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moresound
Loud Sun Studios
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moresound
Loud Sun Studios
How did it die ... do you want to sell it?
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aladdinsane
New member
Greetings...
I own a Dual MP... I stopped using it due to some noise I was getting in one channel... here it is 20 years later... I'm getting the tubes checked... is there anything I need to know about that 12AX7 hybrid tube should I need to replace it?... Is there a direct replacement tube or can I venture to use some modern day wonder-tube?
Thanks!
aladdinsane
I own a Dual MP... I stopped using it due to some noise I was getting in one channel... here it is 20 years later... I'm getting the tubes checked... is there anything I need to know about that 12AX7 hybrid tube should I need to replace it?... Is there a direct replacement tube or can I venture to use some modern day wonder-tube?
Thanks!
aladdinsane
arcaxis
Well-known member
The 12AX7 is a common tube most music retailer should have. Nothing special needed for your Dual MP. A 12AX7 is not 'hybrid' as that would imply something solid state. $20 or less should get you an OK tube. Don't do one of these.... JAN Raytheon 12AX7 
garww
New member
The 12AX7 is a common tube most music retailer should have. Nothing special needed for your Dual MP. A 12AX7 is not 'hybrid' as that would imply something solid state. $20 or less should get you an OK tube. Don't do one of these.... JAN Raytheon 12AX7
Well, I have read that some far east tubes are not up to spec - didn't pay that much attention to it. My DPS is, essentially, two MP, and I pulled out some tubes to listen to. I stopped on the first tube I tried - which was a 1960-ish Masushita I borrowed from a Teac tube deck. I didn't see any reason to stick a good tube in there, just something competent : ) If you want to try old tubes, one can slum around and get some re-branded stuff - like Baldwin, etc..
I've yet to buy new tubes for sometime, now, but I do want to try them - fender had a low gain ax7(?), etc..
witzendoz
Senior Member
Man talk about an old thread, started in 2001 LOL.
Anyway if you want to really try a different tube try a 5751, it is a lower gain tube that replaces a 12AX7, a GE black plate is the best, but they are not cheap. There are other 5751 tubes on the market. You might find the 5751 gives you a more tube sound to the preamp.
Cheers
Alan.
Opps the number is 5751 fixed it now, sorry for the confusion.
Anyway if you want to really try a different tube try a 5751, it is a lower gain tube that replaces a 12AX7, a GE black plate is the best, but they are not cheap. There are other 5751 tubes on the market. You might find the 5751 gives you a more tube sound to the preamp.
Cheers
Alan.
Opps the number is 5751 fixed it now, sorry for the confusion.
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Nola
Well-known member
The best NOS tubes, imo, are the EI Yugo 12ax7. They are made to basically the same specs and using the same tooling as the highly desirable telefunkens are a fraction of the cost. Tubes definitely make a huge difference. I had a russian and chinese compared against an old RCA and YUGO and it wasn't even close.
garww
New member
I could say my ART DPS is a MP clone and there is no way I'd put my Telefunken, RCA, or even Sylvania in there. The Matushita is only in there 'cause I'm swimming in them. Whats the other tube - 7025 ? One of my old pre has a RCA 7025 in it. I'm not all that hot on 12ax7, when I got four 6267 pre, but there is so much to choose from in the 12ax7 family. I see this site no longer list the Fender 12ax7, but I still like how they overview the tubes;
12AX7 Comparison of Current Made Tubes | Amplified Parts
Makes me want to spend some bucks : )
12AX7 Comparison of Current Made Tubes | Amplified Parts
Makes me want to spend some bucks : )
JimmyS1969
MOODerator
Wait, are there people really talking about buying replacement tubes for the ART Dual MP, TPS or DPS?
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RFR
Well-known member
It would seem so.
As far as I know, those are 'starved plate' designs, so tube choice is of little importance.
The tube has about as much impact on the sound as having a lava lamp in your studio does.
As far as I know, those are 'starved plate' designs, so tube choice is of little importance.
The tube has about as much impact on the sound as having a lava lamp in your studio does.
garww
New member
Well, one can still hear the different tubes, or, at least I could on a vid with my slow aDSL connection.
ART Tube MP Preamp Review, Part 3, Tube Change Comparisons - YouTube
I wouldn't deny anyone the cheap thrill factor . A important part of my life, for sure : )
A MIC pre OK, but I didn't bother with my other low current device - the ToneLab ST. The major factor for my DPS wasn't the preamp, but that it had the digital out. Which is why I bought it. Its, basically, used for stereo processing, anyway
ART Tube MP Preamp Review, Part 3, Tube Change Comparisons - YouTube
I wouldn't deny anyone the cheap thrill factor . A important part of my life, for sure : )
A MIC pre OK, but I didn't bother with my other low current device - the ToneLab ST. The major factor for my DPS wasn't the preamp, but that it had the digital out. Which is why I bought it. Its, basically, used for stereo processing, anyway
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RFR
Well-known member
Hah! I had a tonelab st.. I took the tube out and most everything still functioned as before.
