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Phone- >BT Receiver -> C27 -> MC2205 Gain/Volume Settings

M

mtngun

AK Subscriber
Subscriber
Migrating from a Logitech to a 1Mii B06+ due to dropouts of stream.
I was unaware the i Mii BT Reciever/Adapter allowed volume control via the phone.
I previously found it is preferred to always (whatever source) run the MC2205 at Max Gain and to use the C27 Volume control for listening level.
The Logitech that is now out of the loop there was no volume control from phone. The 1 Mii throws me a new twist of allowing it.
I'd like to confirm if it is best for the gear performance set phone Volume from 80% to Max, keep Max Gain on MC2205 and set listening level via the C27.
 
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As long as the level switch on the back of the 2205 is set correctly it seams that you have it all set up in a good config. The only thing I question is the 80% Max setting. If you have other sources you are using I would set this to match their max output based on your ears. I don't think full output will be too much for the pre but the 80% ceiling surely won't hurt anything.

From the user manuals
Mii BT:
  • Analog Output: 3.5mm AUX and 2RCA, offering 2Vrms.
C27:
MAIN OUTPUT 2.5 volts with rated input,
less than 1kohms source impedance, to operate into 22k ohms loador higher.
Maximum output is greater than 10 volts

MC2205:
INPUT LEVELThe input sensitivity of the MC 2205 is 0.75 volts or2.5 V depending on the position of the INPUT LEVELswitch. With indicated voltage applied, the amplifier willdeliver its rated power. All Mcintosh preamplifiers havebeen designed to deliver 2.5 volts output with rated input.For the best signal to noise ratio when using McIntoshsource equipment, always have the INPUT LEVEL switch inthe 2.5 V position and the front panel LEFT and RIGHT/MONO GAIN controls in the fully clockwise position. Ifmore gain is desired the 0.75 V position may be used. Forsource equipment other than McIntosh set the switch inthe position nearest to the stated output rating of the sourceequipment.
 
Thank you! I have the MC2205 set to 2.5v. I appreciate you noting the 2v output of the 1 Mii (which does not exceed the 2.5v input of the MC2205. I'll keep the volume maxed out on the phone and use the C27 for volume control.
It's interesting that the BT converter allows the phone to adjust volume output of the MC2205. I had no idea and not sure I'd ever use the phone to adjust volume.
 
Personally, on amps where the gain/levels are adjustable, usually I set them no higher than necessary to get a good, wide sweep of the volume control to get my max normal playback level.
 
I've often wondered why it's recommended to max gain. It seems doing so leaves a lot of head-room to "blast" speakers (and get power guard to work)..
I'm not super savvy on the circuitry and thought best to ask here. I searched here and www and it's most common to max gain.
I can't wrap my head around how the phone adjusts the output ov the BT converter so that the volume from speakers is "set" by the pre amp and amp. I suppose it is simply less voltage out of BT Converter, and pass through from the Pre amp to the amp is at a lower voltage as well.
 
A couple of things to consider.

McIntosh, in the days of volume (gain) controls on their amplifiers, recommended setting the preamp volume to something like 1:00, then turning the amplifier gains to the max. SPL you expect to use. I’m not entirely sure why but one possibility is that the max gain on the amplifier means amplifying any upstream noise from the preamp with max gain. Later amplifiers eliminated the gain controls on the amplifier, which is what you have with the gain controls max’ed out. I prefer the max’ed out method personally, but I have a quiet preamp, and I no longer have an amplifier with gain controls anyway.

Next is using the BT converter as a volume control. Some of these controls will compress your dynamic range as they decrease gain, some do not. If it compresses and your are frequently running at the low-end of the volume scale you will lose dynamics.
 
SaturationPt said:
A couple of things to consider.

McIntosh, in the days of volume (gain) controls on their amplifiers, recommended setting the preamp volume to something like 1:00, then turning the amplifier gains to the max. SPL you expect to use. I’m not entirely sure why but one possibility is that the max gain on the amplifier means amplifying any upstream noise from the preamp with max gain.
Click to expand...

I believe it's mostly about trying to optimize signal to noise ratio.

Higher signal strength over the inherent noise floor of the gear gives better S/N ratio.

Source level high as you can get without clipping output or input of preamp, preamp as high as you can get it without clipping output or overloading amp input, amp set to max desired level of playback.

That said a lot of gear these days has pretty low noise so it may not matter from a pragmatic standpoint. But, a measurement might show the "old way" works better by the numbers albeit perhaps not audibly significant.
 
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Optimizing signal to noise ratio is a great use for the Gain controls. Also, simply optimizing the Volume control's sweep and position to fit your preferred 'action' expectations is also a reason to deviate from the suggested position. When the kids were young i kept the Gain controls low in case they couldn't help but crank the preamp, or switched inputs without anticipating the volume difference - LOL. There are many situations where the gain knobs come in handy. Maybe you pre amp's volume knob has some balance issues that are better in certain positions.
I have a 2105 and it's Gain controls go to .5V (?) sensitivity at full clockwise position so I hover around the 12 o'clock position on that unit which is where the sensitivity is 2.5V and the Volume knob on the pre feels right.
 
With the above info, I plan to play around with the gain and pre amp vol setting with various input devices. Time for some spreadsheets perhaps.
This will occur through the summer and fall as I now want to check at least 3 TT's, the Receiver once I get an outdoor antenna and maybe rotator (we are very fringe and reception is all by trial even find differences by night/day and weather), the BT Converter, a RR, 8 Tr, Cassette and maybe a CD. I have not explored playlists yet, but have several usb devices that were used in our vehicles due to fringe area and also travel that I may use for occasional. Principally intent is for LP, RR and FM. Friendly gatherings may use the other inputs for less time tending to "flipping".
 
On earlier Mc amplifiers without input sensitivity switching, the 12:00 setting of the GAIN controls provides 2.5 V input sensitivity.

On models with input switching (ie 2.5V or 0.75V) the GAINs are turned fully clockwise to obtain either of those two sensitivities. If highly sensitive speakers are used, it might be advisable to lower the gains somewhat if audible background noise is present.
 
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