Canuck Audio Mart Hifi and Audio ForumCanuck Audio Mart Hifi and Audio Forum
It is currently Tue Sep 25, 2018 6:34 am

All times are UTC - 8 hours




Post new topic Reply to topic  [ 13 posts ] 
Author Message
 Post subject: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 7:34 am 
Offline

Joined: Wed Jun 17, 2015 7:47 pm
Posts: 5
Location: Quebec, QC, CA
Hi!
Question about input/output voltage between my gear. I am switching my amplifier soon to a new one and i wanna know if everything will work well together. Can anyone confirm that it's fine?

My source, DAC is : 2.56V Output. (Audio GD NFB-8)
http://www.audio-gd.com/Pro/dac/NFB8/NFB8EN.htm
//
Im unsure of the value of my pre-amp input? (Yamaha c2a)
The complete specs are here : http://www.thevintageknob.org/yamaha-C-2a.html (click bottom left on specs)
I see 150MV on The AUX in? Which seems pretty low, but i also see a max of 1V (lines)
Output seems to be 2.0V
//
The new amplifier i would get has a 1.4V Input (Mcintosh MC7150)
http://audio-database.com/MCINTOSH/amp/mc7150-e.html

How much flexibility will i have on my preamp to turn the sound on the volume wheel? Would it clip easily? Thanks for the help!

Xeian


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 7:41 am 
Offline
User avatar

Joined: Tue Jun 17, 2008 4:50 pm
Posts: 12406
Location: Toronto, ON, CA
Max input is 1V. Looks like all you need for full output is 0.15 V, and full output from the Pre is ridiculously high.

_________________
I'm sure that the term "resolving" has way more to do with a sense of self worth than any scientific principle. - davinci_redux


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 7:51 am 
Offline

Joined: Wed Jun 17, 2015 7:47 pm
Posts: 5
Location: Quebec, QC, CA
What does this mean?
Im really not an expert on the topic.
Does it mean that my pre is gonna heat a lot? (From the DAC signal)

Between the preamp and the amp, is it fine?


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 7:54 am 
Offline
User avatar

Joined: Tue Jun 17, 2008 4:50 pm
Posts: 12406
Location: Toronto, ON, CA
The input has a max voltage of 1 V. Your unit has above max.

To my understanding, you will overdrive the input stage, causing distortion or perhaps damage.

The output of the preamp is 15 Volts. This is ENORMOUS. With *any* reasonable amp, you will have very little movement on the dial.

_________________
I'm sure that the term "resolving" has way more to do with a sense of self worth than any scientific principle. - davinci_redux


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 8:01 am 
Offline

Joined: Wed Jun 17, 2015 7:47 pm
Posts: 5
Location: Quebec, QC, CA
Im pretty sure the output is 2v, 15 is the maximum.

I think this is the official manual of my pre-amp c2a :
https://img.canuckaudiomart.com/uploads ... lifier.jpg

Im getting worried over here, i dont wanna damage my gear! Damn, i just paid to have the Yamaha c2a fully recapped and serviced Hope it will work.

Anyone else have an opinion on this?


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 11:30 am 
Offline
User avatar

Joined: Tue Jun 17, 2008 4:50 pm
Posts: 12406
Location: Toronto, ON, CA
It says max output is 15V, while sensitivity is 150 mv or 0.15. That is a gain of 100.

Assuming your amp has an input sensitity of 1.5 V, you'll have to keep it under 10% gain.

For a 0.15V input, due to the audio taper, the volume control can be turned to no more than 50% for full power from the amp.

With an input of 2.56 volts, the rotation will be reduced to no more than about 30% -- FOR FULL AMPLIFIER POWER. It's likely that you will be looking at the smallest of rotations -- even smaller if your amp is more sensitive than 1.5 V to full power.

With such a high output, there is no point to having any amplification in the preamp. You should consider using just a buffer. eg. Pass B1. McCormack makes one, there are tube buffers out there etc.... Just unity gain is enough. And you will be able to turn the dial far higher before clipping the amp -- which you probably could with 2.56 volts output.

-- 21 Jun 2018 15:40 --

The other alternative is to buy some attenuators. Basically, just a fixed set of resistors that you put on the preamp-output.

