Foreword
Ryan Turner is a highschool student from Memphis, TN. Having recently gained interest in sound engineering, he has assembled a home project studio. He is a typical guy, although somewhat technical and a computer programmer (PHP). Ryan lacks preamps in his studio, he is stuck using the gain on his mixer; no tube preamps are very limiting.
Goal
To create a dual-channel recording quality tube preamp for general purpose usage. Also, to learn something along the way and share this knowledge with others.
Information
Ryan Turner is a highschool student from Memphis, TN. Having recently gained interest in sound engineering, he has assembled a home project studio. He is a typical guy, although somewhat technical and a computer programmer (PHP). Ryan lacks preamps in his studio, he is stuck using the gain on his mixer; no tube preamps are very limiting.
Goal
To create a dual-channel recording quality tube preamp for general purpose usage. Also, to learn something along the way and share this knowledge with others.
Information
- http://store.tubedepot.com/contact.html - Call these guys for the tubes and higher quality audio components; local and reliable (Friend referred me to them).
- http://www.jameco.com/ - Use them for other less important components; keep getting their 3 of their damn catalogs in the mail every time they make a new one.
- http://www.nmr.mgh.harvard.edu/~reese/RC10/rc10.pdf - Read this about tube info; its from Harvard, its gotta be great.
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Lacking Information- Which type of tube should I design for, assuming I want a general purpose, warm dual-channel preamp?
- How do I convert balanced audio into unbalanced for the tube and then back to balanced?
- Should I even bother doing my own design or should I steal someone else's?
- What other subjects should I read up on besides tubes and then general electronics?
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I have this formatted because I hope to turn this thread into a project thread as well as a tutorial upon completion. So please give me some guidance!
Regards,
Ryan Turner
Ryan,
Welcome! It's nice to see a youngster taking up the cudgel.
You don't convert.
Instead, you use a differential gain block, which has both balanced I/P and balanced O/P.
IMO, you should use a type with modest gain. The 6SN7 is REVERED and certainly would be a reasonable choice. JJ's ECC99 is another possibility. The '99 has the advantage of a very low plate resistance, which makes it a GOOD load driver.
There's very little new under the sun regarding tubes in particular and electronics in general. It's more a matter of combining things in a "new" way. ALL of us "borrow" from circuits we've perused.
Physics and Chemistry, as those sciences impact directly on electronics. While we are on the subject of "boning up" on electronics, run a Google search for NEETS. NEETS is US Navy training material, which will be of considerable benefit. Also, visit a local library and study the 2nd edition of James Brophy's Basic Electronics for Scientists. FWIW, Brophy's work was 1 of the texts this "graybeard" used in college.
Welcome! It's nice to see a youngster taking up the cudgel.
You don't convert.
Instead, you use a differential gain block, which has both balanced I/P and balanced O/P.IMO, you should use a type with modest gain. The 6SN7 is REVERED and certainly would be a reasonable choice. JJ's ECC99 is another possibility. The '99 has the advantage of a very low plate resistance, which makes it a GOOD load driver.
There's very little new under the sun regarding tubes in particular and electronics in general. It's more a matter of combining things in a "new" way. ALL of us "borrow" from circuits we've perused.
Physics and Chemistry, as those sciences impact directly on electronics. While we are on the subject of "boning up" on electronics, run a Google search for NEETS. NEETS is US Navy training material, which will be of considerable benefit. Also, visit a local library and study the 2nd edition of James Brophy's Basic Electronics for Scientists. FWIW, Brophy's work was 1 of the texts this "graybeard" used in college.
Don't know if this is a legitimate concern or not, but I always worry about damaging the inputs of solid state equipment. You never know how much protection they've put in. One tremendous advantage of tube circuits is headroom. The downside is that gives them the ability to pass large transients that the solid state designer might not have anticipated. Thus, IMO it's wise to find out the maximum acceptable *peak* voltages for your equipment, and provide some limiting to protect it.
Thank you all for your replies!
I've decided that the design that makes most sense to me are from Jensen, specifically http://www.jensen-transformers.com/as/as054.pdf
However, I'm a little confused about the whole "See AS016" box. Does that part connect to the "See other schematics" in AS016?
I don't know if thats the one I want to build for sure, but I do plan to purchase the parts and build it on a breadboard to see how it sounds.
I've decided that the design that makes most sense to me are from Jensen, specifically http://www.jensen-transformers.com/as/as054.pdf
However, I'm a little confused about the whole "See AS016" box. Does that part connect to the "See other schematics" in AS016?
I don't know if thats the one I want to build for sure, but I do plan to purchase the parts and build it on a breadboard to see how it sounds.
neoific said:
Ryan,
The circuit you linked is a "mike" preamp. Is that what you want?
Assuming a "mike" preamp is the object of your desire, I strongly suggest you find a different circuit. I find it hard to select a worse candidate for a cascode than the 12AX7.
