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Re-tubing my preamp

Discussion in 'Preamps / Channel Strips' started by Don Grossinger, Nov 18, 2011.

  1. Don Grossinger

    Don Grossinger Distinguished past mastering moderator Active Member

    I currently run an MFA Magus C preamp, modified and hot rodded by the designer, Scott Frankland. I am the original owner, use it at least a couple of hours every day, and love the sound.

    I'm toying with the idea of replacing the tubes: 2x 12AX7, 1x 12AT7, 1x 6DJ8.

    I am wondering:

    Which brands are best? How much of a change in the sound will there be? Is it worth it since the existing tubes seem to be just fine?
    Do I need spares since these have been in place for YEARS? Are the expensive tubes worth it? Are tube sleeves worth it? Anything else special I should know?

    Thanks in advance!

  2. audiokid

    audiokid Staff

  3. RemyRAD

    RemyRAD Guest

    I say get whatever NOS Telefunken tubes you can get. Otherwise buy a boat load of cheap Chinese versions and start picking out which ones sound better than the others. Vacuum tubes can last 40 years or more. If yours are currently fine, what kind of engineer are you? You know our credo is " if it works don't fix it". These tubes don't need periodic replacement unless perhaps they have gone micro-phonic. Metal sleeves are frequently utilized in low-level preamps in order to better shield them from spurious radiations of other electrical interferences. But those are only required extremely low-level preamps. Generally not as necessary at higher line level voltages. Some tubes have smooth plates. Others have corrugated & perforated plates. Those two sound extremely different from one another frequently. The smooth plates generally win most of the time. And just because you might be able to find good Chinese tubes doesn't mean they are good sounding Chinese tubes even if they are better sounding than the bad Chinese tubes. I don't think any of them sound as sweet as old Telefunken Tubes? So buyer beware. Unfortunately, who makes the best tubes these days didn't always make the best tubes. That would be like all of us thinking that digital is better than analog. It's just that they are too inconsistent these days to try and find a bunch that all sound alike. That's where I really prefer transistors, hands-down.

    I don't like mixing in a vacuum
    Mx. Remy Ann David
  4. audiokid

    audiokid Staff

    You know Remy, I'm with you on the tube thing more and more. There was a time I was all over tubes but the future isn't looking bright for them. Makes me wonder about investing in tube gear. They're like Pro Tools in a way. Good for the moment as long as they are on the perfect OS but you can't keep OSX going on the next generation of Apple so where does that leave you whichever way you look at it? Once you run out of places to get old stock, you are done. Apple isn't much for third party.

    But tubes, they do something like nothing else.
  5. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Tube manufacturers have complained for years that 9-pin preamp tubes are too expensive to make and then sell for what the market will pay for them.
    As to the original question, like Remy stated, if the tubes aren't an issue, leave 'em alone. Just have some set aside for that rainy day. I have used NOS Telefunkens in my vintage McIntosh tube gear (I miss you, you chrome-plated bastards, you!) in the past. I have found that JJ 12AX7 and 12AU7 tubes in my tube pre's have been working very well, no noise or "duds".
    As to the "sleeves"...are the tube sockets on your MFA mounted to the chassis or to a circuit board? As I have understood it, the temperature of the tube socket rises with the use of a sleeve, and that the heat is not kind to the PCB that the socket is mounted to.
  6. RemyRAD

