Microphone preamp cloning... Worth it ? Is it reasonable?

[chopstuck]

If I wanted to build a good mic preamp like a Universal Audio 610, where might I start ? Is it reasonable to start from scratch or should I start with a currently available mic pre to mod ? A Hammond organ chassis could provide power and filament current to spare but what about good signal transformers for recording ? Is this reasonable because a 2 channel unit is about 2K.

[Moose]

I built a tube mic pre. Hammond power tranny, cinemag input and output trannies, and reasonably high quality caps inside.

The circuit was similar to the aikido mic pre -- just google it -- and the component values were chosen by using a simuilation. The amp has a buttload of headroom, is super quiet, and cascading two of them will allow you to use lower mu tubes than a 12ax7. You can also use a solid state input instead of a tranny to unbalance the signal and drive the tube portion of the amp harder, giving better transient response and less texture, or you can drive a more standard input stage like in the Jensen schematics.

The quality is very high for a "character" pre as I used the lower end cinemag trannies which impart more transformer texture on the tone. If I had used the High Nickle version, it would have been more transparent, but I wasn't designing transparent.

In the end, I get a very nice texture that is extremely pleasing to the human voice and most instruments from bass to electric guitar range. It also mellows brass nicely. However, it's not good for things like overheads, shakers, etc. as it lacks the crisp transient response of more pure preamps. I would never use it alone on an acoustic guitar, even, so it isn't super versatile.

Total cost was about $300 per channel, though I did a lot of it out of my parts bin. If I had used High Nickle versions of the transformers, or a Jensen, or if I'd used two stages or a gain stage into a cascode to improve that transient response, the cost would have been $350-400 per channel.

So, it's a bargain if you don't value your time. But, there are a LOT of one channel mic pres of similar quality for not much more. Look into API-312s and the various mic pres based around them that are not much more per channel for an extremely pleasing and versatile preamp.

In other words, you can save a dollar or two, but you really shouldn't do it unless you want the fun of building your own.

[Stanz]

I built a Gyraf G9 tube 2 ch mic pre, as well as the G7 tube mic. The G9 uses two ECC82 tubes Per channel. I love it. This is as good of a mic pre as one can buy, or pretty gosh darn close. It has transformers for both input and output, phantom power and a line input. He is a Danish designer who sells high end gear as well as supports DIY studio gear community, has several designs he has shared, and is one of the moderators at Prodigy Pro forums. There are a ton of clones or original designs there for any studio gear you can think of. A few of the more common builds have people who sell PC boards for them, like the G9.



http://www.gyraf.dk/gy_pd/g9/g9pd.htm

also plenty of help at prodigy-professional (although it can be overwhelming at times, not unlike here):

http://www.prodigy-pro.com/diy/index.php

[selloutrr]

you can build a single channel of Neve 1272 /1290 the preamp for the 1073 / 1081 channel strip without a power supply for around $300. Two channels easily fit in a single rack space chassis. It's hard to go wrong with Neve. the same can be said for the API 312 which can easily be mod'd to a switchable 312 / 512 style pre.

The best tube preamps i've heard have been Amprex 351's mod'd and altec lansing both of which i would suggest buying a distressed unit and just rebuild it that's where most of the money is an original unserviced should only be a few hundred far less then you would spend to get started.

OR just buy a couple channel strips, recap them and rack them! look at ADC, Wardbeck, Langevin, and Neotek. all solid state but far move universal.

Not to be a downer but i've found in preamps for studio that tubes often colored the source i was recording in a way that wasn't a first choice for a forward mixing track ( vocal, snare, kick, etc) I really enjoy the sound of a tube mic and tube compressor or eq. But with that said a cheap tube or an old tube can really dull a mix fast, so even the best equipment in that sensitive of and application is often passed over for a tried and true work horse.

best of luck

[Moose]

Not to be a downer but i've found in preamps for studio that tubes often colored the source i was recording in a way that wasn't a first choice for a forward mixing track ( vocal, snare, kick, etc) I really enjoy the sound of a tube mic and tube compressor or eq.

+1 -- that's one good reason to have an API, or a NEVE as you've pointed out (another fantastic unit that is versatile).

I honestly believe the texture most people associate with a tube is not due to the tube, but due to the transformers in many of these pres. non-tube pres I've heard have a similar texture.

APIs, for example (I haven't as much experience with Neve) are really simple circuits but NOT completely pure -- yet they add something. Call it texture, sparkle, the sunshine in the voice, or whatever it is, it's pleasing but still quite natural.

Neves should do the same, and you'll probably know and appreciate the sound as it's all over records you grew up listening to and loving.

If you want a really crisp, unaffected sound for nto much scratch, buy an RNP. You can't beat that on price for a homebuilt.

[benoit]

If you want a really crisp, unaffected sound for nto much scratch, buy an RNP. You can't beat that on price for a homebuilt.

Actually, if you can find the enclosure at a reasonable price you can get into 2 channels of a transformerless THAT 1512 based pre that is said to sound excellent But again, you gotta wanna DIY, so that the sweat equity is reimbursed with fun.

[Reeltarded]

I am a professional recordist.

Please, don't build a UA 610.

Thank you!

Do a Neve, do a Fearn...

[Andy Le Blanc]

I've a pair of Thordarson T-51645h, they came out of an old army projection
set from the early fifties. They have 150 ohm ct primary and a 150k ohm
secondary to match to tube grids. This year maybe. There are several
circuits to try, from a simple one tube follower like you see in a bassman,
to various mu-followers, srpp, etc. That akido thing is mu-follower paired with
a white-follower, its good sounding and simple to point to point. The area that
needs the most attention in a mic-pre is the power supply, unless you plan to run
on batteries, every thing needs to be regulated or very filtered , ripple in the supply will
show up later. Unless a certain noise floor is acceptable to you.
The digital process can be use to "clean up" to a degree, but its better to get it right the first time.

[selloutrr]

I was looking threw a musicians friend catalog last night. The 610 new is under $800 and trading used online for $500-600. It may be best to purchase a used one, your cost to build it from scratch will be at least $450, then after labor you are well in the ball park to just buy it, at least you know it'll work! The other positive of buying an actual 610 is that the unit will have a resale value. DIY stuff isn't often worth the cost of the parts it took to build, it's just a labor of love.

[Reeltarded]

There are better mic pres for under $500 used.

Please don't build, or buy a 610.

If you are going to build a preamp, do a Fearn for tubes, or a Neve-like design. Better yet, buy a decent preamp, and then build a box with switchable transformers. That is useful. Even better than that is to buy a RNP and build an 1176 compressor. The 1176 parts are all over, and it's the sound anyhow. There is a Danish guy who made about 1000 kits a couple years ago, used to be googleable. (*omg did I just type googleable?)

Unless you just feel like it.

[selloutrr]

I've used the 610 with decent results i'm not sure why you are so adverse to it. I'll admit it's not a neve but neve's aren't $500. It's got a nice smooth roll off in the highs i've enjoyed it on drum OH's a few times.

the kits you are thinking of can be found under the search blue 1176 he also made a kit for the LA-2a. he has a DIY recording stuido in Texas.

If you wanted a professional sound and had money to invest in a project this is the signal chain...

Buy an SM57
build a neve 1272/1290
Build a Pultec EQP-1a3
build am LA-2a or 1176LN

This will cover most of the tones we have all grown up on and you have one solid signal path you can be proud of. If you come across a few grand buy an older U87. If you use that mic with the La-2a you're vocals will sit nicely into the mix with very little effort.