Tisbury Audio Mini Passive Pre-amp

[jandl100]

Oooo - I've come across a rather special product - I feel a mini-review coming on!

My luvverly Restek Consens pre has been, just occasionally, playing up a bit ... so I thought I'd get in a backup device just in case it has to be sent off for some TLC.

I'd heard 'word on the streets' that the Tisbury passive pre was interesting, so I have duly invested in one to have a go.

Unbelievably cute, and very well made and finished indeed, this wee beastie measures a mere 11x4.7cm at it's faceplate.




Pretty much any combo of inputs and outputs can be had, as long as there are 4 of them!

Lifting some of the blurb from the eBay ad .....
"A passive preamp with a precision SMD stepped attenuator, silver plated OFC wire with PTFE sleeve, silver plated selector switch, and exceptional quality CMC gold connectors. The enclosure is anodised aluminium with a solid wooden front made from american black walnut. .... The volume control is a precise, audiophile grade 21 step attenuator with an array of laser trimmed SMD resistors, giving a tolerance of +/- 0.25dB .... These are available in 10Kohm (standard) or 50Kohm which can be used with tube based sources.
We also Alps Blue Velvet potentiometers which can be used instead of the stepped attenuator"

I have the stepped attenuator version. The steps in volume are about right with my speakers (mid 80dB/W sensitivity); not too large a jump per step.

The sonics are a bit surprising. Very clear and lucid, the transparency on offer is way beyond the normal run of low price passives, and leaves some high priced ones in its wake as well! It may not have quite the rez in the mids of my very high rez active Restek, but it's still to a very high standard and can make for a more cumfy listen than the 'warts & all' Restek, which can be a little forthright in the upper registers. Another comparison is with the TVC passive pre-amps - it's less cosy and warm than they generally are, ime, and has higher rez across the freq band. I've had several TVC pre-amps and enjoyed them, but imo the Tisbury is better; more accurate and revealing.

Unlike many non-TVC passives, dynamics are not noticeably diminished - TVCs are good at this, as well, ime.
Bass is more than a little astonishing in its clarity, control and power. Really special.
Treble is very extended and open, detailed, focussed and pure.
Imaging is ... well, it's beautiful, both laterally and in-depth. Nicely focussed and very believable.

A great, genuine high end product at a very low price for the sq it delivers, imho. My Restek pre is on gardening leave at the moment.

[Ali Tait]

Looks good value Jerry.

[realysm42]

Sounds good.

Aren't passive preamps meant to not have as much control when it comes to scale and bass?

I've no experience of any preamps; just trying to figure things out.

[jandl100]

Aren't passive preamps meant to not have as much control when it comes to scale and bass?

Yep. But! --

Listening again this morning - the bass is just astonishing in its power, depth articulation and control. I ain't not never heard it this good before -- active (valve or solid state), passive (resistive or transformer based). Hmm. Maybe it's just hit it lucky with the particular characteristics of my system.

[realysm42]

Interesting.

And well done! If its working that week that's great news.

But it makes nothing clearer for me

[jandl100]

But it makes nothing clearer for me

Me neither!

[myles]

I dropped your name across on the 'Wam, as some guy was asking about exactly this.

[jandl100]

I dropped your name across on the 'Wam, as some guy was asking about exactly this.

I've dropped the OP - Steve 'Bourney' - a PM about it already.

I really don't want to get involved in a Wam punch-up about the active/passive debate!

[Tarzan]

Looks interesting Jerry

[apollo]

Congratulations on the pre. I myself use a passive pre in my setup and can attest to the transparency and accuracy.

The thing about resistor based passive is that they are incredibly transparent compared to most of the active preamps, because its extremely difficult to design an active circuit playing with such small signal levels which a preamp works with. Well designed ones are super expensive. OTOH, the resistor based passive because of the use of just passive components with minimum level of signal distortion, can be made very accurate.

However,

• They have no active circuit or a transformer (like a TVC) and hence no impedance matching. Low output impedance from the source and high input impedance of the power amp is required. Also a short low capacitance interconnect between the pre and power is essential to bring the best out of a passive.
• They only attenuate the signal coming from the source, hence a high source output coupled with high input sensitivity of the power amp helps.

I see that you use a Krell 250a, which has a very high input impedance of 100k, allowing the circuit to push enough current. No doubt you are not seeing the loose or uncontrolled bass and reduced dynamics many people face when they dont take care of the impedance matching while using a resistor based passive.

But I will be interested to know what volume levels you need to use on the pre, seeing that the input sensitivity of the power amp is pretty low at 2v. Probably you don't need much of the power which the power amp can provide and hence can get away with a low drive, or your source has a tremendously high output.