Tube distortion adding pre amp compressor recording channel...

[gary o]

Interesting..............6AS6 got some a those ...be interesting to see a schematic or two...I had somewhere a schematic for a pre amp using just a magic eye tube said to have a lot of 2nd harmonics maybe a stage like that patched into your favorite pre amp could be good....maybe a tube stomp box circuit could be used..my problem is I dont know enough about electronics to come up with a design....

How about a vari mu type limiter where the control voltage kinda buggers up an audio stage ie when you sing a loud part instead of the CV turning down the input, it fuzzez it nicely,perhaps by messing with the plate voltage or something,I need someone with some technical no how to step in here .....prob need another limiter to keep levels ok

Could a vari mu control voltage be used to mess with the sound of a tube mic even rather than a pre amp or amp stage.....am i talkin crap...

 

[leadbreath]

gary

do urself a favour and get a quadrafuzz kit from PAIA, i use it all the time especially on vocals, its all solid state using a few ic's but its the best thing i got for getting that '50's style vocal distortion MUCH better than any of the tube units i have.
if u are fimiliar with Cubase/Nuendo software, they have a plug in emulation that also quite good but the hardware version is much more wicked...

as for building a c.u.l.t.u.r.e.v.u.l.t.u.r.e clone now that would be even more wicked!!

 

[RayBlack]

Since I'm currently in the same boat, searching for that distorted 40s/50s Vocal sound I'd like to chime in.

I will equip a small studio within the next weeks, specially made for capturing old music with that special sound of the days back then. We will be using RCA Ribbons, dynamic mics and some condensers, into V672s, LA-610s etc.
I think that a bit of distortion could be gotten, by driving the input stage of the LA-610 and then hitting the Revox A77 Tape Recorder hard with the vocals.

I heard many things about Berlant tube preamps, which can easily deliver that kind of distortion. We already bought one, but it can't be imported to germany till next year. :/

Lets exchange ideas here, for probable DIY solutions...


Greets
Ray

 

[gary o]

Leadbreath thanks for the Quadeafuzz tip Iv dowmloaded a plug in that I will try first.....I do feel like Im cheating on my tubes 7 transformers behind thier backs with the ICs tho...
Ray good luck with your studio bet it will sound great....I have a DIY M610 its sounds nice mostly clean I suppose, tho I like it its not the dirty over driven sound Im currently lookin for, tho overloading a tape stage might be it....Ray I think you'l be able to achieved the vintage sound without DIY boxes once yr studio is set up, as you say you can set stuff up to overload other stuff great ! you lucky man....Sadly for me & some others not got that vintage kit just DIY stuff and digital recorder maybe I/other can DIY a tape input stage to add to a pre like the M610 for the overloading purpose....Im not sure where the distortion Im liking is coming from thats why I started this thread i suspect from a few factors but wanna learn so I can DIY something to give me that sound
Ray would be great to hear how you get on wth your studio , thanks

 

[Matthew Jacobs]

Me too, I'm very interested in a distorted vocal sound. I hear some people like to push a LA2A to distort. I think they use that a lot on rock tracks and I'm not sure if it's the same kind of sound we're after.

I suppose some of that sound is the "hot" output of a valve mic distorting the mic pre maybe? Whatever it is I love the sound, especially the Chuck Berry kind of rock n roll vocal sound. I wouldn't be suprised is the "sound" is in the mic. I've used really old mics and they sound dirty compared to modern ones.

In a valve guitar amp the distorted sound is created by driving numerous gain stages. I'm sure we can design a similar circuit to achieve a similar effect on a mic signal or better yet a line level... I've been thinking for a while about working on a line level tube distortion DIY unit, I think we should give it a go...

JD

 

[RayBlack]

Yeah yeah..keep them ideas coming.

I'll keep you updated with my attempts also. =)

 

[emrr]

I've never gotten these sounds out of any preamp with a big gob of loop NFB going on, they just clip nasty.   You gotta use 1940's ideas.   Collins 6Q (none), RCA BA-2 (none), Gates SA-70 (8 dB), etc etc.  Later stuff almost always has 25+ dB loop NFB, and you just can't get it going on.   Anything from the mid-50's or later is a non-contender for this job.  Gary, look at the dual pot on the RCA BA-3:

http://www.schematicsforfree.com/archive/file/Audio/PRO%20AUDIO/PRODUCTS/MISC/RCA%20BA-3C%20PROGRAM%20AMPLIFIER.JPG

Do that between 3 tube stages similar to BA-2.

