Pre-amps With Very Low Output Impedances

[hired goon]

G'day,

The ME850 amplifier I am getting has an unusually low input impedance of 2000 ohms. Apparently this means that any pre-amp or CD player connected to it must have very low output impedances of 100 ohms or less for optimal sound quality. Resistors can be removed from the ME850 to allow connection to pre-amps with higher output impedances (up to 60k Ohm, apparently), but this seems self-defeating as the quality of the ME850 suffers as a result.

I was checking out some units mentioned here and unfortunately their output impedance seems too high. For example the Creek OBH-22 passive pre-amp has an output impedance of 200 ohm, and the Shanling CDT-100 CD player has an output impedance of 600w for the solid-state output and 100k Ohm for the valve output. Bugger.

Anyway, what I'd like to know is: what pre-amps are available that have very low output impedances?

I'm guessing valve preamps are verbotten here (most seem to have output impedances measured on the 1000's of ohms). My ME15 pre-amp (funnily enough) has an output impedance of 2 ohms, so it's okay, but if for some reason I'm not happy with the ME15, then I'd like to know what else is available that can still be used with the ME850.

--Geoff

[Guest alebonau]

heres a list of pre's I've posted on before geoff showing some on the market. And your particualr required will be somethign you might have to research checkign the links and maybe with the manufacturers.

~

anyways this is a bit list I've posted elsewhere before of the other pre's I'm aware of, particualrly ones with a HT-input which can be an important feature for those with a combined 2ch ht input.

if your keen on 2ch pre's with HT-input from $3.5k upwards

NuForce P-8 $2k?

http://www.nuforce.com/products-preamp.htm

Primare pre30 $3.5k

http://www.sumikoaudio.net/primare/products/pre30.htm

plinius m8 $3-4k? actually think its closer to $5k?

http://www.pliniusaudio.com/pro/pro04.htm

naim nait 202 $3k+ and theres another 2-3 pre's in the naim range

http://www.naim-audio.com/products/nac202.html

musical fidelity a5cr pre $4k

http://www.carltonaudiovisual.com.au/?q=node/view/346

http://www.musicalfidelity.com/products/a5/a5pre.html#

Electrocompaniet 4.7 $4k

http://www.tivolihifi.com.au/index.php?mai...;products_id=73

krell 280p $5k

http://www.lenwallisaudio.com.au/products/...ls.php?pid=1020

Moon p3 $5.2k

http://www.carltonaudiovisual.com.au/?q=node/view/495

http://www.simaudio.com/moonp3.htm

Audio Research SP16L $5.7k

http://www.audioresearch.com/SP16.html

Moon p5

http://www.carltonaudiovisual.com.au/?q=node/view/496

http://www.simaudio.com/moonp3.htm

and theres probably plenty more out there especially going up into the stratospheric price ranges. ~

[/b]

also to add..

Aksa Swift $3.6k

http://www.aksaonline.com/products_1_1.html

Elektra tube pre $4.4k

I imagine the ME pre's with their unusually ultra low ouput impredance are no doubt specifically made to work with ME power amps. It might require that a pre output impedance be made to match and not how much that would infact compromise the pre's design itself. Talkign to someone like arthur at elektra on the topic might be interesting.

Just checking a couple of links both the MF A5cr pre appears to have a 50ohm output impedance and the primare 100ohm. not sure if thats low enough or whether something aroudn the 2ohm output impedace as your ME-15 pre would be more desirable and be a better match for the ME 850 power amp.

you could also consider an impedance matchign device eg. the mf x10-D or x-10v3. Again given the way out impedances here not sure the effect and whetehr this is way out their workign range a well.

Why is it you want to dispense wiht the ME pre ?

[hired goon]

G'day,

Thanks for the links, Al.

you could also consider an impedance matchign device eg. the mf x10-D or x-10v3.[/b]

I looked at the x-10v3 and it's output impedance is 200 ohms.

Why is it you want to dispense wiht the ME pre ?[/b]

I'm not dispensing with the ME pre-amp -- it may turn out that the ME15/ME850 combo is just beaut.

But I'd like to know what options I have should I want to dispense with it for whatever reason (sound, functionality, etc). I want to make sure that my options are not too limited because of the requirements of the amp.

--Geoff

[Guest alebonau]

G'day,

Thanks for the links, Al.

I looked at the x-10v3 and it's output impedance is 200 ohms.

I'm not dispensing with the ME pre-amp -- it may turn out that the ME15/ME850 combo is just beaut.

But I'd like to know what options I have should I want to dispense with it for whatever reason (sound, functionality, etc). I want to make sure that my options are not too limited because of the requirements of the amp.

