Need a preamp?


Hi all, 

I have an older Cary tube preamp and a Bob Latino ST70 with a built in attenuator driving a pair of Proac D30R. The combo seems to be a tad too warm so I tried using the amp without the preamp and it seems to sound better with a wider soundstage and more extended highs. I have a phono amp also so I can also listen to LPs and cds. Is there a reason I need a preamp other than the convenience of switching between the two?  Would a ss preamp or passive preamp add to the sound?  I presume any preamp would only degrade the quality and can't make it better than it is. 


jaferd
We use a preamp in order to drive the amp adequately, as well as for attenuation & switching between sources. One of the problems that may arise without a pre is that the source device does not have a powerful enough output to drive the amp. But, from your own description
I tried using the amp without the preamp and it seems to sound better
it seems you do not have this problem. So, go pre-less, why not :)?
(BTW, have you tried running the phono into your amp, and can it drive the amp?)
jaferd

Is there a reason I need a preamp other than the convenience of switching between the two?
No your Bob Latino ST70 has an input impedance of 280kohm and sensitivity for full wattage output of just 1v in.
With these sort of specs you only need a passive preamp


Would a ss preamp or passive preamp add to the sound? I presume any preamp would only degrade the quality and can’t make it better than it is.
Yes any active preamp will add colouration to the sound.

Just use the built in attenuator as the volume control, and use an input switch box, like this
http://www.goldpt.com/sw4.html

Or leave your attenuator full up and just get a $49 Schiit Sys which has two switchable inputs, you’ll be fine with your cd’s, and you’ll have enough volume with your phono preamp as well if it’s high enough gain.
https://www.schiit.com/products/sys

Cheers George

The Cary is not the most neutral preamp around IMO. So a passive would work quite well in your situation as you already know. I think you can get switch boxes to switch between inputs. Since you already have an internal volume control in the amps (which is the best way to go if you go passive) then the switch box is all you need- if switching the inputs manually is too much of a hassle.
Thanks for inputs. Would the Schiit degrade or color the sound more than the Goldpt cause it's so much more affordable. Also, would either give worse sound than just switching the inputs manually and using the attenuator? Just for my own education, do passive preamp color the sound at all and what about cables? Are there any affordable, I mean in the 300 dollar range, used cables I should look for that do not add coloration?  
Would the Schiit degrade or color the sound more
Not if you get the internal passive in your ST70 completely bypassed (not just bridged out).
Then you’ll only be going through one passive, the Schiit Sys.

Cheers George

All great suggestions except remember the volume control in the Schiit Sys is marginal quality at best. Its fine as 2->1 switch box. 
except remember the volume control in the Schiit Sys is marginal


For $49 a screaming bargain, the Shiit Sys has an Alps 10kohm logarithmic mini, not as good as the Alps Blue Velvet or Black Beauty, but better than many around.
Same as this without the PCB cradle
https://images-na.ssl-images-amazon.com/images/I/51sGHNtCW2L.jpg
Cheers George
Also, would either give worse sound than just switching the inputs manually and using the attenuator? Just for my own education, do passive preamp color the sound at all and what about cables? Are there any affordable, I mean in the 300 dollar range, used cables I should look for that do not add coloration?  
@jaferd  Passive controls easily color the sound if external to the amp. The most common complaint is loss of impact at anything less than full volume.  They are also more sensitive to cables. For these reasons and because you also have a control already in the amplifier, I suggested a simple switching box, which will sound better than any outboard passive you can get in your situation.
I was thinking of using the Schiit sys and leaving it on full volume and use the amp volume control. Would that function as a switch box or is a dedicated switch box better? If so, what's a good switch box?
After a few months, the feel of the schiit controls does not inspire confidence
jaferd, I’d say for $49 and the option to return, the Sys is a no brainer. My comment regarding the quality of the volume control was meant after extensive use. Otherwise it’s well built and functions as it should.
I am with Atmasphere on this one, having gone passive ( permanently ) 2 years ago, and having a few units.
Why limit yourself to only rca with the SYS ?
Go with a nobsound - Has a alps pot , xlr ins and outs as well as rca ins and outs .
But he needs a couple of inputs, and his amp is single ended.
But nice to know the  Nobsound Mini use a proper quad Alps 27 for the xlr instead of wiring pseudo xlr.
 https://ae01.alicdn.com/kf/HTB1FTx5LpXXXXbwXpXXq6xXFXXXj/Japan-ALPS-27-type-10KA-4-quadruple-Audio-p...

