Have you read the (really long) thread on the Lightspeed? Plenty of amps are recommended in there. The sense I get is that it will work with many, many amps, but George recommends an input impedance of no less than 48kohms and input sensitivity no more than 2v, although several people have reported great results even when straying from these guidelines. It's more common for tube amps to have that high of an input impedance, so that's what seems most often recommended.
Here's a Jolida
that fits the bill. Of course, your other components, etc. enter into it.
Hi Dddrrree, your Lightspeed will work into the 10k input impedance of your present amp with no stress to any components.
However it now becomes the source cdp/dac which has to be able to drive the combined impedance of the 10kohm of your amp and the input of the Lightspeed, which equates to around 5kohm combined. This is still fine for the majority of low impedance output sources which have solid state output stages of 100ohms or less.
But it becomes a problem with tube output stage sources cdp's dac's etc, that are usually sometimes over 2kohm output impedances, then you could hear some dynamic compression, still not harmful to any components.
If you want to get the best from your Lightspeed Attenuator, then yes the poweramp input impedance should be over 47kohm which is the industry standard for solid state amps and tube power amps are well over that at 100kohm or more, which are even better.
Thanks for the walk through George. I'm driving the lightspeed using a musical fidelity V-DAC, which is supposed to have an output impedance between 40ohm and 80ohm, which seems to be within the range you mention. (BTW: what is the right email address to use to buy another unit? I sent several emails to the one on your site but never received a response.)
As a complicating feature, I'm using Y connectors to split the lightspeed output signal so I can feed it to a velodyne SMS-1 bass management unit (which I use to drive two subs).
Poprhetor: I should have mentioned that I don't have high efficiency speakers (recommended 100-150W @ 6ohm) so it doesn't seem that the jolida's would work. I'll troll through the huge lightspeed thread for amp recs; the problem is that its information isn't so dense :)
I'm running the Lightspeed into a Dynaco ST-70 rebuilt by Will Vincent. Bought it straight from him through A'gon for just over $1,100. It has an input impedance of 470K ohms and input sensitivity of 1V. How do those numbers sound?
"Dddrrreee As a complicating feature, I'm using Y connectors to split the lightspeed output signal so I can feed it to a velodyne SMS-1 bass management unit (which I use to drive two subs).Dddrrreee"
You can get me on "georgehifi at optusnet dot com dot au"
As with any other system active or passive these "Y connectors and active subs" brings in another added equation to the impedance matching, of system compatibility.
If you use active subs, this makes the load to the Lightspeed and the source even more difficult, then I suggest a buffer after the Lightspeed like the "Burson 100 Buffer" which unfortunately is no longer available new, you may find one second-hand or another equivalent that is a pure buffer with no volume controls or selector switching on it.
I use a Lightspeed clone (Lighter Note by Uriah Dailey) with a Rogue Atlas. Not sure about the exact specs but they are working GREAT together.
Be patient and wait for a used Music Reference RM-10 MkII to come up for sale. You won't be sorry.
Dddrrreee, good advice from Clio09 on the Music Reference RM-10 MkII a quite few Lightspeed Attenuator owners have had great success with this amp, saying it's a match made in heaven.
As does the amps Sam Tellig from Stereophile, he uses the Lightspeed Attenuator with his Quicksilver Silver 70 mono blocks and his much loved low powered Sun 2A3 single ended triode monoblocks, and used the words.
"the harmonic presentation was nothing short of flabbergasting. As a former (very poor) pianist myself, I look for the magic of the moment—the sound, not so much the movement, of the notes. I know that, in musical performance, timing is everything. Still..."
I use a Sumo Polaris 310 the early model. The two following models really sound different to me. The one I have to me sounds like a rowland model 1 that I compared it to for a few weeks but with a very slight more liveliness. That is quite good company. Sumo actually had their pre amp with a passive mode so it works well. It has 47k input imp. and a 1.27 input sens. This amp is twenty years old used on average 12 hrs a week. Never had problem with it. But may be hard to find being that old. The 2 following models were redesigned by someone other than the original designer Rich May. So those are really a different sound, a bit bright imo. From what I hear though some day it would fun to try a proper tube amp. I have had tube amps, arc classic 60 and arc vt70, in the past but not with the LS. The sumo when it comes up seems to be asking about 300..I don't know if he still does, Mike Bettinger use to fix and rebuild sumo and gas gear. I understand he did a great job.
George: thanks for all the insight. I can't seem to find the burston 100 anywhere --- would a musical fidelity x-dac tube buffer work also? There's one in the classifieds now: http://app.audiogon.com/listings/musical-fidelity-x-dac-v-3-tube-stage-buffer
Or are there other tube buffers you consider reasonable for not messing about with the signal?
Dddrrreee: trouble is the xdac is a tube ouput stage buffer you will be back in the same boat trying to drive your 10k amp and ?k two times active subs from it. It needs to be a solid state buffer. with 100ohms or less output impedance.
Thanks for all the amp pointers!
I'm having a hard time tracking down the older recommendations. Does anyone have experience with Muse 150s or with marantz ma-700 monoblocks?
Again, I need something ideally that is more than 100W @ 8ohm.
George: the burson 160 is still for sale. Would that work as well as the 100?
Thanks George. Since you recommended the burson-100, did you have any thoughts on the burson ab-160? The specs look as you suggest:
Input impedance: 500 KOhms
Frequency response: 1Hz (-0.3dB) to 35 kHz (-1dB)
Signal to noise ratio: >120dB at 0dB gain
Output impedance: line out 15 Ohms @ line level
Power dissipation: >10W, internal, regulated power supply
Maximum Output Voltage :12VRMS
Maximum Input Voltage: 6VRMS
Yes, the Burson AB-160 will work just as well. It's just the newer (and ostensibly better) version of the old Burson 100 buffer.
Dddrrreee: Trouble is I think the 160 has a lot of gain, and a volume control that has to be bridged out so the Lightspeed can shine through, the whole reason is not to have contacts (volume pots)in the signal path. The 100 is better if you can get them to make one or a kit.
George, when you refer to the volume control of the 160, are you referring to the front dial or the 3 dB / 6 dB selectable gain? If the front dial, it's just used for input switching.
Oh, ok then then all you need is it set it for 3db gain, and if you can bridge out the rotary input switch, it's not as bad as having a pot in the signal path, if it's a dual leaf switch (that is one leaf either side of the wiper). If single leaf then bridge it out and only use one input.