[tubamark]

Pardon my ignorance, but here's my line of thought:

I only use line-level sources (CD player & Tuner), and don't use the tone and balance controls on my preamp.  At this point it's just an active volume control . . .
Couldn't I simply place a decent audio-tapered stereo potentiometer, and maybe a source selector switch, in between the component(s) and amplifier to satisfy my (only remaining) need for gain control?   Amp is reasonably high impedance Rotel.

Has anyone done this?  'Am unhappy with my preamp's behavior lately, and would love to save some money if I don't need one!

Thanks,

[Steve]

Hi Tubamark,

     Hope this helps.

Is there enough room to install the selector switch and volume control in the amp? I say this because you could eliminate an interconnect cable. This would also mean the entire "normal" preamp would be housed in the amplifier, not just the preamp's gainstage. It would also save some money. Just some thoughts.

[G Georgopoulos]

Pardon my ignorance, but here's my line of thought:

I only use line-level sources (CD player & Tuner), and don't use the tone and balance controls on my preamp.  At this point it's just an active volume control . . .
Couldn't I simply place a decent audio-tapered stereo potentiometer, and maybe a source selector switch, in between the component(s) and amplifier to satisfy my (only remaining) need for gain control?   Amp is reasonably high impedance Rotel.

Has anyone done this?  'Am unhappy with my preamp's behavior lately, and would love to save some money if I don't need one!

Thanks,

yes it can be done, you could buy ready made ones at an electronics store
some boxes have selector only switches but you could install a pot in the
selector box if it didnt came with one, i suggest you use a selector box with
passive/mechanical selector it would make the whole job easier

cheers

[Gordy]

I've built 2 'integrated' chip amps using just a Grayhill selector switch and a shunted Alps pot.  They're probably small enough to work just as Steve suggests!  Here's some info on how to wire up a shunted vol. pot if you're not familiar... http://www.zerogain.com/forum/showthread.php?t=9476&pp=15   Posts 8 through 10 have the info you'll need!

[JeffB]

Tubamark,

What you have just described is known as a passive preamp, as oppossed to active.
A passive preamp is simply a source selector switch and a volume control. 
Passsive preamps work fine as long as your sources and amplifier are properly matched, which is not usually a problem.
See the following:
http://www.rothwellaudioproducts.co.uk/html/passive_preamp_tech.html
 
I don't have any recommendations to make as to the equipment to buy.
Here are some examples, but there are many many more choices.
http://www.musicdirect.com/products/detail.asp?sku=ACIAVPC2
http://www.rothwellaudioproducts.co.uk/html/passive_pre-amp.html
http://www.ftaudio.com/Product_LW1S2.htm

You might also want to read up on TVC based preamps.  Transformer Volume Controls.

[JLM]

For better part of a year I was running a $300 wireless Squeeze Box (music server with the CDs ripped to my PC).  The SB has a digital domain volume control and interface for internet audio streaming (radio).  It includes software and links to free software for everything you need.  My entire system consisted of the SB, monoblock power amps, and single driver speakers (about as simply as you can get it).

Yes, many integrated amps have no active pre-amp circuit, instead the amplifier stages are simply sized to provide some extra signal boost.  Channel Island Audio (see their circle below) offers such amps with 26 dB gain and 32 dB gain options.

Typical volume controls use resistors to vary the signal.  Some simply variably shunt signal or exist in the digital domain.  And then there are the transformer based volume controls (TVC).

Active pre-amp circuits (and TVCs) buffer any impedence mis-matches between amp and source(s).  Active circuits can also provide signal boost.  Check the specifications of your components to see if the rated output signals match the amp's rated input (many combinations don't need boost).  Beware though that many could benefit from better impedence matching.

Passive pre-amps are simplier.  Channel Island Audio sells a couple resistor based volume controls with source switching, in fact a used one just sold on the trading circle above.  And Promitheus Audio has a long thread currently going in the two channel circle for their TVC passive pre-amps.

[David Ellis]

Has anyone done this?  'Am unhappy with my preamp's behavior lately, and would love to save some money if I don't need one!

I have been using a passive preamp for years with great success.

I believe the level of success depends on theinput  impedance of your amplifier (hopefully high) and the "strength" of the CD player output stage.

I have tried some VERY good active preamps in my system and found passives sound better.  For a very inexpensive experiment I suggest trying some of the endler in-line volume attenuators.  They sound surprisingly good.  http://www.positive-feedback.com/Issue19/endlerattenuators.htm

I suggest some reading here:

http://www.high-endaudio.com/RC-Linestages.html

Dave

[Steve]

Problem with the article is that the active (preamplifier) gainstage is now in the amplifier. As such there are advantages and disadvantages.