The transconductance (gm) of the 12AX7 is LOW. High gm triodes are appropriate at the bottom of a cascode "totem pole". Also, while the quality of Jensen trafos is excellent, they are costly. CineMag makes GOOD "iron" too and sells at a lower price than Jensen.If you want to use a cascode gain stage, the 6922 is a good choice. The EF86 audio pentode is a fine alternative to a cascode and many good circuits employing it can be found.
The 12AU7 Jensen shows is not particularly linear. The 6SN7, 6FQ7/6CG7, and 12BH7 are (IMO) better choices.
Eli Duttman said:
Ryan,
The circuit you linked is a "mike" preamp. Is that what you want?
Assuming a "mike" preamp is the object of your desire, I strongly suggest you find a different circuit. I find it hard to select a worse candidate for a cascode than the 12AX7.
If you want to use a cascode gain stage, the 6922 is a good choice. The EF86 audio pentode is a fine alternative to a cascode and many good circuits employing it can be found.
The 12AU7 Jensen shows is not particularly linear. The 6SN7, 6FQ7/6CG7, and 12BH7 are (IMO) better choices.
Yes, the preamp I want to build would be for my studio's mics.
Thanks for the advice, but honestly it means nothing to me; I don't understand much of what you're saying and without a schematic I would be lost.
Ryan,
You asked for it!
Altec microphone preamp here. TFK microphone preamp here. Those links and MANY more can be found on John Atwood's site."Hey Mister, how do I get to Carnegie Hall?" Practice, practice, practice!
Dude, it's time to study, study, study.Ryan,
Have you looked at: http://boozhoundlabs.com/
There are some tubed studio projects listed here. You may find things easier to select someone else's project, make it, test it, then learn how to improve on it.
People on this forum are extremely knowledgeable (myself excluded) about tubes. However, the many differences of opinion, while being very well informed, could result in adding to your confusion.
It seems to me that you're on a career pathway which will allow you to keep learning about all kinds of electronics, so tweaking is something you're likely to do a lot of in the future. My advise - find a project, preferably with good schematic, assembly instructions and part numbers, build it, then learn about the project's shortcommings and work out how to improve it.
Just my two-cents' worth.
Charlie
Have you looked at: http://boozhoundlabs.com/
There are some tubed studio projects listed here. You may find things easier to select someone else's project, make it, test it, then learn how to improve on it.
People on this forum are extremely knowledgeable (myself excluded) about tubes. However, the many differences of opinion, while being very well informed, could result in adding to your confusion.
It seems to me that you're on a career pathway which will allow you to keep learning about all kinds of electronics, so tweaking is something you're likely to do a lot of in the future. My advise - find a project, preferably with good schematic, assembly instructions and part numbers, build it, then learn about the project's shortcommings and work out how to improve it.
Just my two-cents' worth.
Charlie
Thank you all for your replies. I think now I'm beginning to understand bits and pieces of what you're saying; that RCA manual is pretty darn good.
It seems like this Aikido thing keeps popping up wherever I turn, then I finally saw this: http://www.tubecad.com/Aikido_9-pin_Mono_Rev-A_PCB.pdf
I'm a bit confused though, is this the type of preamp I'd want for a mic or not
If this is in fact the design that I am seeking (Aikido 9-pin mono), I am going to order the components tonight and build one on a breadboard to learn about some of this stuff. Once I'm comfortable with it I'll buy the PCB and transfer it all over.
It seems like this Aikido thing keeps popping up wherever I turn, then I finally saw this: http://www.tubecad.com/Aikido_9-pin_Mono_Rev-A_PCB.pdf
I'm a bit confused though, is this the type of preamp I'd want for a mic or not
If this is in fact the design that I am seeking (Aikido 9-pin mono), I am going to order the components tonight and build one on a breadboard to learn about some of this stuff. Once I'm comfortable with it I'll buy the PCB and transfer it all over.
I'm a bit confused though, is this the type of preamp I'd want for a mic or not
AFAIK, the "Aikido" is a line stage. You are looking for a "mike" preamp. Other than the equalization circuitry, "mike" preamps and phono preamps have similar requirements. Obviously, a "mike" preamp should have a linear response graph.
Back to the original point.
A good solution would be a differential cascode 6DJ8 or 6H30 front end, a balanced shunt attuation network and an output driver stage. I have no way of sketching something up at the moment electronically, but I can probably scan a drawing. I've assumed you'd rather have it quite clean and low noise as there are plenty of ways to process that in later, but it's not easy to remove, Most mic pre's have about 60dB of gain capability, and I think it'd be good to keep it tx coupled at both ends.
A good solution would be a differential cascode 6DJ8 or 6H30 front end, a balanced shunt attuation network and an output driver stage. I have no way of sketching something up at the moment electronically, but I can probably scan a drawing. I've assumed you'd rather have it quite clean and low noise as there are plenty of ways to process that in later, but it's not easy to remove, Most mic pre's have about 60dB of gain capability, and I think it'd be good to keep it tx coupled at both ends.
Thanks you guys.
