advertisement


Differences in passive preamps?

foxwelljsly

foxwelljsly

Me too, I ate one sour too.
In lieu of a proper pre-amp, I’ve been using a very cheap hairshirt nobsound dac21 SA pot with a SP19 source selector for some time and am contemplating dropping a few bob on a Rothwell or, more likely, a 10k dual mono Khozmo.

Power amps are a Leak stereo 20 and a class D dual mono IcePower 125asx.

I was wondering:
  • what audible improvements have other passive pre users had noticed from upgrading?
  • Are there any cheaper options than the Khozmo, which’ll be around £400+ including tax and shipping?
Not interested in the Tisbury as it’s pretty much the same pot I already have.

Cheers
 
Last edited:
foxwelljsly said:
Which model?
Click to expand...
Prototype ls model..they have one volume for both channels..mine has a volume for each channel, the stepped attenuators look like a work of art! A handmade masterpiece...there is one on the bay for £600 ish.. word of warning though if your phono amp or cd player etc isn't good enough? This pre amp will show it..one of the reasons I bought the icon audio phono stage as my CA 640 p sounded great but had a brittleness which grated after about five mins..and the rega phono stage sounded awful..all my digital stuff is ok with it on the whole..and it's fussy with cabling too! But it's worth the effort as the sound is wonderful.
VDH cables work ok with it..but LFD cables work best..spiroflex is their cheapest and it's ok..the only passives that you can compare it with is music first or the Japanese handmade kit in my opinion..Walter Becker had a LFD amp..wow!
 
Eoin said:
Any specific recommendation..?
Click to expand...
Used mine with the nobsound dac 21 SA pot (search on e bay) and it sounded great. About £50 shipped from China, but only a single input and output. I'm pretty sure the Tisbury uses the same pot, but every time I've used a Tisbury, it seems to be attenuating at full wick - ie, it won't go loud enough.
 
You might get a pleasant surprise when you try the little TISBURY passive pre.

It is more than just a stepped attenuator and selector. I believe that there is some important impedance matching tricks going on in its clever little circuit.

Any chance you can actually try one?

We LOVE ours!
 
SONDEKNZ said:
You might get a pleasant surprise when you try the little TISBURY passive pre.

It is more than just a stepped attenuator and selector. I believe that there is some important impedance matching tricks going on in its clever little circuit.

Any chance you can actually try one?

We LOVE ours!
Click to expand...
Is there more than one Tisbury? Here's a quote from an article relating to it:

When asked about the input and output impedance of the Mini Passive II, Young clarified that, though the 10 kΩ input impedance remains constant, “…output impedance varies from 0 to 2.5 kΩ depending on volume position” or knob setting.

That is what an ordinary 10k (resistive) pot would do, without any "impedance matching tricks".
 
Just last week I bought a stepped attenuator version of the NVA P50 to compare to my older P50 (which I have always been very happy with).

I am amazed by the difference between the different versions. The P50SA has greater definition throughout frequency range (bass lines/rhythms in particular), faster transients - finger picking of guitar strings better defined/more realistic.
I have found myself smiling when I play tracks which I have “known” for years.

So yes, in my experience, changing type of passive can make large difference, which seems strange given the small number of components in the signal path.

top tip 😊 : Both P50’s give option of “direct” connection if you are using just one source - also worth doing as it bypasses the source selector.

edit: It may not apply in OP’s case but for owners of old style P50, NVA offer upgrade of wiring and change to stepped attenuator.
 
I tried a Tisbury to get a feel for passives and it is good for the money. The Khozmo was a step up to these ears (both with a Leak ST20). I use a dual mono Khozmo but have a stereo spare if you'd like to borrow it.
 
A couple of Audio Synthesis here including the single-input dual mono Passion Pro which is so good ahead of the Leaks I can’t tell the difference with it in circuit or driving the amps straight from a Chord Mojo. The Leaks are an ideal case though as they have such high input impedance (1mOhm).
 
Eoin said:
What’s the considerations with my 606. Input impedance is 20k.?
Click to expand...

That is pretty much the same as a 303 which is IIRC 22k and 0.5V for full out. The 303 works well with my Audio Synthesis passives.

To be honest any problems I’ve had with passive preamps is with sources upstream of them, some stuff just sounds flat and undynamic into them, e.g. I never found a phono stage I felt worked well (I was mostly trying valve ones), though most CD players and DACs seem ok. I think you need a very low output impedance on the source component for best results. I certainly came to the conclusion that I can’t beat the AS passive with the Leaks, but I need to choose my sources carefully. With the 303 I do prefer my Verdier valve pre to the AS, though I’d not argue it was more “accurate”.
 
I only have experience with two passive pre amps, both TVC types.

The first was a Glasshouse Audio and then I swapped that to a Music First Audio Classic V2.

The MFA works brilliantly with all three of my power amps: Quad 909, Radford STA25 and Leak Stereo 20.
 
Eoin said:
What’s the considerations with my 606. Input impedance is 20k.?
Click to expand...
I’m about to buy some TKD 2CP-601 10k pots, to go ahead of my Avondale NCC220s. Their input impedance is 19k, so I’ll report back in the new year.

It’s my intention to have an alternative to the flat-earth sound of my NAC72 preamp. I expect a very different sound, but I just fancy an alternative, for use when I’m in the right mood for a rounder sound.

@Tony L did build those TKD pots into a sandwich box I think. Why did you change them, Tony? Was there any difference?
 
You must log in or register to reply here.


advertisement


Back
Top