Preamplifier functions that you miss

[Beobloke]

I'm not too sure about VU meters on preamps, even if the mighty Yamaha C-1 has them (as does the Nakamichi 610). They make more sense on power amps and recorders.

They make sense on everything.

One day I'd love to put together a system where everything has VU meters - the turntable, phono stage, preamp, power amp, tuner, cassette deck, CD player and speakers. It can be done but I'm not sure how it would sound!*

* Actually, it would sound amazing, thanks to the 8 pairs of VU meters, as everyone knows they improve the sound.

 

[Arkless Electronics]

No need for shouting.
Analog make switches for up to +/-22V, more than most opamps can take.
With +/-15V supplies you could handle the highest output CD player and even apply 10dB tone control boost.
Better to have an optional input attenuator for these extreme examples as you still want to work with old tuners and want the volume control to have a sensible range.
Designed properly, there is no reason why a solid state switching preamplifier cannot exceed 110dB dynamic range

I'm well aware of the vastly superior to 4066 types that have long been available but I would never under any circumstances use them. Real switches with mechanical contacts, including relays and reed relays, are superior in everything but long term reliability (they are literally perfect when in good working order) so why compromise?

 

[John_73]

I wonder if it’d be possible for mini relay pcbs to be developed that could replace the CMOS switches in the Quad 34 and 44s, and just require the old chips being removed and the new boards inserted, or a socket fitted first then inserted? I’m sure with the amount of these particular pre-amps made and their popularity should an upgrade would sell very well.

 

[Arkless Electronics]

I wonder if it’d be possible for mini relay pcbs to be developed that could replace the CMOS switches in the Quad 34 and 44s, and just require the old chips being removed and the new boards inserted, or a socket fitted first then inserted? I’m sure with the amount of these particular pre-amps made and their popularity should an upgrade would sell very well.

Unlikely to be a goer. 4 switches in each CMOS package so the thing would be bristling with relays and it's likely that the PSU couldn't cope with all the relay coils. Nice thought though

 

[John_73]

Unlikely to be a goer. 4 switches in each CMOS package so the thing would be bristling with relays and it's likely that the PSU couldn't cope with all the relay coils. Nice thought though

Ahhh pity. Looks like we’re stuck with the CMOS switches in these preamps them. Upgraded mine to the Maxim types a few years back which did get rid of a slight veil over the music I had before, but I’d be intrigued by any other future solutions (other than getting rid of it that is ).

 

[MikeMA]

I guess preamplifiers are out of vogue now, but they are actually the heart of most hifi systems. In order of importance, here are my must-haves in order of priority:

- stepped attenuator, ideally with resistor ladder rather than wiper variometer.
- three or more line-level inputs
- in-built RIAA stage with switchable MM/MC settings
- MM stage with adjustable capacitance and resistance loading
- two or more tape loops, with separate tape out and monitoring switch
- remote control
- balance control
- mono switch
- variable loudness
- tone controls

I'm sure such a preamplifier exists ...

Actually, a simple loudness button would do me for late night listening.

 

[James]

Actually, a simple loudness button would do me for late night listening.

Vintage 1980s Yamaha does loudness really well. I recall my receiver had a variable dial, and the loudness effect fades as volume climbs. What's not to love?

 

[Jim Audiomisc]

Personally, I'm quite happy with the switches in the Quad 34. Mind you, I prefer the diode switching in the Armstrong 600 series. The 34 is nice because it is easy to modify. Which means I can tweak the input sensitivies and the profile of the bass control to suit me. I think the loss of a balance control and *decent* tone adjustment on modern amps is a great loss for users. I agree, though, the predjudice about them means people steer away rather than give them a try. So for makers it is simpler and cheaper just to pander to the idea that they are automatically a 'bad thing'.

VU meters are a waste of space on anything. If you want meters you want PPMs. 8-]

 

[topoxforddoc]

VUs are virtually useless, but nice to look at. PPMs are definitely the way to go, although most PPMs are XLR connections, given their main use in broadcasting.

 

[Marchbanks]

Vintage 1980s Yamaha does loudness really well. I recall my receiver had a variable dial, and the loudness effect fades as volume climbs. What's not to love?

Perhaps one could try replicating this by connecting the bass and treble controls to the volume control by a (preferably large, complex and clattering) system of gearwheels. Pulleys would be good as well.

 

[Jim Audiomisc]

Given some pretty waggle analogue volt-meters you can make them into PPM action using a few op amps, etc. And IIRC there are some PPM ICs about.

 

[James]

VU meters are a waste of space on anything. If you want meters you want PPMs. 8-]

Except for tape recorders, of course. In which case, you want peak reading ones covering -40 to +10dB.