I have read the first 14 of so pages of that RCA manual and I finally understand whats going on in this stuff, before I had no idea what an anode was or anything. Once I read some more, I'll write the information part of my tutorial covering what tubes do internally and how it can be utilized for audio, a brief one page outline so people atleast understand the concept.
My goal with this tutorial is to take all of you guy's information that is spread across all of these documents and put it in to one source for beginners to get their feet wet; basically so it REALLY explains the circuit for someone with the prerequisite knowledge of how to solder and more of a musical background.
Everyone is throwing all of these tube types and transformer around, its getting confusing for me.
I redefine my question as schematics. Schematics for microphone tube preamps. Clean yet warm, strong (atleast 30dB gain), with phantom power, phase, and maybe even a meter or peak/-20dB LEDs. Maybe these specifications will narrow the field of recommendation?
I have read the first 14 of so pages of that RCA manual and I finally understand whats going on in this stuff, before I had no idea what an anode was or anything. Once I read some more, I'll write the information part of my tutorial covering what tubes do internally and how it can be utilized for audio, a brief one page outline so people atleast understand the concept.
My goal with this tutorial is to take all of you guy's information that is spread across all of these documents and put it in to one source for beginners to get their feet wet; basically so it REALLY explains the circuit for someone with the prerequisite knowledge of how to solder and more of a musical background.
Everyone is throwing all of these tube types and transformer around, its getting confusing for me.
I redefine my question as schematics. Schematics for microphone tube preamps. Clean yet warm, strong (atleast 30dB gain), with phantom power, phase, and maybe even a meter or peak/-20dB LEDs. Maybe these specifications will narrow the field of recommendation?
Glad to be part of such a prestigious community
I have received quite a few valuable PMs, expect my wiki and blog to be up Wednesday and the project to begin!
Oh, and its going to be a nice looking, informative, beginner audio website; basically what everyone else is not doing
Also expect some other tutorials in regards to basic cable making standards, studio design, sound trap building, and anything else I can think of that I already know. Then I'm going to tackle a power conditioner, and finally a headphone amp over cat6/RJ45 with 4 aux mixes adjustable on the units.
/me is a web designer: on the website pretty colors I do want.
Anyways, if anyone else has ideas go ahead and spit them out here, otherwise I'll be waiting for that PM for that magical someone. You know who you are, and thank you.
I have received quite a few valuable PMs, expect my wiki and blog to be up Wednesday and the project to begin!
Oh, and its going to be a nice looking, informative, beginner audio website; basically what everyone else is not doing
Also expect some other tutorials in regards to basic cable making standards, studio design, sound trap building, and anything else I can think of that I already know. Then I'm going to tackle a power conditioner, and finally a headphone amp over cat6/RJ45 with 4 aux mixes adjustable on the units./me is a web designer: on the website pretty colors I do want.
Anyways, if anyone else has ideas go ahead and spit them out here, otherwise I'll be waiting for that PM for that magical someone. You know who you are, and thank you.
12AU7 discussion split off to here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=110571
dave
http://www.diyaudio.com/forums/showthread.php?s=&threadid=110571
dave
RE:Microphone preamps
Ryan: I've been recording since I was a teenager and I'm now 58. I think you need to determine 1. How much gain do you need. 2. How long are your mic cables? 3. What kind of mic are you gona use? (condenser or ribbon or PM dynamic) Real condensers need much less gain than a ribbon or dynamic. I say REAL as apposed to ELECTRET condenser mics. A condenser is hot because it has a built in amplifier at the microphone. This is a very good practice to put the mic preamp as close to the mic as you can get it. You want to drive a long cable HOT! You also want to drive a long cable in balanced mode at close to 0dbv. Once you get the level up out of the noise then you can really work with it. A ribbon mic is the most inefficient of the three and will require 60db of gain in some instances. The condenser may only require 30 db in some instances. There are some very good designs on the web. Look for a PULTEK MB1. Jensen makes good transformers but they are pricey. Cinemag is also a good company. But my favorite is Lars Lundahl. If you look on ebay the old Triad and UTC transformers of the 50s get premium prices. These were used in the classic mike preamps. Ray
Ryan: I've been recording since I was a teenager and I'm now 58. I think you need to determine 1. How much gain do you need. 2. How long are your mic cables? 3. What kind of mic are you gona use? (condenser or ribbon or PM dynamic) Real condensers need much less gain than a ribbon or dynamic. I say REAL as apposed to ELECTRET condenser mics. A condenser is hot because it has a built in amplifier at the microphone. This is a very good practice to put the mic preamp as close to the mic as you can get it. You want to drive a long cable HOT! You also want to drive a long cable in balanced mode at close to 0dbv. Once you get the level up out of the noise then you can really work with it. A ribbon mic is the most inefficient of the three and will require 60db of gain in some instances. The condenser may only require 30 db in some instances. There are some very good designs on the web. Look for a PULTEK MB1. Jensen makes good transformers but they are pricey. Cinemag is also a good company. But my favorite is Lars Lundahl. If you look on ebay the old Triad and UTC transformers of the 50s get premium prices. These were used in the classic mike preamps. Ray
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