Why is 'main in' on amplifiers no longer common?

[xlinknz]

Lots of amps from the 80s to 90s had a separate main in and pre out e.g. NAD etc but now it very rare

This allowed integrated amps to be used as power amps by connecting a pre amp or other amp to main in and bypassing the integrated amps pre amp section, now I see many class D amps have pre out but no main in which is odd as many class D amps are very powerful do don't really need pre out but would benefit from main in to allow more inputs

Why is main in no longer common?

 

[Mart68]

My guess is that it's because the marketing side has shifted from selling on features and facilities to selling on audiophile nonsense.

For example:

• Front face in 10 mm brushed, micro-blasted and anodised aluminium, with high-precision engraving.
• Heatsink and buttons in billet aluminium.
• 2 mm steel frame.
• One toroïdal transformer: 1050 VA for audio section
• One transformer: 1.6 VA for control logic.
• Integral double mono structure:
  – Separate windings for the tracks.
  – 1 attenuator per channel (with switched resistors).
• Bipolar transistor input stages.
• Current sources with bipolar transistors and LEDs to ensure perfect voltage stability.
• Darlington transistor driver stages.
• Audio stages with perfectly symmetrical structure and very low counter-reaction.
• Power stages with MOS FET transistors (8 per channel) are rigorously matched.
• Precise adjustment of the balance and the possibility of memorising it.
• Possibility of choosing the standby mode: Low consumption or preheating.
• Configurable button backlighting.
• High contrast OLED display: ON or OFF mode (after 5 seconds of inaction).

That amp does have pre-out but not main in, pre-out is not even mentioned.

 

[Berwhale]

Why is main in no longer common?

Perhaps because the vast majority of 'integrated' amplifiers sold today are AVRs and it makes very little sense to bypass all of their pre-amplifier and and processing capabilities.

 

[Redacted]

It's probably because many modern amps at affordable prices are very powerful, and if people plug things into a 'main-in", they'd blow their speakers (or even the amps) by not really understanding what they are doing. And then customers moan. Remember that these days, most "HiFi" users are 'consumers' rather than 'enthusiasts' and there is no lower limit for stupidity! Increasingly so.

 

[DonH56]

My opinion!

My guess is a combination of market demand and manufacturing cost, plus the safety concerns voiced above. Preamp outputs and main amp inputs have both become much less common IME. Moving to AVRs with many channels means a lot of extra connectors and space for those connectors that can be used for other inputs like HDMI and so forth. Most consumers do not buy external amplifiers, or want large boxes, so the cost of including all those connectors (money and rear panel space) is wasted and puts you at a disadvantage compared to the competition. I realize that does not directly address the lack of main in connectors but is my high-level view.

Many (most?) AVRs have analog (line) inputs that can be used for "main in". Often those offer a choice of whether to convert to digital for processing like room correction and other surround modes, or a "direct" path that simply passes the analog inputs to the power amps. I do not know about your model, but my old Pioneer SC-25 converted all inputs to digital (input to an ADC) and gave the option of further process or not before a DAC converted back to analog. Other AVRs would allow you to completely bypass data conversion for analog inputs. Given line inputs already available, then extra connections to just the power amps are redundant, or considered so by manufacturers. You can use you integrated amp or AVR as a power amp by using an existing line input (if present -- I've noticed even those have been reduced or even eliminated on some AVRs).

IME/IMO - Don

 

[egellings]

My guess is that it's because the marketing side has shifted from selling on features and facilities to selling on audiophile nonsense.

For example:

• Front face in 10 mm brushed, micro-blasted and anodised aluminium, with high-precision engraving.
• Heatsink and buttons in billet aluminium.
• 2 mm steel frame.
• One toroïdal transformer: 1050 VA for audio section
• One transformer: 1.6 VA for control logic.
• Integral double mono structure:
  – Separate windings for the tracks.
  – 1 attenuator per channel (with switched resistors).
• Bipolar transistor input stages.
• Current sources with bipolar transistors and LEDs to ensure perfect voltage stability.
• Darlington transistor driver stages.
• Audio stages with perfectly symmetrical structure and very low counter-reaction.
• Power stages with MOS FET transistors (8 per channel) are rigorously matched.
• Precise adjustment of the balance and the possibility of memorising it.
• Possibility of choosing the standby mode: Low consumption or preheating.
• Configurable button backlighting.
• High contrast OLED display: ON or OFF mode (after 5 seconds of inaction).