 

[skipwave]

Interesting about the old mixer.......how about I build the worst tube pre ever....I no doug doesnt like the Altec 1566 any votes for the worst tube pre amp ?? ... I like my DIY 1566a, I also like a 438A s 1X 12AY7 pre amp....I just seem to like tube pres ....maybe i could take 2 pres i have & overdrive one with the other.

Yes, the Bogen mixer channel is very close to the 1566, except that the Bogen uses only one half of a 12AX7 for each input stage and all feed a 12AU7, with half configured as a common cathode summing amp and the other half a cathode follower output transformer driver.

As Kingston mentioned, cascading preamps is hard, but multiple distorting stages will produce richer harmonic content. The trick, I think, is to go direct from a tube plate to a tube grid, the same as over driving the second stage within a two-stage preamp and attenuating after the output.

Also, like 3nity said, the FETBoy or Hampton JFP is excellent as a distortion maker. I often reamp a band-limited track through it just to put a little hair on the attacks of an e-bass or some point on a kick drum beater.

 

[gary o]

Ok so I add to my DIY BA2A (no feedback 1940s design pre) an extra stage 1 more 1620 and a daul pot or two pots shouldnt take too long with the crock clips lets see how its sounds........

 

[emrr]

sure, do two separate pots for fine tweaking.

 

[conleycd]

I love mixing with subtle distortion.  It makes for great harmonic excitement.  I first got the idea watching a mix demonstration video by Shane D Wilson (a Nashville mix engineer) who put a Marshall Stack on a "geek" mic in the room of the drum kit.  He mixed it subtly in with the mix liking the harmonics it generated and the sustain of the compression.

Key is subtle.

I had been playing around with the same idea except on vocals.  To me it is the best vocal exciter going.  My current setup is to run it through an old Rockman X100 (which I also read another Nashville mixer does).  I'm pretty sure these are LED clippers in the feedback stage of a TL072 - something like with some filtering.  I kick out a lot of low end with a hi pass filter and then play around with 7khz and 12khz on the distorted portion.  Subtly (I mean subtle ) mix it in with the dry channel - perfect!

When I say subtle I mean, if you think you hear distortion it's too loud.

So... I'm not doing anything with tubes but an old TS808 circuit with some EQ or other distortion overdrive boxes can be real neat.  Of course, if your thing is to hit it only the peaks you can mess around with that in a variety of ways.

CC

 

[lassoharp]

Me too, I'm very interested in a distorted vocal sound. I hear some people like to push a LA2A to distort. I think they use that a lot on rock tracks and I'm not sure if it's the same kind of sound we're after.

I suppose some of that sound is the "hot" output of a valve mic distorting the mic pre maybe? Whatever it is I love the sound, especially the Chuck Berry kind of rock n roll vocal sound. I wouldn't be suprised is the "sound" is in the mic. I've used really old mics and they sound dirty compared to modern ones.

In a valve guitar amp the distorted sound is created by driving numerous gain stages. I'm sure we can design a similar circuit to achieve a similar effect on a mic signal or better yet a line level... I've been thinking for a while about working on a line level tube distortion DIY unit, I think we should give it a go...

JD

Hi Matthew,

In regards to the LA-2, there's an article on the recording of Johnny Cash's Live at Folsom Prison where Bob Irwin describes running each channel of the 4-tracks through a "bank of LA-2As" . . . .

http://mixonline.com/mag/audio_classic_tracks_johnny/index.html  (midway down page)

I've used the same principle of this approach and it works very well.  It's different than trying to get one or two pieces to achieve the desired end.  There's lots of combinations that will work. The key here is multiple generations.  Many of the 50's cuts were likely live to 2 or 3 track - some were bounced from one machine to another out of necessity so there's at least two generations of tape compression.  If you have an analog multitrack, record a vocal then bounce to another track while adding amp/compressor of your choice and hit the tape slightly harder.  If that's not enough, do another.

What's different about what I'm describing vs getting one amp to overdrive nicely is that when using the generation technique you hit the amps/limiters/tape machines more conservatively - slightly hot vs trying to get them to crunch out at one time.  With each generation your track will get more dense and rich and the overdrive will add up nicely.  The sound gets 'hotter' and maintains a better definition than you get when a single mic amp or limiter is pushed to its absolute limits.

Another useful amp to add to the arsenal is a single tube line booster block. Pick any tube and wire it to RC book value at 10-20db of gain. You can use 1:1 grid transformers here.  If you try and chain two mic amps as was pointed out earlier you have to re-pad from line to mic level every time and may run into problems with unintended response curve changes.  A line booster could be put anywhere to give an extra stage using most any tube you wish plus an extra piece of iron or two.