Advantage is that if the volume control and selector switch is positioned inside the amplifier, one saves an IC.

A major disadvantage is that there are musical coupling between the stages in an integrated with a common power supply. This feedback is frequency dependent.

I have a  white paper explaining the situation at:
http://www.sasaudiolabs.com/theory8a.htm

RCA Radiotron Designers Handbook also addresses the issue in some detail, some 50 years ago.

I have another article, midpage down, entitled: "No Gainstage Preamplifier Needed?" located at:
http://www.sasaudiolabs.com/theory6a.htm

Articles, definitions from the library of congress, Stereophile magazine, both explain that an integrated amplifier is an active preamplifier and basic amplifier combined. So this article appears to be changing what has been definition for decades.

Arthur has some good info, but this is not his best work.

If possible, for the best sonics, either one has to separate the active preamp from the basic amplifier (and stil use separate power supplies for each stage), or use a larger chassis and  separate power supplies for Each stage in the integrated amplifier.

Just no way around it.

[Daygloworange]

I'm running a modded SB 3 directly into my 120w per channel SS amp into a pair of 91 db efficient speakers. The modded SB 3 puts out 1.1 volts. My amp is rated to perform well with as little as 1.3 volts.

This combo while sounding good, is just not as loud as I'd like to run sometimes. I'd like something to boost the level closer to 2 volts. I don't want any tone controls, or have a real need for input selectors, but might wanted a real high quality stepped attenuator.

Basically a sonically minimalist method of boosting closer to a 2volt output into the amp.

What are my options? Suggestions? Recommendations?

Cheers

[NewBuyer]

...Basically a sonically minimalist method of boosting closer to a 2volt output into the amp.

What are my options? Suggestions? Recommendations?

Cheers

I don't know what the particular voltage increase might be, but you might consider a non-unity gain buffer like the Burson Buffer. It works great with the SB3 and is spec'd to give you +6db gain.

[Russell Dawkins]

For big bang for small bucks there are the Endler stepped attenuators for $40/channel:

http://mysite.verizon.net/vze4c5pt/index.html

only hitch is you have to be able to reach the power amp inputs to change the volume - at least to do it "right" according to the designer.

[Gordy]

....but might wanted a real high quality stepped attenuator.

Basically a sonically minimalist method of boosting closer to a 2volt output into the amp.

What are my options? Suggestions? Recommendations?

Cheers

An attenuator won't provide any gain, it merely attenuates a given signal.  Maybe a step-up transformer, like used with low output moving coils, would work.   I found this Jensen tranny (JT-11SSP-6M) that looks interesting, hopefully Steve can comment on whether it's applicable or not... http://www.jensentransformers.com/ln_in.html   
data sheet here... http://www.jensentransformers.com/datashts/11ssp6m.pdf

[WEEZ]

Read Steve's 'white papers', as suggested in his post. Either you have enough gain, or you don't.

I have ranted previously on these boards that most systems today probably have way too much gain...mine included. The problem is that many amplifiers have (3) stages of amplification in them, and can be driven to full power with sometimes less than 1 volt of input....indicating maybe 26 to 32 db of gain available...sufficient for most speakers in most rooms. These amps really may as well have the selector and the volume control 'on-board' and be done with it.

Many amplifiers are designed with very high open loop gain; then the gain is knocked down with gobs of negative feedback, but still there is sufficient gain to play loud enough for most speakers. My amplifier has 26 db of gain. However, I tried it without a pre-amp (just a passive volume control just for shits and giggles) with my cd player and it played plenty loud enough. And it sounded okay, I suppose. But with a tuner; and especially with a tape deck; I couldn't get any 'drive' and/or sufficient fullness at moderate volumes to be satisfying. The sound was thinner, indicating that the output stage(s) in my tape deck and tuner are not capable of enough voltage...and more likely, current....to drive my amplifier properly. At loud levels the sound was better, but didn't sound 'right'. Still no 'body'.

To me, a separate pre-amp still provides the best sound for most people with multiple sources. I'll go further and submit that the pre-amp is more important than the amplifier for overall sound quality. (Assuming that the amplifier is suitable for the speakers). If your system sounds bad with a pre-amp, you need a better pre-amp..not the elimination of such a device.

I think of a pre-amp as a 'system conditioner'. 

YMMV...