--Geoff

[/b]

as you said geoff, looks like the me pre and pwr amp here are pretty much made to work together. Given the very unusally low 2ohm output impedance of the ME pre and very low input impedance of the ME power.

Probably nothign stoppign you trying anythign else, Best would be to borrow a pre or two to check out. Thats what I did in my setup to end with the choice I did. And other guys considering pre's are doing the same. I personally think pre and pwr matchign is an important thing. And probably more so in your case given the pre-pwr you have. It might turn out that any of the pre's you try may not be a good match and your better off stickign with what you have. Anyway dont think any way of you knowing really unless you try out for your self.

[hired goon]

G'day,

I looked at the x-10v3 and it's output impedance is 200 ohms. [/b]

I got that wrong -- the output impedance is actually < 33 ohms, not 200 ohms. Maybe the X-10v3 could be used between a "normal" pre-amp and the ME850 to match impedances, but it uses tubes which would colour the sound ...

--Geoff

[Drizt]

Geoff I think I may have found what you are looking for. I hope I read your request correctly? Are these figures low enough ?

Stello P200 -> Click here for link

Stello P200 (click here for where i got details from)

• ANALOG INPUT : 2 Balanced (XLR) / 4 Unbalanced (RCA) / 1 BYPASS (RCA)
  
• ANALOG OUTPUT : 1 Balanced (XLR), 2 Unbalanced (RCA)
  
• FREQUENCY RESPONSE : 10Hz ? 55 kHz (+-3dB)
  
• INPUT IMPEDANCE : 30 k Ohm (Balanced) / 15 k Ohm (Unbalanced)
  
• OUTPUT IMPEDNACE : 100 Ohm (Balanced) / 47 Ohm (Unbalanced)
  
• Separate Digital Volume Control (Dedicated CS3310 per channel)
  
• Full Balanced Class-A Operation
  
• Bypass for Surround Processor
  
• Full Function Remote (Standby, Display, Inputs, Volume, Mute, Bypass)
  
• Dimension (WHD) : 435 x 85 x 350 mm
  
• Weight : 9 Kg
  

If you ever have trouble contacting the importer give me a PM, as I have contacted him before. Cheers

I have also found another website that describes passive pre-amps as having low input impedance which might be worth lookin into (click here)

[Rick]

Geoff I think I may have found what you are looking for. I hope I read your request correctly? Are these figures low enough ?

Stello P200 -> Click here for link

Stello P200 (click here for where i got details from)

• ANALOG INPUT : 2 Balanced (XLR) / 4 Unbalanced (RCA) / 1 BYPASS (RCA)
  
• ANALOG OUTPUT : 1 Balanced (XLR), 2 Unbalanced (RCA)
  
• FREQUENCY RESPONSE : 10Hz ? 55 kHz (+-3dB)
  
• INPUT IMPEDANCE : 30 k Ohm (Balanced) / 15 k Ohm (Unbalanced)
  
• OUTPUT IMPEDNACE : 100 Ohm (Balanced) / 47 Ohm (Unbalanced)
  
• Separate Digital Volume Control (Dedicated CS3310 per channel)
  
• Full Balanced Class-A Operation
  
• Bypass for Surround Processor
  
• Full Function Remote (Standby, Display, Inputs, Volume, Mute, Bypass)
  
• Dimension (WHD) : 435 x 85 x 350 mm
  
• Weight : 9 Kg
  

If you ever have trouble contacting the importer give me a PM, as I have contacted him before. Cheers[/b]

That actually looks quite decent.

Do you know of any prices kicking around, the power amps look pretty good too.

have also found another website that describes passive pre-amps as having low input impedance which might be worth lookin into (click here)

[/b]

Input impedance of the pre-amp is of no concern, only the output impedance.

Rick.

[Drizt]

That actually looks quite decent.

Do you know of any prices kicking around, the power amps look pretty good too.

Input impedance of the pre-amp is of no concern, only the output impedance.

Rick.

[/b]

When I called I was told some really expensive numbers but when I said thank you but its to dear and went to hang up i was told a more realistic figure.

I was told that I could have the P200 preamp and S200 dual mono power amp for a combined price of less than $4000 (an exact figure was never discussed. At that stage i was looking to buy, but I found the mf amp for much less dollars and jumped on it. I never ended up auditioning the gear in case it was that good that I had to buy it )

So I figure the preamp could be had for around $2000, but thats just a educated guess. I dont have any other figures for any of the other Stello gear sorry.

Regarding my comment on input impedance i think i was mistaken, very tired, probably typed the wrong thing. If someone gets the time they can read the article i linked to to find out.

