moamps

Re: When to go discrete and when not to go discrete
« Reply #20 on: February 17, 2020, 03:56:41 AM »
I have often wondered just how much distortion is introduced by the modulator itself in a 10,000W AM transmitter. FM is much less of a problem becuase it can be done at low level but an 10KW AM modulator is a whole different ball game.

The modulation in FM is done at few milliwats (at oscillator), the PLL  is a most problematic part, but linearity of followed stages is also important. The overall THD can be below 0,2% (I measured it), but it also depends of receiver's quality and signal strength at receiving side.
THD on AM  is not important at all  :) . In early days for modulators are often used the same tubes as in transmitter part. The THD was about 10% IIRC at max modulation. A modern digital AM transmitters are better.   
« Last Edit: February 17, 2020, 04:15:36 AM by moamps »


moamps

Re: When to go discrete and when not to go discrete
« Reply #21 on: February 17, 2020, 04:14:53 AM »
I believe you know what I mean. :)  Headroom as a single figure, like 30Vpp or +26dBu doesn't mean much if the complete picture is not drawn. Noise and THD are to be put in the same picture; that's why I wrote "significantly higher headroom", meaning headroom that provides actual better overall performance. In today's world of 5V converters, what's the meaning of that kind of max level? In particular higher level obtained consanguinally to higher noise is questionable.

IMO, it is important to keep the SNr you achieve at the beginning thru the all stages, so high headroom at final stage will help you not to attenuate the signal and (maybe) lower the SNr.  The good question is what is the best level THD-wise at the input of a converter. Is it +4dB or higher, it most probably depends of quality of analog front end of a converter.
For example RME ADI 2PRO FS has
THD @ -1 dBFS: -116 dB, 0.00016 %
THD @ -10 dBFS: -125 dB, 0.000056 %   :)

moamps

Re: When to go discrete and when not to go discrete
« Reply #22 on: February 17, 2020, 04:29:49 AM »
so a less expensive alternative is the IC chip with discrete follower.

First off, sorry for off topics.
IMO, it is worst solution. If you really need high currents, use DOA. Modern ICs can drive 600 ohms, but if you like to load it with two old 600 ohms compressors to get parallel compression you will be in trouble at peaks.
And DOAs are not so expensive today, you can get a 2520 style for USD20 or less.

JohnRoberts

Re: When to go discrete and when not to go discrete
« Reply #23 on: February 17, 2020, 09:54:14 AM »
First off, sorry for off topics.
IMO, it is worst solution. If you really need high currents, use DOA. Modern ICs can drive 600 ohms, but if you like to load it with two old 600 ohms compressors to get parallel compression you will be in trouble at peaks.
honestly how often does that happen to anybody.... ?
Quote

And DOAs are not so expensive today, you can get a 2520 style for USD20 or less.
$20 is still relatively expensive for a single op amp IMO, but I am cheap.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

pucho812

Re: When to go discrete and when not to go discrete
« Reply #24 on: February 17, 2020, 11:36:53 AM »
honestly how often does that happen to anybody.... ?$20 is still relatively expensive for a single op amp IMO, but I am cheap.

JR

that is pricing for kit form with parts, not assembled. 60 bucks for an assembled and tested one.   
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

abbey road d enfer

Re: When to go discrete and when not to go discrete
« Reply #25 on: February 17, 2020, 12:25:55 PM »
First off, sorry for off topics.
IMO, it is worst solution.
Why? There are some very good examples of IC+discrete that work really well (there are also many that are awful).

Quote
if you like to load it with two old 600 ohms compressors to get parallel compression you will be in trouble at peaks.
Parallel compression is not about using two compressors, it sums the compressed signal with the input signal.

Quote
And DOAs are not so expensive today, you can get a 2520 style for USD20 or less.
A mid-size mixer may have about 200 active stages, that's $4000! Compare to about $200 for über monolithic opamps.
Not mentioning current draw.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

moamps

Re: When to go discrete and when not to go discrete
« Reply #26 on: February 17, 2020, 02:16:52 PM »
that is pricing for kit form with parts, not assembled. 60 bucks for an assembled and tested one.

The kit is about USD12/100pcs at CAPI. If you need, I can arrange to you a deal of 100pcs 2520stye DOAs for USD20/pcs.


PRR

Re: When to go discrete and when not to go discrete
« Reply #27 on: February 17, 2020, 02:31:17 PM »
> an 10KW AM modulator is a whole different ball game.

Why should a big amp have any more THD than a small amp? It's just money.

I've seen numbers like 1%-2%. For the audio section.

A good AM transmitter would take NFB from the *RF* output to linearize the class C stage too.

And by about 1940, high-level modulation was going out of style, replaced with various (patent-dodge) types of phase-shift modulation.


moamps

Re: When to go discrete and when not to go discrete
« Reply #28 on: February 17, 2020, 02:36:46 PM »
Why? There are some very good examples of IC+discrete that work really well (there are also many that are awful).
You answered yourself. And this IC+buffer combo which works very well most probably will be more complex than DOA, will takes more place than DOA and draws more current than DOA.
Quote
A mid-size mixer may have about 200 active stages, that's $4000! Compare to about $200 for über monolithic opamps.
Not mentioning current draw.
I didn't said that the all opamps in a strip should be DOA type.
BTW, the mid quality broadcast console we bought 25 years ago from Soundcraft costed about GPB500/channel and was loaded with bunch of 5532 and 072 and crappy ALPS faders. 
Quote
Parallel compression is not about using two compressors, it sums the compressed signal with the input signal.
For sure.  8)
https://www.soundonsound.com/techniques/parallel-compression
"Figure 5: The way parallel compression is implemented is conceptually very simple — one merely splits a signal and passes one half through the compressor, and the other half remains uncompressed. The result is then blended together. However, it's also quite common, where resources are available, to run more than one compressor in parallel."



pucho812

Re: When to go discrete and when not to go discrete
« Reply #29 on: February 17, 2020, 02:46:20 PM »

The kit is about USD12/100pcs at CAPI. If you need, I can arrange to you a deal of 100pcs 2520stye DOAs for USD20/pcs.

are they built and tested?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


moamps

Re: When to go discrete and when not to go discrete
« Reply #30 on: February 17, 2020, 02:49:01 PM »
are they built and tested?

