Question regarding amplifier plug-in location

[Shintsu]

I have heard some claim some amount of loss or some nonsense by not having your amplifier directly plugged into an outlet (i.e. plugged into the back of a preamp). Currently, I have my amp hooked up to a switched port on my preamp. Makes things nice and easy - I power on the preamp and then on comes the amp (manual switch so I always have it in the on position).

I learned as a beginner not to turn on the amp before the preamp. I used to have a Luxman L-480 integrated amp that I was going to use as a preamp but it didn't have a polarized plug on the back and my Adcom would not work with it. So I tried turning the Luxman (setup as a preamp) on and waiting for it to warm up then powering on the Adcom and every time I got a POP from my speakers. Didn't like that, so I sold the Luxman and purchased the NAD preamp and plugged the Adcom into the back of the NAD so I couldn't ever turn it on without the preamp powering it first. Nasty pop eliminated, works like a charm.

Now how exactly is this supposedly "robbing" power from my amp? The amp is a little on the overpowering side for the size of my room and is more than able to become loud at a relatively low position on the volume knob. Is it doing some other sort of harm to the sound of the system? My C3 power filter has a spot specifically for the amplifier but as of current I just have the preamp plugged in its place. All my equipment is chained off the NAD except the TV and nothing has given me any problems.

Just a question of curiosity of whether such a claim had any credibility.

 

[TLS Guy]

I have heard some claim some amount of loss or some nonsense by not having your amplifier directly plugged into an outlet (i.e. plugged into the back of a preamp). Currently, I have my amp hooked up to a switched port on my preamp. Makes things nice and easy - I power on the preamp and then on comes the amp (manual switch so I always have it in the on position).

I learned as a beginner not to turn on the amp before the preamp. I used to have a Luxman L-480 integrated amp that I was going to use as a preamp but it didn't have a polarized plug on the back and my Adcom would not work with it. So I tried turning the Luxman (setup as a preamp) on and waiting for it to warm up then powering on the Adcom and every time I got a POP from my speakers. Didn't like that, so I sold the Luxman and purchased the NAD preamp and plugged the Adcom into the back of the NAD so I couldn't ever turn it on without the preamp powering it first. Nasty pop eliminated, works like a charm.

Now how exactly is this supposedly "robbing" power from my amp? The amp is a little on the overpowering side for the size of my room and is more than able to become loud at a relatively low position on the volume knob. Is it doing some other sort of harm to the sound of the system? My C3 power filter has a spot specifically for the amplifier but as of current I just have the preamp plugged in its place. All my equipment is chained off the NAD except the TV and nothing has given me any problems.

Just a question of curiosity of whether such a claim had any credibility.

You are doing it correctly. The preamp has practically no power draw, so it is no different to plugging it into the wall. Sounds like an excuse for some snake oil dealer to sell a power cord.

It really is a shame that this sort of BS has become prevalent and building since the 80s in this hobby of audio. I think it relates to a very poor job of science education in the school system. I just can't imagine anybody falling for that nonsense back in the fifties and sixties.

 

[Adam]

I didn't look into your particular pre-amp, but I want to make a remark for those with receivers that are reading this. Every receiver that I've seen so far (so, that doesn't mean every one in existence) has a current limit on their auxilary power outlets - generally one amp. Therefore, be careful plugging equipment that draw higher current (such as amps) into those outlets.

 

[TLS Guy]

I didn't look into your particular pre-amp, but I want to make a remark for those with receivers that are reading this. Every receiver that I've seen so far (so, that doesn't mean every one in existence) has a current limit on their auxilary power outlets - generally one amp. Therefore, be careful plugging equipment that draw higher current (such as amps) into those outlets.

His preamp is an old unit. Back then the outlets were usually designed to power an amp. These days we have moved to 12 vol trigger turn on, which is really a better approach.

His amp is 80 + 80 8 ohm. He has been using that outlet without blowing the line fuse, so I thought I was fairly safe thinking that outlet has enough power for his amp.

The only issue is that the back EMF at switch on/switch off, could shorten the life of the power switch on the preamp. However if the switch contacts are shorted with a good capacitor, to contain the surge and minimize arcing, then the risk is low.

By the way congratulations on making Warlord. I think you can type a lot faster than I can!

 

[PENG]

IMHO Adam made a sound advice. We should not make comments related to electrical safety (even somewhat remotely) based on assumptions. I suggest the OP check the rating of that outlet first. I agree older preamps typically have outlets rating higher than modern multichannel receivers but there is no guarantee they are rated for 15A or 1800 VA. I have one that is rated for only 800 VA, not even half of the rating of a 120V wall outlet.

 

[Shintsu]

Thanks guys. Information about the outlets on the preamp as per manual says the two switched plugs are 120V 60Hz Total 4.8A 575W Max.

 

[TLS Guy]

Thanks guys. Information about the outlets on the preamp as per manual says the two switched plugs are 120V 60Hz Total 4.8A 575W Max.

