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Post by rckline on Sept 7, 2016 9:10:12 GMT -7
Greetings Fine Folk:
My lovely Maz18R has slowly developed a "ringing" when I turn the reverb up. The ringing sound gets worse as the knob gets higher. This is over the last 1-2 weeks. My limited(but getting bigger) knowledge of the situation tells me the Reverb driver tube is going.
My question is this: which V# is the reverb tube in a MAZ18R, what replacement will give me the best sound(clean headroom is my game, but I'm not sure the Reverb tube has any effect on the "headroom" of an amp), and am I on the right track?
Yesterday I received 2 new Russian EL84s(the good ones) from the tube store, as the older entire set of tubes which I received as a "replacement package" for the MAZ18R were suitable, but I've used them for all of 10 hours and the reverb whistling thang appeared. The amp sounds great except the whistling reverb. So I'm trying to replace the "replacement package" tubes one or two at a time with better-sounding and more expensive(!@#$%) tubes(hence the EL84 replacement mentioned above). The reverb tube(if there is one) is next.
Thanks in advance for your assistance!
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Post by digs57 on Sept 7, 2016 9:33:24 GMT -7
jan/Phillips at7wc nos and sovtek12ax7wb...for driver has worked for me...fwiw
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Post by Maddog on Sept 7, 2016 9:51:33 GMT -7
Reverb Driver is the one and only 12AT7 (ECC 81) and is in V3 IIRC....
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Post by heynewguy (Ol’ Bill) on Sept 7, 2016 10:17:59 GMT -7
Make sure the reverb tube and all other tubes are seated correctly.
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Post by easyed on Sept 7, 2016 10:26:39 GMT -7
I would suspect the reverb recovery tube, V4, of being microphonic.
The current factory spec is for a JJ 12AX7/ECC93.
On another amp, I subbed a JAN 5751 for the reverb recovery tube and quieted the noise (hiss, buzz) emanating from the reverb.
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Post by greenblues58 on Sept 7, 2016 10:37:14 GMT -7
If you want to get more fine a control over the reverb l have had good results using 12au7 as reverb driver in both my fender amps as recommended by the fender guru in fact l have RCA 5963 which are the equivalent and cheaper.
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Post by Jaguarguy (Mike) on Sept 7, 2016 11:29:34 GMT -7
I would suspect the reverb recovery tube, V4, of being microphonic. The current factory spec is for a JJ 12AX7/ECC93. I believe you meant to type ECC83?
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Post by easyed on Sept 7, 2016 13:04:10 GMT -7
jaguar,
You are correct. Clumsy fingers at this end.
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Post by rckline on Sept 7, 2016 15:59:43 GMT -7
thanks everyone- so I gather there are 2 reverb tubes, the driver (V3), and the reverb recovery tube(V4). I'll replace the recovery tube, I'm pretty sure I have another 12AX7 laying around somewhere. Results will be forthcoming. I'm very grateful for the assistance, it saved me several hours of research and let me play my MAZ today.
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Post by premiumplus (Dave) on Sept 7, 2016 17:26:53 GMT -7
You can even substitute a 12AX7 for the reverb driver to see if that localizes the problem. It's going to sound different but at least you'll know which tube is ringing.
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Post by rckline on Sept 7, 2016 19:08:24 GMT -7
Let's say the whistling reverb is V4(or even V3), could this have an effect on the overall tone? When playing today I definitely noticed a certain "something" missing, even when the reverb knob was all the way down. Seemed very subtle, but my ears were not hearing the same tone I'm used to. I imagine the signal goes through all the tubes whether they are operating at an efficient level or not. Is this so?
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Post by zpilot on Sept 7, 2016 21:46:43 GMT -7
I believe yes. Now I'm basing that on my experience with Fender amps and I think that tube function is similar. V4 actually mixes the reverb signal with the dry signal so it does contribute to the total sound. As a test pull V4 and see if you get sound from the amp. If you don't then that tells you that the dry signal is going through that tube all of the time so your answer is yes.
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Post by premiumplus (Dave) on Sept 8, 2016 5:03:59 GMT -7
zpilot is right. IME, it's usually the reverb driver that affects the tone of the amp more than the recovery tube does. I have noticed big differences in basic amp tone when changing out the driver tube in my Z-Lux, and in Fenders too. My Maz 18 is the NR model but try what zpilot suggested and pull the driver tube. If your sound goes away with reverb turned off, you know it's in the dry signal path.
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Post by rckline on Sept 8, 2016 8:43:07 GMT -7
z-pilot and premiumplus(Dave), what would you specifically recommend for the reverb driver tube if I'm after maximum clean headroom? greenblues58 mentioned a 12au7 instead of the 12ax7 for finer control of the reverb, that sounds great to me! Maddog also suggested the 12at7...
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Post by digs57 on Sept 8, 2016 11:34:00 GMT -7
Could try medium gain ecc 83,5751 (v1)...I liked the mg 83...had enough snot on it to make it not too sterile
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Post by zpilot on Sept 8, 2016 11:59:32 GMT -7
z-pilot and premiumplus(Dave), what would you specifically recommend for the reverb driver tube if I'm after maximum clean headroom? greenblues58 mentioned a 12au7 instead of the 12ax7 for finer control of the reverb, that sounds great to me! OK, to be clear on this, V3 is the driver tube and is a 12AT7. A lower gain tube will give finer control but I don't think it will be worth using a different tube. A 12AT7 will last much longer because it has a greater current capability. If you are after maximum clean headroom you will be better served trying a 5751 or a 12AY7 in V1 first. If that isn't enough try adding one of those in V2. Also, using the Lo input will help. Personally I like a 12AX7 in both of those spots but I use the Lo input. I think it gives me the best balance of headroom and harmonic complexity. I use NOS preamp tubes almost exclusively. I like 12AY7 tubes a lot. That is what is used in the first gain stages of most tweed era Fender amps.
