TOPIC: 22A noise floor

Hi,
after having succesfully solved the channel mismatch problem of my 22A with a DSP reset (thank you devteam!), I would like to ask you another thing.

I repeat my setup: Oppo 105--->22A--->Accuphase P-700. All balanced connections with very good and short, 75cm, cabling.

If I connect directly the Oppo to the P-700, I have absolutely no noise from speakers at zero signal level. You cannot tell if the system is on or off even putting your ear on the midrange cone of the speakers.

If in the chain is the 22A, I can ear some "shhhh" (like pink noise) and some "random sparkles" that seem RF interferences, from the midrange cones. Is very low level, but in this case I can easily tell if the system is on or off.


Notes: I set the 22A to 100% volume, set the Oppo to never exeed 2 VRMS on XLR outputs so I don't saturate the 22A setted at 2 VRMS. I have changed the stock PSU that came with the miniDSP (and failed after 3 days ) with a Linear PSU from Squeezebox (but the noise was there before and remains with the better PSU).


So my questions:

- is this SMALL noise and/or interferences problem normal for the 22A?

- would set the 22A to 8VRMS, output full 4.2VRMS XLR from Oppo 105, and then attenuate volume in 22A provide a cleaner output? (I guess not, but I ask anyway).

- does noise/interferences come from the AD and DA sections or from the DSP?

- would a 22D (and obviously a very good separated DAC) give me a cleaner signal with a lower noise floor?



I stress that is NOT AT ALL a big problem and the 22A is a fine product, but... well... we always want something better

@ Mattia,

Let's see how we can help.
1) Can u clarify how loud this noise is? i.e. do u have to put your hears close to the speaker?
2) How do you know that you're not overdriving the input of the DDRC-22A? (i.e. do you have an RMS calibrated meter on the output of the Oppo)? Per specs of the Oppo (www.oppodigital.com/blu-ray-bdp-105/blu-...DP-105-Features.aspx), its output is 4.2 Vrms (XLR) at 0dBFS. I'm thinking that it's very easy that you're overdriving if not done with care knowing the level difference. especially if you have some boost inside your structure..
3) Worth trying to set the internal jumpers to 8Vrms indeed. Just open the top of the box and you can set the internal input jumpers to 8Vrms. See the OpenDRC-AN user manual. (
4) DDRC-22D is all digital so you're completely removing any AD/DA additional conversions and gain structure mismatch which would mean best performance in all systems no matter how you look at it. You could do an easy test by getting a DIGI-FP (we'd be happy to provide the rear panel). It's a simple replacement of the IO card. Nothing else to be changed. A 10min job.

DevTeam

Hi Devteam,
so, point by point:

1) Is not loud at all, at one meter from the center cone is barely audible. Is just that without the 22A in the chain I have absolutely no noise at all. I know is a bit of a "maniacal" thing, but I'd like to have the cleanest signal as possible

2) Oppo outputs 4.2 VRMS from XLR. The "volume" has steps of 0.5 dB, so by my calculation if I set the volume at "87" or below, I should not overdrive the miniDSP. But the problem is equal at my normal volume levels on the Oppo (40 to 60, depending of the source).

3) and 4) Mmm... interesting! So I just have to buy this ( www.minidsp.com/products/minidspkits/digi-fp ) and tell that I'd like to have the matching rear panel? I'll try that! Wonderful that miniDSP products are modular desings! I'll buy it right now! For a small price, I have all the answers I want, without having to buy another complete miniDSP 22
As for the front panel, that on the 22D has more led, I should buy also another board? In that case please tell me wich. If there is no such possibility and the digi-fp works on 22A and I just don't have the led that indicates wich input is selected, no problem

On question: the digital output of the digital IO is fixed at 24/96?

Thank you!

Mattia,

Thanks for the follow up.

1) Ok, very low level is good to hear.. I understand that you want the best system though..
2) Worth trying if the 8Vrms does the trick.
3) You're indeed correct that you'll need to organize a new VOL-FP so you have Source indication. We'll be happy to provide the front/rear panel for you. Our team will contact you to update your order. Sounds good?

