something new wanted

[dave dove]

hi... first post here

i have built several tube hifi linestages, phonostages and power amps
so i have a reasonable understanding of how to get clean, flat response gain
but now i require something different....
i have a home studio based around a PC
in fact all instruments are virtual..
i would like to render a channel through a high quality "tube warmer" type effect
but i don't need any gain as i don't want to overload the DACs
the digital emulations i have tried are not very good
so any ideas would be appreciated

dave

 

[Andrew]

What about a gain stage that pushes the tubes and then an attenuator? YUM.

 

[dave dove]

yes... that's what i thought
what are the general principles involved with overdriving a valve with fairly predictable results?
i was thinking of using either 12*** and/or 6n1p/6n6p types
i have plenty of these lying around to mess with
is the overdrive/warming caused by driving the grid of the second stage hard
or drawing extra current
or both?
once i've got the general idea i can breadboard something rough and mess until i get it right

thanks

dave

 

[Andrew]

I think you want either a low bias current, or a huge resistor at the grid, or maybe both. I think the amount of "warmth"  sound mostly has to do with the characteristic high input impedance and shunt capacitance of the tube, and how you are setting it up in the circuit, but hey, could be wrong.

 

[clintrubber]

Hi,

Does the warmth need to come from a tube or are other components OK as well ?

This is not meant as some smart remark; it's more or less common belief here that the sonically desirable
properties that you seem to be after won't necessarily come from tubes alone... there are for instance (signal) transformers as well, and the combination of tubes & transformers, solid-state circuits & transformers etc.

Not too long ago the sch. of the TLA 8-ch warming circuit was around (out of production), I thought it uses twin-triodes only, no TXs... but I don't know if it actually did accomplish the desired 'sonic warmth'. There's also the Uli B.-clone, I guess it was based on that... (T-something Magician ?)

Bye,

  Peter

 

[Kingston]

I have a similar project finishing up sometime soon.

Building a NYD one-bottle preamp and disabling the feedback on the gain stages. It's almost as simple as cutting the feedback wire. In fact I was thinking of putting a pot on the feedback loop so it'll "blend". It won't be a smooth blend as the gain will also change but I presume it'll still be usable. It'll then go from a nearly linear and distortion free pre-amp (and as such very usable) to tubed up dirt effect.

In this project, cheaper (read OEP) transformers on the output at least, and it'll definitely warm up stuff (and still sound great).

I'll add a cheap diode clipper with several modes on the output as well. Wavebourn once posted a decent one.

 

[zebra50]

Another thought is the Akido circuit or kit. I'm working on one now for a similar purpose (and as a general use line amp). The boards are excellent, btw.

http://glass-ware.stores.yahoo.net/newhardware.html

 

[JohnRoberts]

There are a number of patents covering tube emulation. Consider reading the sundry patents, and stand on the shoulders of those who have already studied mimicking tubes. I suspect you can get some of the sound qualities you want, without the consequences of running through a tube stage.

Short story, years ago when I was working at Peavey, I was working on trying to sell some slow moving inventory. One SKU I was looking at clearing out was a simple line level in/line level out tube mixer. It was designed for all-tube guitar rigs to combine several guitar inputs and such.  Knowing the irrational attraction for tube paths in recording to add some of that ethereal  "tube sound", I tried to sell these into recording applications. The mixers sounded too clean, so I even added 20 dB of gain to make it easier to overload, still no sale. Apparently the tube mixers didn't sound tubey enough (the Peavey logo didn't help).

I can appreciate the sonic difference between a tube and solid state guitar amp driven into the rails, and some of the solid state imitation tube sound amps were IMO a useful effect. I wouldn't have high expectations for a running a clean signal through a clean tube stage to make a huge difference.

JR

 

[dave dove]

thanks guys

zebra50:
you won't be disappointed with the aikido linestage
as i'm sure you know it is a very "correct" circuit
all my hifi and monitoring amps use variations of aikido driver
my monitor amp is [12ax7>6n6p aikido]>5881 parallel single ended
my hifi amp 6072>[6n6p>6n6p aikido]>300B
my last linestage was aikido and my phono stage is an early broskie style affair:
http://www.tubecad.com/articles_2002/RIAA_Preamps_Part_2/page10.html
so i'm familiar with that circuit
although one can hear very clearly the difference between components and wire
it's immunity to PSU ripple makes it a wonderfully clean cct
which is exactly what one wants for monitoring/listening....
i wasn't sure whether using it as a master insert would be of any use
as john roberts says: it is too clean and not tubey enough

i need to be a little clearer about what i am looking for:
i can build a "warm" or whatever circuit easy enough but
i want to know how to dial in distortion in the form of soft clipping in a controlled/repeatable manner
as a kind of presence enhancer or bass dirtyupper usw
or just to warm up the mixdown
i'm assuming there are some tried and trusted ways of doing this
and some generalisations about which valves are most suitable

thanks for all your replies

dave

 

[clintrubber]

