Digging the audition. :) ... and question...

randog · « **on:** 13 Feb 2004, 10:09 pm »

Curt, I've really been digging the audition of the Purest.

I have one question: I can set the volume to full max and still have some headroom in my amp and speakers. Meanwhile, all the other preamps I'm auditioning (3) are at the same perceived volume between 10:00 and 12:00. From one standpoint it's nice to know I won't blow my speakers, but on the other hand I may want that extra bit out of my setup.

Why is this? Any suggestions?

Thanks,
Randog

(posted here because your answer should be of general interest)

MaxCast · « **Reply #1 on:** 14 Feb 2004, 02:18 am »

What gain settng do you have it on?

randog · « **Reply #2 on:** 14 Feb 2004, 04:55 pm »

Well, I know I can go full range on both 1 & 2. Haven't tried 3, but that's too much bloom for me anyway. At the higher volumes, gain 1 sounds best to me with the higher gains best at lower volumes.

Rocket · « **Reply #3 on:** 15 Feb 2004, 02:02 am »

Hi randog,

What amp are you using in your system?

What is the gain of the amp?

May'be it's a mismatch for your system? I thought the purpose of having adjustable gain settings on the preamp was to avoid this type of problem with system matching.

From what i've read the modification that curt did to the ird preamp, solved the issues of using different gains on his preamp.

regards

rod

randog · « **Reply #4 on:** 15 Feb 2004, 05:11 pm »

Quote from: Rocket

Hi randog,

What amp are you using in your system?

What is the gain of the amp?

May'be it's a mismatch for your system? I thought the purpose of having adjustable gain settings on the preamp was to avoid this type of problem with system matching.

From what i've read the modification that curt did to the ird preamp, solved the issues of using different gains on his preamp.

regards

rod

Hi Rod, I have the Odyssey Khartago and all the other preamps I'm auditioning seem to be in the same ballpark volume-wise. The Purest is the only one that uses the full extent of the knob.

I absolutely love the adjustable gain settings. I can't think of a better feature for my collection which consists of all types of music and all types of recording quality.

Randog

scottpretti · « **Reply #5 on:** 15 Feb 2004, 07:45 pm »

Funny, I'm also running an Odyssey Khartago with my Purist at the moment. On gain one and two or three for that matter I can't get it to the full volume level without causing a long term hearing problem. My other equipment: RAM CDP, Dennis Murphy two ways (Scan Speak 18w/8546 woofer and Morel MDT 33 tweeter), bolder M-80s and Northcreek Poseidon subs. Room size 12X18X8. If you have the volume at max and it's still not loud enough there must be something wrong?! Or maybe I have delicate ears

Curt · « **Reply #6 on:** 16 Feb 2004, 08:39 pm »

Quote from: randog

Curt, I've really been digging the audition of the Purest. :D

I have one question: I can set the volume to full max and still have some headroom in my amp and speakers. Meanwhile, all the other preamps I'm auditioning (3) are at the same perceived volume between 10:00 and 12:00. From one standpoint it's nice to know I won't blow my speakers, but on the other hand I may want that extra bit out of my setup.

Why is this? Any suggestions?

Thanks,
Randog

(posted here because your answer should be of general interest)

It's a matter of overall system gain, not just preamp gain. What is your source output level? What is your amplifiers gain? And what is your loudspeaker efficiency and their impedance?

Tell me this info and I can answer your question. It is important to match your components well, it gives a system better synergy.

The Purist is designed to give maximum volume resolution. This allows precise room SPL control. At full volume on my system the knob is at the 5 o'clock position. You get used to this luxury and IMO it is hard to give up once you have it.

Many fixed gain preamps max out by 10-12 o'clock position (they are high gain), some even less, this can give a touchy volume control and with a pot it can also hurt the channel to channel level matching accuracy.

The Purist has a minimum gain of minus 51dB and a maximum gain of +9.5dB (x3). Some preamps have gain as high as 18dB (x8) which adds more noise (something I don't like), they use a one size fits all approach. IRD is more in to a fitted approach, our gain selector.

I get some high efficency guys saying were too loud and some low efficency guys saying they need a little more gain. I'm listening and as always trying to sort out the input to see if any changes are required.

randog · « **Reply #7 on:** 16 Feb 2004, 09:19 pm »

Quote from: Curt

It's a matter of overall system gain, not just preamp gain. What is your source output level? What is your amplifiers gain? And what is your loudspeaker efficiency and their impedance?

Source is Norh CD-1. I believe you know this unit pretty well.