https://www.amazon.com/Nobsound-Fully-Balanced-Single-Ended-Pre-Amplifier-Controller/dp/B01MXC9HHW

Cheers George


@ jaferd,I used to own a passive preamp (Promitheus Reference C-Core TVC) driving my ProAc D48R and the sound was very transparent. But I changed that to a tubed Backert Labs Rhumba 1.3 and I am rediscovering my music again. Those ProAcs of yours deserve something really good. You will be amazed with the music they make with an active preamp. The Backert Labs does not sound "syrupy", which is what I used to think tubes sounded. It is my first "tubed component".
And yes, @atmasphere was one of the a'goner who suggested that I try a tube. Can't believe I listened to him and moved from a TVC to active :-)
Hi Milpai,

Interesting since any active preamp would seem to add some colouration. Did you have a ss amp with the Blackert? Maybe the tube preamp and ss amp was the right combo. I am currently running the st70 in triode and I do like that sound more than in linear and also with my McCormack. 


The Nobsound doesn’t mention if the two balanced and RCA inputs and/or outputs can be used at the same time. I suspect not. It appears to be just a volume controller for a single source.
Interesting since any active preamp would seem to add some colouration.
That's a matter of intense debate. Many think that no preamp has its own colorations too (of which I mentioned earlier).
@jaferd,
I have the Parasound A21 with my Backert Labs tube preamp.
Many think that no preamp has its own colorations

Then they are kidding themselves

No preamp is "true to the source" with no colourations.
As the output stage of the source is just as matched to a poweramp input, as it is to a preamp input, in nearly all cases.

The "only" time a direct source to poweramp can get "coloured", is when the digital domain volume control is used down too low (<75%), then "bit stripping" can occur, which is a lowering of the 16bit resolution to 14bit or 12bit 10bit ect.

If this is happens then it's best to leave the digital volume control up full, and use a passive preamp, the next least coloured way of controlling the volume, and you can also "use it as a preset" to enable the digital volume control in the source to be used up much higher (>75%) then so it does'nt "Bit Strip" 

Cheers George   
Then they are kidding themselves

Actually they aren't. Loss of impact is the most common complaint aimed at passive controls (the exception being when the control is already in the power amplifier). Loss of impact is a coloration.


The problem is that in many circumstances the digital is making so much output that the volume control can't be run up to full volume, so the user is not able to find out how much impact is affected. And this doesn't happen universally. So like so many other things in audio- you just have to try it and see. But in this case, there's no point in an outboard passive control, since the OP has controls built into his amp. He only needs a switch box.

As I already suggested to the OP.

Just use the built in attenuator as the volume control, and use an input switch box, like this
http://www.goldpt.com/sw4.html

If he doesn’t want to use them the next best is to turn them up full.

Use the $49 Schiit Sys, which has input switching, is 10kohm and a great match for his 270kohm input ST70 with 1v input sensitivity for full output.

And especially better again if the internal volume controls of the ST70 are completely bypassed.

The ultimate is go direct, and to use the source volume control if used at or above 75%, if not use the Schiit Sys as a preset so the source volume can be used at >75% with it’s remote control.

