Active vs Passive Pre amps

David,my former pre was a Consonance Ref 1.3.
It`s a TVC (transformer volyme controll).VERY low background noise and transparent.I have compared it side by side in my system with my present pre( same as Brownsfan CSLS ).
The Coincident is clearly better in every way i can think of. It`s more expensive but you get a lot for your money with the CSLS.

Cheers,

Mikko

Check out Tortuga Audio and their passive line stage. It is built on the LDR attenuator and has been well engineered. Should have the balanced version out by now using XLR connectors.

I bought the DUI kit and am now having the board and encoder installed in my GAS Thoebe preamp. The preamp will have a bypass switch if I want to go direct through using only the passive or have the signature of the preamp using the Tortuga as the volume control.

Thanks for your comments everyone. As to the dynamics issue, if there is one, some of you dispute that, I thought there was a difference between resistor and transformer based passives. My unit uses the same transformers as the MFA Baby reference. Again, my understanding is that transformer based units have less limitation on dynamics and headroom.

It sounds like I am going to have to spend a lot to improve on my passive unit, which only cost me about $1400 second hand, less than the cost of the transformers themselves.

Has anyone any comments on the quality hierachy of the ARC pre's. My understanding is that it would be in this order LS27>Ref3>LS26, I may be wrong.

You are correct David12, this isn't a new subject here at all, in fact, it's quite old. It seems to come up once every week or two.
Just as any debate here on these forums, tubes vs. solid state, digital vs. analog, etc., there will be proponents of both sides. In the end, all that matters is what you think.

David12: The passive seemed more neutral and detailed, the ARC a little rich and lush. I know you are supposed to lose dynamics with a passive pre.

Hi David, first off your system as you have found just by listening, is a perfect impedance match for passive preamps as are most others out there.

Your ARC Ref 75 has a great 300kohm input impedance, 1.5v input sensitivity for full output and your Resolution Audio Resolution Audio Opus 21 has 2.5v output at 100ohms absolutely perfect for any passive.
And your speaker are 96db, efficient no need for extra active preamp amplification.

As for passive and dynamics, if I can explain, this belief is a total "furphy". If a passive preamp is a good impedance match as you have, they are more neutral have better detail and more dynamics than any active preamp.

The only way an active preamp can have better dynamics than a properly implemented passive as you have, is if the active preamp has a "dynamic range enhancer" (DBX) built into it, which sound like rubbish.

An active preamp cannot make better dynamics than what the source is giving, if anything they can only diminish dynamics, as all active components have losses when compared to source to amp direct in, like a well implemented passive can mirror.

Read Nelson Pass's quote on passive preamps.
" Nelson Pass,
We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp."

Cheers George

TVC and autoformer units from Bent,

Drubin, did you assembled the Bent yourself? What type of wires did you use?

Zd, It's all regardless and nevertheless at the same time.

regardless of your output source, input sensitivity and impedance of your amp, it will benefit from stable output impedance of active preamplification.

nevertheless, there are benefits of passive with transparency, but with lower dynamic headroom and volume ranges.

"in reality it's very simple math instead of science:"

That's what I used to tell my professors in college. Unfortunately, they never saw it that way.

" I know you are supposed to lose dynamics with a passive pre."

That's not always the case. A lot of it depends on how good the output is on your source.

I too love the purity of passives and have never felt the need for more gain, or an expanded soundstage. As for "added body, weight and drive an active can supply" it seems to me that here the active is over emphasizing what the source is providing (remember loudness controls?) but if that is what the system needs or the user wants then go active.

That said, the interconnects of course should be as short as possible and present low electrical capacitance when using a passive pre.

I am currently using a Luminous Axiom II Walker MOD XLR stepped attenuator passive preamp and find it perfect in my system in terms of accuracy, detail, dynamics and volume control resolution. I am using Cardas Crosslink XLR interconnects, and have Moon monobloc amps and Sonus Faber Cremona M speakers.

I have been on both sides of the active/passive debate over the years. I love the purity of passives and have never felt the need for more gain, or an expanded soundstage. On the other hand, I appreciate the added body, weight and drive an active can supply.

A year ago, I tried a Music First Baby Reference, the most expensive preamp I had ever had in my system. I felt, as Sam Tellig apparently did, that this was at last the preamp I'd been searching for, so I bought it. It was and is considerably better in my system than a number of other excellent passives I'd tried, including various Placettes, TVC and autoformer units from Bent, and the Lightspeed Attenuator, not to mention going direct from DAC to amp (for digital).

I think I might be able to do as well as the MF (perhaps better, I really don't know) with a truly great active, but I think I'd need to spend well north of $10K to get there without giving up what the MF does so well.

Stick with an ARC preamp. The amp is voiced that way and there is good synergy.

in reality it's very simple math instead of science:

passive volume control will vary resistance from valueA to valueZ where we can assume Z will be the the highest so to control the output voltage.

active volume control(active preamp) will have stable or fixed output impedance to supply variable input voltage to your amp.

by all possible and impossible means it means that supplied stable output impedance is preferable for best amplifier performance.

than you can do the rest of science to decide.

The resistance range on the volume pot is not appropriate for your system. Also, do you know what taper the engineer put in there? It could be swapped out for another pot and solve your problem, that is if you like the sound of it.

Oops.....I should have done my research on this passive before wading into these waters. Your pre is transformer based and pot replacement is not as simple as a non transformer based pre. There are other passives that have 48 gain settings...you might try them. Akustyk is a great option....and can be customized to your needs.

I would just replace the pots in your passive with 42 Stepped Ladder type.....or you might try the more recent smd type pot. I'm using one now and prefer it to ALPS. With a resistor based stepped ladder you can choose the type of high end resistor you like....Dale tend to be faster while Takman seem to be more romantic. I think from what you have described you'll prefer Dale.

So, keep your passive and just replace the pots......you'll save a bundle while upgrading your preamp and providing you the gain control you desire. This is a simple solder job...if you are not comfortable your local repair shop should be able to do it for under $35. The cost of the pots should be around $70.00. Remember to order the correct impedance for you pots to match your amp.

Thanks me later!

David,
I believe it's all a matter of personal tast. I agree with Brownsfan comments totally however for peace of mind you might want to once again demo a preamp in your home. I would think the dealer that you purchased the ARC Reference 75 power amp would be more then willing to bring out a preamp to demo or let you borrow one.

David, If you initially evaluated the Ref 3 and preferred your passive, I don't think that would be the correct move. As I read your post, the driver for you is better resolution in volume control, and perhaps better dynamics.

Usually, the stepped controls have finer resolution in the middle settings, with courser resolution at volume extremes. If the sensitivities and gains of your components allow you to stay in the 10:00 - 2:00 area on your volume controls, and you still don't have enough volume resolution, then you might want to narrow your search to infinitely variable potentiometer designs. As I am sure you are aware, there is a reason why so many good preamps used a stepped volume control rather than an infinitely variable potentiometer.

As a long time lover and advocate of passives, I can heartily recommend the Coincident Statement Line Stage as an active preamp that will satisfy your preference for neutral, detailed, and transparent presentation. It can be very sweet, but would never be described as lush, rich, etc. Israel Blume likes to say it sounds like nothing. It uses a stepped volume control, so you might want to shoot Israel an email to discuss your current equipment with respect to volume control resolution.