WEEZ

[Steve Eddy]

An attenuator won't provide any gain, it merely attenuates a given signal.  Maybe a step-up transformer, like used with low output moving coils, would work.   I found this Jensen tranny (JT-11SSP-6M) that looks interesting, hopefully Steve can comment on whether it's applicable or not...

I know I'm not the "Steve" you were referring to, but... 

Did you take a look at the price for that trannie? $132.70 a pop.

Don't really need a repeat coil for the job. I'd look at something more along the lines of the CineMag CMOQ-4, wired for 1:2. And they're only about $25 each in high nickel.

se

[Steve Eddy]

This combo while sounding good, is just not as loud as I'd like to run sometimes.

Even with the volume all the way up?

By the way, who modded your SB3? Was it Vinnie?

se

[Daygloworange]

Mine was modded by Wayne at Bolder cable. I got the analog output modded with the Sonicaps/and Sonicaps platinum bypass full mod. And a modded Elpac linear PS. No bybees though.

I don't have my CD collection ripped onto my external hard drive yet, I just have a couple of my buddy's CD's on there, stuff that I've never listened to in my system before, so I can't fully apprecaite the difference between my CDP/pre combo and the SB 3. But it does sound really good so far.

Even with the volume all the way up?

Yeah, it's not as loud as before. It's still loud I guess, but quite a bit less than before.

Cheers

[Steve Eddy]

Mine was modded by Wayne at Bolder cable. I got the analog output modded with the Sonicaps/and Sonicaps platinum bypass full mod. And a modded Elpac linear PS. No bybees though.

Ok. So the output is cap coupled?

I don't have my CD collection ripped onto my external hard drive yet, I just have a couple of my buddy's CD's on there, stuff that I've never listened to in my system before, so I can't fully apprecaite the difference between my CDP/pre combo and the SB 3. But it does sound really good so far.

Coolness! Been looking at the SB myself for a while now. Someday I'll finally pull the trigger and get one.

Yeah, it's not as loud as before. It's still loud I guess, but quite a bit less than before.

Ok, just wanting to make sure that it's not loud enough even with the volume all the way up.

Seems kind of unusual with a 120 watt amp and 91dB speakers though. Do you know what the input sensitivity of your amplifier is?

se

[Gordy]

I know I'm not the "Steve" you were referring to, but... 

Any Steve in a storm I always say    Thanks for the CineMag link!  Somebody (you or mgalusha?) posted about them some time back and I lost the name/link.  I still recall the selfless post you made at decware with diy instructions for turning wooden IC barrels like the ones you use with your Tao line   

[Daygloworange]

These are the specs on my amp and my previous pre -amp set up:

Pre-amp : Adcom GFP-345
Output impedance    100 ohms    (normal and LAB)
Output level            2.0 V          (normal and LAB)
Input impedance(high)    22,000 ohms
Input sensitivity(high)     210 mV

Power- amp : ATI 1202
120WRMS into 8ohms with 28db gain
Input sensitivity       1.3 Volts
Input impedance      28k ohms (nominal)
Gain                      24 db (voltage gain)
Slew rate               50 V/microsecond
Damping factor        greater than 400 from 10Hz to 100kHz
DC Output offset      less than +/- 5mV

Wayne does remove the analog section of the SB 3, doing this reverses the polarity of the output. I'm not sure if the output is capacitively coupled, but I believe it is.

What I'd like is to step up the voltage output and have an extra output to send a line level signal to my active subwoofer. I emailed Wayne, he's got something in the works that should take care of that, but it'll be down the road a bit.

The SB is the cat's meow, and the coolest thing since sliced bread . I'll never look back. Having your entire CD collection on your hard drive, being able to scroll through, make playlists, random accessability, internet radio, all from the comfort of being being behind your laptop, or by remote control, with great sound, and a minimalist set up, is a radical concept.

No jitter, no unreadable CD's, no searching, hunting for CD's. No need for CD storage, never having to deal with another broken jewel case alone, makes it worth it for me.

It's way cool.

Cheers

[TomS]

Dayglo,

I am using a Sonic Euphoria PLC (autoformer design) with my Bolder SB2 analog out.  It provides as much as +10db gain (stock is +4db) using the autoformer as well as optional remote, 2 sets of outputs, tape out, and 4 inputs.  My BEL amps require 2v when bridged for full output, so this really does the trick without getting in the way of the sound at all.  There are several on a'gon for $800 or so, possibly without the remote, but it can be added on.  The only downside to using the version with gain is you can't turn the volume all the way off, but who cares since the SB does that for you.

Tom