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This is what I have...A PrimaLuna Dialog II,a Rotel CD player as transport, and a Benchmark DAC1...

Now the problem. It began with a general crackling noise. I figured something dirty and clean the laser and all connectors. The noise persisted. My next guess was a tube BUT, the sound, intermittent and rare, seems to be centered, not isolated to one side or another. If it is a tube, I would think one side or the other would give me the problem...the next step in the problem is the entire sound goes off for a couple of seconds at a time, rarely..As it comes back on I write off a fuse.

Never had this sort of problem before. Can the amp do anything like this? If so, it is indicative of what. If not the amp, which is more likely malfunctioning, the CD player or the DAC?

My next idea is to remove the DAC from the signal path and see if the problem goes away. If not that indicates the CD player or the AMP and I cannot figure a way the amp might be at fault unless I had two tubes go at the same time.

Any suggestions???

If the crackling seems centered, that means it's the same in both channels, which would indicate DAC or CD transport, most likely. Few amplifiers have much common circuitry that would result in such problems, and most of those problems would have other nasty manifestation.

Are the power supplies on those components dual mono or shared between channels? If the later you may have a capacitor in one of your power supplies about to die. Just a guess though. You may also have a problem with a decoder chip that's shared between channels. Impossible to diagnose at a distance though.

Process of elimination is the only way to begin. Cold solder joints are still my fallback for crackling noises but you have to find which component is at the source of the noise. If it were in the amp and tube based it would have to be a tube common to both channels, say, a pre amp input tube. This seems unlikely as PL is using a dual triode, no? Not much chance of both sections of the tube failing at the same time. A solid state rectifier possibly, but not the most likely. Power supplies are common to both channels in most gear, so that would be where you being to look once you've settled on a single component as the culprit. You might check whether the amplifier's tubes are still glowing when the sound disappears. Just for the sake of elimination, pull your interconnect cables from all the units and reseat them, the problem could be a bad solder joint in a cable connector.

If it is the PL at the heart of the problem, it should make noise when no signal is applied but with the volume set to an average listening level. If that's not the case here, then the amplifier is likely not your problem. What is? Don't know, could be a switch or a cap in a muting circuit. Eliminate the DAC and go from there. If it isn't the DAC and it isn't the amp, that only seems to leave one other choice if the cables have passed their test. But where in that one other choice might the noise be coming from? That's more than likely a job for a technician with the proper tools to troubleshoot. The best you can do is deliver the troublesome unit to the shop to cut down on time spent at $65 an hour.

Use the Rotel just as a CD player alone to see if you have the noise. Unhook the Rotel digital input to the Benchmark DAC, but keep it connected to the amplifier. See if the noise is still there. If you can borrow a friends CD player with a digital out feature, you should solve the problem. Play the CD directly into the amplifier. If the noise is gone, then either your transport or DAC is bad. Now connect the digital out to the Benchmark DAC. Connect the Benchmark to the amplifier. If the noise is gone, you have Rotel CD transport problem. If the noise is still there, get the Benchmark fixed. These should confirm the problem, I would think.
Mike

Reverse the direction of those interconnects between the buzzing component. One set a a time.

Buy an Oppo.

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My local audio outlet is selling a used Theta data basic transport. Aside from it being older than dirt, and assuming it still works OK, is this a good choice for a transport.

I do know that the Theta Data Basic II transport had a slight edge over the more pricey Theta Jade transport that listed for $2495 back in 1999.

I also had a friend that owned an audio store in Nashville, TN that swore the Theta basic II was on par with the Classe CDT 1 transport that was contemporary with the Theta basic II. And of course the build quality is top shelf. He described the Theta as 'punchy' with no other unwanted electronic inflections.

So, I would say, go for it.

hope this helps.

JIMV, what's the expected lifetime of the laser in that baby?

I'm just wondering how long it would be expected to live.

Easily repairable/replaceable?

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Got it for review...so far sounds good, at least as good as the old Rotel..I do need a short length of decent digital cable.

Thanks everyone for the advice...

Jim,
I have a balanced 0.5m Acoustic Zen Mc2 digital cable if your interested. 110 ohm.

Thanks,
Mark

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I thought digital cables were 75 ohm..?? What does balanced in your description mean...I thought they had a different termination but the photo I looked at for the cable shows standard RCA, which is what I use.

What are you asking for it?

Shows you how much I know about digital cables..been years since I bought one.

There are two digital interfaces that show up on consumer equipment, "SPDIF" which is single-ended 72 ohm, and AES/EBU which is 110 ohm balanced.

Edited to correct impedence due to brain failure...

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Got it for review...so far sounds good, at least as good as the old Rotel..I do need a short length of decent digital cable.

Thanks everyone for the advice...

"short" length of digital cable?

I've read that one of the most important things in a digital cable is length. It should be no less than 5 feet long.(1.5 meters) This reduces the instance of early reflections which is a main factor in sound degradation.

