Quick noob question about loops/bypasses/outputs

[DrJon]

Quick question: I see that some amps like the Gilmore Lite, Channel Islands VHP-1, etc. have loop out RCA plugs. How does it work to bypass the amp? You have your source input to the amp. And if, say, you want to bypass the amp and listen through speakers do you have to unplug the headphones? And what do you do about the volume when bypassing? Thanks.

 

[mrarroyo]

It depends on the amp. For example on the Heed CanAmp and the Musical Fidelity X-Can V2 or V3 you do not have to do anything. You plug the output of your source to the imput of the amp, and then right besides it there is an adjacent set of RCA plugs from which you take the signal and feed it to your speaker receiver.

Othe amps like the Mapletree Ear Purist + HD have a passive preamp feature. In it you do as above but the volume pot needs to be used to either increase or decrease the level of the signal being fed to the speaker receiver. The reason is passive is that the Mapletree does not have to be turned on.

 

[sacd lover]

Quote:

Originally Posted by DrJon Quick question: I see that some amps like the Gilmore Lite, Channel Islands VHP-1, etc. have loop out RCA plugs. How does it work to bypass the amp? You have your source input to the amp. And if, say, you want to bypass the amp and listen through speakers do you have to unplug the headphones? And what do you do about the volume when bypassing? Thanks.

DrJon,

The loop out is a pass through. The signal from the source bypasses the amp completely; including the volume control.

The loop out is passive and works whether the amp is on or off.

The line level signal from the source is essentially split at the headamps input. Next .... the IC from the headamps loop out sends the same signal to the receiving amp, preamp, integrated amp etc...

The volume is controlled by the receiving units volume control.

The headphones are not in the loop outs signal path .... so it makes no difference if the headphones are connected or not when you listen to speakers.

 

[DrJon]

Thanks guys. I think I understand the concept of a passive bypass (redundant, I guess). So if, say, you have source -> amp -> bypass -> speakers, the speakers get the signal untouched by the amp, Unless the volume control knob is in play. In which case you have to turn on the amp and the knob controls output signal strenght. (At this point it's a preamp.) Correct?

But what if you simultaneously have the headphones and speakers connected. Does this mean both the speakers and headphones are getting the sound? Maybe if the amp is turned off, only the speakers get the sound via the bypass. But if the amp is on, both the speakers and headphones get sound.

I’m trying to have sound in either the speakers or the headphones, but not both at the same time. And my Klipsch computer speakers don't have a power button. And the volume knob is all scratchy, so I can't turn that up and down as needed. I may built my own switch box. But if an amp with a loop/bypass will do the trick, maybe I can just get one of those.

Thanks for the help!

 

[sacd lover]

Quote:

Originally Posted by DrJon Thanks guys. I think I understand the concept of a passive bypass (redundant, I guess). So if, say, you have source -> amp -> bypass -> speakers, the speakers get the signal untouched by the amp, Unless the volume control knob is in play. In which case you have to turn on the amp and the knob controls output signal strenght. (At this point it's a preamp.) Correct? Thanks for the help!

No, the loop out never acts as a preamp. The loop out remains a line level signal. The volume pot only controls the volume of the headphones and nothing else.

 

[mrarroyo]

Quote:

Originally Posted by sacd lover No, the loop out never acts as a preamp. The loop out remains a line level signal. The volume pot only controls the volume of the headphones and nothing else.

Actually it does depend on the amp. As I stated above in the case of amps like the Heed and the Musical Fidelity no. However in the Mapletree Ear Purist + HD100 which I have the unit is also a passive preamp and thus the volume pot has an effect on the signal being sent to an amp (speaker).

 

[sacd lover]

Quote:

Originally Posted by mrarroyo Actually it does depend on the amp. As I stated above in the case of amps like the Heed and the Musical Fidelity no. However in the Mapletree Ear Purist + HD100 which I have the unit is also a passive preamp and thus the volume pot has an effect on the signal being sent to an amp (speaker).

A passive preamp is not a loop out. A true loop out is a bypass and never controls volume.

 

[DrJon]

Thanks for the info, fellas. I think I'm getting it.

I was trying to avoid having to make a switch box to have the audio out of my computer switch between the speakers and the headphone (with amp). But I think I may have to make the switch box. I'll add some cherry to my current wood order. The switch box should be pretty, except that I can't find a switch or knob that is really cool looking.

On a related note, I was thinking about picking up a Gilmore Lite or Channel Islands VHP-1 as my first headphone amp. They have loops or bypasses or whatever. The amp I really want is the Mapletree. But I somehow don't like the case and plastic knobs. So if I'm going to go tube amp, I want to make a new wood and metal case for it. But I'm so busy, I don't know when I can get to such a project (Xmas?).

 

[sacd lover]

Quote:

Originally Posted by DrJon The amp I really want is the Mapletree. But I somehow don't like the case and plastic knobs. So if I'm going to go tube amp, I want to make a new wood and metal case for it. But I'm so busy, I don't know when I can get to such a project (Xmas?).

How about something like this?

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[DrJon]

Quote:

Originally Posted by sacd lover How about something like this? [/

I know I know. I've been oogling that amp for a while. Amazing work. Kudos to Voodoochile. And I must be getting old if I'm oogling electronics, versus other things.

I think I could make something, say, halfway as ncie as between the stock Ear+ and Voodoochile's work. The sticking point for me is finding nice knobs. Not easy. Then how to make a covering for the transformer (?- the things sticking up in back).

If I work slowly, I can do the woodworking OK. And I found a local place that can cut the steel as needed, if I make a template. But my electronics knowledge is scant. Not sure how to mount the headphone pulg, knobs, etc. into a thick wood panel.

One idea is to paint and polish the metal parts to a piano gloss black. Could be nice, but I'm not sure. The mirror polished steel is nice, but only if I could get other parts to match.

Hmmm...

 

[Jahn]

indeed. the Melos has a passive out, an active out, and a loop out. the passive out bypasses the tube gain stage, and sends a line signal out, but is controlled by the vol knob still because hey, it's still amped. the tube gain stage sends a nice juicy active gain to the line signal out, and is controlled by the vol knob.

the two selections above require internal amping, and therefore the amp must be on. but the loop out (on the melos it's called the Tape Out, how quaint) is just a passthrough, and will send an unmolested signal from the source line output to...wherever. no matter if the melos is on or off, totally unaffected by the vol knob. since the melos' amp isn't touching that signal, passive or active-wise.

 

[sacd lover]

Quote:

Originally Posted by Jahn indeed. the Melos has a passive out, an active out, and a loop out. the passive out bypasses the tube gain stage, and sends a line signal out, but is controlled by the vol knob still because hey, it's still amped. the tube gain stage sends a nice juicy active gain to the line signal out, and is controlled by the vol knob. the two selections above require internal amping, and therefore the amp must be on. but the loop out (on the melos it's called the Tape Out, how quaint) is just a passthrough, and will send an unmolested signal from the source line output to...wherever. no matter if the melos is on or off, totally unaffected by the vol knob. since the melos' amp isn't touching that signal, passive or active-wise.

I think you have it covered Jahn. The only difference with my old Gilmore v2-se was my passive did not have to have the amp on to work.