[33na3rd]

Hello Morten & all,

I originally purchased my LDR3X to replace the broken photentiometer in my active Melos SHA Gold.

This worked wonderfully, but I realized that I still had not heard the LDR3X on it's own. This kept bugging me, so I went back inside and hooked up two more out puts directly from the RO & LO of J1. So now, in the same preamp, I have active & passive outputs controlled by the LDR3X.

My question is this--when I'm using the passive outputs, (which sound great!), is the active stage still influencing the sound since it's still hooked up to the RO & LO on J1, even though I'm not using the active outs?

Am I parallel loading the passive stage, and still not truly hearing the LDR3X on it's own?

Thanks for any info!

Jeff

[tortugaranger]

Hello Morten & all,

I originally purchased my LDR3X to replace the broken photentiometer in my active Melos SHA Gold.

This worked wonderfully, but I realized that I still had not heard the LDR3X on it's own. This kept bugging me, so I went back inside and hooked up two more out puts directly from the RO & LO of J1. So now, in the same preamp, I have active & passive outputs controlled by the LDR3X.

My question is this--when I'm using the passive outputs, (which sound great!), is the active stage still influencing the sound since it's still hooked up to the RO & LO on J1, even though I'm not using the active outs?

Am I parallel loading the passive stage, and still not truly hearing the LDR3X on it's own?

Thanks for any info!

Jeff

The LDR3x is indeed seeing both the impedance of your active's input stage in parallel with the impedance of your amp (when the passive out is connected to your amp). Whichever is lower will tend to dominate the resulting impedance. So I would submit there is an influence. Whether this matters or not is difficult to say. If both are substantially higher than the 10k (V1) or 20k (V2) input impedance of the LDR3x then probably not. Devil's in the details. On the other hand, why not simply disconnect the active from the LDR3x outputs and give it a listen.

Two examples:

R3x - 20k

RAc - 50k

RAmp - 100k

R1 = 20*50/(20+50) = 14.3k
Rtot = 14.3*100k/(14.3+100) = 12.5k

If the amp is say 20k then,

Rtot = 14.3*20/(14.3+20) = 8.3k

The more R's in parallel the lower the effective resistance. So overall effect will be to reduce the bridging impedance ratio between the amp and the source. Generally the higher the ratio the better but it also depends on how robust your source is. It all comes down to the delivery of energy from the source to the amp. As the source sees a lower connected impedance it has to work harder (i.e. deliver more current). At some point the output stage voltage of the source may begin to droop. This usually translates into loss of dynamics and bass.

As things stand can you tell a difference between active  out vs. passive out? Do tell.

[33na3rd]

Thank you for the reply Morten!

There is indeed a sonic difference between the active & passive out, even with the active in parallel.

As most folks have already have experienced, the lack of noise is almost startling! My wife said that the music sounded more real, less processed. I can't describe it better than that. On some recordings I thought there might be just a tad less drive, but on other recordings, the music just seemed to flow more easily. I was struck that some pop recordings that sounded harsh/brash, sounded much less so through the LDR3X. Perhaps less distortion on top of distortion?

Everyone fears diminished bass. The bass was there in full force, but seemed much much tighter.

I thought using the passive outs would mean having to turn the volume up a lot more, but it wasn't really all that much more. It would appear that my system has plenty of gain already! It probably doesn't hurt that my Rogue Medusa has a Zin of 200 Kohms, and my old Moscode 300 a Zin of 274 Kohms.

My old Quicksilver Phono Unit has a Zout of 3 Kohms, so I was expecting the highs to be rolled. I was wrong, everything was there.

Since you've explained the situation, I will have to try the LDR3X with the active stage disconnected.

Does having the active in parallel with LDR3X act as a buffer?

I asked the buffer question before I had seen the numbers you posted!

So, if I disconnect the active stage I will have a better impedance ratio & even better sound than I am experiencing now?

BTW, My LDR3X is V1. It looks like there's a V2 in my future!

[robertopisa]

I had a similar impression when using the Tortuga attenuator (DIY LDR3x.V2), as I was used to active preamps. After a while, I got used, and realised that the active preamp was colouring the sound. In this way I could spot some points to improve in my rig that were masqueraded by the active preamp (an expensive famous brand). In some cases, an active preamp can compensate the weakness of the rig or the acoustic environment, so it a  coloration in the good sense. But I prefer transparency to coloration (I have a treated room with over 30 bass traps and acoustic panels). It is possible to get transparent active preamps, but prepare to spend a lot of money.

As most folks have already have experienced, the lack of noise is almost startling! My wife said that the music sounded more real, less processed. I can't describe it better than that. On some recordings I thought there might be just a tad less drive, but on other recordings, the music just seemed to flow more easily. I was struck that some pop recordings that sounded harsh/brash, sounded much less so through the LDR3X. Perhaps less distortion on top of distortion?

[33na3rd]

I'm leaning more & more your way.

I used to think that one was forced to chose between truth & beauty, but I detect no loss of beauty here!

[tortugaranger]

I'm leaning more & more your way.

I used to think that one was forced to chose between truth & beauty, but I detect no loss of beauty here!

I've had numerous customers tell me that after auditioning our LDR preamps that they went ahead and sold their $10k+ tube preamps.