Why Use A Dedicated Preamp When My Computer Is The Only Source?

[Gary.D.Olson]

Hobby (short for "The Audiophile Hobby") keeps telling me the stereo system I once considered "great sounding" is actually pathetic and in dire need of upgrades. True or false? HA! Irrelevant, of course. Hobby NEVER lets up on the snobbish whispering. "OKAY, OKAY!" I say. "I'll upgrade already! NOW will you shut up?" Satisfied with himself, Hobby ignores me and comfortably settles in to the "wait-and-see" position. The torment continues.

 

In defense of Hobby (could he exist if we didn't defend him?), my rig has been powered by the same component for a quarter of a century. What's worse is that it's a stereo receiver. ANATHEMA! So I've been searching the various secondary markets for a replacement to the aforementioned unholy component and believe I may have found it, but I have to buy three components to get it.

 

This weekend I'll be replacing my late 1980's TOTL Denon 125wpc Class-A receiver with a vintage Yamaha M-70 200wpc power amplifier bundled with the matching C-70 preamplifier and T-70 tuner - all for a paltry $250.00.

 

(Here's where my question comes in) Should I use the preamp, or should I plug my Schiit Modi DAC directly into the power amp?

 

As the title indicates, I have no turntable and won't be using the bundled tuner, my computer AND the power amplifier can provide volume control, and I never use tone controls or loudness buttons. And yet I can't shake the thought that a good preamp does something more... to stabilize or even improve sound quality. If not, it would seem those who spend multiple thousands on high-end preamps are being duped. Is Hobby that evil?

[mav52]

Hobby (short for "The Audiophile Hobby") keeps telling me the stereo system I once considered "great sounding" is actually pathetic and in dire need of upgrades. True or false? HA! Irrelevant, of course. Hobby NEVER lets up on the snobbish whispering. "OKAY, OKAY!" I say. "I'll upgrade already! NOW will you shut up?" Satisfied with himself, Hobby ignores me and comfortably settles in to the "wait-and-see" position. The torment continues.

 

In defense of Hobby (could he exist if we didn't defend him?), my rig has been powered by the same component for a quarter of a century. What's worse is that it's a stereo receiver. ANATHEMA! So I've been searching the various secondary markets for a replacement to the aforementioned unholy component and believe I may have found it, but I have to buy three components to get it.

 

This weekend I'll be replacing my late 1980's TOTL Denon 125wpc Class-A receiver with a vintage Yamaha M-70 200wpc power amplifier bundled with the matching C-70 preamplifier and T-70 tuner - all for a paltry $250.00.

 

(Here's where my question comes in) Should I use the preamp, or should I plug my Schiit Modi DAC directly into the power amp?

 

As the title indicates, I have no turntable and won't be using the bundled tuner, my computer AND the power amplifier can provide volume control, and I never use tone controls or loudness buttons. And yet I can't shake the thought that a good preamp does something more... to stabilize or even improve sound quality. If not, it would seem those who spend multiple thousands on high-end preamps are being duped. Is Hobby that evil?

 

Some will tell you NO don't use a pre=amp others will tell you use it.. I say, try it for yourself and let your own ears provide that answer. I use a pre-amp as I happen to like the volume control of my pre-amp vs a dac. . I used to own a Mytek DSD DAC and didn't like like the volume control.

[Snowmonkey]

How are you going to integrate your Velodyne sub into the system if you plug your DAC straight into your power amp?

[Gary.D.Olson]

How are you going to integrate your Velodyne sub into the system if you plug your DAC straight into your power amp?

 

Preamp "out" / Y-connector / 1/2 to power amp & 1/2 to sw. With the receiver, the Y-connector was connected to its "Pre-Out" and half the signal went right back in to its "Main-In". I would much prefer the sonic integrity of no sw/crossover, but my Canton's aren't particularly earth-shattering. However, that may well improve with 400 watts of robust Yamaha power. I'll be listening to the new setup both with and without the sub and will report next week, barring problems with Yamaha-gettage.

[elcorso]

Since they are volume controls, and... they are volume controls...

 

One of the more expensive parts and hard to achieve is a "volume control".

 

If the DAC control de volume by truncating some bits, I would stay out of this. There are some very expensive DACs than handle digital volume control from 69 bits, that could be nice, and the SQ remains the same, but I never tried it (like the Total DAC). Maybe @dallasjustice can talk about.

 

The others DACs that handle volume control from analogue, I'll compare this one to preamp volume control, and stay with I like better.