_________________
I'm sure that the term "resolving" has way more to do with a sense of self worth than any scientific principle. - davinci_redux


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 1:43 pm 
Offline
User avatar

Joined: Tue Feb 28, 2006 5:40 am
Posts: 484
Location: Hamilton, ON, CA
Probably the most misleading specs on audio equipment are output level and input sensitivity.
Your DAC's output may be 2V, but it doesn't get that high under normal usage unless the signal it is receiving is at full digital level (0dB). Most digital signals are kept well below this. Besides, that's what the volume control is for. To attenuate the signal to your desired level.
Maximum output on a preamp is very seldom reached. That's just the level where it clips. Again, the volume control is there to control this. Most preamp sensitivity specs are incomplete. They might say something like "200mv" for a line input. Useless unless you know the gain, and/or the output levels. Same with amp specs. An amp with an input sensitivity of 1.5V MUST specify that is the level for max power. If it does not, it is meaningless or at the very least assumed. Also since a lot of power specs are a pipe dream of the manufacturer anyway, the sensitivity spec is pretty much useless.
What I'm getting at is, don't sweat it. Almost all audio equipment today is capable of running downstream components. What is more important is impedance matching (and only to a point) and total system gain so that you get a reasonable fell on the volume control, and have adequate adjustment range.
You won't damage anything by overdriving the preamp, you will certainly hear distortion from a clipping amplifier or fried ears before that can happen.
Quote:
It says max output is 15V, while sensitivity is 150 mv or 0.15. That is a gain of 100.

No. The input sensitivity at 150mv is for the 2V output (and quite possibly for a 1V output). A gain of 22dB (or 16dB@1V out). Again this is why that spec is useless for the most part.

_________________
Dan Santoni
http://www.dtsaudioelectronics.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Thu Jun 21, 2018 6:44 pm 
Offline

Joined: Wed Jun 17, 2015 7:47 pm
Posts: 5
Location: Quebec, QC, CA
Thanks a lot.
Will give feedback saturday when it's all setup!
Cheers.


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Fri Jun 22, 2018 7:44 am 
Offline
User avatar

Joined: Tue Jun 17, 2008 4:50 pm
Posts: 12406
Location: Toronto, ON, CA
dtsaudio wrote:
Probably the most misleading specs on audio equipment are output level and input sensitivity.
Your DAC's output may be 2V, but it doesn't get that high under normal usage unless the signal it is receiving is at full digital level (0dB). Most digital signals are kept well below this. Besides, that's what the volume control is for. To attenuate the signal to your desired level.
Maximum output on a preamp is very seldom reached. That's just the level where it clips. Again, the volume control is there to control this. Most preamp sensitivity specs are incomplete. They might say something like "200mv" for a line input. Useless unless you know the gain, and/or the output levels. Same with amp specs. An amp with an input sensitivity of 1.5V MUST specify that is the level for max power. If it does not, it is meaningless or at the very least assumed. Also since a lot of power specs are a pipe dream of the manufacturer anyway, the sensitivity spec is pretty much useless.
What I'm getting at is, don't sweat it. Almost all audio equipment today is capable of running downstream components. What is more important is impedance matching (and only to a point) and total system gain so that you get a reasonable fell on the volume control, and have adequate adjustment range.
You won't damage anything by overdriving the preamp, you will certainly hear distortion from a clipping amplifier or fried ears before that can happen.
Quote:
It says max output is 15V, while sensitivity is 150 mv or 0.15. That is a gain of 100.

No. The input sensitivity at 150mv is for the 2V output (and quite possibly for a 1V output). A gain of 22dB (or 16dB@1V out). Again this is why that spec is useless for the most part.


Thanks. I was using the wrong spec.

A bit of searching finds this from DIYaudio:

"It is normal to quote sensitivity in either of two alternative forms.

1. the input voltage to produce maximum rated output power.

2. the input voltage to produce a standard output voltage."

1 is commonly used for amplifiers, 2 for preamps. I was using version 1.

So let's do the exercise again using definition 2.

At the the voltage of the sensitivity spec, one full rotation on the volume control will give you standard output.

The DAC has a 2.56 V output voltage. The sensitivity figure says 0.15 volts/2.56 volts = 6% of the DAC output is actually required. Which means you only need 6% of the gain of the unit to get to the standard voltage. The audio taper chart says that will happen at about 30% rotation.

