Input impedance is too low for many good tube preamps. 10k is just too low. I really dislike it when I see amps with input impedances that low. Just a shame and should be avoided by the builder.
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I agree. Passive preamps won’t like that either. The Purifi front end eval board (FE02A) has a 5K impedance per phase....even worse. I change that in my mods to 148K.....mucho better. Designers are trying to squeeze every number. Lower impedance means less noise can get in....so maybe it measures one db better.....but you loose dynamics and openness. 30K per phase should be the lower limit. Even the older Hypex NC500 eval board had 47K per phase.
Input impedance is usually set by a resistor to ground on each phase. So, the 10K resistors could probably be changed by someone to a higher value. Pretty simple for those with a little skill.
Mytek's cheaper class D amp is suppose to be great for the money........so this 8 times the price pair of mono blocks could be killer. However, $20K is a lot of money.
Just got an email back from admin, they can’t do it.
Input impedance is too low for many good tube preamps. 10k is just too low. I really dislike it when I see amps with input impedances that low. Just a shame and should be avoided by the builder.Yes I mentioned this also in another thread, that it’s not tube preamp friendly or passive pre friendly.
It’s just wrong and there is really no reason (except one) to design poweramps to have input impedances this low, they should all be >47kohm (which was the industry standard) like many tube and even SS amps are.
I said "except one" reason.
Years ago, there was a power amp manufacturer that did the same silly low input impedance, and it gave his 10ohm output impedance preamp the sonic edge into his poweramp/s over all other preamps in and A/B shootouts. (marketing ploy??)
10K Ohms is too low for tube preamps? Since when? That’s relatively, but not absolutely, high. Low impedance to me is in the 600 to 5K range.
Please keep in mind that a "low impedance amplifier" is not the same as with low impedance speakers. The amps present a flat, resistive load. This means that there are no hills and valleys in the response curve like with a speaker attached to a tube amp.
Worst case scenario for most tube preamps is that you will lose a little bass due to the output coupling capacitor which is in the 1uF to 4uF range and a little maximum gain (which you don’t use anyway).
A tube pre with 1uF output caps could be down around 5 dB at 20 Hz (I’m in the middle of a few things so my math could be a little off). With 2uF caps around -2.9 dB. This may actually be helpful in the right room!
Look at this example:
It handles 600 Ohms output just fine. My point is, we can't universally exclude 10K input impedance amp from use with tube pres. Some may do awful with it, but I suspect many will be fine.
Our preamps can drive 10K ohms no worries. Our MP-1 and MP-3 can driver 600 ohms no worries.
Having said that a 10K input impedance will exclude ARC preamps and a good number of other tube units as well as sources if a passive volume system is used. I don't see why the input impedance would be that low for consumer gear; the input circuit is opamps anyway, which can be set up to have input impedance as high as 1M.
the input circuit is opamps anyway, which can be set up to have input impedance as high as 1M.
Higher impedance = higher noise, but 25K to 50K is more typical than 10K for a solid state amplifier. It’s not exactly low either to me... it is still 17x more than 600 Ohms.
I'm not surprised at all your preamps can drive 10K. ;-) Most should.
The input impedance on my modded IceEdge amp that I was playing with was 47K after the first mod. I then raised that resistor to 148K and it sounded noticeably better. This was driven by a 50 ohm source that is biased with 10 ma of current on its discrete output stage (using a low capacitance 2 foot balanced cable). So, if a 50 ohm source sounds better with 148K.....why would you want less? There was no difference of noise idling or otherwise with the 148K.......dead silent.
You have to do listening tests to know anything. This is not theory......this is reality......your ears know what is real.
Nuprime is using 1meg input impedance in their latest 2 top of the line class D amps. They say it sounds better.
Ask to have Tammy contact youThat’s what was done, too late now this thread now stays.
You’ll only get noise with high (100k) input impedance amps, if there’s nothing plugged into that input, which no-one would do anyway.
Think I remember all Rouge M120 and M150 monoblocks when I had them here for reco all had 1meg ohm input impedance, anything could drive them.
04-07-2021 jwcondo 6:30am
Can you tell us where you got this 1.5mhz switching frequency info from?
No, I don’t think so.
If you go to that thread I say they (Mytek) mentions "higher switching", and I queery "But don’t give any details of the switching speed" then jwcondo says
"It does indeed use the 1.5 mhZ switching frequency. I am a dealer and I should be receiving the first one in Canada next week as they have landed on our shores.Only he will be able to say positive and give us a link to it.
I believe he is talking about the Technics.....It is a Technics thread
Yes I can see now you "could" be right, but I was discussing the new Mytek Empire before his post, and then he posted.
If it is confirmed the that it is the Technics SU-R1000 that is 1.5mhz switching frequency that's great also. I believe that it could be destined for great things and is going to be something to rival the Gryphon and Luxman integrateds maybe, at half the price, and with all the goodies it has.