Discrete sounds better than integrated? a possible reason

[Whoops]

That Melodium mic seems interesting, were the originals considered as good as the RCA 44 or ?

I don't know if you asked about the 42B or the 75A as Abbey referenced both.

The 75A mic I don't know it, never seen it or tried.

But the 42A is a great microphone and personally I find it as good as the RCA 44.
I love Horns recorded with the 42A

 

[abbey road d enfer]

Then 75A mic I don't know it, never seen it or tried.

And you haven't missed much. It was a PA mic, no bass no highs.

But the 42A is a great microphone and personally I find it as good as the RCA 44.
I love Horns recorded with the 42A

I never had a chance to use a good working 42B. All were in a more or less derelict state.
Most had a crushed ribbon, after a shock, because the construction would allow the pole pieces to move. Others had a non-working switch. I must admit it's a good 40 years since I put my hands on one.

 

[Winston OBoogie]

the 42A is a great microphone and personally I find it as good as the RCA 44.
I love Horns recorded with the 42A

Are you taking about the remade one by Kerwax or the old one?  Or both?

 

[Whoops]

I never had a chance to use a good working 42B. All were in a more or less derelict state.
Most had a crushed ribbon, after a shock, because the construction would allow the pole pieces to move. Others had a non-working switch. I must admit it's a good 40 years since I put my hands on one.

Are you taking about the remade one by Kerwax or the old one?  Or both?

There's a local studio here that has one in good conditions, well at least its sounds pretty good.
I like to use it when I have a recording session there.

This is the old original unit, I was not even aware there was a remake. Thanks for letting me know

These Melodium 42B mics were used in the national TV and Radio around here.
This is a link to RTP virtual museum, our national TV, showing the Melodium, even has the manual translated to Portuguese:

https://museu.rtp.pt/en/tv-radio-collection/radio-objects?type=1&page=2

 

[Winston OBoogie]

Thanks for the link Whoops, some interesting stuff on there.

One thing I noticed which I've never seen before is an EMI BTR-4 tape machine.

A mate of mine had, I think it was, a BTR-3, but there were very few of those made.

I thought EMI got out of the tape machine business after that but, obviously not.
A few shots of the 1st BTR-1 beast on there too.

And if course, the Melodium 42B.  Now I'm itching to hear one 

 

[Winston OBoogie]

"... Without getting too esoteric, but warning what follows is pretty esoteric ... "

I found it interesting John.
I suppose, were we building a phono pre today (less likely than 35+ years ago of course), or operating an op-amp at high noise gain in a summing bus (not the best way to do it as you know ), then a better device would be one where the compensation is brought out externally.
Naturally this isn't as 'plug-and-play' as just wrapping feedback around a unity-gain stable device and demands some more knowledge on the part of the 'designer' ...  But a two-pole, or output transitional compensation scheme that's way above your highest RIAA time constant, or keeps phase at a healthy distance (say 12dB) from instability with the high noise gain summing would be good.

Perfect application for discrete in my book .  But having access to, and implementing a more suitable compensation scheme in an I.C.  would do it. 
No?

 

[L´Andratté]

Still brooding over if or why discrete sounds better than integrated... ;D

 

[abbey road d enfer]

Still brooding over if or why discrete sounds better than integrated... ;D

The answer is it depends...

 

[ruffrecords]

Still brooding over if or why discrete sounds better than integrated... ;D

To summarize and simplify what I said in the very first post.

Some discrete amplifiers from long ago used a technique whereby the amount of NFB was more or  less constant no matter what value the gain was set at. Apart from considerably simplifying managing the stability of the amplifier it meant that you could then have the same amount of NFB at all frequencies in the audio spectrum so any distortion the circuit produced was the same at all audio frequencies and all gains.

OP amps do not use this technique. Instead they take a brute for approach to stability. The result of this is that the amount of NFB declines by 6dB per octave with increasing frequency in the audio band and it also decreases as gain increases. Less NFB means more distortion so op amp distortion increases at 6dB per octave with increasing frequency in the audio band and it also increases as gain increases.

I am suggesting these differences may explain the difference in tone between them.

Cheers

Ian

 

[matriachamplification]

Others have suggested that the transformers are a major contributor

Like most all things this took me some time to absorb and digest prior to commenting.

