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Would a small cap roll off any hiss from tape noise on cd's without stressing the amp?. If so about what would the value be? Tweaker
Follow Ups:
Won't do what you want.
A Zobel is worthwhile on some systems, 0.1µF + 10Ω is a common value found on the output of most amplifiers. A similar network on the back of the speaker can help in areas with high RFI.
Walker Audio makes the above for use across speaker terminals. The intent is to block very high frequency noise, RF and the like. I think Al Sekala once figured out that inside is a 10R or 100R resistor in series with a .01uF capacitor. This network does not operate at frequencies low enough to eliminate "hiss". If you want to do that, you could experiment with using higher value capacitors, but I think it would be a trade-off between blocking actual treble content along with the hiss. Most of us, no matter how superannuated, can hear hiss, which means it is well down below 20kHz in frequency, where some of the music also lives. If you try this,I do think you would be best off with an RC network, not just a C.
nt.
Which is to say that the Walker HD Link is not by definition a Zobel network. It's just a filter for RF, and it works great, by the way. A Zobel network is also an RC but it is placed at the output of the amplifier and is designed to improve the impedance match between the amplifier and speaker or to shape the frequency response. So the values used will have to be custom calculated to suit any particular amplifier/speaker combo.
I read that most of the hiss is unfortunately around 3k. I'd hate to put a resistor or another resistor in the signal path. Not that keen on a shunt cap either, but?? What has happened is that through improvement in capacitor quality and removing the output caps of the dac more hiss along with much improve sound in general is coming through. I'm wondering how big a cap would have to be to take a little of the edge of the hiss off without blowing the amp. One major example of how the professionals, recording "engineers" don't know WTF they are doing. Hiss on recordings is IMO one if not the biggest downside to this hobby. I know of one person who uses tape before digitizing. God only knows why but he records at a high level and very little if any hiss can be heard. Most recording "professionals" deserve a firing squad! Tweaker
Maybe you should put those caps back in you took out of your DAC. These caps are there for a reason and to remove them just because what you have read or you think it sounds better is not a good idea. You need to have some way to see the signal to see if it's a clean or oscillating signal. I have mentioned this to you in past threads about having a scope and to see what is going on with the changes you are doing.
Also you may be having oscillation from those I.C.s due to what you have done to that DAC.. Hiss is a good indication there is Oscillation somewhere in that DAC.
Try this, put those output caps back in and see if that hiss goes away. Some times the load of the circuit follow the output of the DAC (without those caps) can cause the circuit to oscillate. Also, try to barrow a scope to see what is going on.
You have done so much to this DAC, if you're not satisfied still then maybe it's time to look at another DAC or look else where in your setup.
Just trying to help you out! let use know your results!
It's a common idea, especially here, that most audio products are poorly engineered and built to cost. Hence the reason for all these expensive upgrade components that are in many cases the same cheap part with a fancy skin applied - notably audiophile capacitors.
But if you believe that, then why would a cost cutting manufacture add coupling capacitors if they were not needed? I mean even the cheapest caps cost pennies not to mention the added board manufacturing costs.
Doesn't make much sense does it? This equipment is cheaply designed yet they add parts that serve no purpose?
Hmmm
Gusser,in this case one channel has .3mv and the other channel had 12mv. I think this is way below what one needs to worry about going to an amp even if the amp does not have input dc blocking amps but there are others out there who can correct this if incorrect. But, in fact my amp has input caps to block dc so there is no need for two sets of caps. The improvement in sound quality without the output caps, which were way way better than the crap that came with the unit, is dramatic. I believe the output dc blocking caps are put in out of an abundance of caution to prevent a problem in all situations. Hornblower is a good point person on this subject. T
Edits: 07/27/16
Is it possible that in your zeal to use the most robust possible parts, in terms of voltage and power ratings, that you've stuffed some physically over-sized parts into the chassis, especially capacitors, such that you then had to run much longer than original length leads from the new parts to the PCB or wherever they are supposed to connect? If so, this creates an antenna for RF, every time you do it. And hiss can result. I don't know who wrote that "hiss" is by definition a 3KHz noise (as you mentioned), but that is not far off the range where it might lie. You obviously cannot filter that out without losing a lot of music, which defeats your whole purpose in tweaking. I suggest you go back to the drawing board and take a look at whether you have some long leads in the circuit that are picking up stuff and amplifying it. And IF you still wish to install a filter, it had better be an RC type, not just a C, in this frequency range. Otherwise, your amplifier will be looking at a dead short at frequencies above cut-off. But fix the core problem is my recommendation. Then you won't need no stinkin' filter.
Lew, the system is quiet when there is no cd. T
nt
The circuit being described wont impact tape hiss. Its also a parallel filter so nothing in series with the signal path. So its .01 film cap and 10 ohm resistor, the bettervthe components the better the skund and image improvement. The recipe is on the DIY section of my site.
A preamp with too much gain into a sensitive high z power amp can be a recipe for hiss. This would be audible through all inputs and phono more than others even when no music is playing.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
You said you removed the coupling capacitors on your DAC. Well no doubt you upset the output filter and that "hiss" is actually ultrasonic oscillation or clock noise getting through.And it's slowly destroying your tweeters!
The "incompetent" electrical engineer put those caps there for a reason. What makes you think you can pull just them out based on internet audio fokelore?
Also putting caps of in the MFD range directly across speaker terminals is a good way to destroy a solid state amp. Many amp circuits become unstable when faced with a high output capacitance.
Edits: 07/27/16
I'm well aware a cap across the speakers can hurt the amp. That is part of my question. Looks like a cap by itself would have to be to large. The system is just as quiet as it was when the cap was in the circuit when no music is playing. It is in fact hiss that is on the cd. T
Edits: 07/27/16
If the hiss is actually on the recordings then you have achieved what you were after correct? a DAC that is transparent and lets everything on the recording through! So take the good with the bad, the DAC is now doing what you wanted. Hiss is just part of the recording and you can live with it or not. This is what happens when a system reaches a certain level transparency and you start to here things you never heard before good and bad.
This type of stuff doesn't bother me cause I know it's on the recording so like other post said I just ignore it.
If you really want to get rid of that hiss you will be putting back what you were trying to remove which is a slight veil over the music via EQ, DBX, Dolby or any other type of filtering like that cap resistor you are talking about.
Maybe look into speaker cables like Transparent or MIT that have a filter network inside. :)
Oddly enough Cougar the increased hiss came in part from the last group of Elna Silmic II's. I was a bit worried they would roll things off too much. Very much improvement in treble so your taking the good with the bad comment is appropriate. I could put a low pass filter on it but then there would be a dreaded extra resistor in the precious signal path. Horror of horrors! Ah what to do. I do have a different set of output tubes I haven't listened to yet. The zobel filter tweak is new to me and although not designed to roll off highs there are comments that it quiets down the treble in one or two comments on the web. Lots of respect out there for the zobel. Tweaker
When we recorded back in the 50's and 60's the way we combated hiss was to record at as high a level as we could. Also we started recording at 30ips. None of my recordings have any audible hiss. When you get a recording that has audible hiss it has probably been mastered from a second or 3rd generation tape. By the way, we tried dolby A for a short time but it had other problems so we stopped using it. You say "Hiss on recordings is IMO one if not the biggest downside to this hobby" Nonsense. I have thousands of recordings and very few have hiss. Plus I can easily block out hiss when listening just like I can block out ticks and pops on vinyl. Maybe your system is too bright. Get a narrow band equaliser to notch out the hiss. You can do this with little loss of material.
Alan
Alan
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