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Post by premiumplus (Dave) on Sept 8, 2016 12:31:09 GMT -7
Good advice. The reverb driver works hard. I'd stick with the stock JJ ECC81 (which is a 12AT7) there.
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Post by rckline on Sept 8, 2016 13:26:05 GMT -7
z-pilot and premiumplus(Dave), what would you specifically recommend for the reverb driver tube if I'm after maximum clean headroom? greenblues58 mentioned a 12au7 instead of the 12ax7 for finer control of the reverb, that sounds great to me! OK, to be clear on this, V3 is the driver tube and is a 12AT7. A lower gain tube will give finer control but I don't think it will be worth using a different tube. A 12AT7 will last much longer because it has a greater current capability. If you are after maximum clean headroom you will be better served trying a 5751 or a 12AY7 in V1 first. If that isn't enough try adding one of those in V2. Also, using the Lo input will help. Personally I like a 12AX7 in both of those spots but I use the Lo input. I think it gives me the best balance of headroom and harmonic complexity. I use NOS preamp tubes almost exclusively. I like 12AY7 tubes a lot. That is what is used in the first gain stages of most tweed era Fender amps. Most excellent. I just emailed The Tube Store and got a reply that tells me exactly what you do, a 5751 or 12AY7 in V1 for headroom. He also recommended staying with the 12AX7 as well. Thanks, I mean it. I have always used the Lo input, it works better for me and has something more forgiving about it. I'm now off to my little studio to put all this into practice. Cheers!
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Post by easyed on Sept 8, 2016 13:39:35 GMT -7
Without having a schematic diagram in front of me, I can't say this with absolute certainty, but you can test for yourself.
In Fender amps and most other amps that have a tube driven reverb, both halves of the reverb driver (V3) are used to pass maximum current to the reverb transformer. You should be able to pull this tube and still play the amp.
The reverb recovery (V4) involves only half of a tube and the other half is used as a gain stage. If you pull this tube. You should not get any sound output. (If you have an amp with a "Normal" channel and a "Vibrato" channel, then the normal channel may work with the reverb recovery tube pulled.)
Tuning your reverb: If the reverb is too saturated, replace a 12AT7 driver with a 12AU7 - it won't put as much signal into the input side of the reverb tank (the springs aren't shaken as hard). If your reverb is producing constant hiss or buzz, then subbing a 5751 or 12AY7 for the reverb recovery should result in a quieter amp. The hiss or buzz could be coming from a bad resistor or capacitor, but those are less likely suspects. If the reverb isn't giving enough duration, then using a 12AX7 may help (it won't be as durable as a 12AT7).
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Post by rckline on Sept 12, 2016 14:26:44 GMT -7
I removed the JJ ECC81 (thanks for id'ing it for me PremiumPlus, there is no other info on the tube). I replaced it with an old 12AX7, and the ringing disappeared. Returning the original JJ ECC81 to the amp, the ringing returned. Clearer sound, but the JJ tube went bad pretty much right away. I will be sticking with the 12AT7, as the difference in reverb tone was startling! Sounded good with both, but more "gritty" with the 12AX7. The Tubestore recommended Tung-sol as a replacement. I'll probably order today.
Lots of advice from DRZ forum, all of it worthwhile. Muchos Gracias! This makes me curious as to what people did for support before the information age. Library? Trade manuals? I'm guessing a strong network of friends, family and acquaintances was of crucial importance...and still is!
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Post by premiumplus (Dave) on Sept 12, 2016 15:49:06 GMT -7
Good job! I've found that the reverb driver tube makes a significant change in overall tone. If you're bored sometime, get some different ECC81 or 12AT7 tubes and try them out. It doesn't make near as much difference as V1 does (that's the first tube your guitar signal goes through, and establishes your base tone and gain) but it's cool to be able to kind of "fine tune" your amp's tone to your liking.
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Post by rckline on Sept 13, 2016 10:34:49 GMT -7
You can even substitute a 12AX7 for the reverb driver to see if that localizes the problem. It's going to sound different but at least you'll know which tube is ringing. yep...that totally worked!
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Post by vaderz on May 2, 2019 8:05:44 GMT -7
I've been having the same issue as the thread starter rckline was having. I can't turn up my reverb past about 9-10'o'clock before I get a ringing that eventually builds into feedback. Once I turn down the reverb it's gone. I've swapped out both v3 and v4 with multiple tubes and it's still there. Any other suggestions? Maybe an issue with it being to saturated? I don't have a 12AU7 as easyed has recommended. I'm currently using all the recommended tube types that the Doctor recommends and they are all less then a few weeks old.
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Post by digs57 on May 2, 2019 10:16:50 GMT -7
By all account even in the audio world a "microphonic tube" is likely culprit...check cables,clean inputs to verb unit...bad verb unit...ther not to terribly expensive...my 2 cents.
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