"Hot output of the valve mic distorting?"  Those vf-14s were known for that.

 

[Matthew Jacobs]

Cool info man, thanks

I have a Fostex R8 1/4" 8 track I will experiment with.

Re: Tube line amp, what do you mean by "RC Book"? Do you mean built to the manufacturing spec in the datasheet?

J

 

[lassoharp]

Cool info man, thanks

I have a Fostex R8 1/4" 8 track I will experiment with.

Re: Tube line amp, what do you mean by "RC Book"? Do you mean built to the manufacturing spec in the datasheet?

J

RC Book was referring to the RCA tube manual section on resistance coupled amplifiers, so yes.  Some individual tube data sheets include these as well.

 

[leadbreath]

hi guys

i think the secret here lies in achieving harmonic distortion as opposed to clipping of the waveform. any mic/pre/eq/compressor can create clipping distortion if driven hard enough but it doesnt always sound good.on the other hand if the waveform is distorted and maintains its peaks it will sound a lot better in my experience.thats why i think the old gear (due to their limitations) would achieve this easily, but to recreate these old tube units will be very difficult because all components/tolerances/designs are much better quality nowadays??!!
this effect can be achieved by tape saturation but the sound gary is on about is NOT made by tape, tape distortion in my opinion is unuseable.(remember i specialize in noisenik/garage/punkrock music).
i would still suggest looking at a recreation of a culture vulture type unit where u can introduce specific harmonic distortion(even/odd) and control the amount of distortion thats introduced.this will be a very versatile unit that can be used on anything.
i remember seeing a clip about a guy here in london called theo who also makes a tube type distortion box and he passes drums thru his unit and its totally brutal....!!!!

 

[leadbreath]

http://www.tube-electronics.co.uk/studioeq.htm

 

[gary o]

Ok the Fuzzpre is born....... I have my RCA BA2A (DIY)as the input of my fuzzpre just 1 of the 1620s... the second half is a whole DIY Gates SA70 pre amp that has no neg feedback using transformer from a feerograph reel to reel as OP tran .....result is it does sound fuzzy very soft and furry maybe, very warm so hard to discribes sounds but I like it.

Doug I have NO pot across the input at the mo so not as BA3C as yet cant get that schematic to appear at the mo.....will fiddle & listen with this more soon......

 

[lassoharp]

Gary,

Not to jump off topic too far here but since they came from roughly the same era I was wondering if you've ever came across any of these and how they compare to the american stuff.

http://www.btinternet.com/~roger.beckwith/bh/typea/typea1.htm

 

[RayBlack]

Hi,

sorry for my noob question...what do you mean by "big gob of loop NFB" ? (anything with feedback?)

You link doesn't work....and where can I get the RCA Book in PDF Form or something like that.
Would be interested in a DIY RCA BA-2...


Greets
Ray

I've never gotten these sounds out of any preamp with a big gob of loop NFB going on, they just clip nasty.   You gotta use 1940's ideas.   Collins 6Q (none), RCA BA-2 (none), Gates SA-70 (8 dB), etc etc.  Later stuff almost always has 25+ dB loop NFB, and you just can't get it going on.   Anything from the mid-50's or later is a non-contender for this job.  Gary, look at the dual pot on the RCA BA-3:

http://www.schematicsforfree.com/archive/file/Audio/PRO%20AUDIO/PRODUCTS/MISC/RCA%20BA-3C%20PROGRAM%20AMPLIFIER.JPG

Do that between 3 tube stages similar to BA-2.

 

[gary o]

Lassoharp thanks for that link i love reading stuff like that would love to use any kit like that 7 would like to find schematics too, sadly i havent got much experience with any old kit thats why i have to DIY.

ray black what Doug means is big gob LOT OF NFB negetive feedback....where portion of the output is sent back thru the amp via tertary winding on the op tran or directly to lower distortion & older amps like the BA2A dont have this and therefor may produce a nice distorted sound...Iv DIYed about 14 amps and I usually prefer those without the NFB.

The DIY BA2A isnt a kit or project sorry if i gave that impression.....they are easy to make from schematics tho...may I suggest the gates SA70 cheaper easier to find OP tran sounds as good and easy to DIY....il try n find links as info is all here.... EMRR posted some schematics & gave us good advice as youl see, dougs a lucky fella as he has many original pre amps and a wealth of info.