[THROWBACK]

Not a bad question. I recently switched from a preamp to the Bent Audio TAP (bentaudio.com/index2.html), a passive device. My sources are vinyl, through an ss phono preamp (Dynamic Sound Associates-DSA- Phono One), and my computer, through an Ayre QB-9 DAC. Both have plenty of gain to drive my amps, so all I need is a really good volume control: i.e., the TAP. Really works great in my system.

[THROWBACK]

Not a bad question. I recently switched from a preamp to the Bent Audio TAP (bentaudio.com/index2.html), a passive device. My sources are vinyl, through an ss phono preamp (Dynamic Sound Associates-DSA- Phono One), and my computer, through an Ayre QB-9 DAC. Both have plenty of gain to drive my amps, so all I need is a really good volume control: i.e., the TAP. Really works great in my system.

[WireNut]

Not a bad question. I recently switched from a preamp to the Bent Audio TAP (bentaudio.com/index2.html), a passive device. My sources are vinyl, through an ss phono preamp (Dynamic Sound Associates-DSA- Phono One), and my computer, through an Ayre QB-9 DAC. Both have plenty of gain to drive my amps, so all I need is a really good volume control: i.e., the TAP. Really works great in my system.

Hi Throwback,

 I’m currently looking at a Bent Audio AVC-1 and that’s how my question came about. My current line stage preamp has 22db of gain which drives a bi-amp system thru an electronic crossover. The volume control (attenuator) goes from 7 o’clock to 5 o’clock. If I listen at the 11 o’clock position it is really cranking. The AVC-1 has a max gain of 7db I believe. Seems like 7db would be enough for my bi-amp system. Maybe Davey is on to something about 6db of gain being enough, at least for my system.




 

[Steve]

I believe we need a preamplifier with gain if for no other reason that we use
a separate power supply (including transformer) which eliminates frequency dependent feedback
between stages through the power supply itself.

The other way around the problem is to incorporate the preamplifier in the basic
amplifier itself, called an integrated, But use a separate power supply for that first
stage. However, it does take alot of space, which most chassis are lacking in
if it is to be done properly.

Otherwise we have a compromise situation in the integrated amplifier.
The integrated is less expensive for those on a budget, which we must honor.

Cheers.

Steve 

ps. 8db or so is usually enough gain.

[Steve]

Well the "gain" could be current gain and not voltage gain.  Also, gain could be negative and still considered voltage gain. 

Dave.

Nope to both.   

Cheers. I agree with Frank. And using a volume control in a box is just asking for problems.

[Steve]

If you have speakers that are 100db efficient and a power amp with 32db voltage gain, is voltage gain in the preamp "not bad at all?" 

Dave.

Then you have a problem matching the proper amplifier to the load, the speaker.

Correct the real problem, the amplifier gain problem.

Cheers.

[avahifi]

By the way, we can, and I suspect many other vendors can too, adjust the gain of our amps and or preamps to give you useful volume control rotation with very sensitive speakers.  Its no big deal if we know you need this.

Frank Van Alstine

[WireNut]

By the way, we can, and I suspect many other vendors can too, adjust the gain of our amps and or preamps to give you useful volume control rotation with very sensitive speakers.  Its no big deal if we know you need this.

Frank Van Alstine

Hi Frank,

That's a good piece of info. I wasn't aware of it. I can't help but wonder how that would be accomplished in a preamp.
 


   

[SteveFord]

I can answer that one: two resistors and some solder.
It helps if you buy from someone helpful like Frank!

[bummrush]

Whether it matters or not since I'm at unity gain, I'm still able to use my volume around high. 50s to. early 70s out of 99 steps

[Quiet Earth]

 I’m currently looking at a Bent Audio AVC-1 and that’s how my question came about. My current line stage preamp has 22db of gain which drives a bi-amp system thru an electronic crossover. The volume control (attenuator) goes from 7 o’clock to 5 o’clock. If I listen at the 11 o’clock position it is really cranking. The AVC-1 has a max gain of 7db I believe. Seems like 7db would be enough for my bi-amp system.

I like my TVC a lot, but I would not recommend one (or an AVC) if you know for sure that you need 6dB of gain, or if you know that you will be using minimal attenuation (volume control near unity gain). The more attenuation you use, the friendlier a TVC becomes. I imagine an autoformer is similar.

Typically you want a TVC set to  -14 dB for the very loudest you would ever play your system. And that is without the +6dB engaged. When you attenuate a TVC between -14 and 0dB, the in/out impedance relationships fall apart and become unfriendly. At that point, you are really in active preamp territory.

I'm not saying that an AVC/TVC at unity gain to +6dB won't work at all. I'm just saying that it will perform poorly compared to the way it performs when it is 20 to 40 dB down. That is really where they do their thing.

[Steve]

By the way, we can, and I suspect many other vendors can too, adjust the gain of our amps and or preamps to give you useful volume control rotation with very sensitive speakers.  Its no big deal if we know you need this.