You might want to research that to see how substantiated that is.
Perhaps JJ could comment.

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Got it for review...so far sounds good, at least as good as the old Rotel..I do need a short length of decent digital cable.

Thanks everyone for the advice...

Jim,
I have a balanced 0.5m Acoustic Zen Mc2 digital cable if your interested. 110 ohm.

Thanks,
Mark

Balanced cable (AES/EBU) 110 ohm, is the industry standard for professional recording studios world-wide. Balanced cable has the same equal impedence from one end to another thus using very long runs of cable are not an issue. Unbalanced (RCA)75 ohm digital cables have unequal impedences and long runs could be an issue. Thats about all I know.

Sonically, I can hear no differences between the two. Both sound great.

The cable cost $300 new. Im selling mine for $100. Even though my cable is an older version, it is practically new and in great condition. The cable looks like this one but with black Neutrik connectors and is a little darker gray in color than this one.

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I think I am better off with a setup with RCA termination..Thanks for the offer though. Too close to Christmas for another purchase...

For my own info...As I understand it, the Theta has a balanced out, the benchmark has balanced BUT the amp does not have a balanced in. I need to run balanced to the DAC and then to the amp do I not?? That would involve more cables and an amp that can run balanced, or do I have this completely wrong. I have never run a balanced setup.

The one digital cable will go from your transports digital (output) to the DAC's digital (input). I don't think it really matters if you run balanced or unbalanced I/C's from DAC to preamp. But, I'm not sure from a technical aspect. Never really considered that. Interesting, I will have to research it.

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"short" length of digital cable?

I've read that one of the most important things in a digital cable is length. It should be no less than 5 feet long.(1.5 meters) This reduces the instance of early reflections which is a main factor in sound degradation.

You might want to research that to see how substantiated that is.
Perhaps JJ could comment.

If something like that is a problem, then the cable is the wrong impedence, or the ends are improperly terminated. In this day and age when nobody seems to know analog electronics (well, except for some of the guys here who do things like tube amps) any more, who knows what's really set up.

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I think I am better off with a setup with RCA termination..Thanks for the offer though. Too close to Christmas for another purchase...

For my own info...As I understand it, the Theta has a balanced out, the benchmark has balanced BUT the amp does not have a balanced in. I need to run balanced to the DAC and then to the amp do I not?? That would involve more cables and an amp that can run balanced, or do I have this completely wrong. I have never run a balanced setup.

The digital cable and the analog cable do not have to have the same kind of termination.

If your digital cable is balanced, and both the DAC and transport are balanced, that's good. If the analog out from the DAC is then unbalanced, standard RCA is likely your weapon of choice.

Now, if you're sending the digital signal two places, splitting it does create a problem.

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Thanks...

Initial impressions on the transport...The weakest link in my audio setup is my speakers, a very old set of Energy C2's from the mid 90's.

I agree. Although those Energy C2 speakers are no slouch in the microdynamics. Good speakers. You might want to think about reconing them yourself. Very easy process. That would save some money and the Bass response would improve.

Before I retired them, I had reconed my old JBL L-80T's 4 times since 1985, and every time the Bass was as tight as it was new. Not sure what would remedy the high frequency 'muted' characteristic you are now experiencing.

They are very musical from the mid range up but till now have exhibited no evidence of base. This new setup almost reverses that. All of a sudden I have lower midrange base. Actual punchy base (not vague rumbles)...never expected. The trade off seems to be with the treble. The speakers always gave me a very well defined treble, even with tubes. Now that seems to be muted...almost like going from push pull tube sound to triode.

I suspect the treble might be 'fixed' by using a real audio digital cable between the transport and the DAC. Today I am using a 1ft monster cable 'video' cable of undetermined cost and age, all that I have at the moment.

If you want to save money here, I would suggest the StraightWire info-link digital cable with RCA's. GREAT! cable and huge bang for the buck. Very inexpensive and quite nice aesthetically to boot. I have used almost every StraightWire speaker cable, and I/C with great results. Like Audioquest, StraightWire is a tried and true cable. You could probably pick up a new/used one for about $90 on AudiogoN or Canuck Audio Mart.

While I can ill afford to have an audio failure right now as they are always hits to the wallet, I am having a very good time playing..

On a related note...my towns record club (Boise's Vinyl Preservation Society) had its annual record sale on Sunday. Lots of dealers and lots of foot traffic. The local university PBS radio station donated its entire collection of records as a fund raiser and I had to organize maybe 500 records with poor jackets BUT, great actual records in amazing condition. At $1 each, I stocked up and have not played a clunker yet! So, my living room basic vinyl setup is getting as much play as my serious digital system. I have been playing more music over the last week then in a long time. So many records I am running out of record cleaner.

70% Isopropyl alcohol and distilled water would be cheaper. Mix it 50/50 and you are good to go. That's what I did when I was into Vinyl. I should have my butt kicked for getting rid of all my audiophile pressings because the Transrotor turntables have me captivated at the moment