 

Anyway, I feel it could be 'safer' to handle it from my preamp, if the DAC goes nuts from some software, internal chipset or driver failure in order to protect the speakers.

 

Roch

[Gary.D.Olson]

Some will tell you NO don't use a pre=amp others will tell you use it.. I say, try it for yourself and let your own ears provide that answer. I use a pre-amp as I happen to like the volume control of my pre-amp vs a dac. . I used to own a Mytek DSD DAC and didn't like like the volume control.

 

Try it for myself and make up my own mind? Where's the fun in that? (kidding) Yes, that's on the agenda and I'll report back with my take. I was kinda hoping someone here would teach me something important about when to use and when NOT to use preamps. I used to trust my ears a lot more than I do now, but my hearing ain't what it once was. Getting pointed in the right direction might lessen the odds of my perception getting in the way.

[Gary.D.Olson]

Since they are volume controls, and... they are volume controls...

 

One of the more expensive parts and hard to achieve is a "volume control".

 

If the DAC control de volume by truncating some bits, I would stay out of this. There are some very expensive DACs than handle digital volume control from 69 bits, that could be nice, and the SQ remains the same, but I never tried it (like the Total DAC). Maybe @dallasjustice can talk about.

 

The others DACs that handle volume control from analogue, I'll compare this one to preamp volume control, and stay with I like better.

 

Anyway, I feel it could be 'safer' to handle it from my preamp, if the DAC goes nuts from some software, internal chipset or driver failure in order to protect the speakers.

 

Roch

 

 

The thought of changing the volume being sent to the DAC as "modifying the digital stream" had never occurred to me. Yes; it makes far more sense to handle volume control post-DAC. That alone is probably worth having the C-70 preamp.

 

Very helpful! Thanks!

[bluesman]

Is Hobby that evil?

 

Aw, Gary - in your heart, you KNOW the answer to that question....

 

To best understand whether and why you might need a "preamplifier" between a DAC and a power amp, visualize the path a signal travels as it's transduced from creation as electromotive force in a phono cartridge, tuner, tape head, PC etc to an audible analogue emanating from your speakers or headphones. Sources generate signals in microvolts (weakest moving coil phono cartridges, magnetic tape heads) to millivolts (moving magnet cartridges) to volts (DACs and crystal phono cartridges, which are of historic interest only). A typical power output stage requires an input signal of 1 or 2 volts to drive it to its full rated output. So different sources need different amounts of voltage ("pre-") amplification to drive a power output stage and the speaker on the other end. A DAC needs none - its output voltage is already high enough to drive a power amp.

 

But unless you interpose some kind of attentuation in the connection between DAC and power amp, the full output voltage of the DAC will drive the power amp to its full rated output - i.e. it will always be at full volume. Almost all volume controls attenuate the signal as it emerges from the voltage gain stage(s), limiting the sound output level by limiting the input voltage to the current gain stage(s). If present, a "volume control" on a separate power amp controls its input level and is, therefore, redundant in a traditional phono-preamp-amp analog system - but it's not redundant when the entire system is a DAC and an amp.

 

DAC circuits achieve their best rated performance specs at a designed-in signal level. DACs without a "volume control" are set to generate that optimal voltage with typical source material. DACs with variable attenuation indicate the optimal level as 0 db (the decibel is a ratio of the measured signal to a stated reference voltage) and should be operated there for best sound quality. But you need to be able to control the volume, and that's essentially all a "preamplifier" does when used between a DAC and a power stage.

 

And here's where Hobby rears its ugly head. Whether you can hear it or not is debatable - but in theory, you'll get "better" sound quality if you use a simple, high quality passive attenuator between DAC and power stage than if you use a traditional preamp because the signal will be "processed" through additional active circuitry in a preamp even if set for unity gain. So Hobby will tell you to buy an attenuation stage to go between your DAC and your power amp - you don't need the preamp at all unless you have analog sources as well and need the input and switching flexibility of a preamp (which is the only reason I still have one). There are several passive volume controls out there, e.g. the Goldpoint.

 

I resisted the call of the wild hobby and use my 30+ year old Apt Holman preamp as a volume control. And I feel no guilt at all - but your mileage may vary.......

[bluesman]

PS: If I were you, and you can place the power amp so that the volume control is readily accessible, I'd just use that and call it a day.

[AudioDoctor]

I do because I still have thousands of vinyl records I like to listen to.