DevTeam

Hi,
also ordered VOL-FP. Perfect.

So I just have to unscrew and unplug the old boards and install new ones?

No firmware changing or new activation involved?

That's correct. Unscrew, replace the VOL-FP and DIGI-FP and you're good. Nothing else involved.

Received the goods, installed (very easy indeed!) and WOW, what a difference!

Now I have a pitch black noise floor: absolutely no noise whatsoever. Also the sound is in general crystal clear and very precise.
Perfect! Thank you for the support!

I have just a quick additional question, but is a minor one.

Is there the possibility to set the 22D to output a 48Khz PCM instead of 96 Khz? I have an old but sweet sounding Accuphase DC-91 DAC, and would like to try it in the chain, but it only accept max 48 Khz input.

If it's impossible, no problem, is still wonderful sounding!

Oh good to hear and good job on the rework!
Sorry but unfortunately we can't downsample to 48kHz.. 96kHz is the default rate of the DSP and modifying the whole DSP structure + Dirac software + firmware is very unlikely going to happen... Time to get a new DAC i guess or there are some SPDIF ASRC box I believe.. maybe one way to deal with that...

DevTeam

It was very easy and self explainig job to do.

Regarding the DAC, no problem: I have newer DACs that accept 24/96, is just that the old Accuphase DC-91 is so sweet sounding... ah well, for it time to go on second chain

Thank you again,
Mattia

P.S. If and when you will decide to commercialize a "Digi-FP mark 2" with more optical and coaxial inputs, let me know because it would be most useful

Just trying to understand this thread.

You change a DDRC-22A to DDRC-22D, right ?


Lastly .... Root-cause(s) of the extra noises from the DDRC-22A is still not know, right ?

I'm interested to know the root cause(s) because 1Q next year, likely I'll insert a 22A between my pre & power amp.

My pre-amp is ARC DS-pre which according to the spec has the following:-
[Rated Outputs: 2V RMS 1Hz to 100kHz into 200K ohm balanced load (maximum balanced output capability is 15V RMS at less than 0.5% THD at 1kHz).]
Max rated at 15V, even the 8V jumper can't cope, right ?

To be exact,
I purchased the extra material to transform a 22A to 22D.

First of all I stress the fact that the noise was very low and only audible at 50cm max from the midrange cones, but
surely in my case the source of the noise was the AD/DA converter board, I don't know if this board picked up some external RF interference, some interference from the SHARK board or what, but changing to a digital I/O board solved the problem.

Thanks.

If it is cause by RF noise pick up (either by the unit or the connecting cables), I'm not so worry.

But if the AD/DA is the one that is generating the noise - that I'm worry.

Would not want to solve one problem (ie DRC) and create another (ie noise) - cause currently, my combo is zero noise, would not want to have even a slight noise at all.

I also have a zero noise chain, even by putting your ear into the speakers, you can year *nothing* at all.

With the 22A I could ear a slight RF interference and a slight "shhh". But i underscore slight and only very near to the speakers

Cables are not the problem: 2 pairs of good quality balanced 50cm cables shouldn't pickup any RF.
I think that in my case the RF was picked up by the AD/DA board. With di digital I/O board the noise is absolutely ZERO.

Before changing the input board I also purchased a very good quality linear 5V PSU, but the slight noise was still there. So I am inclined to put the blame on the AD/DA board.

Anyway, the problem was NOTHING in comparison to the great benefit Dirac equalization brought to the sound quality.

Hello I bought it has 2 week the DDRC22A and after optimization and started, I notice a noise (breath) in 0db.
How can we make to have no more noise? I have also the problem in the Chain at 0db with the 22A on service.
I have a good 5V psu and 4 good cables.

Hi,
I tried all the 22 solutions: A, DA and D.

I found that only the D version in my case has a perfectly silent floor at 0dB level. Both DA and A show a slight noise.

I upgraded the stock PSU with a very good linear one, but it didn't change the noise floor. So if you are after a zero noise solution, the only thing to do is buy a D and add an external DAC.

I remind however that with normal signal level and music program, the slight noise of the A and DA are not, in my case, audible. It is more a "mental" problem than a real one