    RemyRAD Guest

    I neglected to mention that the metal sleeves also generally have a tiny spring inside since they have a bayonet mount. Conversely, the tube socket must be of the mounting type that includes the bayonet mount DOT to secure the sleeve with which helps to ground it to the chassis providing greater electrostatic protection and hum rejection. So it's not just a mental sleeve wrapped around the tube by itself but an integral part of the design of the preamp. You can modify anything for improved performance if you so wish to invest the time and effort. But you really have to ask yourself why you are doing this if there is not a problem to begin with. One of those don't fix it if it ain't broke issues. I mean just because our automobile engines run better with tuned headers doesn't mean we keep installing those on our cars unless you want that. They work fine just the way they are supplied from the factory. Hobbyists, enthusiasts and professionals may choose to add turbochargers, superchargers, headers, industrial-strength fuel injection kits, special camshafts, special manifolds, different gearing, specialized heavy duty transmissions. Audio stuff is no different. I bought a Neve because I like the way they sound. Could it be better? Sure it could and then it will sound like something else and not necessarily a Neve anymore. Everybody out there is making improvements upon the original Neve design. So they sort of sound like a Neve but they don't. That's not what I want. I'm one of those people that actually knows what I want. I don't reinvent the wheel even though I could. Sometimes, you do this because of a compatibility issue due to newer technologies in use. But that's not the case with something like a Neve. I mean who would want to modify a Rolls-Royce to look like a Corvette stingray? That's goofy. That doesn't make any sense. And people do this all the time with audio stuff. Why? I don't know? They have too much hand on their time. Whereas I'd rather get time and a half for doing nothing. Except maybe fixing it? Which is always a worthy thing to do when something is broke. Of course many cheap microphones and other inexpensive entry-level equipment can be hugely improved with as many $$$ that you want to throw at it. To my thinking, one should have waited and saved longer to get what they really wanted. For instance, you can purchase Neve designed knockoff stuff by other manufacturers for a lot less money. You can even find already prepared DIY kits to build Neve/API like clones at huge savings in comparison to the original items. Home built 1176's is one that comes to mind such as what Fab has over at FLUX recordings in NYC. That thing only cost a couple of hundred dollars to build in comparison to its $1500 going prices for the original pieces. His looks the same. His sounds the same. And I think most audio engineers as a rule certainly need to learn how to solder, create microphone cables, wire your control room properly and understand what your equipment is capable or not capable of doing. Too many folks just want drive-through recordings as if you were to buy me a hamburger today I would happily pay you on Tuesday. And that's Wimpy of me. So I think it's a good thing to get some old blown out electronics equipment. Then you sit down with a voltmeter and a soldering iron. Measure some things, replace some things, then plug it in. Once you watch it blow up, then you can figure out what blew up and how to fix it. Then you can start at the top again. When you get to the bottom of the slide you look around and go back up to the top, then go for a ride... and you do it again. Yeah yeah yeah

    Paul was right
    Mx. Remy Ann David
  7. Don Grossinger

    Don Grossinger Distinguished past mastering moderator Active Member

    What a pleasure to hear from all of you!!

    Thanks for the (why am I not surprised) educated and illuminating responses.

    I think the only thing to do is buy NOS Telefunkens as reserves and keep using the ones I've got. They sound great.

    If it ain't broke.......

    Best Regards,

    PS: I missed the AES convention entirely and was regretting it. Looks like I didn't miss much. The party at Masterdisc was well attended and fun. Met old friends and new folks as well. That alone was worth going to.
  8. RemyRAD

    RemyRAD Guest

    Yeah, it's really hard to attend all of the parties in a single AES convention visit. In my 39 years of attendance, I just went to my first studio party. I usually create my own party when I go up. Besides, you can lose track of time with all of the important alcohol consumption we have to accomplish in a short period of time. Not to mention the other slightly illegal goodies. And if you are like me (which I know most folks here are not like) it's incredibly difficult to find any kind of parking space for a full-sized Chevy van anyplace in NYC. Thankfully it's also a portable hotel with enough room to comfortably sit 6 folks. And while the car stereo is rather crappy it's all good music and mostly mine. The radio stations in NYC ain't bad either like everywhere else. WBLS Comes to mind, since it basically puts me back into the R&B of Detroit where I came from originally. It doesn't matter even if the shows are not stellar anymore like they used to be. Oh well...

    Glad to hear you came to your senses and ours
    Mx. Remy Ann David
  9. BobRogers

    BobRogers Well-Known Member

    Ben Lindell at Fab's PureMix talks about his DIY 1176 units in this clip.
  10. BobRogers

