen to the Wadia. In the CAT that's quite a gain reduction.

>> I wish you were closer ..I could quickly prove your
>> hypothesis wrong.
well, my hypothesis is, for the SN Saru DAC+ which uses a strong enough output buffer than can drive my 1m interconnect + my preamp input capacitance, that badly recorded CDs sound terrible thru it 'cuz the dominant effect is poor jitter performance in the recovered clock from the input data stream. The poor jitter performance xlates to poor DAC performance as the DAC uses this jittery clock to perform a D-->A.

(Were I to additionally remove the negative feedback in the output buffer would I get even better sound? probably!
I think that in my DAC the jitter performance dominates over the negative feedback in the output buffer).

Fair enough my friend..at least we agree on something.LOL
I do understand what your saying. Maybe this is the problem you hear in your DAC or transport..I really don't know. Honestly I've never cared for the stock Sony 7700 players analog outputs, they are quite the ear bleeders in my book.
I never got a chance to try it as a transport..sold it off in a hurry.LOL

Wow your DAC really kicks the gain up. I can adjust the gain on my Single Power MPX3 Slam. This is what I use as a buffer not the BvAudio unit.
It does have gain where the BVaudio does not. 600 volts of clean quiet power in reserve really takes the sound up a few notches!

ATB,

Gmood1,
I think that we have been agreeing on almost everything all along & just didn't read close enough to recognize that.
I think that re-stating what my hypothesis could have helped clear the air a bit - I was/am looking for the dominant cause for my case.

>> Maybe this is the problem you hear in your DAC or
>> transport..I really don't know. Honestly I've never
>> cared for the stock Sony 7700 players analog outputs,
>> they are quite the ear bleeders in my book.
well, I think that you might have indirectly hit upon something I wanted to mention in my prev post but it got too long: the issue, I think, lies in my stock DVP-S7000 DIGITAL output (I'm using it as a transport to the SN DAC so the analog outputs do not feature). The S7000 digital outputs have very sloppy rise & fall times, which has the tendency to aggravate jitter issues. Sending it in for a mod to improve this should give me good ROI because it is the digital data stream that the SN DAC sees as its input & it is from this data stream that it extracts a clock & lights up the "lock" LED on the front panel. If an improved digital output buffer adds minimal distortion to the data stream, the performance is bound to improve.

I didn't think that the analog output of the S7000 was an ear-bleeder as much as it was very dull/flat sounding.

BTW, I wanted to clarify that your transport having the Superclock3 has much less to do w/ the DAC jitter performance compared to the quality of your digital output. What is making the bigger diff in your case is the mod to your digital output. Don't get me wrong - the Superclock3 makes a positive diff but it is 2nd only to the superior modified digital output. The Superclock3 would have a dramatic effect if you were using the Pioneer internal DACs i.e. using it as an integrated player, 'cuz this low jitter clock would be connected to the DAC, which would have kicked its performance up a few notches (iffff the internal DACs are good quality in the 1st place). The data stream that your Audio Sector DAC sees is just a 1-0 pattern. Whether it is correct or incorrect data, the DAC doesn't care nor does it know. The job of the Superclock3 in extracting the data from the CD is complete by this time & it is the quality of the digital output that will affect the overall sound.
It is no wonder that the websites of many 3rd-party modders lists the Superclock3 mod as a separate line item & don't always push you into getting it if you are using the unit as a transport. (or, maybe they still do 'cuz they want your money anyway!!)

>> There's a reason why APL,RAM and other modders
>> concentrate so much on the output stage of their
>> players. Which includes doing away with the negative
>> feedback opamps in some cases. I noticed most of them
>> use single ended designs with no negative feedback and
>> powerful output transformers in their top
>> players.
Another point I wanted to clarify - there isn't a single electronic device on planet Earth that can work without negative feedback! Trust me on this - I'm 110% certain! I think that you meant to say that the top CDP modders use output stages with extremely localized feedback to make them sound the best. I agree w/ that.

