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In Reply to: RE: Thank you to you and Kal posted by 1973shovel on August 25, 2024 at 17:08:13
> Both my main amp and sub amp have a 10K input impedance, so if the Pre90 can drive a 5K load, that will be one consideration off my mind.
I could be wrong, but I believe the two outputs are individually buffered. Therefore, I don't think you would be connecting both amplifiers in parallel. In other words, each output would be driving a 10k-ohm load separately. However, I can't find anything in the specifications that answers this concern. Therefore, I think the only way you will know whether or not your system is compatible will be to try it, and most dealers allow you to return a product if you're not satisfied. I bought my Topping Pre90 from Amazon, which allows returns.
> I'll have to check the specs on both my phono stage and DAC. If they'll work with the Pre90 then I might order one.
The input impedance of the balanced inputs is rather low at 2k-ohms. However, my FiiO R9 sounds just fine connected to the Topping's balanced inputs.
The input impedance of the unbalanced inputs is 9.9k-ohms, which should work just fine with nearly all components.
Good luck!
John Elison
Follow Ups:
"I believe the two outputs are individually buffered"
Do you remember what caused you to draw that conclusion, John? Not that I've read everything out there on the Pre90, and I simply may have missed that description of how the circuit is configured.
Some of the responders to the Audio Science Review (a site I'd never been to prior to this) of the Topping Pre90 voiced similar concerns as mine regarding the low input impedance of the Pre90 measured in their review, questioning whether it would work with some "legacy" components. Or what we on the Asylum more often refer to as Vintage or Classic pieces of audio gear.
For 'sound quality', I'm certainly willing to trust my own ears, lest anyone draw a conclusion because I'm referencing Audio Science Review. But electrical laws do apply, and I'd like to be sure ahead of time that I'm not trying to fit a square peg in a round hole where the Pre90's 'unusual' impedance issues are concerned.
If buying and trying the Pre90 is the only way for me to have my questions answered, then I may have to go that route. But I'm trying to avoid having to send it back simply because I didn't do my homework in advance. Trying to find out information regarding potential electrical compatibility issues shouldn't be this difficult, in my estimation. For example, in the measurement section of Kal's review, John Atkinson wrote:
"The balanced input impedance was low, at 2k ohms from 20Hz to 20kHz, which might give a bass-light balance with source components that have a tubed output stage."
Rather than state something as ambiguous as "a tubed output stage", an actual range, like "I wouldn't use a source component with an output impedance below [insert number here] with the Pre90" would have been far more useful, in my estimation.
Thank you again, John. You and Kal Rubinson have both been very helpful in trying to address my concerns.
Sorry, I don't remember what caused me to think the two outputs were buffered. Perhaps they're not! However, the Pre90 drives my monoblocks and my subwoofer simultaneously without any audible problems that I can detect.
The outputs are individually activated. Perhaps this is why I thought they might also be individually buffered.
Since you seem to be so concerned about this feature, I would recommend looking for a different preamplifier. My Pass Labs X1 preamp has balanced and unbalanced outputs, and they are definitely individually buffered. At least that's explicitly stated in the owner's manual. This preamp originally cost $5,800, but I prefer the sound of the Topping Pre90. I feel the Topping Pre90 has a more transparent sound quality while the Pass Labs X1 sounds more like vacuum tubes. However, it definitely has individually buffered outputs and I'll be happy to sell it to you if you're interested.
Good luck!
I'm inclined to agree with you, John. Thanks.
Well, you could always do what Kal is doing. You could buy two Pre90's and connect one to your main speakers and the other to your subwoofer. Then you could use a Y-adapter to drive both preamps with the same input signal.
Kal bought three Pre90's to use as a volume control for his 5.1 channel home theater system.
As far as I'm concerned, my Pre90 is the best sounding preamp I've ever heard regardless of price, and it drives all my amplifiers just fine.
If you'd like to buy my Pass Labs X1 preamp, I'll be happy to sell it to you for $1,500 plus shipping. It definitely has buffered outputs and it also has a separate power supply. Of course, you could buy two Pre90's for $1200 and they'd probably sound better.
Good luck!
Your Pass X1 should go fast at that price.
"Well, you could always do what Kal is doing. You could buy two Pre90's and connect one to your main speakers and the other to your subwoofer. Then you could use a Y-adapter to drive both preamps with the same input signal."Or you could simply buy one and use the balanced and unbalanced outputs simultaneously fot the main pair and the sub. Been there, done that.
Sometimes, people completely overthink the issues, get distracted and, in desparation, make a poor choice. Been there, done that.
I think that you (Tod, not John) may be getting there.
Edits: 08/31/24
That's sometimes true, and I can be a notorious over-thinker about some things. But I don't believe my concerns over impedance qualify as unfounded concern, because it's not a subjective issue. I emailed Apos Inc. Someone named Peter got back to me, writing:
"Thanks for reaching out. Before giving you an answer, let me confirm with Topping on my thoughts. I don't want to tell you incorrect information, so I'll let you know as soon as I hear back from them.
I was impressed with how quickly they got back to me, and even more impressed that they didn't just say, "Don't worry about it. Just order one!" which is the advice I appear to be getting here.
I already have a buffered line stage called The Truth, which is reviewed at the link below. Regarding the Truth's impedances, here's what the manufacturer says about it:
"It has an input impedance too high to measure, output impedance is a couple ohms".
Too high to measure with a a common multi-meter anyway, and my meter measures up to 60 Megaohms. So a high input impedance, and a few ohms on the output, which assure me it's going to work with anything I connect to it. If I had that same confidence in the Pre90, I'd have ordered one by now.
The only reason I'm considering something other than my Truth is that I ordered it years ago, with only one set of inputs and outputs. A selector switch and two or three more pair of RCA jacks will remedy that, but I wasn't looking forward to doing the work. It looks like I'm going to have to rethink that, unless Apos has some good news for me.
> Or you could simply buy one and use the balanced and unbalanced outputs simultaneously for the main pair and the sub.
Kal: I agree with you wholeheartedly!
This is exactly what I do. My Hypex Nilai 500 monoblock amplifiers are connected to the Topping's balanced outputs and my Rythmik Servo Sub is connected to its unbalanced outputs. It works just fine for me.
Moreover, I don't even have a problem with its remote control.
Happy listening!
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