Cheers George
So I got the Schiit sys but it seemed to have muted the top end. Didn't sound as lively even with the volume turned all the way up. Waiting for my switch box to see how that performs (or ideally not perform 😉). Currently I have my itune from MacBook airplay to airport express and optical link to dacmagic and then directly to the amp. Using the itune volume control, I'm running amp at full volume. This has given me the best sound to my ear at least.  Unfortunately,  the airplay limits transfer to 44khz so best I can get is 16/44 and not the higher resolution files.
So I got the Schiit sys but it seemed to have muted the top end. Didn't sound as lively even with the volume turned all the way up.
This is also a common complaint of passive controls. I'll be interested to hear what you think of the switchbox.
@jaferd,How are the dynamics with the Sys?

Ralph, any downside to source switching with CMOS electronic switches instead of relays? 
@milpai, I didn't listen to it very critically when I realized right away that it didn't sound completely transparent. I want to say maybe a tad less dynamic but YMMV. My feeling is that a preamp or anything that is introduced to a signal can only degrade it so I wasn't completely surprised. I even think a switch box wont be as good as without anything but the degradation may not be noticeable to me. I think a preamp that "improves" the sound just means that it added some colouration and/or minimized some faults to the source signal so that it sounded nicer to the reviewer. I'm sure my taste for tube sound is nothing like what the source really sounds like without any colouration. My 2 cents. 
Ralph, any downside to source switching with CMOS electronic switches instead of relays?
Yes- there is a reason we still use mechanical switches. CMOS is pretty good- but have a higher resistance and more diode effect than actual switches.
I didn't listen to it very critically when I realized right away that it didn't sound completely transparent. I want to say maybe a tad less dynamic but YMMV. My feeling is that a preamp or anything that is introduced to a signal can only degrade it so I wasn't completely surprised. I even think a switch box wont be as good as without anything but the degradation may not be noticeable to me. I think a preamp that "improves" the sound just means that it added some colouration and/or minimized some faults to the source signal so that it sounded nicer to the reviewer. I'm sure my taste for tube sound is nothing like what the source really sounds like without any colouration. My 2 cents.
Its a lot more complicated than that! And I'm only going to put this in a nutshell:
The reason we are able to have a hifi industry is due to the ear's masking principle. The ear is keenly sensitive to higher ordered harmonics which are made by *all* electronics. Tubes tend to make more harmonic distortion in this regard, but because they also have either a 2nd or 3rd harmonic (which is substantially less with solid state), that particular distortion is able to mask the higher ordered harmonics. This is why tubes sound smoother than solid state. Solid state makes these lower harmonics also, but not as much, so they are unable to mask the higher orders *as much*.


The odd thing is that the injection of a 2nd or 3rd harmonic also allows the ear to hear better lower level detail and increased soundstage width and depth! This is why tubes generally are more detailed and have better soundstage. However, the ear also interprets distortion as tonality; if the tube electronics have *too much* of these lower orders, it can sound more 'romantic' or 'rich' than is reality. So a designer has a fine line to walk- too much distortion and the gear is 'colored'; not enough and the gear is bright and harsh.


The bottom line is we can't make amps and preamps that don't make distortion. So this masking principle is important- without it hifi would not exist. 


Passive systems OTOH have their own issues- they effectively raise the output impedance of any source (as far as the power amp is concerned) and this seems to be why impact is impaired. They can also cause high frequency rolloff; even though that rolloff and be ultrasonic, the phase shift that can be introduced is interpreted by the ear as a rolloff. To prevent this, the interaction of the control and the associated capacitances (interconnect cables) has to result in a rolloff above 200KHz.


For these reasons, a tube preamp, if designed correctly, can often sound considerably more neutral with greater low level resolution than a passive or active solid state system.


@atmosphere. That's very informative. Thank you. I'm glad there are science and answers behind the different perceived sounds. 
I got the 60 dollars simple Douk audio switch box and can't discern any differences. However, my system is not the most revealing. Not elegant but works. 
@jaferd  I'd argue that point- your system easily revealed one of the most common complaints leveled at passive controls. But the switch box doesn't seem to cause any harm?? That sounds to me like your system is revealing, and that in your case it is an elegant solution, even though it might not **look** elegant.