My sis-in-law lives in ATL. If I'm visiting her, I'll email you & we can probably get together & compare my SN DAC w/ your Audio Sector?
Like-wise, my friend, all the best & enjoy the music! :-)

Bombaywalla, What exactly is done to just modify the Digital out with no clock mod's? Just wondering, cause this would seem to be much cheaper to do than changing the clock.

Also, I have seen some Mods to NOS-DAC's that add a Re-clocker type unit to them, would this be worth simply getting the Digital out modification at the transport and more effective putting the Re-clocker in the DAC itself for the cheapest approch to handle the Jitter issues and get resonably better sound?

Thanks

Undertow,
As I understand it, when mods are done that EXCLUDE the clock mod, the modifications are (1) improving the power supplies - digital & analog, (2) upgrading coupling capacitors, (3) improving the rise & fall times of the digital output to the 1-2nS range from something much higher (like 20-30nS range) & (4) ensuring that the digital output is 75Ohms so that the power/signal transfer to the DAC module is maximized.
If you do this in a DIY fashion, you do not need to mess w/ re-attaching a Superclock3 or Tent XO, etc to the CDP, which is very specific for each CDP & can be quite a pain if there is no guidance. Doing the above mentioned mods (tho' tedious) are relatively simply to do & the parts are freely available from multiple vendors (DigiKey, Newark, Percy Audio, etc).

Yes, I have also seen people add a re-clocker unit/jitter reducer like a Monarchy DIP between the digital output & the DAC input. These type of units seem to be quite cheap esp. on the used market.
I don't know how easy it is to add a re-clocker to the DAC chassis itself - maybe there is a DIY forum where they have discussed how to interface a clock module to a digital receiver like the 8414?
Adding a separate chassis re-clocker seems to be cheaper & easier to do. The sound should improve IMHO.

There is another way stated by a few members already & a growing trend :- use a PC hard-drive as your transport & a sound card to put the data out on a USB port. People like Scott Nixon & Wavelength Audio & Headroom are producing USB DACs to enable this.
Then, you do not have to deal w/ this jitter issue 'cuz you rip the CD to your hard-drive & the sound-card (which has a high quality clock + digital buffer) feeds the DAC.

If you are willing to spend money to upgrade your CDP transport, re-channel that same money into getting a plug-in sound card for your PC, a USB cable & exchanging your DAC to one having a USB input port.

Interesting... I got a little lost on the Re-attaching the XO or superclock, I was looking not to purchase these in the transport and just use the cheap osillator or whatever in there? And ad the better clock in the dac, I am not really completly looking to do this but this is something I have seen done, so upgrading everything but the clock in a CD player used primarily as a transport would be a good idea or not without the clock? Thanks

>> 04-05-06: Undertow
>> I got a little lost on the Re-attaching the XO or
>> superclock,
look at this page
http://www.tentlabs.com/Support/Support.html
click on "XO 2 and 3" to read the mounting instructions to understand what I'm talking about.

>> so upgrading everything but the clock in a CD player
>> used primarily as a transport would be a good idea or
>> not without the clock?
good idea (if you don't want to go the PC route).

Hudsonhawk, I've owned the Bel Canto 1.1, Ack dAck 2.0, Kora Hermes 1 and Audio Mirror D1. Of them, my favorite is the Audio Mirror, for the reasons cited previously, their organic sound. I also felt the Audio Mirror was more dynamic with a greater sense of scale than either the Bel Canto and especially the Ack which to me sounded small. The Audio Mirror couldn't match the lucid midrange of the tubed Kora, but it comes close. And with all its other attributes is an amazing bargain at under $550.

Long-dead thread, but since there was some question as to the difference between the two versions of the DAC-AH (the stock one and Pacific Valve's modded version) I thought I'd let people know that I wrote a review / comparison between the two models.

Pacific Valve was kind enough to let me borrow the stock one for comparison.