Dynavector P75 preamp making "shhhhh" noise. Ideas?

Bought a used preamp to go along my new Prime and 20X2L cart. The noise floor of the preamp is rather high as I can clearly hear a lot of "shhhh" even at lower volume, especially between tracks and when the needle isn't on a record. Everything is grounded properly. Without it, I hear a ton of hum so I know that's taken care of.

I'm using the Phono Enhanced mode. Does that have anything to do with it? Otherwise, everything sounds fine, but the internal preamp of the VPI Nomad I have is utterly silent but this P75 which is supposed to be a huge step up makes that noise and I'd like to get rid of it.

Ideas?

Full disclosure. I'm not using a dedicated phono cable. Would that make that big of a difference?

 

I think the Nomad phono stage has only 35 dB gain -- I assume you weren't using that with a 20X2L. The P75 for LOMC has either 60 or 63 dB gain. Most of the time that's going to mean more background hiss for sure. You want lower noise with a low output MC you might be better off using less gain and a SUT in front of an active gain stage, though I'm sure there are high gain phono pres with active MC stages that are more or less noisy.

 

According to Dynavector literature, the Phono Enhancer mode (PE) amplifies the current from the cartridge as opposed to the voltage. Wonder how that affects the background noise and whether this is normal or not.

Hope other owners chime in.

 

Perhaps a stupid question, but have you fully disabled the internal preamp of the Nomad? If you haven't, you would have an incredible amount of gain (gain on top of gain) which would probably explain the situation.

If you have, disregard that and focus on setting up the P75 properly for your cartridge. There are 3 different versions of the P75 I believe so they may well have different adjustments but a quick look at the manuals for the Mk 2 and Mk3 indicate that you would have to set the P75 properly to the low resistance setting in PE mode as your cartridge has a low internal impedance of 5 ohms.

If your P75 has adjustments for gain in PE mode (I don't believe MK 2 and MK 3 versions do, so probably only if you have the original), 60 dB should be adequate. 63 dB should not be that much noisier but you could try out the different gain levels to see.

 

Something sure isn't right. I have the same cart and same preamp and don't have anything like what you're describing. I would definitely try a dedicated phono cable.

 

Not using the Nomad but the Prime. Only mentioned the Nomad as a comparison.

 

I'll post an audio file on Sunday to show what I mean.

 

Which output level in PE mode did you select ?

And this is a P75MK3 ? You need to be certain, as the layout for the jumpers is different, at least from MK1 to MK3.

http://www.dynavector.com/pdf/P75_mk3_emanual_ r2v0_a4.pdf

 

Yes, definitely an MK3. Using Low option on PE mode.

Contacted the seller on Audiogon but didn't hear back. It was my first experience. Wondering if the unit is defective. The seller was quite communicative so I doubt he was trying to pawn off a defective unit on me.

Unfortunately, I don't have another phono preamp or this would be easy to test. Any other ideas?

 

Apologies for the delay. Things have been quite crazy around here.

This is the sound I hear from my speakers when the volume is set to 75db on my AVR350 (mid-level listening) ;

https://app.box.com/s/r73591b2y7ieszcsp0w55h8hcn0pk9ql

Keep in mind I recorded this next to the tweeter as I wasn't picking it up when sitting at my listening position.

The previous owner suggested moving it away from the amp. Doing so did nothing but interestingly enough, moving it closer to the amp introduced hum. Of course, I moved it away from the amp to remove the hum but no distance can fix the hissing.

I'll be trying a dedicated phono cable next.

 

A little hiss right up near the speaker that you can't hear at the listening position when you're using 60+ dB of gain is not terribly surprising or unusual. A cable isn't going to change that.

 

I do hear it. What I actually wrote is that my phone's mic wasn't picking up the hiss at my listening position. But I do.

 

What does the P75 sound like in MC mode ? I'm seeing some instances where PE mode had more hiss than the MC mode.

 

I'll certainly give it a try. Thought I'd use PE mode as everything I read about it stated it sounds superior to the MC mode.

 

Well, after doing a lot of research, it looks like a bunch of people experienced the same thing I did. Apparently, the PE mode is what creates the hiss.

I'll do some comparisons to the standard MC mode and see if there's a difference, apart from the hiss. To some, PE mode is a night-and-day difference whereas for others, it makes no difference. If it doesn't, I might as well use the MC mode.

I'll first see if the MC mode gets rid of the hiss. Let's start there.

