Pre amp for bus use

[TalismanRich]

Could it be the compression

Compression would maintain the waveform shape, just decreasing the size of the wave. 2:1 compression means above the threshold, 2dB in yields 1dB out. If you look at the wave forms throughout the track, it's more of a cutoff, which is limiting or clipping. Snip off the top above a certain level. 2dB in is 1dB out, but 2.5dB and 3dB in is also 1dB out. Anything above the threshold is gone. You lost your continuity. And, it's asymetrical, only chopping off one side of the wave. This is done with the arrangement of clipping diodes in some pedals.

I'm assuming it's the TC02 we're talking about, and now I see a button for polarity. That would account for the inversion. I would be playing with it to see if the clip follows the inverted signal. Is it always the top, or if you flip the switch, does it cut the bottom of the signal? Did you use it for compression or just the preamp?

I've been looking at the TC02. The tube is just for preamplification. The compressor section is optical. I can't find any signal layouts to see how it's designed.

It's funny that when I searched for the TC02. there was one for $115 in Germany, and another for $400 in UK. A modified one in Nashville is $435. Threads from years ago were showing them being sold new for $90 to $170.

 

[FrankD77]

no idea.
To be honest i didn't analyze it like you did i just listened.

But it's very interesting
Seeing you can't link the channels i could be doing something wrong with the levels.

I'm working on a track now so when that's done I'll run it through without hitting the limit. This track was run through it with occasionally the red led blinking. Maybe that's the culprint.

There is not a lot of info about these. What i could find was very positive so for 120 i took the gamble.

 

[TalismanRich]

It says it's a Class A preamp, so if you hit the red light, it could be what's happening. Everyone today talks about "you have to hit it hard to drive it into saturation" to get the "tone". To me, it's like running your engine at red line, and trying to use your transmission to control speed.

 

[FrankD77]

It says it's a Class A preamp, so if you hit the red light, it could be what's happening. Everyone today talks about "you have to hit it hard to drive it into saturation" to get the "tone". To me, it's like running your engine at red line, and trying to use your transmission to control speed.

That could be it, sounds logical.

As long as it gives the results i like i don't really care what happens

But it's very interesting to see what happens. And something to experiment with. Will drive it less the next time

 

[CoolCat]

all this sound comparison is why I bought a headphone amp and decent openback headphones, because if the monitoring isn't pure and consistent all the sound-samples are part room, or part speakers, influenced. Its always "can my ears hear it ?" and "can I see it on a graph?".
BiPolar....right brain art and left brain julian krause specs.

I'm curious pop up some clips of A vs B...run a poll thread or something? a blind-shoot out.

I've not had much luck with preamps and transformers adding some big change on a vocal mic, but on guitar it seemed much more noticeable like a 73pre overdriven, then running a MIX through one? Ive never done that, seems it would be more energy than just a voice mic, maybe more than just a guitar.

I flipflop from Grace design Millenia clean to JoeMeekOptoAphextubeShimmerTransformer Color........or usually ISA stuff is a nice middle, not sure why? its silent, but has "weight" or whatever word it is, loud, full.

its all good stuff, right?

 

[FrankD77]

As long as it inspires
For one it's a 2101 for the next the axe FX.

 

[TalismanRich]

I like to know why and how things work. I used to take things apart to see how they worked.

It's the difference between "I press the gas and the car goes" and "have I got a 3.5L V6 or a 2L turbo under the hood? Does it need premium gas? Overhead cam or pushrods?".

 

[Slouching Raymond]

I've not had much luck with preamps and transformers adding some big change on a vocal mic, but on guitar it seemed much more noticeable like a 73pre overdriven, then running a MIX through one? Ive never done that, seems it would be more energy than just a voice mic, maybe more than just a guitar.

I gather the technique is not to overdo it.

 

[FrankD77]

@TalismanRich
That's the way to be able to recreate something

The phase issue does however make me wonder.
And how important it is in the end. More testing.

 

[FrankD77]

Did a new test

Microsoft OneDrive

1drv.ms

Didn't drive the pre-amp into the red this time, just below.
And a very slight compression on the Pre-amp track from the Pre-amp itself.

New track is called "Magic mountain puppet show"
Drums are supposed to be a bit "dirty"

 

[Slouching Raymond]

Did a new test

That was really good!

 

[FrankD77]

Thanks man.
Im always open for collabs or tips to improve.

On the pre amp topic.
The difference is very subtle however i do have a slight preference for the pre amp, the standard mix is a bit more "massive" but also slighty less detailed.

I do know that not being able to link the two channels is not handy. Its easy to solve by using the meter and test untility but it's more work than running a plugin.

 

[ecc83]

"Perhaps Dave can comment on if this is due to diode clipping vs tube clipping." "Clipping" is such a pejorative term thrown in for almost any kind of distortion mechanism. Bit lazy TBH.

