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Amplifier input sensitivity

I have found that the use of in-line attenuators (-10dB, Rothwell jobbies) not only made more of the volume control's arc usable, as you'd expect, but also removed a harsh, edgy feel to one particular amplifier. It certainly sounded like the amp was distorting in some respect, on a 2V CD input, despite the input sensitivity of the amp being pretty typical and around 150-200 mV (IIRC). Any thoughts as to what might be going on here?

I tried a few as my old Audio Note DAC was pumping out a rather hefty 3-4V but whilst it gave me more scope on the volume range it killed a lot of the dynamics in the music.

Might have been just been me but couldn't get on with inline attenuators. Bit weird as they are just a resistor and in theory should just be the same as changing the link resistor in a stepped attenuator.
 
I have found that the use of in-line attenuators (-10dB, Rothwell jobbies) not only made more of the volume control's arc usable, as you'd expect, but also removed a harsh, edgy feel to one particular amplifier. It certainly sounded like the amp was distorting in some respect, on a 2V CD input, despite the input sensitivity of the amp being pretty typical and around 150-200 mV (IIRC). Any thoughts as to what might be going on here?

Does the amp have a gain or buffer active stage in front of the volume control? If so, it might have been overloaded or clipping.
 
Echoed! Yes, I have trying asking the BBC where they get announcers with voices as loud as a full orchestra. Can be a real annoyance.

Dear Jim,

I read this with a bit of a smile as I completely disagree with your premise about the relative balance of the announcer and the orchestra at a large orchestra concert.

The announcer is usually in a broadcasting box, which is necessarily like any other posh box with a forward view of the players and probably largely closed in on five faces. The impression is of the announcer literally being in the same small space as the radio listener, rather like sitting next to them or across a small table. Thus I set the volume initially according to a natural spoken voice level for the announcer ...

Then consider the orchestra. A good broadcast [of a natural performance on un-amplified instruments playing in ensemble] will tend to give the impression of very considerable distance from the performance. Rather like the perspective from a good seat in the hall from the roughly the centre, between one third and two thirds the way from the stage towards the back. If you imagined anyone in the orchestra [or the conductor] speaking from that distance it would be quite difficult to make out their words even if you could tell that they were talking.

The correct level of reply volume is that which preserves this natural distance and natural loudness or softness, and so when the announcer reappears at the end [in a radio relay] they will sound once again at a natural spoken level as if sitting a few feet from you if you have let the music play at a natural volume to emulate the reality of listening at a live performance in the hall itself

This has the great advantage that you can hear what they are saying without having to turn the volume right up after listening to the music at the appropriate natural level.

I must have told this story before, but it is worth it to again ...

I took a girl acquaintance to a concert in the then relatively new Symphony Hall in Birmingham - many years ago now. The CBSO and a large choir made up of BBC [choral forces] and local choral societies fully filled the choir stalls. The orchestra was large, and the music was Beethoven's Eighth and Ninth Symphonies. I think Walter Weller was conducting ... We sat in the most expensive seat right in the middle.

It was a rather fine evening of music, and I was delighted. I asked my colleague what she thought of it, and she said she was terribly disappointed that it was nothing like as loud as her record player! I said little, except to note that she was certainly playing the recording too loud in that case!

Best wishes from George
 
Dear Jim,

I read this with a bit of a smile as I completely disagree with your premise about the relative balance of the announcer and the orchestra at a large orchestra concert.

The announcer is usually in a broadcasting box, which is necessarily like any other posh box with a forward view of the players and probably largely closed in on five faces. The impression is of the announcer literally being in the same small space as the radio listener, rather like sitting next to them or across a small table. Thus I set the volume initially according to a natural spoken voice level for the announcer ...

Then consider the orchestra. A good broadcast [of a natural performance on un-amplified instruments playing in ensemble] will tend to give the impression of very considerable distance from the performance.

FWIW I've been in the past to many concerts which were broadcast, and, indeed, to many R3 venues as well as public halls, to hear BBC arranged performances. My experience was totally different to yours.

When an announcer spoke he was at nothing like the level of a full orchestra. Indeed, anyone would struggle to sound 'normal' if they tried to be as loud as an orchestra st full belt.

