[raif]

First a notice. There were some power issues at the meet were morsel and I did testing of the amp. That really did not make a noticable difference untill the pot was turned to above 12 o'clock then got progressively louder. Also, it was more of a hum/buzz.(to me) At the levels that I listened, there was the familiar hiss, that did not change in volume. Another issue was that the listening was in a meet setting so take the following post with a grain of salt.
--------------------------------

I took my ppa to the bay area meet. After some extensive testing I was able to confirm that there was indeed a hiss present in the ppa with my cd3ks. However, it was also present in the prototype ppa that kurt brought to the meet. Another thing is that not everyone could hear it.

My conclusion is that there is a barely noticeble low level hiss when the ppa is combined with closed, high-sensitivity, low impedence headphones.(or at least the cd3k) Combined with other higher impedence headphones(sennheisers, beyers) the noise completely disapeared. Also, in the large gilmore at the meet(v2?) the hiss dissapeared, so it isn't a headphone issue. Hopefully some of the others that were present for the testing(kurt, morsel, neilpert) can chime in with their impressions, which undoubtedly will provide a better interpretation than the one I have already beat to death on this forum.

Some people will never hear it, if so enjoy it, because the sound quality, presentation and value of this amp is great. For others though, a slight word of caution.

I think neilperts comment best describes the issue.
[after listening closely for a moment]
"Oh, my god, I hear it. I thought you might have been mistaken, but I can hear it. It is very faint though, I wouldn't have noticed it if you hadn't told me what to look for.

EDIT: I did hear the same hiss in the other gilmore present at the meet. It is very possible that it was a power issue, though, I just felt I should include that because this could just be a personal issue with high power amps.

 

[doobooloo]

I have built like seven or eight PPAs but on all of them, I could hear a slight but very audible background hiss through my CD3Ks. The hiss was greatly reduced by reducing the gain by half, but then that kind of kills flexibility to drive higher impedance phones and weaker portable sources...

What REALLY made the difference, though, is going battery power. That almost eliminated the BG hiss even at the high gain of 11. On all my other tests I was using the Elpac WM080 wallwart.

So it's really the PSU. If you have access to a higher quality PSU or can put together a battery power source, try it, it'll really make all the difference.

 

[Sovkiller]

Quote:

Originally posted by doobooloo I have built like seven or eight PPAs but on all of them, I could hear a slight but very audible background hiss through my CD3Ks. The hiss was greatly reduced by reducing the gain by half, but then that kind of kills flexibility to drive higher impedance phones and weaker portable sources... What REALLY made the difference, though, is going battery power. That almost eliminated the BG hiss even at the high gain of 11. On all my other tests I was using the Elpac WM080 wallwart. So it's really the PSU. If you have access to a higher quality PSU or can put together a battery power source, try it, it'll really make all the difference.

It has to be the PS, in mine there is no hiss, at any volume....I have a linear PSU or wahtever voodoo drop in there, not the Elpac for sure....

 

[ppl]

Q quick and Easy solution is to provide more open loop gain that in addition to futher reducing distortion also reduces hum and noise. A good power supply is manditory also.

Reduce the Valure's of R1,R3,R4 and R5 by half the default values on tahgents site. Leave the 1 meg resistors R2 and R6 alone and leave them at 1 meg. note the Bass Boost capacitor if used will also have to be twice the default value.

 

[davidmiya]

I use the PPA with both the CD3000's and HD600's.

Any audible humming is a direct result of not grounding the RCA common channel to the chassis. (This cleared up my hum problem) Any barely audible hiss is most definitely a result of dirty power as Sovkiller said. My PPA unfortunately doesn't have a battery board (it's not like I'd ever need one anyway). However, the PSU that Voodoochile installed in the chassis is pretty darn silent. In fact, the hiss only becomes audible at max volume with CD3000s and 3/4 max volume with ER-4P's. Then again, this is not the hiss that you hear when a tire is leaking, but more of the hiss you hear from a REALLY old tube television.

As an experiment, I moved the amp to a middle of a room, threw the breaker on the rest of the house, and plugged it in. Believe it or not, the hiss decreased by nearly 60%. I'm no DIYer, but I believe you can make the hiss inaudible if you somehow manage to:

1) Isolate the amp from all sources of interferance
2) Get good PSU or use battery board

 

[raif]

where were you guys a week ago!?!?!

Seriously though, I tried buying an on-line power conditioner and it had no effect.(cyber power AWR1000) I am sure a real quality power supply would help drop the hiss. It seems that where I am at though, it will take either a sum of money, or soldering skills to fix my problem.