If 100% is at 360 degrees, then 30% is 108 degrees. ( if 100% is more, then 108 is too low ).

Note that if the standard output voltage is 2V, which is likely, as that is where the spec took the output impedance figures, 30% rotation is probably going to drive the amplifier into clipping.

So if 100% open is at 360 degrees, the amount of rotation you have to play with may easily be less than 90 degrees.

That ought to be fine.

_________________
I'm sure that the term "resolving" has way more to do with a sense of self worth than any scientific principle. - davinci_redux


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Fri Jun 22, 2018 8:29 am 
Offline
Moderator
User avatar

Joined: Mon Dec 01, 2008 9:16 am
Posts: 759
Location: Surrey, BC, CA
dtsaudio wrote:
Probably the most misleading specs on audio equipment are output level and input sensitivity.
Your DAC's output may be 2V, but it doesn't get that high under normal usage unless the signal it is receiving is at full digital level (0dB). Most digital signals are kept well below this. Besides, that's what the volume control is for. To attenuate the signal to your desired level.
Maximum output on a preamp is very seldom reached. That's just the level where it clips. Again, the volume control is there to control this. Most preamp sensitivity specs are incomplete. They might say something like "200mv" for a line input. Useless unless you know the gain, and/or the output levels. Same with amp specs. An amp with an input sensitivity of 1.5V MUST specify that is the level for max power. If it does not, it is meaningless or at the very least assumed. Also since a lot of power specs are a pipe dream of the manufacturer anyway, the sensitivity spec is pretty much useless.
What I'm getting at is, don't sweat it. Almost all audio equipment today is capable of running downstream components. What is more important is impedance matching (and only to a point) and total system gain so that you get a reasonable fell on the volume control, and have adequate adjustment range.
You won't damage anything by overdriving the preamp, you will certainly hear distortion from a clipping amplifier or fried ears before that can happen.
Quote:
It says max output is 15V, while sensitivity is 150 mv or 0.15. That is a gain of 100.

No. The input sensitivity at 150mv is for the 2V output (and quite possibly for a 1V output). A gain of 22dB (or 16dB@1V out). Again this is why that spec is useless for the most part.


It would be nice if the manufactures gave a bit more information to quantify the spec's given
For Example the preamp i am using has a nominal output of .63 V RMS and a Max of 17 V RMS and an input sensitivity of 150 mV Nominal with 6 V being its saturation level
I am finding that newer equipment is increasingly sold with very few published specifications, this may be due to the increasing belief among some that specifications are meaningless


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Sat Jun 23, 2018 2:52 pm 
Offline

Joined: Mon May 23, 2016 1:19 pm
Posts: 401
Location: Mississauga, ON, CA
Kvn63, u r right on the money. The industry reports specs that r not real, the amp outputs being the worst. I have seen 700W on the front sticker of equipment that consumes 250W. This machine makes energy lol.
Still preamp output of 15-17V is waaaay to high, most likely a typo.


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Sat Jun 23, 2018 3:45 pm 
Offline
User avatar

Joined: Tue Feb 28, 2006 5:40 am
Posts: 484
Location: Hamilton, ON, CA
15v would be the maximum output the preamp is capable of, most likely with a large input signal. This is not unusual.
I see many preamp capable of 10+ volts output. You'd never use that, but the capability is there.

_________________
Dan Santoni
http://www.dtsaudioelectronics.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Input/Output Voltage
PostPosted: Sat Jun 23, 2018 3:49 pm 
Offline
User avatar

Joined: Tue Jun 17, 2008 4:50 pm
Posts: 12406
Location: Toronto, ON, CA
dtsaudio wrote:
15v would be the maximum output the preamp is capable of, most likely with a large input signal. This is not unusual.
I see many preamp capable of 10+ volts output. You'd never use that, but the capability is there.


Your would use that if you were driving an First Watt F4. That amp has unity gain. All of the voltage gain is done by the preamp.

_________________
I'm sure that the term "resolving" has way more to do with a sense of self worth than any scientific principle. - davinci_redux


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 13 posts ] 

All times are UTC - 8 hours


Who is online

Users browsing this forum: No registered users and 7 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group