Hey, nothing wrong with a cheap thrill.
Many with lava lamps swear their mixes are better since getting it.
Hey, nothing wrong with a cheap thrill.
Many with lava lamps swear their mixes are better since getting it.
garww
New member
In both cases, I think its just mixed in output drive. You don't want to drive the modeling, ( or, Variable Voicing)
arcaxis
Well-known member
Replacement of the tube may not even fix the noise the OP has in one channel. 20 year old piece of gear could have a cap or two that needs replacing or some other problem. Cheap tube would be the way to go.
Tube section of the Tube MP (the Dual Tube MP likely similar) below for those that can follow it. Cathode follower design...
Tube section of the Tube MP (the Dual Tube MP likely similar) below for those that can follow it. Cathode follower design...
Attachments
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ecc83
Well-known member
Obliged for the circuit Mark, do you have a link to the full Monte? A very good, good value ECC83/12AXY is the TAD 7025 HG. Loss his and microphony and worked very well as the front end of guitar amps. Here about £12-£15. A lot of the valves touted on the internet are re badged crap, Some GENUINE NOS can be good but you really need a valve tester to prove they meet spec' .
N.B. There is no such thing as a low or high 'gain' 12AX7! The amplification factor, 'mu' of a triode is determined by the cathode/grid/anode spacing and the tolerances are microscopic. If a '12AXY' does NOT have a mu of 100, it ain't a 12AX7! Other factor will also be out of whack such as slope resistance and bias requirement.
There are sonic differences between valves but since there is so much 'old sold for new' ***t about it is very hard to be sure. In any case the differences for a given type are not huge. That is not to say some valves are not better than others. Morgan Jones has done the tests and some double triodes produce about an order more THD than others. One of the worst valves for distortion was the ECC83 and the ECC82 (12AU7) but since the former was really designed as a driver in amps with NFB and the latter in tellies (not for audio!) should we be surprised?
Dave.
N.B. There is no such thing as a low or high 'gain' 12AX7! The amplification factor, 'mu' of a triode is determined by the cathode/grid/anode spacing and the tolerances are microscopic. If a '12AXY' does NOT have a mu of 100, it ain't a 12AX7! Other factor will also be out of whack such as slope resistance and bias requirement.
There are sonic differences between valves but since there is so much 'old sold for new' ***t about it is very hard to be sure. In any case the differences for a given type are not huge. That is not to say some valves are not better than others. Morgan Jones has done the tests and some double triodes produce about an order more THD than others. One of the worst valves for distortion was the ECC83 and the ECC82 (12AU7) but since the former was really designed as a driver in amps with NFB and the latter in tellies (not for audio!) should we be surprised?
Dave.
arcaxis
Well-known member
Dave, the schematic came from Service manual, eprom result list | ElektroTanya | Service manuals and repair tips for electronics experts . It's actually the 'Tube MP Studio', but I suspect the other versions wouldn't be too different.
A good number of years ago I got lucky when the company I worked for had retired its last bit of tube based communications gear and they were discarding an old Hickok 600A tube tester. I happily acquired it. Previously I had been using a 'Knight Kit' tube tester I had built back in the 60's. Do you have any recollection of the 'Knight Kit' stuff? It sort of competed with 'Heathkit'.
A good number of years ago I got lucky when the company I worked for had retired its last bit of tube based communications gear and they were discarding an old Hickok 600A tube tester. I happily acquired it. Previously I had been using a 'Knight Kit' tube tester I had built back in the 60's. Do you have any recollection of the 'Knight Kit' stuff? It sort of competed with 'Heathkit'.
garww
New member
Well, with a MIC, you need gain and then you don't. A tired tube can work for me, unless I want to explore distortions. For guitar, I would want one pre tube to be full gain : )
Ya, a Hickok would be nice, but I just need the good/bad meter ! Many people can hear if the tube is performing, anyway. Modern tube MICs and such are limited by what they can source for production and it looks like demand for better tubes is paying off - here and there. There's the production part, but some things like transformers and knives do better with good ore, in my estimation
Ya, a Hickok would be nice, but I just need the good/bad meter ! Many people can hear if the tube is performing, anyway. Modern tube MICs and such are limited by what they can source for production and it looks like demand for better tubes is paying off - here and there. There's the production part, but some things like transformers and knives do better with good ore, in my estimation
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steve.swain
New member
I just warmed up a MP tube that I have not used for a while,,,
Changed the stock tube for a JJ,,,
Just recorded some awesome sounding voiceover's,,,,
Changed the stock tube for a JJ,,,
Just recorded some awesome sounding voiceover's,,,,
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ecc83
Well-known member
Ooo! Can we hear a "new/old A/B test? A voltage table would also be interesting...
Mark. Not heard of "Knight" kit. I had a Heathkit valve audio oscillator for many years.
Dave.
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