That amp does have pre-out but not main in, pre-out is not even mentioned.

That transistor is bipolar? Poor thing. Some Valium could help that transistor.

 

[john61ct]

I stick to Power Amps, no digital anything. I might let it slide to include a volume level, used strictly as gain adjustment handy level matching against all the other power amps.

I have no use for AVRs, if I wanted proprietary mch decoding I'd go AVP only but dog they're unreasonable overpriced!

Something like Wiim Amp Ultra would indeed have greater value if it allowed stereo out at line level concurrently with the speakers, especially if the DSP did stereo bass management.

But tbh I happily use Wiim Ultra as stereo source and switcher and no problem if that + my choice of power amp may end up costing a little more, freedom is not free

 

[JeffS7444]

Today's desktop-sized "integrated amps" are actually power amplifiers equipped with volume control and multiple inputs. Except as a centralized control center, there is seldom a need for actual preamplifiers, given that most of today's source components have low output impedance, and work just fine when plugged directly into the amplifier.

Trivial information I learned the hard way: Typical pre-out from a vintage receiver or integrated can have mediocre output impedance, so best to keep cables short. Extra money spent on a separate preamplifier got you a line driver stage, which worked much better with longer cables.

 

[xlinknz]

All thank you for your replies

As some of you may know the amps that did have main in and pre out usually had a pair of jumpers like this:

These required to be installed to use of the amplifier without a separate pre amp or power amp (or disconnected to allow the amp to be used as a power or pre amp only)

@Redacted I found even on my modern Fiio DAC it had PO button on the DAC's remote which bypasses the DACs volume control and send max signal to a connected power amp, a dangerous feature for the uninformed!

All, What I find odd is many class D amps from China have an aux or pre out and I am not sure why as most of them are 100w+ into 8 ohms with a 48v 5A power supply so why would anyone want to use a 100-300w amp as a pre amp?

I am considering a class D amp to use as a power amp for a vintage pre amp that has multiple inputs e.g. phono. Not many class D's have more than 1 analogue RCA input

 

[Redacted]

All, What I find odd is many class D amps from China have an aux or pre out and I am not sure why as most of them are 100w+ into 8 ohms with a 48v 5A power supply so why would anyone want to use a 100-300w amp as a pre amp?

I am considering a class D amp to use as a power amp for a vintage pre amp that has multiple inputs e.g. phono. Not many class D's have more than 1 analogue RCA input

A power amp with an an aux or pre output? Are you thinking about an integrated amp that uses a class-D power amp built in? Please provide us with a link to illustrate what you have seen....

Most pre-amps, bar single-usage one like phono amps or headphone amps, have multiple inputs that are selectable, and have a line-level output controlled by a volume mechanism - it's kinda how you define a typical pre-amp. Generally, power amps, class-D or otherwise have one input - but this may be a choice between balanced (XLR) pair and unbalanced (RCA) pair. Many power amps also have a some user-selectable choices concerning input sensitivity (voltage)

 

[xlinknz]

A power amp with an an aux or pre output? Are you thinking about an integrated amp that uses a class-D power amp built in? Please provide us with a link to illustrate what you have seen....

Just 2 examples are the Ampapa D1 (reviewed here) has a 3.5mm pre out, the Fiio Level One has dual RCA pre outs. Perhaps the issue is terminology as often these class D amps are called power amps, my point is these powerful type of class D amps whatever they are called have pre out and I'd welcome they had main in or an ability to bypass their pre amp stages

 

[Redacted]

Ampapa D1 and Fiio Level One both look like integrated amps to me - line-level in, 300W speakers outs, using TPA3255 chips for the power amp section. I'm not following your idea at all - perhaps it's lost in translation?...

 

[Mean & Green]

My personal opinion and please keep in mind it is an ‘opinion’. Modern HiFi is junk compared to 20 years ago. We live in a dumbed down society that has no technical prowess at all.

Look at old amplifiers from the 70s with ‘Tone’, ‘Turnover’, ‘Monitor’, ‘Subsonic’, ‘Loudness’. Not many people today would have a clue what any of it was for, yet back then it was standard issue. People had some gumption and actually cared more about listening to music once upon a time. They knew how to operate and connect a system. Now as some others have pointed out a ‘Main In’ on an integrated amp now would lead many to blow up their speakers with a full level signal wondering why the volume dial on the front panel isn’t functioning.