Without going into the pshycological or biological imprints sound can triggers... I am all about the placebo effect. If my subconcious jives with it, I'm good.


On the subject of transformers; although my exprience deals with tube amps, we can officially say there is a huge sonic impact transformers have on tone. My neigbour Ted (passed away) was a Canadian pilot in WWII and a amp designer. I remember him explaining to me that transformers were speedbumps, they almost always leave a impact on sound. We did some testing with a Sunn Model T and Marshall Superbass that was quite fun.

That said, even in the case of Helios where little transformers were used, this "should" impact sonic properties to some degree. Outside of that... its not Vacuum Tube!

Thanks for taking the time to read my thoughts.

Be Well

 

[abbey road d enfer]

On the subject of transformers; although my exprience deals with tube amps, we can officially say there is a huge sonic impact transformers have on tone.

Indeed. Nobody denies that. The ways transformers impact the electrical response are well known.
The B-H curve, the Barkhausen effect, the resonances due to capacitance and leakage inductance, the eddy current losses, all this is extremely well documented.
What is still somewhat a mystery is why all these faults result in something that is musically pleasant.
It can partially be explained by the fact that most of these effects tend to soften transients.
Another factor is acquired taste, but it can't explain everything.

 

[matriachamplification]

Indeed. Nobody denies that. The ways transformers impact the electrical response are well known.
The B-H curve, the Barkhausen effect, the resonances due to capacitance and leakage inductance, the eddy current losses, all this is extremely well documented.
What is still somewhat a mystery is why all these faults result in something that is musically pleasant.
It can partially be explained by the fact that most of these effects tend to soften transients.
Another factor is acquired taste, but it can't explain everything.

Thanks for the input about transformers.

My grasp of NFB and looped fixed gain is weak at best. When I am better versed maybe I will stumble upon some insight.

I do like the idea of imperfections creating perfections. Sounds poetic. 

Be Well

 

[JohnRoberts]

I found it interesting John.
I suppose, were we building a phono pre today (less likely than 35+ years ago of course), or operating an op-amp at high noise gain in a summing bus (not the best way to do it as you know ), then a better device would be one where the compensation is brought out externally.

I killed way too many brain cells thinking about this stuff.

Way back when, all opamps required external compensation or stipulated non-zero minimum closed loop gain. For example the ever popular ne5534 was only stable down to closed loop gains higher than +10dB without additional compensation.  The much disrespected LM741 was the first internally compensated unity gain stable integrated circuit op amp (and slower than dirt). 

Naturally this isn't as 'plug-and-play' as just wrapping feedback around a unity-gain stable device

Just about is, modern premium op amps could probably beat that pants off of many well regarded legacy designs.

and demands some more knowledge on the part of the 'designer' ...  But a two-pole, or output transitional compensation scheme that's way above your highest RIAA time constant, or keeps phase at a healthy distance (say 12dB) from instability with the high noise gain summing would be good.

Good luck finding an off the shelf op amp with flat open loop gain to above audio bandpass, but technically the highest RIAA time constant is a pole at 75 uSec (so only roughly 2kHz).

Perfect application for discrete in my book .  But having access to, and implementing a more suitable compensation scheme in an I.C.  would do it. 
No?

I am less confident in my ability to design a discrete op amp better than I can buy off the shelf. The last time I rolled my own DOA was back in the late 70s/early 80s for use inside a console sum amp because the LM394 super match pair made a much lower input noise op amp than I could purchase. (I need to mention our own Sam Groner who has published some very respectable DOA designs.)

For large bus structures there are better ways and I have been writing about them since the 80s, like Paul Buff's "Transamp" which is a variant on Cohen's topology where open loop gain increases with closed loop gain for constant loop gain margin, and my current source summing that delivers modest (low) noise gain.

JR 

 

[analag]

Older is not better because its older. The older I get the more certain I am about that.

JR

PS: RIP for Rupert

I guess you have never heard about...wine?

All my custom gear are discrete electronics. They do sound better if they are built right!

 

[Whoops]

I guess you have never heard about...wine?

Older Wine can become vinegar

All my custom gear are discrete electronics. They do sound better if they are built right!

Like any other piece of gear discrete or not, if they are designed and built right they will sound "better"

 

[clintrubber]

To summarize and simplify what I said in the very first post.

