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Passive pre-amp


CECAA850

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It's about a bit more than voltage... Your source really needs allot of drive current capability and your amp needs to be a very easy load. I couldn't get totally happy using one. They will sound great at a point of the volume control, then adjust the volume, and all goes to shit.

 

A better option would be a TVC. Transformer volume control, as these do not vary the output impedance like passive's do. BUT! Here again, your source needs allot of drive to run the transformers properly. If it does not have the drive, your bass will suffer big time.

 

That said, what components are you wanting to use with this?

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I have used some form of passive for ~10 years now. I have owned transformer and autoformer volume controls and only recently replaced my AVC with an LDR which uses an LED to attenuate volume. This is by far the best preamp I have ever owned. Here are a few of the active preamps I have owned over the years.

 

Audible Illusions Modulus 3A

BAT VK3i

BAT VK30

Cary SLP-98

ARC SP9 II

ARC LS3

Conrad Johnson Premier 17LS

Art Audio VPS

deHavilland Ultraverve

JJ Electronics 243

 

I know I have left some out, but those are the heavy hitters. All of them were good to varying degrees. But a TVC or LDR in a passive friendly system should show any of them the door. Pay attention to:

 

Output voltage of your source

Input sensitivity of your amp

Sensitivity of your speakers (shouldn't be an issue in this neighborhood :) )

 

and you should be fine. Just be aware that all passives aren't created equal. Those using resistors for attenuation are the least desirable. While they can be transparent, they can rob the life and dynamics out of the music. Transformer/Autoformer based and LDR passives do not generally suffer from this problem.

 

Shakey

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I think you will be fine on the amp end. Most tube amps are very easy loads. The issue with a passive with a DAC or a TVC with a DAC is the drive capability of the DAC. You will need a good DAC, one that has a discrete output stage with plenty of drive. You could possibly be successful with a DAC that has opamp outputs and a passive, but you still want good drive if you want the life to remain in your music. Lack of drive makes the interconnects act like antennas, bass suffers, and life is gone.

 

Hook a TVC up to a DAC with opamp outputs and it will fall on its a$$. This limits you to the more expensive DAC's, likely in the $2500 plus range.

 

What DAC's are you looking into? Or do you have a DAC that you plan to use?

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I think you will be fine on the amp end. Most tube amps are very easy loads. The issue with a passive with a DAC or a TVC with a DAC is the drive capability of the DAC. You will need a good DAC, one that has a discrete output stage with plenty of drive. You could possibly be successful with a DAC that has opamp outputs and a passive, but you still want good drive if you want the life to remain in your music. Lack of drive makes the interconnects act like antennas, bass suffers, and life is gone.

 

Hook a TVC up to a DAC with opamp outputs and it will fall on its a$$. This limits you to the more expensive DAC's, likely in the $2500 plus range.

 

What DAC's are you looking into? Or do you have a DAC that you plan to use?

you can interface with a buffer between the TVA and the amp which makes everybody happy. you don't have to spend a lot to get a good sounding buffer.

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Which model LDR did you get?

I got one from Abacus Music. It uses the Tortuga Audio LDR board. Here is one for sale that is different than mine, but uses the same board from Tortuga.

 

 

 

http://www.audioasylumtrader.com/ca/listing/Preamplifier-SS/Tortuga/Preamp/127333

 

 

 

That's not the one you had for sale in November?  Did you sell yours?

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Low budget for the DAC is not going to work in your favor, especially using a PC (USB) source. This would fit your bill, and I did not know it was updated until recently:

 

https://wyred4sound.com/products/digital-converters/dac-1-le-limited-edition

 

The issues are that you will not only need a great DAC with plenty of drive for the passive pre (or TVC), you will also need a DAC with a very good and well implemented USB input. Both these are met in spades with the one in the link. Do get the Femto upgrade also! It is well worth it... For what you are getting with this kit, this is a major steal of a price!

 

Cheers!

Edited by paul79
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the reason for getting a quality (more expensive) DAC would be to extract more info from your disks. No preamp can make more information come out of your DAC. A better volume control system, one which does less to the information given to it by the source will let you hear more clearly what was extracted from your disk. The idea of a passive is that it does less so it has less opportunity to mess up the sound. Better DAC's mean better digital cables and you may well find that you have exceeded your available budget. I think that most folks simply want to do the most with what they have (available budget). I have had extremly good results with entry level DVD players which can be purchased off the floor for $15 -20 bucks or new for $25.00 - $40.00. Every couple of years they throw a little new technology at the DVD to keep it fresh and I simply buy a new one. I do modify mine and no I am not sharing what I do. Stock DVD players from Sony and Toshiba are now 24 bit 196KHz sample rate and make very good sounding CD players for next to nothing. Buy one at Walmart if you do not like it take it back. Cost you nothing to try but your time. I am running a Toshiba right now because it has track ID on the player but I actually prefer the new Sony and it has a better/nicer remote and is the same price. Best regards Moray James.

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