In other groups and forums, it’s common to encounter people replacing an old faulty integrated with a new modern one only to find it has not enough RCA inputs, and no way to incorporate their EQ. The ‘budget’ end of the market today from the legacy brands offer worse SINAD than my 15 year old NAD C326 BEE and with less connectivity.

I decided to rebuild an old NAD C350 for my second system that I’ve had for 26 years, as it was cheaper to perform a recap and replace faulty relays than replace it with something new. It is better technically than modern equivalents, along with the connectivity that I require. I couldn’t replicate it with anything new at a comparable RRP. I appreciate I am in the minority and sound like an old fart, but I don’t want DACs and streaming in my amplifier.

I do not agree with the comments that most are using AVRs now, it’s is still a fallacy that AVRs are inferior to 2 channel amps in the audiophile world and this advice still gets pushed onto newcomers outside of ASR. Also not everyone wants or needs the extra functionality of a multichannel component.

There are still many ‘traditional’ integrated amps, but they do not offer the same connectivity as old ones. Much fewer RCA inputs, no ‘Pre Out - Main In’, even ‘Sub Out’ is not that common. Recording/Monitor/Processor loops? Forget it. It’s all Bluetooth and MM Phono inputs with a selection of SPIDIF/toslink. It seems analogue only amplifiers with good SINAD are now ‘boutique’.

 

[Spyerx]

My not very old (509x) Luxman integrated allows this. Has a “separate” button on the front which allows you use use the pre amp and amp sections separately.

I’ve used it to mess around with the preamp of my Eversolo a8.

 

[Chrispy]

To me "amps" means power amps and none had such features. If you mean integrated amps, this was possibly a feature. If you have an actual pre-amp then the power amp is a simple add-on. It is too bad many integrated amps lack such basic features as this, bass managment, etc.

 

[thunderchicken]

I do not agree with the comments that most are using AVRs now, it’s is still a fallacy that AVRs are inferior to 2 channel amps in the audiophile world and this advice still gets pushed onto newcomers outside of ASR. Also not everyone wants or needs the extra functionality of a multichannel component.

Not a fallacy- show me a home theater processor that measures as well as the DIY Class D stereo preamp. I run one of the best AVRs available at any price (Anthem MRX) and it is at least one order of magnitude worse in overall performance. I love the MRX for its simplicity, feature set, and extremely good room correction, but it doesn’t get anywhere near the Hypex preamp.

 

[Chrispy]

Not a fallacy- show me a home theater processor that measures as well as the DIY Class D stereo preamp. I run one of the best AVRs available at any price (Anthem MRX) and it is at least one order of magnitude worse in overall performance. I love the MRX for its simplicity, feature set, and extremely good room correction, but it doesn’t get anywhere near the Hypex preamp.

With what types of inputs, tho?

 

[xlinknz]

Ampapa D1 and Fiio Level One both look like integrated amps to me - line-level in, 300W speakers outs, using TPA3255 chips for the power amp section. I'm not following your idea at all - perhaps it's lost in translation?...

Exactly you cannot use the D1, Level One or similar amps that don't have main in as a true power amp i.e. bypass their preamp and volume circuits. 'Main in' inputs on integrated amps that have them allow the volume and pre amp sections to be bypassed and use the integrated amps power amp section only as @Spyerx has said he can do on his Luxman

Main In or an ability to bypass volume and pre amp section on an integrated amp was common but not anymore

 

[xlinknz]

My not very old (509x) Luxman integrated allows this. Has a “separate” button on the front which allows you use use the pre amp and amp sections separately.

I’ve used it to mess around with the preamp of my Eversolo a8.

oh my that amp all 30kgs of it...

 

[Mean & Green]

Not a fallacy- show me a home theater processor that measures as well as the DIY Class D stereo preamp. I run one of the best AVRs available at any price (Anthem MRX) and it is at least one order of magnitude worse in overall performance. I love the MRX for its simplicity, feature set, and extremely good room correction, but it doesn’t get anywhere near the Hypex preamp.

It is a fallacy, becuse when listing to music it will be audibly transparent. The market I’m talking about outside of ASR don’t care about SINAD. It’s been a myth for decades that an AVR in 2 channel mode ‘sounds bad’. In reality it doesn’t.

It’s also a fallacy that class D doesn’t sound as good as class A/B in ‘audiophile’ circles.