Pro-Ject RPM5 Improved rumble noise floor

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

You may find here a link with a sample recording of the improved motor suspension.
I recorded a classical LP at is side A end track including the cut out region, armtone lifting, altering the LP to side B and playing it from the early outer beginning.
Pay attention to the vinyl surface noise where no HUM or rumble can be detected. Also pay attention to the very low noise during the armtone rest (the silent region).

The sample format is 44.1KHz/16bit WAV.

Sample.wav - 8.62MB

henkuk · Posted: Mon Nov 02, 2009 1:45 pm Post subject: RPM5 mods for RPM4

Hi,
I own an RPM 4 and although I am pleased with it's performance, I think it has the same issue as the RPM5 being the rumble. Looking at the manuals, it has the same design in terms of motor placing and construction so it comes as no surprise it has a similar issue.

I know you are in negotiation with Pro-ject to see whether they are interested in your mods as a commercial product.

In the mean time, would you be willing to share a little more with a select audience? It's a bit disappointing reading about potential upgrades and improvements whilst not being able to go through this.
Thanks,

Henk

flavio81 · contributor Joined: 16 Sep 2009 Posts: 519 Location: Lima

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

Dear Henk,

I'm aware about the desire of Pro Ject turntable users to get their machine to become one league better or even more. Believe me I want to share my solution with all users.
My solution is so simple in the idea concept and so low cost but have the ability to make the big difference it the TT performance.
I think users may encourage their Pro Ject dealers to accept positively a new concept of motor suspension. Beside of the technical improvement, it is business wise to place their TT in a better ranking (a better branding).

I'm still lokking forward for getting some other raw material to test my concept in order to finalize it.

I'm adding last night graphs. this time all measurments (gain wise) are actual true values.

As you can see, there is still some residual noise of 100Hz harmonic. However it is not noticed during the listening to the record, I'm still trying to auppress it as I did to the 50Hz. The previous recorded sample is including the 100Hz harmonic and it is not possible to hear it.

henkuk · Posted: Mon Nov 02, 2009 2:50 pm Post subject: Whoa

That is a rather significant improvement that the graphs show. I always thought it had a rather high noise floor and wsa never sure that I bought the right product. Since I got mine really cheap, I figured, just run it for a year or two and see how you get on. We are now 5 yrs down the line so no point considering a return to the dealer.

I hope you get to go to market with your solution, either as an idea or as an actual product. Depending on price I would definately be interested in purchase.

Feel free to PM me if you can reveal more around price etc.

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

I was able to "kill" the 100Hz rumble harmonic. My design is at its completion state.
Stay tuned about the kit availablity.

This is the updated spectrum graph:

flavio81 · contributor Joined: 16 Sep 2009 Posts: 519 Location: Lima

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

Last night I made an additional slight improvement and I was able to reduce snother -2dB of the 50Hz rumble (keep in mind that this cannot be heard, just the spectrum analyzer is able to capture it. But my aim is to reduce all noises as much as I can.

But the most surprise will be this one. During my last experiments (which I used the same setup and LP for the measurements) I found a strange small nin heard hum of 60Hz and 120Hz. This is typical to American line frequency and equipment that is hooked up to it. From my analysis I may say with high confidence that the 60Hz/120Hz is pressed on the record. The European as well as the Israeli line frequency is 50Hz so it is not rooted in my equipment. I assume that the 60Hz/120Hz HUM leakage comes from the process of the recording equipment somewhere within the chain. The 60Hz is the fundamental frequency and my be generated via a ground loop or not 100% wire shielding within the recording equipment. The 120Hz is probably coming from some power supply ripple as the power suplies rectifier bridge is dual path which doubles the ripple frequency compared to the fundamental line frequency.

I think that this is demonstrating well how much I was able to lower the noise floor of the RPM5. I cannot express the sound of that turntable.

henkuk · Posted: Thu Nov 05, 2009 10:05 am Post subject: Take 3 improved rumble figures

Hi Hanan,
I am really intrigued to see what you have done to improve the figures in this way. Been looking at the way the motor is suspended and can not see a way to get a smaller surface area where the motor suspension touches the plinth, putting the rumble through to the platter. Maybe isolating material or packing round the motor might help but that might be counterproductive as it enlarges the surface area for rumble to be put through.