I figured I could use the opportunity to expand my headphone horizons, so I am trying the sennheiser hd650s. According to jmt there is absolutely no noise on any of his headphones, and I couldn't hear a thing with the senns and beyers I listened to at the meet. I figured this would instantly solve my problem, then later, when more concrete solutions are out there, I can see about fixing the amp.(when my wallet recovers) Thanks for you help though, I am sure there are others that will want to stick with their cd3ks and this should help.

 

[davidmiya]

Quote:

Originally posted by raif I figured I could use the opportunity to expand my headphone horizons, so I am trying the sennheiser hd650s.

Smart choice

The great thing about high-impedance phones is that it's darn hard to get a hiss, even with noisy A/C amps with cheap power

 

[Voodoochile]

By the way, I am starting to ground the signal common (in) to the chassis by default. It has not been a requirement at my place, but it seems in some other places, or places with perhaps questionable wiring, it's needed.

Yes, I realize it's recommended.

But not required. Even without a chassis cover, on the benchin front of my monitor, with overhead fluorescent lights, and the furnace burner motor running nearby, I do not get noise. Not even with Shure earbuds, or Grados. That's just for the record, I'm not suggesting anything here. My pot shaft is not attached to the chassis, and there is the internal PSU, so if it was quiet without the signal>chassis ground, so be it.

Anyway, I wanted to point out that both Sov's and David's amps have an ordianary IEC going to the PSU. No pi filter or filtered IEC inlet on either. I guess I was not aware of this propensity for background hiss... maybe it's mainly with a wallwart? Again, I don't know. My point (it's in here somewhere) is that I went to no special measures to make the PPA quiet. There are a few more things that could be done such as the filter, to improve even further. But if you can't hear it with CD3Ks, well, is it needed? Easy to implement, either way. You can throw money at one of these hand over fist if you like, but most people back down after a point. I know I do.

I do not even have a shield panel separating the PSU from the PPA board. So, I am inclined to agree that a decent PSU has much to do with the noise issue. The one I use is not magical or uber-high end, but it is most definitely not a wallwart. I'd categorize it as median, perhaps.

 

[Sovkiller]

Quote:

Originally posted by raif where were you guys a week ago!?!?! Seriously though, I tried buying an on-line power conditioner and it had no effect.(cyber power AWR1000) I am sure a real quality power supply would help drop the hiss. It seems that where I am at though, it will take either a sum of money, or soldering skills to fix my problem. I figured I could use the opportunity to expand my headphone horizons, so I am trying the sennheiser hd650s. According to jmt there is absolutely no noise on any of his headphones, and I couldn't hear a thing with the senns and beyers I listened to at the meet. I figured this would instantly solve my problem, then later, when more concrete solutions are out there, I can see about fixing the amp.(when my wallet recovers) Thanks for you help though, I am sure there are others that will want to stick with their cd3ks and this should help.

Well, well, well....This is just my opinion and don't take it personally, OK ? But I don't think is a very understandable idea, because you have a problem in the amp, PSU, power, etc....change your headphones, sorry I don't understand that, if you were not satisfied with the headphones, this movement is OK, but was that the case? OTOH a change in the amp would be more understandable IMHO....

BTW, and this is even more personal opinion, I personally, do not see the fun or consider an upgrade, to go for any other headphone at this same level, (HD650, HD600, RS-1, DT880) after owning the CD3000, and being satisfied with it.
I just do not think you will get any such improvent in the sound, OTOH, to try them in a meet is OK, just ot have an idea or maybe to see if you consider them better suited for you or not, having just a different presentation of the music, a little better here, and maybe a little worst there, and IMO you are just making a side movement in the best case.
Well just to expand you horizons as you say, is OK, but keep in mind that you are going in circles, not forward, IMO....maybe you preffer that sound but my question is, you never stated that you were dissatisfied with the CD3000, so why the change? Becasue of the noise on the amp.
Well, anyway this was your decision, but IMHO, HP-1, R-10, the new AT or to go for an electrostatic, would be another story, is like a little scary IMO, as the problem is still there in the amp, just that you can't hear it now....so what you did basically, was masking the problem, period....this is not the solution IMO, the noise is still there, interfering with the music, in one way or the other, in your shoes and this is just me, (an obssesive guy BTW, just ask voodoochile if you don't believe me) I should get a 16 ohms headphone, or a 8ohms, instead and chase the darn hum down to the cave and try to eliminate it......but if you are happy this way is OK with me, if everybody is happy, I'm happy.....

 

[NetRunner]

This is probably a lame ass suggestion, but would adding a ferrite ring or several to the ps cable help? Or is the conflicting signals of lower frequency than the ferrite dampens.. *Dunno..*

 

[Voodoochile]

Quote:

Originally posted by Sovkiller ...(an obssesive guy BTW, just ask voodoochile if you don't believe me)...