Peeps often use the term "diode clipping" when in fact the circuit is doing no such thing! Yes! There ARE diodes in circuit but most of the time they are in the feedback loop of an op amp. This circuit results more in compression, crude perhaps but, depending upon the circuit values, the op amp will just have less and less gain as the input signal rises. Diodes being very non linear means that this process causes ever increasing distortion...AND FFS! There is almost always TWO diodes back to back and so distortion is symmetrical i.e. ODD harmonics! (you could fudge the output centre point of the op amp to get more 2nd+ harmonics, anyone thought of that Sporks? Class A and all THAT swaddling!)

The Blackstar HT-5 was much berated (mostly here!)_ as not a "true valve" amplifier. "It has a diode clipper in it FFS!" Not so, is had a diode feedback circuit as above the purpose of which was to stop the signal driving the ECC83 stage too hard and causing nasty noises. You CAN have too much distortion...even "latchup" which sounds REALLY ****! Ten minutes with a scope and sig gen will show that 90% of the OD sound comes from the double Triode.

A true diode clipper has a pair or diodes across the signal source fed from a resistance and at about 0.7V the diodes 'clamp' the signal..at less than 700mV there will be odd harmonic distortion but over a very small dynamic range. Often there is an post clipper make up amp.

Dave.

 

[ecc83]

"Perhaps Dave can comment on if this is due to diode clipping vs tube clipping." "Clipping" is such a pejorative term thrown in for almost any kind of distortion mechanism. Bit lazy TBH.

Peeps often use the term "diode clipping" when in fact the circuit is doing no such thing! Yes! There ARE diodes in circuit but most of the time they are in the feedback loop of an op amp. This circuit results more in compression, crude perhaps but, depending upon the circuit values, the op amp will just have less and less gain as the input signal rises. Diodes being very non linear means that this process causes ever increasing distortion...AND FFS! There is almost always TWO diodes back to back and so distortion is symmetrical i.e. ODD harmonics! (you could fudge the output centre point of the op amp to get more 2nd+ harmonics, anyone thought of that Sporks? Class A and all THAT swaddling!)

The Blackstar HT-5 was much berated (mostly here!)_ as not a "true valve" amplifier. "It has a diode clipper in it FFS!" Not so, is had a diode feedback circuit as above the purpose of which was to stop the signal driving the ECC83 stage too hard and causing nasty noises. You CAN have too much distortion...even "latchup" which sounds REALLY ****! Ten minutes with a scope and sig gen will show that 90% of the OD sound comes from the double Triode.

A true diode clipper has a pair or diodes across the signal source fed from a resistance and at about 0.7V the diodes 'clamp' the signal..at less than 700mV there will be odd harmonic distortion but over a very small dynamic range. Often there is an post clipper make up amp.

Dave.

Valve "clipping" Fergot! (old, meds) You can see a valve (op or small signal) "clipping" on a scope but if you zoom into the clipped part of the waveform you can often see some "smoothness" for mild clipping, i.e. it is not a square wave. You really have to push valves very hard to "square off" and it sounds bad and often you will be close to "farting out".
I wish I still had access to the facilities. It is very instructive feed a valve amp a signal just overdriving say the second triode and following the progress through the amp...noting the way EQ changing the wave shape for just one thing.

 

[FrankD77]

Awesome reply.
I'm very sensitive for the higher frequencies (always used ear protection) and when I run it through the pre amp i have no idea if it's really what I'm hearing but the highs are just smoother for my ears. It's super subtle but it is clear for me.

 

[ecc83]

Awesome reply.
I'm very sensitive for the higher frequencies (always used ear protection) and when I run it through the pre amp i have no idea if it's really what I'm hearing but the highs are just smoother for my ears. It's super subtle but it is clear for me.

What are these "high frequencies" of which you speak? I have had nothing past 2kHz (yes! TWO!) for years.
ALWAYS good to protect ears!

Dave.

 

[TalismanRich]

I finally got a chance to dive into the new track.

First.. I like the tune! I'm not hearing the raspy sound that I was getting on the previous test. Actually to me they sound identical. Maybe what you're hearing is above my threshold, which is pretty much in the 10-12K range. (You'll find out when you hit your 60s and 70s! )

As before I threw them both into Reaper so I could flip between the two. The polarity is still inverted, but I don't see any sign of the limiting/clipping that was present in the first test. I think that clipping of the first test was what I was hearing as raspy.

You mentioned the high frequency area. I threw it into BlueCat spectrum analysis to see if there was anything obvious. About the only difference I see is a slight roll off when you get up to that 18-22K range. Obviously that's not something I can hear, nor would Dave. You said it sounded "smoother" which I find most people say when you remove something they don't like. Cymbals are an example where I miss the shimmer that I used to hear. It's also something that a few people I know DON'T like.

I wonder if I chopped the tracks up and pieced them together randomly if you could id which is which. You say it's obvious, so you would hope the differences should stand out.

 

[FrankD77]

I'm pretty sure i would not.
It's subtle and i hear it after a few times a/b.
I think the price of the pre amp didn't set the expectations high but i love to experiment.

The raspiness was probably the clipping. On the previous track i was driving it into the red on some parts. Not a lot but probably just enough.

I'll try a different tube next week.
About the high frequencies. I did the apple test and scored almost perfect. at 55 it proofs protection works

No idea while it flips the polarity ??