    BobRogers Well-Known Member

    Are you in this?
  11. RemyRAD

    RemyRAD Guest

    Yeah, I've seen these. The only thing that is missing from these 1176's is the integrated off switch in the attack control. The older 1176's utilized 2 matched FET transistors. The all important one is for the actual gain reduction. The other one was simply for the meter which in later units has been replaced with an IC chip. And that none of these have that special output transformer with the secondary tertiary winding used within the feedback loop of the original discrete operational amplifier. Plus I am sure with these newer units that have transformer inputs, they are not the old-fashioned, dual gang potentiometer, 600 ohm input but rather the Jensen 10,000 ohm bridging line input transformer or a differential input to an IC chip op amp. And that's one of the reasons why all of these all sound different from each other. Plus the bias setting on the gain reduction FET is quite critical and somewhat confusing for a lot of folks to perform. Getting that bias set not quite right will make any 1176 completely different from any other 1176 even if they were manufactured identically to each other. And since the adjustment is within a very small window of perfection, it's quite challenging. I also enjoy the fact that the kit version has a tiny circuit board in comparison to the original which is almost as big as the entire case. Laying out a circuitboard differently will also cause these 1176's to sound significantly different since circuitboard traces can change impedances within the circuit ever so slightly. That too causes changes in sound. And who hasn't been shocked (not electrically) by the huge difference in the sound you will here when you replace the capacitors in any equipment. There are times when I feel that even though I replaced all of the capacitors in my vintage Neve console it sounds considerably different now than the way I remember it to be, when it was virtually new. That's regardless of the fact that I used quality capacitors. In some ways, I actually preferred the sound of the original worn-out electrolytic capacitors to the new ones. And that is what is so amazing about analog audio. It's all like fine stringed instruments. Some cost $200 for a violin others cost $2 million for a violin yet there may be no general perceptible difference in sound to most. But that doesn't matter. It matters to what you want to hear. So kids, even a small change such as a capacitor change can make your gear sound completely different. No, I don't put polystyrene capacitors in everything. I even don't insist on non-polarity oriented capacitors as other folks do. I think electrolytic capacitors are fine and certainly have their place in the audio world.

    I knew this guy that had a nice studio back in the late 1970s. He modified his console and removed all electrolytic capacitors. He then had to custom select 5534 IC chips that had no DC offset present. He was quite pleased with the sound yet, I didn't hear the quality and found it virtually bizarre sounding. Later he was hired by MCI who were also into that sort of thing. But then again, today, who is talking about the precious sound out of their MCI consoles? Nobody that I know. They were nice and versatile but I never liked those although they did well by the Bee Gees, the Eagles, thousands of others. But I could hear and identify those consoles every time I heard one. Yuck! While they could pass good square waves, I don't typically record musicians playing square waves. So I found that unimpressive along with their marketing hype. I still work on those from time to time but only in a maintenance capacity as I don't care to record or mix with them.

    I remember I went to some large studio in Fort Lauderdale as an authorized MCI's service technician to fix an MCI series 500. I asked the music engineer there what his favorite console was? This guy indicated he didn't care what he worked on. I thought that queer because an MCI sure as hell doesn't sound anything like an API nor Neve. In fact I actually hated the Yamaha PM 1000 used for the console at the studio I was employed at because the Transformers were crap. But I liked it a whole lot better than an MCI 500 and of course it was also referred to as a " baby Neve ", which was sort of close to the truth, first pass through. After the first pass through, the sound quickly went downhill. And that's why it's a PA Board not a recording console. Either way, I had to make do with very sophisticated and highly orchestrated jingles that required multiple passes. OMG it got awful so quickly. In the end, I pulled out the output transformers which helped immensely. And without any ground loop issues, sounded a lot better that way. So I like good transformers not crap transformers. It wasn't important to install any new output transformers from folks like Jensen or UTC, triad, etc.. In fact I like unbalanced control rooms since you have to make sure the grounding scheme is virtually perfect. I think Bob Ludwig or was it Bernie Grundman whose Mastering console was specified as all unbalanced BECAUSE IT SOUNDS BETTER. It's true. Balanced stuff includes additional circuitry to create the balance. Additional circuitry equates to more grunge. So I like my stuff to be as straight as possible in spite of the fact that I'm not.

    Give me a wire. WIRE!!! Give me a joint... Hey? Where did everybody go? Wait, I didn't get any. Wire that is.
    Mx. Remy Ann David
  12. BobRogers

    BobRogers Well-Known Member

    That's easy to learn working on electric guitars. In my experience, the kids sitting in GC trying 30 Stratocasters to find the best one are really looking for the one with the right capacitor. People talk all day about tone woods and that $.10 cap is the single most variable component (+/- 10-20%) with the most effect on tone of anything in the guitar. If I see big bags of them in junk shops I pick them up. Put a pair of alligator clips on the tone knob and swap them out till you find the right one. Makes a huge difference.
  13. JoeH

    JoeH Well-Known Member

    I missed AES completely this year, too. duh My only excuse was too much work, every day. Couldn't even hop on a train for a few hrs. Totally squeezed out.

    I won't get to the West coast version next year, either, I'm sure, so I'll just have to wait another two years to run into Remy again!
  14. Davedog

    Davedog Distinguished Member

    Hi Don! Long time etc....Tube information can be assessed by contacting these folks----> Eurotubes

    Tubes are like women. Some hotter than others........

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