[Drizt]

I have just done a bit of a google to find some prices but im not having much luck...

I did find this site which has quite a bit of information and pictures -> http://www.aprilmusic.com/products/products_p200.htm

Heres a review of the Pre that also has a DAC (DP200) included by 6moons -> http://www.6moons.com/audioreviews/stello/stello.html

It seems that the Pre that has DAC included is around the $1800USD mark....

Sorry can't find any prices.

[Drizt]

Geoff would you like us to keep looking or is there enough info for you now ??

I have found another one that looks the goods with a 50 Ohms output impedance.

Manley Labs Shrimp Preamplifier - (click here for review) (click here for review 2)

www.manleylabs.com</div>

[Drizt]

I found another preamp with low output impedance

www.advanceaudio.com.au

K-5xe preamplifier

Weight

25 pounds (11.5 kg)</span>

[/i]</span>[/b]

<span style="color:#0000ff">

[Drizt]

The Ayre preamp (K5xe) has a RRP of $6,495. Not sure what the going price would be after the usual discounts.

[nfi42]

The Ayre preamp (K5xe) has a RRP of $6,495. Not sure what the going price would be after the usual discounts.[/b]

I paid $5000 for mine, but it was a demonstrator runout.

[Young Skywalker]

but it uses tubes which would colour the sound[/b]

This may come as a surprise to some people but EVERYTHING in the signal path colours the sound to some extent, not just valves but transistors, capacitors, resistors, cables, transformers, etc. One reason why systems that employ fewer gain stages, good impedance matching and simple loudspeaker designs typically sound more transparent... the less of anything, be it valves or transistors, there is in the signal path the less potential colouration you will hear.

I am yet to find an uncoloured solid state or valve anything and even if I did find one would I be able to identify it? What is our reference point for "uncoloured" reproduction? Surely it can only be what the recording engineer intended before the master was sent out for mass production of CDs, SACDs, DVDs or vinyl pressings. We will never know what the recording engineers intentions were or how close he or she came to meeting those intentions. Hopefully, all recording engineers aim to capture a sound that mimics what you would hear under ideal circumstances at a live performance, neither perched on top of the orchestra or too distant in the concert hall, jazz club, etc, so that when our uncoloured system reproduces the performance everything is as it should be.... if only we lived in that perfect world.

Sorry for straying off topic (as usual) but I am so tired of this valves = coloured concept.

You could always build an uncoloured room, known as an anechoic chamber, but I don't fancy listening to my music in one.

OK, finished choking on my angry pill... I should change my name to "Grumpy" except we already have one here on StereoNet.

Aaron

[JA]

I found another preamp with low output impedance[/b]

Hello Drizt,

I would be good to hear from MickM on this issue. In a post not so slong ago he spoke of a design of his with very low (near zero) output impedance. I am not 100% sure he was speaking of a preamp though.

Perhaps he could comment- Mick?

Best

JA

[Keith_W]

OK, finished choking on my angry pill... I should change my name to "Grumpy" except we already have one here on StereoNet.[/b]

You could always be "Curmudgeon" except that you're too young to be one

[JA]

You could always be "Curmudgeon" except that you're too young to be one [/b]

Or go for "G2"

Hello Keith and Young Skywalker,

Best

JA

[statman]

Hello Drizt,

I would be good to hear from MickM on this issue. In a post not so slong ago he spoke of a design of his with very low (near zero) output impedance. I am not 100% sure he was speaking of a preamp though.

Perhaps he could comment- Mick?

Best

JA[/b]

No I wasn't speaking of preamps , but poweramps. Interestingly I just finished a 50 watt PSE 845 amp with output impedance of 0.0 ohms (damping factor = infinity) This thing almost makes me take back my previous criticism of SE amps , and is unlike any of the 50 or so SE amps I've built over the years. SE amps are like Sirens- they entice and tease, but never deliver 100%. This one delivers to the limit of it's power capacity , more than enough for high effeciency speakers, but still not enough for 80% of speakers. But i like lots of headroom , and that doesn't seem to be a big thing for others. The slightest bit of distortion unsettles me .

But getting back to tube preamps- one of my preamps has an output Z of 15 ohms , which is very low and will drive any power amp, but the design needed to get that low does require some compromise , which although gives great technical performance on the scope , just doesn't sound as nice as a pre designed to sound musical. But Z can still be as low as 200 ohms , quite capable of driving a SS amp with input Z of 2000 ohms .