Some discrete amplifiers from long ago used a technique whereby the amount of NFB was more or  less constant no matter what value the gain was set at. Apart from considerably simplifying managing the stability of the amplifier it meant that you could then have the same amount of NFB at all frequencies in the audio spectrum so any distortion the circuit produced was the same at all audio frequencies and all gains.

OP amps do not use this technique. Instead they take a brute for approach to stability. The result of this is that the amount of NFB declines by 6dB per octave with increasing frequency in the audio band and it also decreases as gain increases. Less NFB means more distortion so op amp distortion increases at 6dB per octave with increasing frequency in the audio band and it also increases as gain increases.

Hi,

Nice thread! Didn't manage to identify those dual setting sections in the design-examples you mentioned, do you have any direct links to schematics where both open & closed loops gains are changed in tandem?

Would be interesting and possible to experiment with this (one day...);
if certain circuits don't have the open loop setting possibility, it could be added.

For 'opamp'-open loop gain, the biasing could be changed (say CA3080, LM13600/13700), or the degeneration resistor values of the first diff pair could be changed (/added).

Bye 

 

[ruffrecords]

Hi,

Nice thread! Didn't manage to identify those dual setting sections in the design-examples you mentioned, do you have any direct links to schematics where both open & closed loops gains are changed in tandem?

Would be interesting and possible to experiment with this (one day...);
if certain circuits don't have the open loop setting possibility, it could be added.

For 'opamp'-open loop gain, the biasing could be changed (say CA3080, LM13600/13700), or the degeneration resistor values of the first diff pair could be changed (/added).

Bye

Here is a link to the three transistor Neve input stage.

http://www.jlmaudio.com/neve_ba283.htm

The gain of the first stage (TR1) and hence the open loop gain is determined by the ratio of R4 to the parallel combination of R10, R11 and any resistor connected between pins T and V. At the same time, the closed loop gain is determined by the ratio of R9 and the same parallel combination of R10, R11 and any resistor between T and V. To change the gain you add a resistor across pins T and V which both incresaes the open loop gain and the close loop gain.

Here is a link to the Helios three transistor mic pre scehmatic:

https://groupdiy.com/index.php?topic=58393.msg742685#msg742685

The gain of the first stage (VT1) and the open loop gain is set by the ratio of R5 to the series combination of R3 and any resistor connected from C5 to ground. At the same time, the closed loop gain is set by the ratio of R4 to the value of any resistor connected from C5 to ground. To increase the gain you reduce the resistance from C5 to ground which increases both the open loop and closed loop gains.

Hope that helps.

Cheers

Ian

 

[L´Andratté]

What elegance! Very obvious now that you point it out ( :) but totally escaped me before, thanks for pointing that out! And thanks clintrubber for asking ;D

 

[abbey road d enfer]

When transistors were expensive, many preamps used just two of them, and benefitted from the same advantages.
When transistors became cheaper, many used differential stages, which traded the disadvantage of having varying gain margin against the convenience of eliminating coupling caps.
AFAIK I've never seen a transimpedance amp that eliminates coupling caps in the signal path.

 

[JohnRoberts]

Here is a link to the three transistor Neve input stage.

http://www.jlmaudio.com/neve_ba283.htm

The gain of the first stage (TR1) and hence the open loop gain is determined by the ratio of R4 to the parallel combination of R10, R11 and any resistor connected between pins T and V. At the same time, the closed loop gain is determined by the ratio of R9 and the same parallel combination of R10, R11 and any resistor between T and V. To change the gain you add a resistor across pins T and V which both incresaes the open loop gain and the close loop gain.

Here is a link to the Helios three transistor mic pre scehmatic:

https://groupdiy.com/index.php?topic=58393.msg742685#msg742685

The gain of the first stage (VT1) and the open loop gain is set by the ratio of R5 to the series combination of R3 and any resistor connected from C5 to ground. At the same time, the closed loop gain is set by the ratio of R4 to the value of any resistor connected from C5 to ground. To increase the gain you reduce the resistance from C5 to ground which increases both the open loop and closed loop gains.

Hope that helps.

Cheers

Ian

Open loop gain that tracks with closed loop gain is a well explored characteristic of the "cohen" topology (also used inside modern mic preamp ICs).

I mentioned this in passing in my 1980 console performance article (when describing Transamp used in a summing amp).

JR