[Jud]

I use one because (1) for my digital front end, my preamp is a better piece of equipment than any DAC-with-volume-control or passive attenuator I would want to afford, and (2) the preamp has a built-in phono stage and I would need to use it for my TT anyway, so it simplifies the system overall (fewer boxen).

[Gary.D.Olson]

Aw, Gary - in your heart, you KNOW the answer to that question....

 

To best understand whether and why you might need a "preamplifier" between a DAC and a power amp, visualize the path a signal travels as it's transduced from creation as electromotive force in a phono cartridge, tuner, tape head, PC etc to an audible analogue emanating from your speakers or headphones. Sources generate signals in microvolts (weakest moving coil phono cartridges, magnetic tape heads) to millivolts (moving magnet cartridges) to volts (DACs and crystal phono cartridges, which are of historic interest only). A typical power output stage requires an input signal of 1 or 2 volts to drive it to its full rated output. So different sources need different amounts of voltage ("pre-") amplification to drive a power output stage and the speaker on the other end. A DAC needs none - its output voltage is already high enough to drive a power amp.

 

But unless you interpose some kind of attentuation in the connection between DAC and power amp, the full output voltage of the DAC will drive the power amp to its full rated output - i.e. it will always be at full volume. Almost all volume controls attenuate the signal as it emerges from the voltage gain stage(s), limiting the sound output level by limiting the input voltage to the current gain stage(s). If present, a "volume control" on a separate power amp controls its input level and is, therefore, redundant in a traditional phono-preamp-amp analog system - but it's not redundant when the entire system is a DAC and an amp.

 

DAC circuits achieve their best rated performance specs at a designed-in signal level. DACs without a "volume control" are set to generate that optimal voltage with typical source material. DACs with variable attenuation indicate the optimal level as 0 db (the decibel is a ratio of the measured signal to a stated reference voltage) and should be operated there for best sound quality. But you need to be able to control the volume, and that's essentially all a "preamplifier" does when used between a DAC and a power stage.

 

And here's where Hobby rears its ugly head. Whether you can hear it or not is debatable - but in theory, you'll get "better" sound quality if you use a simple, high quality passive attenuator between DAC and power stage than if you use a traditional preamp because the signal will be "processed" through additional active circuitry in a preamp even if set for unity gain. So Hobby will tell you to buy an attenuation stage to go between your DAC and your power amp - you don't need the preamp at all unless you have analog sources as well and need the input and switching flexibility of a preamp (which is the only reason I still have one). There are several passive volume controls out there, e.g. the Goldpoint.

 

I resisted the call of the wild hobby and use my 30+ year old Apt Holman preamp as a volume control. And I feel no guilt at all - but your mileage may vary.......

 

That is some very helpful information. I believe the power amplifier's volume control consists of two separate knobs - one for each side. That's a bit too clunky even for me. I doubt the missus would find it appealing either. I'll beat Hobby to death before spending $400.00 on a volume knob for my lowly system. Now, if I had a sweet ass-whooping rig (as is common around here), "the knob" would be appropriate. Maybe someday...

[bluesman]

the preamp has a built-in phono stage and I would need to use it for my TT anyway.

I do because I still have thousands of vinyl records I like to listen to.

 

But the OP has no such needs. He seems to be asking if we think using the preamp is his best option for sound quality or simply pointless audio excess:

 

I have no turntable and won't be using the bundled tuner, my computer AND the power amplifier can provide volume control, and I never use tone controls or loudness buttons.

 

I don't think a Yamaha C70 is quite as inert a volume control as a current passive attenuator, Jud. It's certainly not in the same league with your Spectral - the C70 had a weird concentric volume control setup with a variable "loudness contour" and (as far as I can recall after all these years) no true bypass.

 

for my digital front end, my preamp is a better piece of equipment than any DAC-with-volume-control or passive attenuator I would want to afford

[bluesman]

I'll beat Hobby to death before spending $400.00 on a volume knob for my lowly system.

 

Take a look at the $120 NHT or the $60 SM Audio, Gary. You can always return it if you don't like it, and my bet is that either will sound fine with your rig. Yamaha amps were excellent back then - I used a B2 for several years and was very happy with it.

[Gary.D.Olson]

I don't think a Yamaha C70 is quite as inert a volume control as a current passive attenuator, Jud. It's certainly not in the same league with your Spectral - the C70 had a weird concentric volume control setup with a variable "loudness contour" and (as far as I can recall after all these years) no true bypass.