Or is that the key as it wil disperse the motor energy more efficiently?

Cheers,
Henk

Conrad Hoffman · senior member Joined: 01 Aug 2007 Posts: 311

A couple things. My efforts to reduce the motor noise in my tt were a dismal failure. I was able to convert the several large peaks into more peaks of different frequencies, or maybe fewer larger peaks, but I never got the good results you've been able to. I attribute that to not wanting to do major mods to my plinth, and there's no room to do much in the way of motor suspension or isolation. Still, Good Stuff on your part!

Second, there is no reason to publish graphs at the resolution you have. There are still some of us with dial-up, and we don't have the patience to see them. My screen is about 1280 wide, so anything over about 6-800 wide is a waste of bandwidth. Get a photo editing program and downsize the stuff! It will look just fine and come up in a flash.

Best,
Conrad

flavio81 · contributor Joined: 16 Sep 2009 Posts: 519 Location: Lima

Man, you are a genius. Congratulations. You should be in charge of the turntables at Pro-ject.

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

Dear flavio81,

I think Pro Ject are "cold as ice" in this case. I really wanted to share with them my idea. they are just ignoring it and not as serious as I would or any other would expect them to be.

I'm sure that many Pro Ject turntables of that "family" have that inherent problem, but the shy users are too shy to talk about that. Maybe they cannot observe the problem. An "experienced" audiophile will observe the problem right away.

Pro Ject can improve their turntable series just by the "thumb" effort and they are ignoring it. I can tell you that not many turntables with built in the plinth AC motors have reached this low noise floor. The signal output at the silent areas of the record is only the stylus tip rubbing on the vinyl without any additives !

Anyhow I got this afternoon some sample raw material to produce a first prototyping kit batch to check stability and long term reliability.

I have more wonderful crazy ideas for Pro Ject if they would be more warm in attitude.

WmAx · Posted: Fri Nov 06, 2009 9:58 pm Post subject:

To the user that says audiophile tables are essentially a rip off: this is not always the case. Some models actually have very good engineering and measure excellent, and are far higher in performance that other similarly priced units.

-Chris

flavio81 · contributor Joined: 16 Sep 2009 Posts: 519 Location: Lima

chalmh · member Joined: 14 Oct 2009 Posts: 40 Location: ISRAEL

I would say that the RPM5 is a very good turntable in general. The main engineering problem of it is the motor suspension system. It is obviously a mistaken suspension concept, probably in their whole line of products which maybe all published product reviews missed it out.

If some of you are "old" enough and remember that during our childhood we used to build a "phone" using two small cans and a nylon wire hooked up as a string between the two cans bottom membrane. Our partner was talking into his can as we were listening to his voice attaching the ear to our can.

Analyzing the problem on the motor suspension rubber belt on which the motor is hanging, I can say 100% that it is the same. The rubber belt is stretched as a string in four corners and vibrates X4 times following the motor vibration. The vibrations are passing and even amplified by the sustaining effect of the rubber string into the plinth. The plinth material fails to absorb the vibrations and they have a free pase towards the arm and platter mechanism. What is more interesting was that when I fastened the motor with its "transportation security screws", the fundamental vibration noise wasn't changed much. This means that the motor suspension is not doing its work.

The overall engineering of the turntable is very good except the above problem. After I was able to isolate the motor vibration, the sound of the turntable changed very much. The lower frequencies came back to natural life by generating pure bass sound.

My solution is a very simple and cheap solution. Pro Ject turntable users who noticed that problem may feel frustrated due to the manufacturer's ignorance of the solution. This have implication of the past sold turntables as well of the future selling turntables.

Since I'm not a "company" and have another job in life, the solution will not be marketed, unless the manufacturer will do it. I think it is time for the users to assert the manufacturer to improve.

The intention of the thread is not to criticize Pro Ject negatively but helping them to improve their products and the effort is not too big for their shoulders.