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judicata
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Joined: Jun 26 2008 - 11:55am
Preamp and Headphone Amp?

I've been very close to grabbing a WooAudio WA6 headphone amp for my AKGs (701s). My questions is two fold (1) does the following make sense technically and in terms of quality, and (2) might it solve my problem below.

First, instead of grabbing the WA6, which is a head amp only, I was thinking about getting the WA2 which is a headphone amp and preamp. (here). Right now I just have a Marantz PM7001. I'd like to use that for a power amp only (it lets you) for awhile before I can afford a separate power amp (probably 4-6 months or so). Does that make any sense, or am I better off just sticking with the Marantz until I can afford both (i.e., will using the WA2 and the Marantz as a power amp be worse or no better than what I have now). If it doesn't make sense, I could just use the WA2 as a head amp until I get the separate power amp, if I'm sure that's what I want to do.

Second, on to my problem. I have a Rega P2 with an Exact 2 cart (yes, I finally upgraded), a Bellari VP-530 tube phono preamp (basically a VP-129 with a usb out), the Marantz PM7001 and some AKG K701s (also the ProAc Tablette speakers, but they aren't relevant to this question). I have a Classic Records release of James Horner's score for "Glory" (if you haven't heard it, it is beautiful). Through the headphones, when things start to get really heavy (loud timpanis and such) it gets really muddled and distorts. To troubleshoot, I tried turning the volume on the phono preamp up most of the way, and the volume on the Marantz (which is currently driving the headphones) down. It sounded worse - which I expected. Then, I turned the phono pre volume down below where it was before. It sounded much better, but I had to turn the volume on the Marantz up all the way, and I still don't have the volume I want. If I switch to the speakers, they get plenty loud. (that is, I have to turn the volume up higher when I use the headphones).

I'm not well versed in how amplification works, at least not well enough to figure out whether the distortion is coming from the phono preamp or the amp (or somewhere else - I hope not).

Would a headphone amp perhaps solve this problem?

Jan Vigne
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Re: Preamp and Headphone Amp?

Sorry, I can't help with the first part of your question though I suspect, if I read the question correctly, you'll have to try the Marantz to determine whether it is "better" than your present set up. But I'm confused why you have duplicated or want to duplicate so many functions in your system. You have two headphone outputs, two phono pre amps and essentially two amplifiers for driving headphones. And now you're thinking about adding another "pre amp" and another headphone amp? Ay chijuajua!!!

Rgearding your second question, you haven't done enough troubleshooting to allow for a really good answer. There's always the possibility the distortion is inherent in the disc or is the result of improper set up in your turntable. If I assume all your other material sounds OK when played on the same set up, then I would say your problem is possibly one of gain/output voltage and overload sensitivity between your phono section and the Marantz integrated. When you turn the gain up on your phono pre amp you are increasing the voltage input to the Marantz and it likely doesn't care for the excessive amount of output voltage the Bellari is producing.

However, that doesn't assure you the phono pre amp is not the source of the distortion. Typically, a volume control will be placed before the output gain stage of a device which would mean you are lowering the input voltage to the tube by lowering the "output" level. I have no idea how specifically the Bellari is configured so there is no way to make a good guess whether this could be the issue in your system. Assuming that it is, a clean sound when the volume control is lowered might mean lower input votage to the tube is preventing the tube from being overdriven while the higher gain setting means the tube is being driven into distortion and merely passing that to the Marantz.

From what you've posted I can only assume the speakers are not distorting under the same conditions as the headphones. That could mean you are simply overdriving the headphone amplifier.

You have sufficient versatility in this system to do more troubleshooting. From what I see and read you have two phono pre amps available to you and two headphone outputs along with the ability to separate the main power amp from the pre amp of the Marantz. Driving the Marantz power amp with the Bellari line oputput would be another option to try as you sort out where the distortion occurs. Ignore where the volume control sits, 10 O'Clock or 5 O'Clock doesn't matter. If you have sufficient volume level, that's all that counts.

You don't have to be extremely well versed in how amplifiers work to do some deeper searches into how your system is operating. All it takes is a logical approach to ins and outs and a bit of an understanding of what might be causing problems. Typically you begin with the simplest system set up possible and add or subtract components until something tips you off that you are on the right or wrong track. Take notes if necessary and follow a logical path to how you now have the system running. When you find a connection that causes the problem or makes the problem disappear, you have to stop and think about why that would occur.

If you are running the Bellari into the line level inputs of the Marantz - you're not running it into the phono inputs I suspect, you might try taking the outboard phono section's output into the "tape monitor" inputs. That input might have a higher overload sensitivity and this might solve the problem. But until you do more searching on your own, that's about the best I can suggest.

judicata
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Re: Preamp and Headphone Amp?

Thanks! This is very helpful (as always).

On the first part, I'm afraid I wasn't clear - right now I have the Marantz integrated amp that I'm using as my preamp and power amp (but I'm not using its internal phono stage - it kinda sucks). Then I have the Bellari phono pre (going into the Aux or CD input). I don't have another headphone amp or another preamp. You're correct that I have two headphone outputs - one in the Bellari and one in the Marantz. I never use the one in the Bellari, because it doesn't drive the headphones (insufficient volume even when turned all the way up). Incidentally, if this helps at all, the Bellari has a separate output knob and headphone level knob, and the output knob level doesn't affect the headphone level at all, and vice versa.

I'm thinking about eventually replacing the Marantz with a separate preamp and power amp. The preamp I'm thinking about is also a headphone amp (and a very good one from what I've read). I was hoping to use the Marantz as the power amp until I can afford to get a dedicated power amp, since the Marantz has the "separate" option to just use it as a power amp. So, eventually, I just want 1 phono pre, 1 preamp, 1 power amp, and 1 headphone amp (and the preamp and headphone amp will be the same thing if I go this route). Since I won't be using the Marantz as a preamp, it won't be duplicating anything.

You've given me plenty to play with when I get home. I didn't think about trying to feed the Bellari directly into the Marantz while bypassing the Marantz's preamp function (i.e. using it has a power amp only). And I didn't have any idea that the tape inputs might be different - I'll give that a shot. You've also made me think of a few other ideas - I'll report back.

I'm not concerned with the position of the volume knob, except that I'm afraid it is just not quite loud enough when I have the phono pre output set below my suspected distortion threshold.

As far as I could tell, I could only duplicate the distortion on the speakers when I turned the phono preamp way, way up. I'll play with it some more. If I'm pushing the headphone amp too far, then getting a separate headphone amp should do the trick.

judicata
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Re: Preamp and Headphone Amp?

I played with this some more, and I think the phono pre is overdriving the headphone amp. I switched between the speakers and the 'phones. I found I could turn up the phono preamp's volume much higher with the speakers without distortion (regardless of the volume knob), although I eventually did get distortion at pretty much any volume when the volume on the pre was jacked all the way up. When I used the marantz as a power amp only, the problem persisted. It sounds smooth as silk through the speakers if the preamp's volume is set moderately. The problem is that I can't turn get it loud enough through the headphones. It looks like a headphone amp is in order. I think I'll go with my proposed route after I do some more exploring.

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