C2500 phono stage question

ghost rider

ghost rider

Active Member
Now I only have a few hours on the PS and maybe 20 on the C2500 as a whole. I did a few needle drops and there is a little more noise in the bottom end as you can see from the screenshot. So I wanted to see if this is normal. The sendspace link is a 90 second sample of the drop if anyone knows how to use the link, you only click on the blue download from sendspace link all everything else is an ad.


Also if you are not familiar with Izotopes RX2 this view show the very bottom is 0 Hz and the very top is 47K Hz abd the brightness show the level.




https://www.sendspace.com/file/77z418

jpg images
 
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How does it sound at higher loadings like 400 or 1000 ohms? AT specifies a minimum of 100 ohm loading for your cart. Many low output MCs sound and measure flatter at higher loadings.

Thanks,
Ron-C
 
ron-c said:
How does it sound at higher loadings like 400 or 1000 ohms? AT specifies a minimum of 100 ohm loading for your cart. Many low output MCs sound and measure flatter at higher loadings.

Thanks,
Ron-C
Click to expand...

Wow at 400 ohms it sounded much more 3 dimensional. Almost too much Stevie Ray’s guitar sounded more to sides. I’ll have to listen to it this way for a while. The Project tubebox has knob that goes from 0-1000 ohms and has very little effect on the sound.

Thank you!!!

I backed off to 200 it was kind of annoying. The noise level is about the same.
 
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My experience with OC9s has been that they can indeed sound a tad bright but that loading them below 100 ohms addresses this. You will also lose output and increase noise this way so be forewarned if you do not have a really quiet phono preamp. Ron I am curious why your experience is the opposite. There are any number of threads on many audio boards about "taming" the high end of bright Low output MCs and in every case the answer is to go with really low loading 20-40 ohms typically). My own experience with OC9s, 33EVs and a Denon DL-S1 confirms this.

Maybe you were addressing the noise complaint and suggesting a higher ohm loading would sound "better" because it would be louder? The OP complained about brightness in another thread so I am just questioning whether this is really going to be the right course of action.

Jblnut
 
This was something I discovered this with the tubebox but it kind of sounded muffled around 50. I EQ my needle drops and lowered the treble on the MC input to -4 and it seems to be OK.
 
Everyone has their own experience with the system they have. McIntosh recommends 1000 ohm on the Blue Point we supply on MT5 and 400 to 500 ohms for the LOMC we have on MT10. They both measure the flattest at these settings with our active MC phono stage.
Take something like the Denon DL103 which is 40 ohms internal impedance but will need 1000 ohms loading for a flat response just like Denon loads it when they print out the frequency response graph included with each cartridge. I just checked some cartridge-selling web sites and they recommend 100 ohms loading.
No wonder many are confused with loading. Each MC will be unique so no sweeping rules apply.

Thanks
 
So 25,50,100,200,400,1000 are the options. To me all of them sound good it's a matter of what sounds best to you.
 
I did some test recording and I have determined that this is normal grove noise. It seemed brighter when I viewed it in RX so that’s what peaked my curiosity. I recorded the same record using my Project tubebox and the noise was not as "bright" (in the view) but covers a larger area in the spectrum. It was actually slightly louder. So it would appear that the C-2500’s grove noise it compressed to a smaller lower frequency range.

Most important when I listened to both samples the C2500 sounds better.
 
Ron are there any other phono stage options, such as subsonic filter? Also it appears the level trim does not pass to the record outs. I saw nothing in the manual about phono stage adjustments.
 
A sub-sonic filter would solve this issue. I used a highpass brickwall filter at 20Hz on a needle drop and it fixed it. If I play records directly there is a sub-sonic thing going on that should be removed at the phono-stage. Is there any hope they can fix that with a software update?
 
Just trying to understand fully, what you actual problem is here, and why you think you need this brick wall filter....