And for me the point of a R3 concert broadcast is to get a level which gets some way to replicating what I'd heard *at* the recording. Which means the announcer is absurdly loud.

R3 generally do a good job of providing the dynamic range of an orchestra. But compared with that, the announcer is often tens or hundreds of times too loud.

Yes, at the RAH or RFH the annoucer isn't on stage. But that is, frankly, an irrelevance because the point is to get the *music* dynamics correct - leading to the over-loud announcements. If I adjust the sound level to suit the announcer being 'in the room' then the music from an orchestra is far too low level.

And at MV, etc, sometimes the announcer was in the studio, sitting at a table. Comparing that with home made the change in levels obvious.
 
FWIW I've been in the past to many concerts which were broadcast, and, indeed, to many R3 venues as well as public halls, to hear BBC arranged performances. My experience was totally different to yours.

Same here. My reaction to the larger orchestral works played live - Mahler and Shostakovitch for example - is how loud they are, and also how 'open' they can sound. The sound blooms in a way it rarely does in domestic replay.
 
Dear Jim,

We seem to be a complete cross-purposes here.

Most radio announcers are NOT heard in the hall itself, but only on the broadcast relay.

When an announcer appears on the stage [a great rarity in pure classical concerts] then naturally he will either have to project like like an opera singer or have a spot microphone and amplification to make him intelligible to those in most seats in the hall.

I have been to a huge number of concerts in London, Birmingham, Cardiff, Bristol, Gloucester, Cheltenham, Poole, Hereford, Worcester, Malvern, Warsaw and Krakow. The only time there was any vocal introduction was in Hereford where the concert was also a Church Service and introduced by a prayer from a Clergyman, over the PA system, massively amplified to be intelligible to people in every corner of the Cathedral.

To get an idea of that specific balance then try Choral Evensong on R 3 on Sundays and Wednesdays. The BBC usually get this amplified spoken voice against the choir and organ remarkably well, if not always.

Best wishes from George
 
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Does the amp have a gain or buffer active stage in front of the volume control? If so, it might have been overloaded or clipping.
No, the input went to the volume pot as you’d expect. I suspected some sort of input overload but couldn’t see why attenuators would make such a difference in that case.
 
Dear Jim,

We seem to be a complete cross-purposes here.

Most radio announcers are NOT heard in the hall itself, but only on the broadcast relay.

Yes. You may be missing the point that when we listen to R3 we are listening at home, not in the hall. But to get a satisfactory representation of the real dynamics we find the announcer's voice annoyingly loud.

This doesn't happen with something like a string quartet or other small work because the difference in levels between a performance and someone speaking is much smaller.

I suspect the problem arises because the BBC are concerned that most people *won't* be listening on a good audio system, or at anything like a representitive level of an orchestra.
 
No, the input went to the volume pot as you’d expect. I suspected some sort of input overload but couldn’t see why attenuators would make such a difference in that case.

The source impedance presented to an amp can affect the amp's distortion level, frequency response, etc. But I'd not normally expect that to matter much. Devil would be in the details. Is there a circuit diagram, etc?
 
I have found that the use of in-line attenuators (-10dB, Rothwell jobbies) not only made more of the volume control's arc usable, as you'd expect, but also removed a harsh, edgy feel to one particular amplifier. It certainly sounded like the amp was distorting in some respect, on a 2V CD input, despite the input sensitivity of the amp being pretty typical and around 150-200 mV (IIRC). Any thoughts as to what might be going on here?


Thank you for posting this. My DAC input to my exposure XXIII pre is very high . At the 8 o' clock position it is loud . Very little range. After reading your post i ordered a set of 15 dB rca attenuators from Rothwell. 2 days later they are in . Much better range on the volume pot now. Have read claims that changing levels between pre and power can improve S/N ratio . I prefer the new sound . Feels more dynamic and unexpectedly the stereo image is improved and seems to have gained height. This is new to me . Really pleased with the result. For the cost - highly recommended.
 