Hey, if anyone ever calls you obsessive-
believe them.

Obsessive, but thankfully not compulsive, right?

Netrunner: I could not tell you without trying it.
But woould be inclined to guess no effect on this.

 

[Nefarion]

"Another thing is that not everyone could hear it."

"Some people will never hear it, if so enjoy it, because the sound quality, presentation and value of this amp is great. For others though, a slight word of caution."

The previous two statements regard to the fact that some people can/cant hear specific frequency humming.

Then Sov says:

"It has to be the PS"

In other words, according to sov, this specific frequency humming can be heard by all or none. Everyone hears it the same... This is what he meant because it HAS to be the power supply. It couldnt possibly be that his PPA actually hums and he cant hear it... Just not a possibility...

Then he goes on to do the all-so-familiar b.s., unwarranted anti-sennheiser rant. He just used the fact that changing headphones over a hiss (over changing the amp) may not be the best idea as a buffer for more anti-sennheiser spamage.

Just thought id point that out...

 

[raif]

no need to bash on sov.

I see his point and I would follow it too, except that I have had everyone from jmt, to morsel, one of the designers of the amp for heavens sake, try and help me.

Unfortunately the power situation at the meet affected my ability to fully pinpoint the issues, but I did hear similiar noises in a gilmore v2, and the sugden headmaster.

To tell the truth this experience, combined with others, left me a little exasperated with the cd3ks ability to shove every environmental inconsistancy directly in my face. So rather than wrap my ppa in tinfoil, buy a new psu, re-resistor the board, and drop the gain I just decided to spend an extra 20 bucks on the 650s and be done with it.

 

[radrd]

Quote:

no need to bash on sov.

Apparently you don't read many of Sov's posts...

 

[Sovkiller]

Thanks raif you seem to be more rational than him, even when I do not understand the move you made....anyway I was writing this answer to his, and you answer that, so I will post it anyway, as it was written already.......so:

Quote:

Originally posted by Nefarion "Another thing is that not everyone could hear it." "Some people will never hear it, if so enjoy it, because the sound quality, presentation and value of this amp is great. For others though, a slight word of caution." The previous two statements regard to the fact that some people can/cant hear specific frequency humming. Then Sov says: "It has to be the PS" In other words, according to sov, this specific frequency humming can be heard by all or none. Everyone hears it the same... This is what he meant because it HAS to be the power supply. It couldnt possibly be that his PPA actually hums and he cant hear it... Just not a possibility... Then he goes on to do the all-so-familiar b.s., unwarranted anti-sennheiser rant. He just used the fact that changing headphones over a hiss (over changing the amp) may not be the best idea as a buffer for more anti-sennheiser spamage. Just thought id point that out...

Man what are you talking about? Nobody has any problems with any other hum/hiss, in PPAs before, but him, sorry but mine is dead quiet, I bet, and I do not want to look arrogant, but I strongly doubt, that his hearing is far better than mine, or yours, he is not a freaking bat, he hears exactly the same as we the majority hear here, period, a hum is not a freq that you or me could possibly miss, in very inside the audible spectrum, if he is hearing a hum, and BTW others in the same meet hear the same hum, as he stated, the hum was there period, there no such an argument on that, his amp has a hum, and the other amp at the meet has a hum, because many members hear that hum, but that does not mean IMO, that all PPAs has the problem, sorry but this is not true, mine does not has this problem, at all.
OTOH as I'm not using the Elpac, maybe the Elpac is causing that noise, as he says that the other PPA in the meet has the same hum/hiss, and I assumed, and maybe I'm wrong on that sorry, that the other was also connected to another Elpac, as it is more or less the universal power supply for this amp used here in the forum....I think is logic to think is the PS......BTW I don't see why you complained, in the last case, he has the right to do it, not you.....

About the other "rant" as you call it, first it was expressed as my very personal opinion....and it was not anti anything, read again, it was in the last chance maybe because I do not understand his way of solving the problem in the amp, changing the headphones.
IMHO this is not very understandable, but that was the way he choose.
IME if you have a problem in the amp the logic procedure is fixing it, not masking it, he is free to do whatever he wants, but IMO, the headphones has nothing to do with his amp problem, the hum is in the amp, not in the headphones, as he tested it and stated that....if you see that logic, I do not sorry.....
There is no such anti senns BS rant or anything like that...I do not consider to go from the CD3000 to the HD600 and upgrade, nor the other-way around neither, DT880, HD600, CD3000, RS-1, Etys, etc...all of those are more or less on the same category, and I consider that a lateral movement, many will agree with me on that, others maybe not, but I never say that he did a downgrade, going from CD3000 to the HD600, he never evne epxress that as such neither, so where is the anti Senns BS rant?