I have no issues (if I am understanding your problem, which I am not sure I do) at all with my phono input on my C48.....
 
ghost rider said:
A sub-sonic filter would solve this issue. I used a highpass brickwall filter at 20Hz on a needle drop and it fixed it. If I play records directly there is a sub-sonic thing going on that should be removed at the phono-stage. Is there any hope they can fix that with a software update?
Click to expand...

What turntable and tonearm are you using? Have you tested the resonance of the tonearm/cartridge combination? Have you optimized the anti-skating? There are many factors that can lead to increased groove noise and susceptibility to "rumble". Years ago I switched from a Rega turntable to a Linn Sondek LP12...I was amazed at the reduction in groove and low frequency noise. No need for any filter in the phono stage. However, the cartridge/tonearm/turntable must be set up properly.
 
kevzep said:
Just trying to understand fully, what you actual problem is here, and why you think you need this brick wall filter....

I have no issues (if I am understanding your problem, which I am not sure I do) at all with my phono input on my C48.....
Click to expand...

I have a VPI Scout with a JMW-9T tone arm and an AT-OC9ML/ii low output MC cartridge. Here is a graph showing the bulk of the noise is below 20Hz. you don't want these frequencies pushing you amps and speakers needlessly.

A subsonic filter would nip it in the bud. Being that these are generally not audible I bet more of you have them than you think. I only knew it because the software clearly shows it. My understanding is any good PS with a MC input will have a subsonic filter.

pic upload
 
ghost rider said:
I have a VPI Scout with a JMW-9T tone arm and an AT-OC9ML/ii low output MC cartridge. Here is a graph showing the bulk of the noise is below 20Hz. you don't want these frequencies pushing you amps and speakers needlessly.

A subsonic filter would nip it in the bud. Being that these are generally not audible I bet more of you have them than you think. I only knew it because the software clearly shows it. My understanding is any good PS with a MC input will have a subsonic filter.
Click to expand...

I am an audio engineer, I understand whats happening here, and I know I don't have anything like what is going on in your graph....
I've never used high pass filters on any of my phono stages, if your table is set up right and you have the right compliance cart for your tone arm, you don't need it....

I think you need to get to the real source of the problem, I think at this point you are barking up the wrong tree to be perfectly honest....

The bulk of what you see on the frequency response graph is below the frequency response of the cartridge.
I think you have resonance issues with you tone arm, isolation and associated issues in that area.....

So firstly I would look at this area before you look at the performance of the phono pre....
 
kevzep said:
I am an audio engineer, I understand whats happening here, and I know I don't have anything like what is going on in your graph....
I've never used high pass filters on any of my phono stages, if your table is set up right and you have the right compliance cart for your tone arm, you don't need it....

I think you need to get to the real source of the problem, I think at this point you are barking up the wrong tree to be perfectly honest....

The bulk of what you see on the frequency response graph is below the frequency response of the cartridge.
I think you have resonance issues with you tone arm, isolation and associated issues in that area.....

So firstly I would look at this area before you look at the performance of the phono pre....
Click to expand...
You may be correct. As far as setup I used the VPI jig and I did a much better job than what the dealer did. The tone-arm rests on a point more expensive models have a oil reservoir that is said to help.

I did some checking and I was wrong about all PS having subsonic filters. From what I can tell the more expensive units don’t or you can’t tell from the website. Just because the project did I guess I figured incorrectly. My apologies.

I’m curious if you or anybody else listened to the audio sample that I posted.
 
ghost rider said:
I have a VPI Scout with a JMW-9T tone arm and an AT-OC9ML/ii low output MC cartridge. Here is a graph showing the bulk of the noise is below 20Hz. you don't want these frequencies pushing you amps and speakers needlessly.

A subsonic filter would nip it in the bud. Being that these are generally not audible I bet more of you have them than you think. I only knew it because the software clearly shows it. My understanding is any good PS with a MC input will have a subsonic filter.

pic upload
Click to expand...

What exactly is this a graph of? What was the test frequency? A sweep? Is this a graph of your cartridge output playing a test signal? The preamp output?
 
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