sagebrush
New Member
Learning to play again after 20years, searching for the perfect Dr. Z amp.
Posts: 6
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Post by sagebrush on Oct 21, 2017 6:39:01 GMT -7
I have a new in the box Maz 18 NR, hissing noise, especially when the master is cranked up. I examined the tubes and found the 12AX7 tube is dark, no light coming from it at all. Will this cause the noise issue?
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Post by KeithA on Oct 21, 2017 6:48:35 GMT -7
Sometimes the glow of a 12ax7 is not highly visible. I doubt that would be the issue. However, a tube can be giving trouble without showing any outward signs.
If you have a fresh (known) good 12ax7 I'd swap in all sockets to see if the hiss goes away. Unfortunately that the joy of modern day tubes !
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Post by digs57 on Oct 21, 2017 7:04:41 GMT -7
How high the cut knob? and are you aware that this is going to cause some hiss to signal?
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Post by DeanG on Oct 22, 2017 9:07:24 GMT -7
With all knobs at noon, no input connection. Library whisper quiet. With a sound meter app running on my Android phone, mic positioned 1 inch from the speaker ~40-45dB measured. With Tele in Hi input, open string strum ~90-95dB. Meter gives some extent of the delta in signal to noise ratio. Also, having a baseline reference could be helpful if one deems noise floor has changed.
With a higher gain V1 one can experience increased noise floor. As did the Tung Sol and CV4004 in my experience. I went back to Doc's tube prescription in V1/V2 JJ ECC83S. Currently running PI and EL84s per Doc's tube recommendation too.
Yes, Cut and Treble will increase noise hiss.
Noise hiss can be subjective to one's own perception and sensitivity too.
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Post by easyed on Oct 22, 2017 10:27:18 GMT -7
Since there are three 12AX7's in the amp, it would be helpful to know which one you're suspecting. If it's the Sovtek 12AX7 LPS (used in PI), then the filament glow is hard to see - and visibly less than the ECC83's in V1 & V2. I'll go along with DeanG on V1 being the most likely culprit in producing hiss, and some tube rolling may be what you need.
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Post by zpilot on Oct 22, 2017 16:28:48 GMT -7
A tube that causes some hiss is not necessarily bad. Is the noise only excessive at extreme settings that you probably won't use anyway? Unless it is causing a ring or squeal that prevents it's use a tube that is a little microphonic might actually sound good. Also, a tube that may be too noisy for the studio or church may be fine for other venues.
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sagebrush
New Member
Learning to play again after 20years, searching for the perfect Dr. Z amp.
Posts: 6
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Post by sagebrush on Oct 23, 2017 9:43:27 GMT -7
It is the V3 tube, which tests good. I am being told that the loud hissing is normal by most, but others say their amps are quiet as church mouse. I am confused as to what to do. I love the tone of the amp at around level 3, but adding pedals and foot switch concern me with more noise added.
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Post by easyed on Oct 23, 2017 16:33:55 GMT -7
Even though your V3 is "dark" it is unlikely the source of the hiss.
V1 is the most likely culprit, with V2 a less likely (but possibly) source of your hiss.
Try swapping the two. If there's no change in the noise floor (hiss) then the problem is somewhere other than V1 and V2.
Since your amp came "new in box" V1 and V2 should be JJ ECC83S (factory spec). It could be that one of them is noisy.
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Post by purpletele on Oct 23, 2017 17:28:31 GMT -7
You really have to consider the EL84 tubes as well.
I think I have had more issues with Power Tubes on the new amps than Pre-amp tubes.
I would recommend trying two new power tubes just to rule it out.
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