That is just about enough for that amp at full power. However an amp never is at continuous full power on program, so you have reserve. So the outlet will provide at least five times the quiescent current that amp draws. You are fine.

 

[Shintsu]

That is just about enough for that amp at full power. However an amp never is at continuous full power on program, so you have reserve. So the outlet will provide at least five times the quiescent current that amp draws. You are fine.

So, how much wattage would I need stereo for it to become a problem? I can't foresee it being a problem - 80 watts in this small room is overkill as is shown every time I turn the volume up even slightly and it's too loud (I'd say at the 9 o'clock position it is pretty loud - I never go any higher). Heh, if I turn on muting it becomes much more controllable though.

While I'm speaking about my amp, is there any benefit to getting a lower powered amplifier since I don't need the extra power in this room? I'm thinking a good 30-50 watts per channel would be enough in this room. I just happened to find this and thought 80 watts x 2 was a good starter amp (which this is - the first amp I've bought for $125 several months ago). I just find it's hard to find something lower wattage that isn't vintage (pre-80's) or that isn't a really cheap looking model.

 

[TLS Guy]

So, how much wattage would I need stereo for it to become a problem? I can't foresee it being a problem - 80 watts in this small room is overkill as is shown every time I turn the volume up even slightly and it's too loud (I'd say at the 9 o'clock position it is pretty loud - I never go any higher). Heh, if I turn on muting it becomes much more controllable though.

While I'm speaking about my amp, is there any benefit to getting a lower powered amplifier since I don't need the extra power in this room? I'm thinking a good 30-50 watts per channel would be enough in this room. I just happened to find this and thought 80 watts x 2 was a good starter amp (which this is - the first amp I've bought for $125 several months ago). I just find it's hard to find something lower wattage that isn't vintage (pre-80's) or that isn't a really cheap looking model.

The amp you have is fine and a good one. I would leave everything alone.

 

[Shintsu]

Yeah, I thought about it more and that seemed wisest. One question though, someone told me with the really high powered amps/good preamps the volume doesn't start getting loud until the halfway mark on the volume. I'd really like that quality since it makes the level more adjustable and linear. As opposed to now where it's linear from minimum volume up to 8 o'clock. It's just annoying as I find if I use the remote it makes it go from just not quite loud enough to way too loud then back down to too quiet again. It's really finnicky about position. Everything from a Technics SA-EX140 100 wpc receiver, to a 72 wpc Luxman L-480, to this Adcom 80 wpc - all have not been very linear as far as volume is concerned.

What would I need to change to achieve this quality (Amp, Preamp, or ???)?

 

[TLS Guy]

Yeah, I thought about it more and that seemed wisest. One question though, someone told me with the really high powered amps/good preamps the volume doesn't start getting loud until the halfway mark on the volume. I'd really like that quality since it makes the level more adjustable and linear. As opposed to now where it's linear from minimum volume up to 8 o'clock. It's just annoying as I find if I use the remote it makes it go from just not quite loud enough to way too loud then back down to too quiet again. It's really finnicky about position. Everything from a Technics SA-EX140 100 wpc receiver, to a 72 wpc Luxman L-480, to this Adcom 80 wpc - all have not been very linear as far as volume is concerned.

What would I need to change to achieve this quality (Amp, Preamp, or ???)?

Your problem is sensitivity and gain. You have an older unit. Domestic units used to have outputs in the 100 mv range. Now it has gone up to the 1 to 2 volt range. I think you said you preamp had a button that made things quieter. That is really changing the gain I suspect, so leave it engaged.

 

[Shintsu]

Your problem is sensitivity and gain. You have an older unit. Domestic units used to have outputs in the 100 mv range. Now it has gone up to the 1 to 2 volt range. I think you said you preamp had a button that made things quieter. That is really changing the gain I suspect, so leave it engaged.

Well, it's really muting. The only reason I hate doing this is I fear I'll bump it and given how loud the speakers are at lower levels, it has to be up much higher blow the speakers up (Not to mention hurt my ears). It's a rather cheesy way to achieve this, and I can see myself with it at a moderate level going "Hey, let's mute it *PUSH* OH NO! I forgot I already had muting on and just turned it off!" *POP*. I would be as cautious as I could but I could still see it happening one time I'm not paying attention and that's all it takes.

I thought some of the older Carver stuff along with others had pretty linear volume like so? I know I've heard old equipment that is linear so I wouldn't imagine only newer stuff would have it. How old is my preamp really - I thought it was 90's which isn't really that old.

 

[highfigh]

You are doing it correctly. The preamp has practically no power draw, so it is no different to plugging it into the wall. Sounds like an excuse for some snake oil dealer to sell a power cord.

It really is a shame that this sort of BS has become prevalent and building since the 80s in this hobby of audio. I think it relates to a very poor job of science education in the school system. I just can't imagine anybody falling for that nonsense back in the fifties and sixties.