Personally I dont think there is anything wrong with a bit of tube coloration in a preamp- this is the place to have it imo, and will always sound better in any system, whether powered by SS or tube power amps. I have never found anyone who disagreed , or found it objectionable , on hearing it. Of course I'm not talking about 50's design slow, warm , "rosy" tube pres (and there are plenty of them made in the present)

I think the high feedback , switching sound of a SS pre is also coloration , but much more benign .

A properly designed tube pre can be ashtonishly fast and transperant , maybe even faster than SS , but with zero feedback , it can just kill a SS pre loaded with negative feedback to make it work.

Impedance isn't everything, it's quite important, but everything has to be considered to make something that is more than just capable.

MickM

[Super Mustud]

No I wasn't speaking of preamps , but poweramps. Interestingly I just finished a 50 watt PSE 845 amp with output impedance of 0.0 ohms (damping factor = infinity) This thing almost makes me take back my previous criticism of SE amps , and is unlike any of the 50 or so SE amps I've built over the years. SE amps are like Sirens- they entice and tease, but never deliver 100%. This one delivers to the limit of it's power capacity , more than enough for high effeciency speakers, but still not enough for 80% of speakers. But i like lots of headroom , and that doesn't seem to be a big thing for others. The slightest bit of distortion unsettles me .

But getting back to tube preamps- one of my preamps has an output Z of 15 ohms , which is very low and will drive any power amp, but the design needed to get that low does require some compromise , which although gives great technical performance on the scope , just doesn't sound as nice as a pre designed to sound musical. But Z can still be as low as 200 ohms , quite capable of driving a SS amp with input Z of 2000 ohms .

Personally I dont think there is anything wrong with a bit of tube coloration in a preamp- this is the place to have it imo, and will always sound better in any system, whether powered by SS or tube power amps. I have never found anyone who disagreed , or found it objectionable , on hearing it. Of course I'm not talking about 50's design slow, warm , "rosy" tube pres (and there are plenty of them made in the present)

I think the high feedback , switching sound of a SS pre is also coloration , but much more benign .

A properly designed tube pre can be ashtonishly fast and transperant , maybe even faster than SS , but with zero feedback , it can just kill a SS pre loaded with negative feedback to make it work.

Impedance isn't everything, it's quite important, but everything has to be considered to make something that is more than just capable.

MickM[/b]

As usual, a great post Mick. Thanks.

[Young Skywalker]

Mick,

Can you please tell us more about this 50W PSE 845 amplifier? Is it a stereo or monoblock design? What 845 tubes is it designed around (Chinese, KR Audio, NOS)? Is it destined to become a commercial product? 50W is oodles of power and headroom for the sort of speakers that interest me.

Aaron

[ophool]

Interestingly I just finished a 50 watt PSE 845 amp with output impedance of 0.0 ohms (damping factor = infinity) This thing almost makes me take back my previous criticism of SE amps , and is unlike any of the 50 or so SE amps I've built over the years. SE amps are like Sirens- they entice and tease, but never deliver 100%. This one delivers to the limit of it's power capacity , more than enough for high effeciency speakers,[/b]

Mick, I think it is not only SE amps that like to entice and tease, I can think of one builder of them who seems to be doing exactly that here :biggrin:

c'mon spill the beans, will this be a production model?

[TigerScent]

Hey i have the same issue, removing the resistors worsened the sound...there must be a chi-fi 50$ solution out there...at present am using a guanzo (allegedly Mattisse clone - simple but sounds good) valve buffer (cost 50$) as temp preamp to Rotel 990BX amp with surprising results, ...finding something similar to a valve headphone amp they say will have typically low impedences for my ME550 II

 

Does one really knead to spend mega $k to get a good sound??

Edited April 23, 2023 by TigerScent

[TigerScent]

But then again, i spend a lot on tonearms 

Edited April 23, 2023 by TigerScent

[andyr]

10 hours ago, TigerScent said:

Does one really need to spend mega $k to get a good sound??

 

No, but one needs to use an ss preamp, for a Zout low enough to cope with the ridiculous ME Zin.

 

10 hours ago, TigerScent said:

Hey, i have the same issue, removing the resistors worsened the sound...there must be a chi-fi 50$ solution out there...at present am using a guanzo (allegedly Mattisse clone - simple but sounds good) valve buffer (cost 50$) as temp preamp to Rotel 990BX amp with surprising results, ...finding something similar to a valve headphone amp they say will have typically low impedences for my ME550 II

 

Your Rotel 990BX amp will probably have a standard Zin of 40-100k.  So it is not as critical as the OP's ME amp is, to a preamp's Zout.  So I'm sure your Guanzo valve buffer probably sounds very good.

 

[sir sanders zingmore]

Hopefully after 15 years the OP found a solution…