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Dears Sirs,I have two monos of which I like the sound very much.
They have a sensitivity of 0,5V for max power and an extremely and strangely low input impedance of about 5 kohm.
My question is: can it be driven with a passive pre ?
What the drawbacks could be ?
Anyone using passive pre with very low input impedance power amps ?
Thanks and regards,
beppe
Follow Ups:
I thank all of you for your kind and very valuable reply.
In the next days I will try a simple dual pot of 5K placed very close to the power amps, about 50 cm of cables, and listen for the outcome.
Just to establish a reference.
If the result will be satisfactory I will test different types of 5K attenuator.Thank you very much again.
Kind regards,beppe
I also advise against passive with such a low input impedance...its just asking for trouble. Try a Transcendent sound Grounded Grid, its cheap and very good. If you can stretch to 700 euro I know where to get an excellent Silvaweld preamp and since you are in Italy it is not inconvenient to get it from Switzerland to you.
Hi!"can it be driven with a passive pre ?"
Yes!
"What the drawbacks could be ?"
None.. unless your source is AC coupled?
"Anyone using passive pre with very low input impedance power amps ?"
Yes, 2k input impedance. DC coupled SACD player (with Zapfilter2) with good drive.
Use as low impedance as possible for the attenuator (as long as the source can handle it) and preferably a shunt or lather (SP?) type.
Short cables between attenuator and amp input, shielded or coax. I have used a twinned pair with a shield in a singel ended setup. Now I use balanced config.
> > They have a sensitivity of 0,5V for max power and an extremely and strangely low input impedance of about 5 kohm.
My question is: can it be driven with a passive pre ? <Any passive can drive this monoblock, but will sacrifice bottom end energy and dynamics due to the very low input impedance -- 5K in this case!!
> > Anyone using passive pre with very low input impedance power amps ? < <
I did try this combination over decade ago, never success!! Sorry!
However, if you're talking about passive magneitc preamplifier, then it might be another stroy!
Hi!"Any passive can drive this monoblock, but will sacrifice bottom end energy and dynamics due to the very low input impedance -- 5K in this case!!"
Not necessarily. If the source has a cap on the output or a very poor outputstage this could be true but as a rule.. nope!
I have used a 2k amp with 1k shunt attenuator with very good results. No loss of bottom extension and dynamics at all.
its HF that suffers more in passive setups
Well not really.. not if dimensioned correctly.Done right it's the highs that really shines in a passive solution.
The reason you can experience rolled of highs is due to a pot or attenuator of to high impedance paired with IC's of high capacitance. Better to do it the right way ans avoid those problems.
Right now I am using the Promitheus TVC as the second (or the first:) preamp in my system - with the 10k poweramps. No issues at all with 100 ohm source. In case your CDP is 50 ohm, that't exactly my situtation.I tried also 2 other TVCs, S&B and another DIY one, they both work great.
Just relax and go ahead, if you buy TVC and match it right, you will never have an active preamp again.
You might want to try a transformer volume control (TVC), which is more immune to impedance matching than the resistive passive preamps. Your input sensitivity on the amps is fine. Ideally your digital source should put out > 2V, and as previously mentioned have a low output impedance.I have provided a link below that may help explain the philosophy of TVCs. If you can find an S&B based TVC (Music First, Django, K&K, etc.) I would encourage you to try it.
Sources play a role as well. Very low output impedance (less than 100 ohms)is ideal. My 50 ohm sources work well in my setup. 5K might be tough. As you said the low sensitivity could help. I would be worried about HF issues. Best of luck.
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