I think it's more a situation of the marketing department being given free reign to make it up as they go along, with little or no editing from the company management.

 

[highfigh]

Yeah, I thought about it more and that seemed wisest. One question though, someone told me with the really high powered amps/good preamps the volume doesn't start getting loud until the halfway mark on the volume. I'd really like that quality since it makes the level more adjustable and linear. As opposed to now where it's linear from minimum volume up to 8 o'clock. It's just annoying as I find if I use the remote it makes it go from just not quite loud enough to way too loud then back down to too quiet again. It's really finnicky about position. Everything from a Technics SA-EX140 100 wpc receiver, to a 72 wpc Luxman L-480, to this Adcom 80 wpc - all have not been very linear as far as volume is concerned.

What would I need to change to achieve this quality (Amp, Preamp, or ???)?

That's because of the taper of the control. Audio taper and linear taper are wildly different and it can definitely be annoying.

 

[TLS Guy]

That's because of the taper of the control. Audio taper and linear taper are wildly different and it can definitely be annoying.

I never saw a volume control that was taper. I have only ever seen log.

 

[TLS Guy]

Well, it's really muting. The only reason I hate doing this is I fear I'll bump it and given how loud the speakers are at lower levels, it has to be up much higher blow the speakers up (Not to mention hurt my ears). It's a rather cheesy way to achieve this, and I can see myself with it at a moderate level going "Hey, let's mute it *PUSH* OH NO! I forgot I already had muting on and just turned it off!" *POP*. I would be as cautious as I could but I could still see it happening one time I'm not paying attention and that's all it takes.

I thought some of the older Carver stuff along with others had pretty linear volume like so? I know I've heard old equipment that is linear so I wouldn't imagine only newer stuff would have it. How old is my preamp really - I thought it was 90's which isn't really that old.

It would be in a more linear part of the control, if we make an attenuator for the lead between pre amp and amp. What is the voltage from your pre amp output at full modulation, and what is the source impedance? It should be in your manual. I also need to now the input voltage of your amp for full modulation and the input impedance.

If you give me that data, I can get you sorted out if you want.

 

[Shintsu]

Sorry, I'm still a newb when it comes to that stuff but I'll list what sounds like what you're talking about and you may know from that (I'll throw in some stuff that sounds helpful as well):

Pre-amp
Input Impedance R = 50k
C = 200pF

Maximum Input Level = <5V

Maximum Output Level > or = 5V


Amp
Input Sensitivity for 1 watt = .1 Volts
for 80 watts = .9 Volts

Input Impedance = 49.9k ohms

Gain = 29 dB

It doesn't have input voltage on here though.

 

[TLS Guy]

Sorry, I'm still a newb when it comes to that stuff but I'll list what sounds like what you're talking about and you may know from that (I'll throw in some stuff that sounds helpful as well):

Pre-amp
Input Impedance R = 50k
C = 200pF

Maximum Input Level = <5V

Maximum Output Level > or = 5V


Amp
Input Sensitivity for 1 watt = .1 Volts
for 80 watts = .9 Volts

Input Impedance = 49.9k ohms

Gain = 29 dB

It doesn't have input voltage on here though.

There is you problem. You have a 5:1 voltage mismatch between the output of your preamp and the input sensitivity of your amp. You need to reduce the output from your preamp to a fifth of its current level.

At the input of your amp you need to have an 80 K ohm resistor in series with a 20 K Ohm resistor, between the live output from the preamp and ground. The live from the preamp needs to connect to the free end of the 80 K ohm resistor, and the ground to the free end of 20 K ohm resistor. The input to your amp needs to be between ground and the the connection between the 80 and 20 K resistors. A network like that is called an L-pad. You would need one for each channel.

Can you accomplish this?

 

[Shintsu]

There is you problem. You have a 5:1 voltage mismatch between the output of your preamp and the input sensitivity of your amp. You need to reduce the output from your preamp to a fifth of its current level.

At the input of your amp you need to have an 80 K ohm resistor in series with a 20 K Ohm resistor, between the live output from the preamp and ground. The live from the preamp needs to connect to the free end of the 80 K ohm resistor, and the ground to the free end of 20 K ohm resistor. The input to your amp needs to be between ground and the the connection between the 80 and 20 K resistors. A network like that is called an L-pad. You would need one for each channel.

Can you accomplish this?

Being completely honest, no. Heh, that went right over my head...I believe I have always equated what you're talking about to meaning I just need different equipment. Is it possible to describe this in layman's terms/with pictures or diagrams? Sorry, I appreciate the help I'm just a bit confused.

 

[walter duque]

If you're max is 575 watts of your pre-amp and you're amp needs more than 5.22 amps at max output then you should change to an outlet. 575 watts is not a lot. My poweramp needs 5800 watts at max power.