 

That's a bummer. This is a known issue with the mkIII version of this preamp?

 

In PE mode, yes.

Since the PE mode sounds so great (again, according to user reviews I read), people have pretty much accepted the hiss as in some cases, it's mild. In others, not so mild and can be heard during playback. Whether this is something you'd be OK being exposed to is up for you to decide. The synergistic relationship between the P75 and Dynavector carts has made a lot of people simply live with it. The impact of using the PE mode versus the traditional MC mode is (again) entirely dependent on the system it's used in. Whereas it's a giant difference on one system, it's barely audible in another.

That is why I plan on experimenting later today to determine whether the difference is pronounced enough to warrant living with the hiss which, in my case, is audible when the needle isn't on a record. And I suspect that using a dead-quiet preamp (or the MC mode) would result in quieter/blacker background noise between tracks or silent sections of songs which one might or might not determine to be a huge advantage. It also depends on one's listening habits and the type of music one favors.

I intend to report back in case anybody else is interested in the conclusion to this issue. The preamp sounds very nice. The hiss isn't a dealbreaker but if I can get the same or almost identical performance minus the hiss, I'd certainly favor that.

 

I had massive issues with my Classic with interference/hum/etc. Do you have the table and pre grounded? Have you tried any other pres with the prime or is this table new and your just trying it out for the first time with it?

btw you don't need anything spectacular with the table as far as cables go. Unless your getting a huge tax return and don't want to take your family anywhere I'd just swap it out with another cable your using to see if that helps. try wrapping the cable from the arm to connection box with tinfoil too.

Have you tried posting on VPI's forums? Maybe call VPI directly? I'm sure they will be.... super helpful.

 

The hiss is coming from the preamp ; not the turntable.

I believe I've got the cause nailed down, especially in light of the many many threads on the topic.

 

Yes, experimentation seems to be in order. And also, don't discount the importance of grounding schemes. The sound may be emanating from the phono preamp, but it may be caused by an interaction upstream.

I have the MKII version of this preamp. When I first got it, I used it with a Dynavector 10x5. It really was a revelation to finally get the perfect amount of gain for that cartridge, after trying it with several other phono preamps over the years. When my 10x5 bit the dust, I upgraded to the 20x2L, and switched the jumper configuration to the PE mode. Again, very nice performance. A little more background noise, which is to be expected moving to a low-output cartridge and an active MC gain stage. But it was still very nice. I actually really love the 20x2L, and I always felt that I could have gotten quite a bit more performance out of it if I had upgraded the phono preamp.

I am still using the P75 MKII, but I now use it in MM mode, in conjunction with a step up transformer, to drive a Zu Denon 103. I also used the SUT/MM mode for a while with the 20x2L, and it was definitely an improvement over using PE mode. Blacker backgrounds and more tactile textures. The P75, while not the final word in phono preampfification, is definitely a nice unit and it excels in multiple areas. It has been very flexible for me, in 3 different modes, each one improving on the previous one. It is definitely worth troubleshooting this issue and figuring everything out. Best of luck!

 

I had the mk.III version of the P75 along with a Dynavector XX2 mk. II and didn't have any problems with hiss. Sure if you put your ear right up to the speaker and raise the volume a bit, you could hear a little, but nothing that would be audible when in a listening position.

 

Thanks!

The Prime is grounded properly. Everything is dead-silent but the preamp does add hiss. I'll try the MC mode to see if the change in performance is negligible on my system. If it is and I benefit from blacker backgrounds and a hiss-free playback experience, I'll be thrilled. Otherwise, I'll live with the hiss.

Out of curiosity, which SUT are you using?

 

Were you specifically using PE mode?

 

exactly. I had the same issue with my Classic. Hum/buzz etc. Bought a new phono pre (Rogue Aries) better but still there. Got rid of the VPI for a Rega. Dead silent. Good luck though in eliminating it. The tonearm wires used by VPI are not shielded and pick up all kinds of crap. Temperamental to say the least.

 

It's that little loop of wire of exposed unshielded wire they have coming out of the arm tube. No phono wires inside any manufacturer's tonearms are shielded I think, they're all set up so that the tonearm wand itself is grounded and it acts as the shield. But only VPI has a little loop of exposed unshielded tonearm wire outside of the arm at the back end (though many have a little exposed unshielded wire at the headshell end of course), that's gotta be susceptible to environmental sources of hum.