Help-New Tube amp TOO loud?!

Why do you often reply without reading the thread? This has been addressed thoroughly.

 

They are microphonic. Yes, they are defective, hence the low price. I know it's tempting to buy cheap but with tubes, buying with a reputable source is always the best bet. Otherwise, you run the risk of experiencing the issue you have.

Only other possibility would be that your phono preamp or your preamp is too close to your amp. But I doubt that is occurring right now. Still, it's worth distancing your amp away just to see if the problem goes away. If not, return the tubes and buy another matched NOS pair of RCA 12AT7 triple mica black plate tubes from a reputable dealer who has thoroughly tested them for microphonics and any other extraneous noise.

 

Thanks for your very helpful replies! What are your thoughts on me trying 12AY7's which I read have even lower gain than the 12AT7?

 

You can but remember that whether you choose to get another pair of the same 12AT7s you've tried and liked or try your hand at 12AY7s, you *need* to do business with a reputable dealer! I'll bet you a beer those were bought on eBay or a similarly unqualified source. That's just asking for trouble, especially if you're unfamiliar with tubes, what to look for, how to verify they're the real deal and not a fake or mislabeled model, etc.

Do it right and you're far more likely to get results you'll be satisfied with. Cheapening out with NOS tubes is, again, asking for trouble.

For instance, a matched pair of the lowest noise/microphonics GE 6072 (low-noise version of 12AY7) black plate triple mica from this dealer (who *is* a reputable source) is $85. Welcome to the world of tubes, my friend. You asked for it!

ANOS GE 6072 Blackplate Triple Mica 1950s | KCA NOS Tubes & Amplifier Repair

 

Yup these were untested but the seller had great feedback. I totally see what you mean. This whole NOS world is daunting, especially next to the cost of new production. I understand that they are supposedly that much better then new, but its such a crap shoot especially on Ebay.

 

And that's why you don't buy there. Cheap/untested from untrustworthy source = not a good choice.

 

See if the seller has other "tested" tubes for sale. "Untested" is often a euphemism for "bad" by weasels.

 

I've previously owned one of these amps and didn't have the issue you describe until I removed the negative feedback loop and then gain went through the roof.

I can't help but wonder if the NFB loop in your amp was not soldered in correctly causing this steep gain?

If I recall it was just a resistor that needed to be replaced so not a big job.

When I had the amp I also changed the coupling caps and volume pot to an Alps Blue for a big step up in SQ.

Then changing the tubes really made another big difference.

There is a very help Yaquin page on facebook. They may be able to direct you to some who could help out...

 

Thank you. I just joined that Facebook group. My issue is I'm not too tech savvy or good with a solder gun so I don't want to make things worse!

 

It would be worth making an inquiry to see if anyone local may be able to take a look for you.

 

From experience, a tech will usually charge quite a bit to perform even simple work, sometimes even only to take a mere gander.

If you spend the $ on that, you'll need to go back to your stock tubes and the sound quality will suffer in contrast to the RCAs you bought. I can only speak for myself, but the $ spent on a tech would instead go towards a proper pair of RCAs from a reputable dealer and I'd save the $ later to have a tech look into it if it still bothered me. Meanwhile, I'd enjoy better SQ and would revisit the issue later.

 

So tube seller says he does not test for microphonics since it is amp specific meaning they may sound quiet on one but noisy on another. Is that true?

 

It can be that some amps are revealing of the microphony than others. The tubes are consistently loose inside though. That's a major problem with "NOS" tubes. And as my quotation marks indicate. what is sold as NOS often is just OS but with unknown amount of use. Even when these tubes were new they could have defects and variances n sound quality, and as your seller suggests, can vary with the circuit they are used in. They might work n a table top radio just fine for instance. Just being around for 50 years and handling can have its toll on fragile items, even if they really were unused, they certainly are no longer "New".

Your idea of trying a 12AY7 is a good one. Better than the 12AT7 results IME. I had suggested that you just try a pair of 12AU7, and I still do. They should produce the results which you are hoping for. I'd get a pair of JJ 803S (they are not Chinese made, BTW). They are affordable, new, and have a warmer sound than many other types.
-Bill

 

No. One amp might draw more from one tube when compared to another amp which would worsen the existing issues but microphonics would rarely go unnoticed if they are half as bad as you describe. In some cases, the tube(s) might sound fine at regular volume but microphonics could be heard at higher volume. Either way, these are obviously defective. Send them back.