 

I remember reading something about that loudness contour on the C-70 but the author gave it a positive spin. Maybe I should pass on the Yamaha gear and keep looking.

[Guidof]

Preamp or no preamp, that is the question.

 

To which there is probably no generally valid answer.

 

Personally, I tried listening both with and without my preamp in the chain, as well as with the preamp in active and passive mode. In my system, passive mode preamp in the chain sounds a lot better, clearer, more tonally balanced, more three-dimensional than all other options. But I use the digitally controlled analog volume control in my DSPeaker Dual Core DAC/EQ instead of the volume pot in the preamp. More transparent.

 

I have no idea why this setup sounds best, but I'm happy to go with that. Tell hobby to get off your back and let you enjoy what sounds best to you ;-).

 

Best regards,

 

Guido F.

[Gary.D.Olson]

Take a look at the $120 NHT or the $60 SM Audio, Gary. You can always return it if you don't like it, and my bet is that either will sound fine with your rig. Yamaha amps were excellent back then - I used a B2 for several years and was very happy with it.

 

Thanks for the suggestions. Both of those products have XLR inputs and/or 1/4" outputs; a miss-match all the way around for my gear.

[Gary.D.Olson]

Take a look at the $120 NHT or the $60 SM Audio, Gary. You can always return it if you don't like it, and my bet is that either will sound fine with your rig. Yamaha amps were excellent back then - I used a B2 for several years and was very happy with it.

 

How about this $200 passive? Anyone know anything about it? New Release Luminous Audio Axiom MK II Passive Pre Amp | eBay

[AudioDoctor]

But the OP has no such needs. He seems to be asking if we think using the preamp is his best option for sound quality or simply pointless audio excess:

 

and I stated my reasons for having a pre-amp.

[bluesman]

Thanks for the suggestions. Both of those products have XLR inputs and/or 1/4" outputs; a miss-match all the way around for my gear.

 

That's why the audio god made adapters. You'll need to connect your DAC to your preamp with cables anyway - just use RCA-to-XLRs instead of RCA-to-RCAs.

[bluesman]

and I stated my reasons for having a pre-amp.

 

as did I:

 

you don't need the preamp at all unless you have analog sources as well and need the input and switching flexibility of a preamp (which is the only reason I still have one).

 

But to be honest, I listen less and less to anything but computer audio. When we retire and sell the house in a few years, I'll give my vinyl (and the Thorens it rode in on) to my son, and be quite content with computer audio in our 2 bedroom condo apartment. I may even give him my entire system and start again with pure digital. This old dog's learned some new tricks.

[Gary.D.Olson]

That's why the audio god made adapters. You'll need to connect your DAC to your preamp with cables anyway - just use RCA-to-XLRs instead of RCA-to-RCAs.

 

That was my first thought when I saw your post about the passive attenuators. Then I heard a whisper coming from either Hobby or Idiot Within saying "adapters are yet another link in the audio chain and are sure to cause sound quality degradation!" (Well, that was more than a whisper.) If that's not the case, an adapter plus one of those units would be a great solution.

 

Thanks!

[Gary.D.Olson]

How are you going to integrate your Velodyne sub into the system if you plug your DAC straight into your power amp?

 

Sorry, I originally misread your post. That's an interesting question. I don't know if the DAC has the output to be split in two by a ghastly y-adapter. I'm sort of hoping the robustness of power coming from the Yamaha amp coaxes a sufficient amount of additional bass from my little Canton's that I could do away with the sub. But I'm not going to hold my breath on that one.

[Snowmonkey]

Sorry, I originally misread your post. That's an interesting question. I don't know if the DAC has the output to be split in two by a ghastly y-adapter. I'm sort of hoping the robustness of power coming from the Yamaha amp coaxes a sufficient amount of additional bass from my little Canton's that I could do away with the sub. But I'm not going to hold my breath on that one.

If your Velodyne is like mine, you could connect the DAC to the line-in of the sub and then connect the line-out of the sub to the amp and let the sub's high pass filter do the work, but that means you have added a layer of circuitry to the path and to some extent negated the advantage of eliminating the pre-amp. I have fiddled with these various combinations with my system, using the volume control in JRiver to replace the pre-amp, which allegedly causes negligible signal degradation, but in the end, I am terrified that one day I will inadvertently leave or set the software volume on max. and blow my speakers to pieces (my DAC has no volume control).

[wgscott]

How are you going to integrate your Velodyne sub into the system if you plug your DAC straight into your power amp?

 

Speaker-level inputs.