Tone defeat / source direct. Is there any point to it?

After five years of ownership I have just discovered that my Arcam A-18 amplifier has a tone defeat function. Since buying my Dali Opticon 2 speakers a few weeks ago I find that I am running bass and treble flat (i.e. at zero) all the time anyway. Will using tone defeat therefore make any difference to the sound? Does tone defeat simply set the tone controls to zero or, in shortening the circuit path, does it actually make a qualitative improvement?

 

Well, depending on how the circuit is implemented, you'll bypass the tone pot or pots and whatever other circuitry is associated with the tone controls, so, yeah, you very well could have a degree or two greater transparency, low level detail, and image focus. Click it and listen. You're not using the tone controls anyway, so why keep the tone circuit in the chain if you have a bypass? But you'll have to tell us how it sounds. Personally, I'm one of those old school audiophiles who is a believer in getting extraneous circuitry out of the signal chain. How much changes of transparency of this sort will be obvious in part will depend on the noise floor in your listening room and the kind of music you're listening to -- if you're listening to hot, rock recordings make with multitrack overdubbing of parts recorded in iso, you might not hear the level of difference you might hear with more dynamic music with p to ppp passages and recordings that attempt to capture the performance space and image location in that space.

 

This particular receiver is not old school - the audio doesn't go through a bass or treble knob. Instead, bass and treble is a function of the Rohm Semiconductor BD3811K1 analog sound processor chip (still using external passive components though). Bass or Treble can only be adjusted in 2dB steps, and the gain setting can be +/- 2dB in error also - not so precise. Bypass is a true bypass (if the firmware does it right), but it looks like the "bass boost" component is still in the mix.

Follow the audio from the lower left - it goes through the tone components (and two more op-amps) only if the switches are engaged.



Almost everything on this receiver, volume, input selection, etc, is done inside this one IC.

This part of your receiver is all analog, but other AV receivers might put all audio through a DSP, with an ADC/DAC - digital processing which is only bypassed in a "pure direct" mode.

... more about how the tone circuit works in the chip:

 

As @chervokas wisely states, only if you can hear the difference. In my case, rarely is anything bypassed as I might leap for the tone control and eq at any time given the nature of the recordings I listen to.

 

Arcam says it’s a true bypass, so engage it to find out if you can hear an improvement. No reason to hesitate - you won’t hurt anything - so you might as well find out if you like your system sound with the bypass engaged.

 

I don't know the circuits, but my old integrated had one and the shift is sound was subtle but worth while. My Oppo disc spinner has an audio only selection that shuts down the video circuitry. It is also noticeable.

 

Thanks for the all the thoughtful and interesting replies! I suppose the proof of whether there is any qualitative improvement in sound is in the listening. I shall spin a few discs this evening and report back tomorrow...

 

I've got an old Arcam Alpha 7 integrated amp in our second system, it does sound a bit better in "direct" mode- imaging and resolution is improved.

 

It's definitely worth trying. I have source direct on all the time on my Denon amp. It does give a shade more transparency.

 

Reporting back...

I didn't have time last night to do a completely exhaustive trial (a whole evening flicking the direct source button on my remote would probably drive me to distraction in any case!), but I did experiment on two or three tracks. First of all I can say without hesitation that if there is a difference between a) running bass and treble flat with the direct source switched off and b) running the amp with the direct source switched on, it is miniscule...so small as to be virtually undetectable. After that you are in the realms of going with gut feeling based upon the tiniest of margins which may, in all honesty, be a figment either of one's imagination or prejudice.

Flicking backwards and forwards I just felt more comfortable with the direct source switched 'off'. The sound certainly wasn't any worse with it switched off and I just had the tiniest notion that the sound may have had a bit more 'air' without the tone defeat. Pure gut feeling and not something I could demonstrate to someone or a difference that is in the remotest sense quantifiable.

I have pretty sensitive hearing. I find the bass and treble increments on the Arcam's tone controls are waaay too large for my liking. I obsess about miniscule differences in bass and especially treble settings. When it comes to the tone defeat setting I couldn't really hear anything at all.

 

Glad you found what worked for you. If I was designing the software for this device, I would put the sound chip in tone bypass mode automatically when bass and treble are set at 0.

That might be what is done, and the direct button is otherwise used for turning off tone while remembering the previous tone settings.

 

Oh yes! These so much talked-about “tone defeat”, “source direct” etc. make out of you a real “slave” of LSs’ objective spectral electro-acoustical parameters and of their reciprocity effects with the acoustical reaction of the listening room in the chosen listening point.

Because they deprive you of any possibility to manage the real frequencies distribution of the sound spectrum (i.e. band equalization) in this chosen listening point.

 

Thank you. That's cleared everything up nicely. These things are so much easier to understand when they're explained in plain old English!

 

I've a feeling that's why those switches are there. For those that find such controls anathema.

 

I think what you’ve discovered is that Arcam’s tone control circuits are superbly well designed. The tone defeat may be incrementally better by technical measurement, but too small to hear in your particular listening room. Good news, actually. I’d say it’s yet another reason that the Arcam A18 remains a fine integrated amp.

 

I'm pleased you rate it. My impression seems to be that whilst the professional / magazine reviews of the A-18 were positive, people on hi-fi forums tend to regard it less favourably. 'Boring' seems to be a typical description that I come across.

 

Naturally transparent to the source is how I describe the A18 and the newer FMJ generation A19 through the A39. I’m not personally completely happy with the monster A49 mind you, but that’s a whole other thread.

 

English is a foreign language to me. I’d say quite foreign. The only thing I wish, in technical forums like this, is to be understood in some technical matters of English-speaking forums, where I have something to express. According to my personal experience.

So, in this case, your irony missed. Good luck with your perfect English!

I stay open to concrete technical questions concerning these so much talked-about “tone defeat / source direct” etc. If there are some, besides my “plain English”.

 

Sorry, Fedot. I really didn't mean to offend. It is easier when we communicate face to face to understand each other. I really appreciate you coming onto this thread and contributing.

 

Exactly. How the "defeat is implemented is everything. FWIW: I have found that tone defeats can have a noticeable impact on transparency too. But this is improvement is not audible in all designs, nor in all systems.

 

My Yamaha A-S501 has a Pure Direct switch and it's always on. Gimme what's coming' through the wires only, warts and all, sez I!

 

I thought direct mode was so you could leave the tone controls at the desired position and defeat them without remembering where they were.
But then again I am a multiple offender 2t’s and 2b’b baby!