Frank Van Alstine

It would seem better, although another component, if one were to design around the gain of the speaker. Using a 100db sensitive speaker,
rid the amp of a stage if possible and gain better fidelity.

If not, then use the amp vol setup, but remember, FR will be compromised compared to without the vol setup. The sonics will be compromised, depending upon the source output impedance (Z) and/or output coupling capacitor value. The sonics could easily lack bass response or compromised highs.

Cheers.

[Steve]

This is not the case today. We use digital source components with high gain stages and strong output voltage capacity, which in turn play hot recordings (always at 0dBfs peak and often compressed). Most of these dacs are robust enough to drive a power amp on their own. There is no need for more gain in this scenario (an active preamp).

Unfortunately, players/dacs have analog gainstages in them which are inferior to the best preamplifiers.
(General public) Bypass the analog/mute stages and you will hear a nice improvement in sound.
I made a reference quality player by doing just that.


Cheers.

[WireNut]

I like my TVC a lot, but I would not recommend one (or an AVC) if you know for sure that you need 6dB of gain, or if you know that you will be using minimal attenuation (volume control near unity gain). The more attenuation you use, the friendlier a TVC becomes. I imagine an autoformer is similar.

Typically you want a TVC set to  -14 dB for the very loudest you would ever play your system. And that is without the +6dB engaged. When you attenuate a TVC between -14 and 0dB, the in/out impedance relationships fall apart and become unfriendly. At that point, you are really in active preamp territory.

I'm not saying that an AVC/TVC at unity gain to +6dB won't work at all. I'm just saying that it will perform poorly compared to the way it performs when it is 20 to 40 dB down. That is really where they do their thing.

Hi Quiet Earth,

Thanks for that info. Once I get my Pass B1 preamp built (buffered / 0 Gain) I'll have a better idea if I need additional gain or not.

WN



 

[G Georgopoulos]

Hi Quiet Earth,

Thanks for that info. Once I get my Pass B1 preamp built (buffered / 0 Gain) I'll have a better idea if I need additional gain or not.

WN

You need to build a preamp with gain to have a better idea,if you build a preamp with 0 gain you wont be able to see the difference ,a gain of 2 is a good way to start, avoid 0 gain is no good way to see how a preamp is performing...

what i have found is ,is better to have some cliping than to have limited gain in the pwr amp and preamp
...

[WireNut]

You need to build a preamp with gain to have a better idea,if you build a preamp with 0 gain you wont be able to see the difference ,a gain of 2 is a good way to start, avoid 0 gain is no good way to see how a preamp is performing...

what i have found is ,is better to have some cliping than to have limited gain in the pwr amp and preamp
...

 That well give me 2 different preamps to try since my current pre has 22db of gain. Seems like since the B1 will have 0db of gain and my current pre has 22db of gain that between the two of them I'll get a better idea of how much gain I really need. Really I'm trying to figure out if the preamp I'm looking at purchasing in the future which has a maximum of 7db of gain will work in my system. The only way I know how to figure it out is by experimenting with what I have. Ok, what I've been considering is a Bent Audio AVC-1 which uses autoformer volume controls and has a max gain of 7db.





 
   

[Davey]

There's a lot of commenting in this thread that doesn't relate to the topic. 

Take note of the highest volume control position you ever utilize with your existing (22db) preamp.  (Use some of your program material that you know to be recorded at lower levels.)
When you've identified that position use a test CD or signal generator and voltmeter and measure the input and output voltages and determine the gain.  That's the minimum gain you need. 

Cheers,

Dave.

[poseidonsvoice]

...
Take note of the highest volume control position you ever utilize with your existing (22db) preamp.  (Use some of your program material that you know to be recorded at lower levels.)
When you've identified that position use a test CD or signal generator and voltmeter and measure the input and output voltages and determine the gain.  That's the minimum gain you need. 

Cheers,

Dave.

Bingo! That's exactly what I would do ...unless of course you (Wirenut) are dying to build Nelson's B-1 which I understand as DIY is a craze...I've got the disease!

dB = 20 log (voltage ratio)

This link should help with doing the calculations fairly easily, providing that you have a signal generator/Test CD and a voltmeter to get the values:

dB calculator

Best,
Anand.

[Quiet Earth]

I'm pretty sure my comment was dead nuts on, and very much related to the topic since we now know the goal is to try a AVC, and not just a general question about gain.

I will offer up one more suggestion related to gain and TVCs/AVCs. If you think that you want to try a TVC or AVC, just try your source component with a simple 20k volume control driving the power amp and see where that gets you first. If you can get your system to play plenty loud before 11o'clock on the dial, but it just sounds lifeless or wimpy, then you probably have enough system gain to try a TVC/AVC.

If you need to have the volume control up quite a bit just to get a decent level, then you need an active preamp.

It's not much harder than that. Good luck and have fun with it.