Of course.

Re: When to go discrete and when not to go discrete
« Reply #31 on: February 17, 2020, 02:51:21 PM »
Correct me if I'm wrong but I think that at some point before transistors and ICs became the norm hobbyists and engineers were trying to develop "discrete" amplifiers with passive components for applications where using a valve would've been impractical. As to how the circuits worked in practice is another thing, using common sense I'd expect all kinds of noise, hum, supply voltage bleed to the inputs/outputs etc but the idea was probably to get the circuit function as if it was what we know today as a semiconductor transistor/IC.

These types of circuits and their later developments are highly sought after in the audiophile market for example, currently the term "discrete" usually refers to a transistor-based circuit and it does indeed have some benefits over integrated circuits, for example (aside from the ability to drive larger loads) heat dissipation; ie. the transistors in a Darlington pair can be physically placed further away from each other and heat-sinked, compared to the large number of transistors in a dual-inline package (DIP) which is usually plastic and about the size of a fingernail.

Some ICs however are "streamlined" for audio work and have better THD and SNR values than their discrete counterparts (very basic circuits made of transistors that were originally designed for switching etc)

Someone here in another thread touched the subject of audio hobbyists getting hold of early computer ICs (I guess very similar to todays "top-end" audio ICs in terms of switching characteristics) and using them in preamps etc back in the 70's or so which fits in the picture too (but it's no reason why anyone should steer away from them, or desperately try to find NOS unless it's a restoration or something)

JohnRoberts

Re: When to go discrete and when not to go discrete
« Reply #32 on: February 17, 2020, 03:17:16 PM »
This is a very old topic, but indeed early operational amplifier modules, were used inside analog computers, not for audio but for mathematical sum/difference operations, integration, etc. Not for audio.

Audiophools are impressed by scarcity, more than performance in my judgement, but I am not smart enough to know what everybody else thinks.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

abbey road d enfer

Re: When to go discrete and when not to go discrete
« Reply #33 on: February 17, 2020, 03:21:55 PM »
And this IC+buffer combo which works very well most probably will be more complex than DOA, will takes more place than DOA and draws more current than DOA.
Only if a less-than-competent designer did that.

Quote
  I didn't said that the all opamps in a strip should be DOA type.
Then you loose the headroom the higher rails are supposed to give. There are many excellent mixers that use an IC+4 transistors solution when more current is needed.

Quote
BTW, the mid quality broadcast console we bought 25 years ago from Soundcraft costed about GPB500/channel and was loaded with bunch of 5532 and 072 and crappy ALPS faders. 
So build cost would have been £125. What do you expect? A single P&G fader cost about £60 at the time. then you have £65 for the rest, metalwork, PCB's, labour, you can't put DOA's in the picture.

Quote
However, it's also quite common, where resources are available, to run more than one compressor in parallel."
IMO, when one needs more than one compressor on a channel, the problem is not how to drive them; the problem is in their head.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

JohnRoberts

Re: When to go discrete and when not to go discrete
« Reply #34 on: February 17, 2020, 03:26:47 PM »
What Abbey said....  8)

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

ruffrecords

Re: When to go discrete and when not to go discrete
« Reply #35 on: February 17, 2020, 03:41:31 PM »
> an 10KW AM modulator is a whole different ball game.

Why should a big amp have any more THD than a small amp? It's just money.

Because things often do not simply scale - its like the difference between throwing a plank across a stream and and a bridge across an estuary.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: When to go discrete and when not to go discrete
« Reply #36 on: February 17, 2020, 03:50:58 PM »
Then you loose the headroom the higher rails are supposed to give.
Supposed is the operative word. Going from a single 24V rail to +-15V gives you less than 2dB improvement. Going to +-18V  gives you 3.5dB and +-24V still only gives you 6dB.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

moamps

Re: When to go discrete and when not to go discrete
« Reply #37 on: February 17, 2020, 04:20:25 PM »
...A single P&G fader cost about £60 at the time....
I said ALPS crappy faders (USD10). Nevermind.

You said first..
Quote
Parallel compression is not about using two compressors, it sums the compressed signal with the input signal.
then when I showed you that this isn't correct ..
Quote
IMO, when one needs more than one compressor on a channel, the problem is not how to drive them; the problem is in their head.
so you like to twist things. I'm done here.

mjrippe

Re: When to go discrete and when not to go discrete
« Reply #38 on: February 17, 2020, 09:14:43 PM »
And this IC+buffer combo which works very well most probably will be more complex than DOA, will takes more place than DOA and draws more current than DOA.

How would that even be possible?  One IC replaces several transistors and other components so it is LESS complex and draws LESS current.  Compare a Neve BA440 transistor amp with the BA640 IC version. 

Re: When to go discrete and when not to go discrete
« Reply #39 on: February 26, 2020, 05:31:52 AM »
For recording  pure sine waves, non discrete is fine.
For recording a bunch of guys playing music together in a studio, discrete with transformers usually gets everyone's juices flowing.

   
 






 

If you want to sound crazy please tell me about THE DEEP STATE.


 

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