 

[Jim Audiomisc]

PPMs are peak reading. For digital +10dBFS doesn't mean more than "gross error on the part of the op", though. 8-]

For analogue tape +10dB tends to mean "we like distortion, not hifi".

For peak-reading, really a question of if you want ye olde BBC type or some alternative.

 

[Marchbanks]

PPMs are peak reading. For digital +10dBFS doesn't mean more than "gross error on the part of the op", though. 8-]

For analogue tape +10dB tends to mean "we like distortion, not hifi".

A studio sound engineer friend of mine recently boggled my mind when he told me which producers favoured which brand of analogue tape because of the different results you got from oversaturating - and how you could now buy software plugins to replicate them all!

 

[Jim Audiomisc]

A studio sound engineer friend of mine recently boggled my mind when he told me which producers favoured which brand of analogue tape because of the different results you got from oversaturating - and how you could now buy software plugins to replicate them all!

Yes, it tells us more that we might like to know about what studio people get up to that they had get software engineers to produce digital plugins to fake analogue tape saturation! Hence my comment about "we like distortion".

I've got no problem with, say, Jimi Hendrix, deliberately adding distortion-based effects. But I certainly don't want *more* added years later by someone else. Nor do I want any to 'improve' well made acoustic recordings of classical music, jazz, etc. Matter of if people want the added peak distortion or not.

Mind you, (ahem) at least HDCD sort-of gives you a choice.

 

[Robert]

There are much better CMOS switches than the cd4000 series that Quad used

Yes you can swap them out easily enough with pin compatible modern variants.
That said, the distortion performance of even ancient 4000 series switches is highly dependent on operating voltage and impedance - and conditions inside the 44 keep distortion low enough.

Ditto the lowly TL071 used in much of the circuit. Fine if you don't load it down.

Back to good full feature pre amps, the Audiolab 8000C just about scrapes in as vintage.
Excellent phono stage, plenty of facilities, good tone controls, quiet.

 

[davidsrsb]

The better switch parts can control +/-15V powered switches from low voltage logic.The 44 has a clever design to use the 4066, which has a crude logic control, but this has caused some reliability problems and has compromised the design.

 

[James]

For analogue tape +10dB tends to mean "we like distortion, not hifi".

Back in my youth and when I had sharp hearing, tapes recorded on my lowly TEAC A-103 would start to distort audibly if the VU meters strayed past 0dB during recording. Yet, my friend with a Pioneer CT-F900 routinely recorded on the same TDK-D tapes with his peak meters topping out at +8dB without any audible distortion. Those tapes he recorded for me showed similarly healthy saturation, but no distortion when replayed on my TEAC.

What gives?

BTW, I can record on my Nak at up to +8dB without audible distortion, but my ears ain't what it used to be.

 

[Jim Audiomisc]

Back in my youth and when I had sharp hearing, tapes recorded on my lowly TEAC A-103 would start to distort audibly if the VU meters strayed past 0dB during recording. Yet, my friend with a Pioneer CT-F900 routinely recorded on the same TDK-D tapes with his peak meters topping out at +8dB without any audible distortion. Those tapes he recorded for me showed similarly healthy saturation, but no distortion when replayed on my TEAC.

What gives?

BTW, I can record on my Nak at up to +8dB without audible distortion, but my ears ain't what it used to be.

One factor can be that different decks may not all be calibrated in the same way. So 0dB on one set of waggle meters may not equal 0dB on another set. And if calibated against a given flux level *when recorded* may vary depending on the tape the maker used for their 'standard'. But assuming that isn't the reason for the above...

Some possible causes of the differences:

1) The saturation behaviour depends on the bias level and the equalisation. This is why some late designs of cassette deck adopted the trick I think B&O devised of 'ducking' the recording bias level for musical/HF peaks. That gets you a few more dB with lower distortion.

2) Saturation may also arise due to the limits of the recording head design and state. e.g. might need a demag. But may be the *head* saturating. For 'metal' tapes new head designs were certainly needed to cope. More than one recorder would record and play them, but not all did it well.

Nak made *very* good heads, etc. Not all other brands used them or did as well, or bothered to correctly calibrate their machines.

 

[Marchbanks]

One day I'd love to put together a system where everything has VU meters - the turntable, phono stage, preamp, power amp, tuner, cassette deck, CD player and speakers. It can be done but I'm not sure how it would sound!*

* Actually, it would sound amazing, thanks to the 8 pairs of VU meters, as everyone knows they improve the sound.

VU meters are a waste of space on anything. If you want meters you want PPMs. 8-]

My lovely old ex-BBC Glensound desk has LED PPMs. Best of both worlds - blingtastic and useful!