… when we listen to R3 we are listening at home, not in the hall. But to get a satisfactory representation of the real dynamics we find the announcer's voice annoyingly loud. …
Yes. I think it is no more complicated than just that. I just dug out the high-level objectives I wrote down in 2017 to guide the purchase of some better loudspeakers:
"1. Much better bass quality (transient response)
2. Much less congestion at comfortable but not excessive high audio volume
3. Somewhat deeper bass frequency response
4. Slightly less polite top end
5. Slightly less forward on BBC R3 announcers’ voices compared to the music"

I am pleased to discover that number 5 is not something just I used to experience. I did achieve number 5 and it's no longer an annoying effect. I was wondering how that had worked. It's possible I now get better musical dynamics while listening at a lower level, through achieving some of the others. But I really don't know why.
 
I suspect the degree to which this shows up depends on factors like the 'close room' effect. IIRC John Crabbe commented on this in one of the later columns he wrote for HFN after he ceased being editor.

At home we get an added room acoustic overlaying the acoustic from the broadcast. The speakers then interact with this to alter the sound. Usually the response is nothing like flat, and the echoes are 'close'. To a a large extent our brain actually 'processes out' this once we've become acclimatised. But it affects perception.

Add in what George said. Quite often the announcer is in a small booth or room. Not in the concert hall. So we can sense the 'difference' but not really always cope with it. Add in that the annoucer *is* too loud in real relative terms for us sitting in a hall to listen to an orchestral concert, and the effect tends to make the announcer 'stand out' in a noticable way.

Whatever the reason, the effect is a PITA. But given the variables, will vary in effect depending on details of the home system, etc.
 
I tried a few as my old Audio Note DAC was pumping out a rather hefty 3-4V but whilst it gave me more scope on the volume range it killed a lot of the dynamics in the music.

Might have been just been me but couldn't get on with inline attenuators. Bit weird as they are just a resistor and in theory should just be the same as changing the link resistor in a stepped attenuator.
People do seem to report different experiences. I can report a good result in this situation:
  • My CD player/preamp puts out a whopping 14.5 V RMS at CD full scale on its XLR connectors.
  • My active loudspeakers have a default 1 V sensitivity (into 10 kOhm per leg) for 112 dB SPL output (very loud).
Inserting 10 dB Rothwell XLR pads (just three 8.2 kOhm resistors in a "U" arrangement) puts the effective sensitivity up to the point where the volume control is not too critical, and there are no noticeable degradations.
 
I suspect the degree to which this shows up depends on factors like the 'close room' effect. IIRC John Crabbe commented on this in one of the later columns he wrote for HFN after he ceased being editor.

At home we get an added room acoustic overlaying the acoustic from the broadcast. The speakers then interact with this to alter the sound. Usually the response is nothing like flat, and the echoes are 'close'. To a a large extent our brain actually 'processes out' this once we've become acclimatised. But it affects perception...
Perhaps counterintuitively, omnidirectional speakers (assisted by DSP room correction and some physical treatment) seem to reproduce recorded acoustics of both orchestral and chamber music far more successfully in my smallish room than direct-radiating speakers ever did (and I tried a few).

Perhaps becoming "acclimatised" is part of the explanation... but that having happened, for me there is no way back from omnis!
 
The source impedance presented to an amp can affect the amp's distortion level, frequency response, etc. But I'd not normally expect that to matter much. Devil would be in the details. Is there a circuit diagram, etc?
No circuit diagram to my knowledge. I also wondered whether it might be that my CD player (dCS Puccini) wanted a higher input impedance than it was seeing?
 
I tried a few as my old Audio Note DAC was pumping out a rather hefty 3-4V but whilst it gave me more scope on the volume range it killed a lot of the dynamics in the music.

Might have been just been me but couldn't get on with inline attenuators. Bit weird as they are just a resistor and in theory should just be the same as changing the link resistor in a stepped attenuator.
I had an amplifier with built in attenuation on the CD input. I thought the CD signal sounded cleaner and more dynamic through the tuner input.
 
I have no idea why they thought CD needed to be so much louder than preceding source components, but here we are!

I think it came out that way because that's what you get when you stick a unity gain buffer after the I-V converter.
 


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