Which preamp with Pass Alph J ? (LDR,B1...) ?

[mattworld]

Which buffer with my Pass Alph J ? (LDR,B1...) ?

Hi everyone,

I am wondering which preamp should I match with my Aleph J ?

The Aleph J have 240 Kohm input impedance. I can not make a choice between four preamp: the B1 Buffer, the B1 buffer with LDR volume control,the Lighter Note or the standard Lightspeed Attenuator designed by George Stantscheff.

Which one is for you the best sounding preamp with the power amp ?

Thanks for the advise

 

[stoN_Cold]

NS 10.

 

[biju55]

I am currently using " Pumpkin " with my Aleph J, and very pleased with its fascinating sound . A wonderful combination for me .....

 

[KatieandDad]

The B1 and the LDR are not pre-amplifiers.

The B1 is simply a buffer and the LDR is just another form of attenuator. Neither have any gain, in fact they both insert a loss.

Do you require extra gain - ie a pre-amplifier, or just control of the input signal level - ie an attenuator.

 

[mattworld]

You are right KatieandDad, the title is wrong and I'll edit it. I only need a buffer stage before the Aleph J. The 25w is enough in my room and I do not need extra gain.

I found four buffer/attenuator listed in my first post which should match the amp but I prefer to ask advises on the forum before to buy or start building the buffer. Perhaps people have already experienced it with the Aleph J.
I found good reviews on each of the buffer but no comparaison between them (or with the Aleph).

biju55, zeonrider : thanks for your answer, I will search informations on these models.

 

[KatieandDad]

I would do a bit of homework with the LDR option. IMO it just adds extra distortion which is clearly audible. OK the LDR can be better matched L-R but IMO there are better options available. I eventually opted for a decent ladder attenuator in a B1.

 

[mattworld]

What do you mean by "doing a little homework" ? That I have to do some test ?

If I understand, you advise me to do either the B1 with a ladder attenuator or LDR attenuator but not use the two together ?

I have a B1 on the bench and I'm waiting for some matched LDR which should come next week.

 

[OllBoll]

The no preamp, just use digital volume management before the DAC and you are good to go =)

 

[mattworld]

This is what I do for the moment, I use the computer before my DAC to control the volume. I need to set it at 50% to have a correct sound level.

But I think it is not a good solution because when you use a digital volume control , you reduce the number of bit for the digital to analog conversion, and finally the sound dynamics. Correct me if I am wrong.

 

[6L6]

Bit reduction for digital level out is the way some software does it, yes. So an attenuator or buffered attenuator is a very good idea.

Try just a high-quality potentiometer or attenuator to begin with, it may be all you need. If not, then look into one of your choices, any will work very well.

 

[OllBoll]

Loss of bits is only a problem if the gain structure is bad. As long as you don't have to attenuate too much ( within -48 dB on a 24 bit DAC ) then there is no noticeable loss.

And if there is too much gain we can just add a fixed passive resistor ladder to reduce the gain and then use digital attenuation anyway =)

 

[Mr. dB]

Will the ~2V output of an average DAC drive the Aleph J to full output?

 

[6L6]

Yes.

 

[OllBoll]

Will the ~2V output of an average DAC drive the Aleph J to full output?

Assuming 8 ohm speaker:

25W => max voltage needed is 14.14V ( sqrt( 25*8 ) )

Thus the question if 2V + 20 dB gain is at least 14V. And well, it is =)

20 dB ~ 10x ( 20/ 6 = 3.333, 2^3.333 = 10 ) gain so 1.4V gives 25W into 8 ohm.

 

[mattworld]

Hi,

I took time to read some post on the forum and I'm not more advanced. Some people say that the B1 is better with LDR, others that it is better with a potentiometer because of the distortion added by the LDR .

I also read very good review on the George's lightspeed attenuator and saw a schematic based on LDR published by that Nelson Pass here :
http://www.diyaudio.com/forums/anal...tspeed-attenuator-new-passive-preamp-137.html

Have you test this solution ? How does it compare to the others ?

So, at the moment I don't have the answer for the Alpeh J. I think I'll have to try all the solutions. I'll finish my B1 today after work

Next week I'll have a quad of NSL-32SR2S.

 

[mattworld]

I think I'll do the two buffer fisrt. One B1 , one lightspeed attenuator and listen to them.
What is the minimal input impendance and the maxiamle output impedance with the lightspeed ? Is it compatible with the Alpeh J ? Thanks !

 

[KatieandDad]

What do you mean by "doing a little homework" ? That I have to do some test ?

If I understand, you advise me to do either the B1 with a ladder attenuator or LDR attenuator but not use the two together ?

I have a B1 on the bench and I'm waiting for some matched LDR which should come next week.

Have a read of some of the reviews about LDR attenuators and some of threads on here, they are not the "Be All" answer they claim to be.

An LDR is an active device, all active devices have their pro's and con's.

 

[georgehifi]

An LDR is an active device, all active devices have their pro's and con's.

You are half right.
While the LED portion of the 4x quad matched Silonex NSL32SR2S's in Lightspeed Attenuator is active, the LDR portion is not, it's passive.
And this is the only portion that the signal goes through, so indeed it can be called a passive attenuator as there is no active circuitry that the signal passes through.


Cheers George

 

[juanitox]

i have LDR , classic carbon pot , film pot , and shunted vishay attenuator.
i will put in this order for my taste.

1 vishay attenuator (goldpoint, KOSMO, ) ( precision, transparency, channel matching, perhaps a little too straight)

2 LDR ( a nice mix of transparency and body but a little muddy at low level and not as precise in channel matching at very low level)

3 plastik film pot ( TKD) good all round pot , nothing in particular

4 carbon pot ( PEC ; cosmo ) very big sound , a little muddy too at low level, bad tracking not as transparent as the others

 

[koja]

this seems to have boiled down to a choice of passive attenuator rather than a preamp with voltage gain? well for attenuation nothing beats a resistor ladder with good relays. if you wanted to protect for adding gain to it after all, an Aleph P preamp with internally adjustable gain and a 1k stepped relay attenuator at output (look at Mikkel's stuff at Dantimax.dk), would be the ultimate answer. and if you got the balanced source, running it all balanced would make full use of both Alephs .

btw: in the gain calculation above 20dB (x10) gain was used for AlephJ. Is that for running it unbalanced?