Dunno how messy it needs to get, but the 'dirt box' thread from a while ago came to mind again:

http://www.groupdiy.com/index.php?topic=5593

Bye,

  Peter

 

[emrr]

i need to be a little clearer about what i am looking for:
i can build a "warm" or whatever circuit easy enough but
i want to know how to dial in distortion in the form of soft clipping in a controlled/repeatable manner
as a kind of presence enhancer or bass dirtyupper usw
or just to warm up the mixdown
i'm assuming there are some tried and trusted ways of doing this
and some generalisations about which valves are most suitable

my thoughts:

attenuator, iron, tube stage, iron, attenuator.  should be able to deliver clean output exceeding the following inputs max capability.  attenuators will let you dial in the desired euphonics level and achieve desired signal level. 

variable feedback / no feedback.  many methods and forms to vary the harmonics content and knee of clipping. 

select output iron for sonic characteristics and headroom.  can't answer that one; all to your taste. 

same for tube type.   i like lower gain stuff which eats more current, and generally octal tubes.  but you may want that 12ax7 high gain gtr amp sound. 

basic PP amps tend to leave you with more 3rd harmonic content and minimal 2nd.   SE can gob up the 2nd harmonic (the warm, to most people).   two options there.    oh; third:  SE driving phase splitter or interstage transformer with PP output stage.  some of both harmonic effects; most like the big Fender/Marshall thang. 

lots of ways to cook this pig. 

 

[dissonantstring]

hi dave (and peter),
i'm not sure if this ever came up in another thread (i do recall something), but there was mention of the RSP Saturator circuit.  this has been a discontinued product for some time now.  i have one of the early models that we used with one of the first versions of the DA-88.  i've never opened it up so i don't know how complicated it is and it's been a long time in storage, but when i have time (next week maybe) i can try to begin tracing the circuit if there is any interest.
mind you, i'm not very versed in tracing circuits so hopefully it is pretty simple.
be warned though, it might take a while with the holidays fast approaching.
regards,
grant

 

[clintrubber]

hi dave (and peter),
i'm not sure if this ever came up in another thread (i do recall something), but there was mention of the RSP Saturator circuit.  this has been a discontinued product for some time now.  i have one of the early models that we used with one of the first versions of the DA-88.  i've never opened it up so i don't know how complicated it is and it's been a long time in storage, but when i have time (next week maybe) i can try to begin tracing the circuit if there is any interest.
mind you, i'm not very versed in tracing circuits so hopefully it is pretty simple.
be warned though, it might take a while with the holidays fast approaching.
regards,
grant

Hi Grant,

Is that the blue rackmount box ? (the pic is missing from the link below)

http://www.sweetwater.com/publications/sweetnotes/sn-spring95/Spr95_07.html

Had the chance to buy one time ago, EU100, might have been stupid of me that I passed, dunno.
Either way, it'll probably be hard to clone one for under that amount 

But first of all, how cool/subtle/happening is it ? Maybe the 'long time in storage' bit tells half the story already ?  : 

Bye,

  Peter

 

[clintrubber]

Other site did have a pic:

http://kijiji.ebayimg.com/i3/08/k/000/7c/58/2a63_20.JPG

Yep, this is indeed the same box I skipped  :-\

 

[dissonantstring]

hi peter,
yup, that's the one.  it indeed has been in storage, but mostly because my life has not allowed me as much time to record and my "new" recorder since that time is an MCI JH24 which does not need a saturator.

the character IIRC is soft clipping/thickening and the unit is not all that quiet hiss-wise (but that's when pushed).  there are input and output level controls which allows for driving the signal to your liking.  nothing really harsh sounding though even when driven with input and output to 10.

From the description you linked:
"The tubes and their associated circuitry are the focus of a minimal signal path constructed of only premium quality components, resulting in pure tube richness without excess noise or unwanted coloration."

it did add some nice thickening WITH excess noise/hiss (can't say which part of the circuit caused this though like most tube circuits it can happen when pushed).
regards,
grant

 

[analag]

I made one and ended up selling it to a DJ some 10 odd years ago, he still uses it and refuses to work without it. One of the things I did was I biased the thing to work in the non linear portion of the characteristic curve for loads of second harmonic distortion. Then you should voice it by ear until you are satisfied with the result.12ax7 works well for tube effects because it is not a particularly clean sounding tube and Sovtek makes a wide variety of various sounding ones.

analag

 

[MartyMart]

About 12 or so years ago, I bought a product called a "VKP-1" from a small company called "Energy"
It's designed to be a "Valve keyboard pre-amp" - hence the name and was mostly used for adding a
bit of dirt and presence to Organ type keyboards.
They were based in Chiswick - west London but are not around anymore, the owner Dave was a real
nice chap.
It's still in my rack and gets used now and then for some "warming up" of line level signals.
It's real nice on a stereo drum Bus for instance.
12AX7's IIRC with gain and presence controls.

MM.

 

[okgb]

Hey JR , i had wanted one of those peavey line mixers
for effects return but i don't know if any made it to my
city and they seemed expensive to order ,
in fact i could still use one