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Phono stage revealing limitations of cartridge?

Hi,
I just purchased an Ear 834P for my system. This is my first experience with tubes. I hooked it up and I immediately noticed an improvement over the stock phono stage on my integrated. There was a much more three dimensional presentation. However, after listening for a few minutes, I realized the sound was very thin, light on bass, and the highs were bright and grating. Also, the output of the Ear is really high, so much so that the volume knob on my amp is almost all the way at the bottom and moving it very slightly results in a dramatic increase in volume. I'm wondering what is causing the bright sound. Here are the possibilities I've come up with:

1. The Ear 84P is just revealing the limitations of my cartridge which the stock phono stage had just smoothed over.

2. The stock tubes in it have gone bad. (I'm planning on trying out some Jan Philips 5751's on it to see if that lowers the gain a bit.)

3. The unit is defective/the person that modded it screwed something up.

4. I'm getting some very low level RF interference. You can't here it at all when music is playing, but if you turn it up all the way you can hear it. Perhaps this is causing the brightness.

5. The Ear and the Rotel integrated are a mismatch.

I've tried using a different cable from the phono to my integrated and that didn't change anything. I also tried using a different input on the amp. I tried both MM and MC to confirm that I am using MM.

Does anyone have any suggestions? I'd be really grateful if someone could help me get this sorted out. I know there's a lot of questions here, but I thought tubes would result in warmth, not brightness!!!

BTW, my system: VPI Scout/JMW-9, Sumiko Blue Point No. 2 (2.5 mV), Signal Cable Phono Cable, Ear 834P Deluxe Phono Stage (modded but w/ original tubes), Rotel 1062 Integrated Amp, Blue Jeans speaker cables, Infinity 3500 speakers (circa 1981)
sinisterporpoise68
sinisterporpoise68 OP
63 posts
 
I'm nervous that if I went with the low output Dynavector, the RF interference I'm getting would be amplified. If I understand correctly, if I used the high output Dynavector, I'd be able to use it in the MM section of the Ear, just like I'm using the Blue Point right now. I wouldn't have to change the loading or impedence, right? But I'd still be in a position in which I have too much gain.

Although, when I have turned on the MC section of the Ear, I haven't been getting the interference when I turn the volume up all the way... There are too many variables here!!

I'll have to wait to make a decision until I get the 5751 tubes with lower gain to see if that helps me at all.
dgarretson
2,588 posts
 
Think about querying AA member Flemke about how he resolved the same problems with his EAR.
larryi
3,719 posts
 
My first guess as to the source of your problem would be improper loading. Although the manufacturer of the cartridge may specify a particular loading, in reality, the proper loading differs from one phono stage to the next so one must experiment with different loading. When a cartridge is not loaded down enough (remember, the HIGHER the number, the lower the amount of loading--e.g., 47k is a very high number, so the cartridge is not being loaded down much), it will sound bright, edgy, sibilant and thin in the bass. Let's say you loaded the cartridge at 200 ohms with one phono stage, in a different stage, that same number may be way off the mark. So, experiment with loading before dumping the cartridge.

Choice of tubes can make a BIG difference so some experimentation there could yield a satisfactory result. If you are substituting the original tubes with 5751s to lower gain (your phono stage uses 12AX7s?) you could also get other sonic benefits because those vintage tubes sound pretty good. This substitution usually can be made without any problems, but, you might want to check with the manufacturer because it is not just gain that is different; the operating parameters are slightly different.

You also mentioned concern with lower output cartridges and RFI. If you have RFI concerns, you must be certain that all your interconnects carrying small signals are shielded cables. Also, I have found that cartridges that loading down a cartridge (lower number value for the loading resistor, e.g., 100 ohms or lower) dampens the top end response of the cartridge and significantly improves RFI rejection.
ducatirider
111 posts
 
I would make sure the cartridge is set up correctly first. Then get a test record to confirm. Your description sounds like it could be VTA that your old phonostage could not resolve.
lloydc's avatar
lloydc
734 posts
 
Are you using the mc setting or the mm setting? your cartridge output is exactly between what you need for either input, so I don't see how you could have an overload issue on the mm setting. A loading/impedance mismatch seems possible - you will be amazed how important that is. the transformers in the EAR834Pare are very much the weak link, especially if you've had good mods; they sound a little thin to me.
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