Let me save you some time and trouble. There is no secret way to get that sound cheaply. You're free to try but you've already experienced a situation where trying got you nowhere. Use a reputable source and spring more for the right stuff... once. Not what you want to read but judging from your replies and what transpired, I'm under the impression you'd like to try to pull a rabbit out of a hat for a cheap price which ain't gonna happen. You can choose between the combinations of NOS/amazing/expensive or current production/fine/cheap.

The bottom line is this ; with tube gear and the tubes themselves, getting quality stuff will always be expensive. Certainly more so than sticking with solid-state. It's best to mentally prepare yourself for it and to make peace with that concept. I've got an amp which uses 300B tubes and the pair I'm using costs $900 US. Did I *want* to spend that money? No way! Was it worth the SQ upgrade? It sure was. Some pairs go for almost 2K. Yes, the tube world is crazy. The sound can be great but you'll definitely grow poorer (not richer!) if you value the changes better tubes can bring.

 

Those GE 6072 are all sold out and almost impossible to find out there. This NOS stuff is sure a crap shoot. Any other reputable sites out there you can recommend? I think I'm done trying Tubes on Ebay.

 

NOS isn't a crapshoot. Just like anything, if you buy elsewhere than from reputable sources, you'll very likely run into trouble.

Here are some other reputable sources.

http://www.audiotubes.com/12at7.htm

NOS Tube Store

NOS Date Matched Pair RCA USA 12AT7 ECC81 Black Plate Top [] Get Vacuum Tubes

12AT7 / ECC81 / CV4024 / CV455 / A2900 / B739 / ECC801S

RCA 12AU7 6189 JRC NOS Black Plate- Cryoset Online Store- RCA

 

This is super helpful. Thank you!

 

I need something like this. I have an EAR 834P Chinese "clone" Phono preamp that has a too high output. My standard listening level with my Pioneer A/V receiver is -22 dB while playing music with my TT and the EAR 834P "clone" while when I listen tomy Topping D50 D/A level is at +14. Do you think these attenuators are what I need? Do they add much distorsion (if any)?

 

They will certainly quiet down the input to your amp. When I did back and forth with and without them, I felt that they certainly changed the sound to a less warm, more clinical sound. Others in the room felt the same. However I bought the Harrison brand so maybe the Rothwell are different.

 

Well, I'm probably not the right person to ask regarding the technical side or the pros & cons of attenuators.
With my previous amplifier, I found them an easy solution to give me more room to move with my volume control, to use a bit more of the dial.

I became interested in them after reading a few things online about how the output voltage of your CD player relates to the input sensitivity of your amplfier and how that can be a contributing factor to how far you can turn your volume control before things get really loud, really quickly.

However, someone here with more technical knowledge than I should be able to advise you better as to whether attenuators are the best approach for your particular situation.

One thing I can say is that I found attenuators require some experimentation, as there's different levels of attenuation you can apply and too much can appear to suck the life out of your amp.

 

I disagree with the idea of changing the tubes. I think this would only reduce levels by 2 or 3 dB at most and might compromise the performance of the amp. The reduction would largely depend on the amount of negative feedback (if any) in that part of the circuit.

It sounds like the OP needs a reduction of at least 6 dB.

The OP can easily determine the ideal amount of attenuation needed by using an SPL app on his/her phone. Adjust the volume control for the SPL at that you want at (for example) the 10 or 12 o'clock position, then set the volume to that actual position and measure SPL again. The difference in dB between the two is the amount of attenuation to aim for. (It will be easiest to do this with highly compressed music, or something with a relatively constant overall level. Pink noise would be ideal and even "low quality" pink noise from Youtube or something would work well.)

Attenuators would be the best and cleanest way to go way to go.

 

I tried 12db attenuators and while it padded the sound enough (actually not all that much), I did not like overall sonic change. The attenuators allowed me to take the knob from say 7 o’clock without them, to about 8 with them using the same source. The overall sonic change wasn’t worth the small increase in headroom.

I’m trying tube rolling but might just end up with a passive Pre for the higher gain sources (CD & Phono pre).

 

Thanks for your reply. I think I'm not taking the chance with attenuators, One thing I like the most about my EAR 834P clone is how detailed and warm sounds and I don't want to loose that.

 

I hope you get your amp straightened out. I have a yaqin too, its the brother of your model mc-100b with 4-kt88. its not like that at all.

 

The best thing to do would be get an amp and speakers that work well together. Synergy is the thing.