Amp is Odyssey Khartago. Input impedence is 10K Ohms, gain is 28-30 dB

Speakers are Ellis 1801b. Sensitivity is 84-85 dB. Lowest impedance is 6.2 ohms.

What do you think?

Randy

randog · « **Reply #8 on:** 16 Feb 2004, 09:46 pm »

Quote from: scottpretti

Funny, I'm also running an Odyssey Khartago with my Purist at the moment. On gain one and two or three for that matter I can't get it to the full volume level without causing a long term hearing problem. My other equipment: RAM CDP, Dennis Murphy two ways (Scan Speak 18w/8546 woofer and Morel MDT 33 tweeter), bolder M-80s and Northcreek Poseidon subs. Room size 12X18X8. If you have the volume at max and it's still not loud enough there must be something wrong?! Or maybe I have delicate ears

Scott... interesting. What is the efficiency and impedance of your speakers? How far can you go on Gain 1 to what you would consider max volume (position out of 24 clicks)?

Thanks,
Randy

Rocket · « **Reply #9 on:** 16 Feb 2004, 10:52 pm »

Hi Randog,

Sounds like the problem could be your speakers which are fairly inefficient.

Have you tried the ird preamp on gain 3? This might solve your problems.

Regards

Rod

randog · « **Reply #10 on:** 17 Feb 2004, 12:38 am »

Hi Rod,

I don't think I'd listen to much on Gain 3. I like acoustical music and it sounds very accurate on Gain 1.

Curt, would any passive or active preamp at 0 db gain have this issue with my setup or are there other considerations with the preamp design that help determine the actual volume at the preamp's volume settings (besides gain)?

Thanks,
Randy

Curt · « **Reply #11 on:** 17 Feb 2004, 10:20 am »

Quote from: randog

Quote from: Curt
It's a matter of overall system gain, not just preamp gain. What is your source output level? What is your amplifiers gain? And what is your loudspeaker efficiency and their impedance?

Source is Norh CD-1. I believe you know this unit pretty well.

Amp is Odyssey Khartago. Input impedence is 10K Ohms, gain is 28-30 dB

Speakers are Ellis 1801b. Sensitivity is 84-85 dB. Lowest impedance is 6.2 ohms.

What do you think?

Randy

If everything is working to spec, the speakers are the largest contributor to the problem. They require more power, thus need higher gain. Don't forget, room size and distance from the sweetspot also effects the loudness.

I use ProAC 1SCs (86dB @ 1W1m : impedance similar to yours) and Purist gain 1 to achieve full volume at the 5 o'clock position. My MB-100 amps are 26dB and I'm using the CD-1. I measured everything and am sure these components meet the stated specs. Room size is 18'x14'x8'.

Your system seems like something else could be wrong. What is the sensitivity of the Khartago amp? I could not find it on Odyssey's website. A low amp sensitivity could be compounding the situation. Or perhaps another component is out of the stated spec, any CD-1 mods?

Assuming all is in order and you don't want to change any components, to increase the volume you need to increase the gain, no other option.

To increase gain with the Purist select what level is required, use gain 3 only when you need maximum volume. With the other preamps your stuck with one high gain level at least with the Purist you can improve the sound by cutting back the gain when you don't need full volume.

BTW, for the record, all preamps will sound better when the gain is reduced, or worse when the gain is increased, this is basic electronics. With IRDs selectable gain you get to optimise your system for different components, different CDs, and even different types of music but you also get to hear the different gain options, for better or worse. The sonic changes from gain 1-3 are subtle but noticable, just as I would expect they would be with any other preamp.

Curt · « **Reply #12 on:** 17 Feb 2004, 11:14 am »

Quote from: randog

Hi Rod,

I don't think I'd listen to much on Gain 3. I like acoustical music and it sounds very accurate on Gain 1.

Curt, would any passive or active preamp at 0 db gain have this issue with my setup or are there other considerations with the preamp design that help determine the actual volume at the preamp's volume settings (besides gain)?

Thanks,
Randy

You would hear a difference with any preamp when changing gains. No gain, or lower gains, always sounds better.

The circuit in the Purist does not change only one resistor value that adjusts the gain changes when 1-3 is selected. All signal paths and components remain the same. You just hear the gain change.

Perhaps this is why most companies don't give adjustable gain, not only does it cost more but it also causes some customer confusion.

I like the gain option and could never go back to a high fixed gain with a big pot to attenuate back down to the level I need. IMO that's such a waste of S/N ratio and too much of a loss of sound quality.