Whatsisnaim
pfm Member
I really wanted to like the Allegri enough to use it as a replacement for my 282, but it couldn’t match it. I’ll give it another try at some stage before I give up.
Quality passive preamp?
- Thread starter Rosewind
- Start date
Mr Underhill
pfm Member
Damn you Peter!
Yes, I bought Mike's Allegri. Listening to it through different cables and playing with support etc. Certainly enjoying what it does. My 868 will probably be a phono stage!
M
Rosewind
Lost in Translation
Interesting M. Now you can have it both ways when the fancy takes you. In this way you can also get a real impression of the strenghts and weaknesses of a "passive" preamp. I know that it cost you something extra over just sticking with the EAR 868PL as a full pre. I hope it will be worth the extra cost.
If / when I make the same move, I will have to sell off the Herron VTSP2a first. Still, I am tempted to do just that.
If / when I make the same move, I will have to sell off the Herron VTSP2a first. Still, I am tempted to do just that.
Mr Underhill
pfm Member
Hi Peter,
I am REALLY enjoying this. I think it has pulled my line level quality up to that of the LP12, if not beyond. I had arranged with George to try the Allegri before your question, but I love to spread the blame and not look to much at my lack of self control!
M
I am REALLY enjoying this. I think it has pulled my line level quality up to that of the LP12, if not beyond. I had arranged with George to try the Allegri before your question, but I love to spread the blame and not look to much at my lack of self control!
M
hifinutt
hifinutt
very cheap price you got it for , look forward to your thoughts .
Mr Underhill
pfm Member
Hi Phil,
Having listened to George's I was very much in two minds. The 868 is excellent, but the Allegri was better in many aspects and the question was could I ameliorate the aspect I wasn't enjoying through setup. The only way to know was to live with one and when Mike's didn't sell as fast as I thought it would I let it eat at me for all of an hour and thought, 'What the Hell!'.
The cables are variations on what I tried last week and they have robbed the Allegri of a tiny amount of dynamics, but also that bit of edge I didn't like too. The Klimax Renew sounds brilliant.
Out of interest did you have an Allegri? I know you had some Townhend Fractal cables and I was wondering if you used them together & what your thoughts are?
Cheers,
M
Tim Jones
pfm Member
It was a P50SA - the single pot, stepped attenuator one.
There were many things to like about the NVAs, and indeed I raved about them here IIRC, but ultimately I couldn't live with them.
Salamander
pfm Member
Thanks Tim, I'm using the P90sa, replaced a P50, and enjoying it.
hifinutt
hifinutt
Thanks M, I only had the dct 300, the fractal are too much sadly. Never had an allegri but folks seem to like them .I have to have a remote on a pre amp so it's not an option at the moment. I would think the ear might have a better midrange perhaps? The tvc are always very clean and very linear in my experience. Some like this and some do not .
Mr Underhill
pfm Member
The area where the 868 won last week was vocals. With the different cables it is a LOT closer. I would say that with the 868 the vocals seem to project a tad more. But the Allegri seems of have very little noise floor and so you hear more into the recording, cymbals have more sheen, brass more rasp and the bass seems deeper.
We are NOT talking night and day differences. Incremental, but nice increments.
Listened to Led Zep II last night, amongst a lot of other stuff, and I have never heard it better at home.
We are NOT talking night and day differences. Incremental, but nice increments.
Listened to Led Zep II last night, amongst a lot of other stuff, and I have never heard it better at home.
Rosewind
Lost in Translation
Can someone shed some light on the advantages and disadvantages of the various principles behind the socalled "passive preamps" that are really "passive volume controllers" meant to provide volume control and multiple source selection:
- pots / stepped attenuators
- light dependent resistors (LDRs)
- transformer based "passive preamps" (the same as "magnetic" passive pres?)
Again I suppose that the secret behind a very good passive pre is the care that has been taken in the component selection and the implementation of whatever principle lies behind the actual passive pre.
- pots / stepped attenuators
- light dependent resistors (LDRs)
- transformer based "passive preamps" (the same as "magnetic" passive pres?)
Again I suppose that the secret behind a very good passive pre is the care that has been taken in the component selection and the implementation of whatever principle lies behind the actual passive pre.
Arkless Electronics
Trade: Amp design and repairs.
The best is a stepped attenuator.
LDR's have zero advantages but the disadvantage of generating some distortion.
Transformer based ones, actually usually autotransformers, can, by switching lots of taps on the autotransformer, theoretically have lower output impedance. Transformers of any type in the audio path are a bad idea as they limit bandwidth and have some distortion plus are likely to have some colouration... which no doubt some will see as a plus point!
Stepped attenuator every time for me. No contest. They will all sound about the same no matter how much they cost as all they are is a string of resistors and a switch.... More expensive ones will usually (hopefully!) have a more robust and long lived switch. Khozmo are a good choice and 20k a good general purpose compromise value wise.
There are several variations on stepped attenuators designed to minimise the number of resistors in the signal path (series, shunt and ladder). I favour a bog standard series one but there should be minimal differences between them. Ladder likely to cost more.
LDR's have zero advantages but the disadvantage of generating some distortion.
Transformer based ones, actually usually autotransformers, can, by switching lots of taps on the autotransformer, theoretically have lower output impedance. Transformers of any type in the audio path are a bad idea as they limit bandwidth and have some distortion plus are likely to have some colouration... which no doubt some will see as a plus point!
Stepped attenuator every time for me. No contest. They will all sound about the same no matter how much they cost as all they are is a string of resistors and a switch.... More expensive ones will usually (hopefully!) have a more robust and long lived switch. Khozmo are a good choice and 20k a good general purpose compromise value wise.
There are several variations on stepped attenuators designed to minimise the number of resistors in the signal path (series, shunt and ladder). I favour a bog standard series one but there should be minimal differences between them. Ladder likely to cost more.
The issue with resistor based attenuators is care needs to be taken with impedance matching and the impact that can have on frequency response especially at high attenuation levels (low volume levels). This can be made worse if using valve CDs or power amplifiers. This could account for why some people find resistive attenuators dull the sound and rob it of dynamics. With transformer-based attenuators this is much less of an issue. So check and take care with resistors.
On frequency response for the Allegri, Martin Colloms measured it and found: The gains were as specified, with accurate channel balance and very wide frequency responses, better than 3Hz - 50kHz -1dB for almost all settings. This is as good as many active preamps and some resistive passives. Of course, some TVCs have ringing at very high frequencies but if it is above 50 kHz then I am not sure you could hear any problems.
On frequency response for the Allegri, Martin Colloms measured it and found: The gains were as specified, with accurate channel balance and very wide frequency responses, better than 3Hz - 50kHz -1dB for almost all settings. This is as good as many active preamps and some resistive passives. Of course, some TVCs have ringing at very high frequencies but if it is above 50 kHz then I am not sure you could hear any problems.
Arkless Electronics
Trade: Amp design and repairs.
The worst position for a passive is the electrical midpoint of the control. Valve power amps are usually an easier "load" than SS ones... Beyond that I've explained all this in great detail several times before so I don't intend to repeat it all yet again!
Good so assuming MC can measure correctly the Allegri does not seriously frequency limit the output.
Impedance matching is important for resistance attenuators and 'rules of thumb' can be found on the internet although it is not a serious issue for valves ( I was wrong there). Lengths of cables are important due to capacitance effects and the very long cables favoured by our US colleagues could run into problems. Nelson Pass makes a buffer for his resistive passive due to the unusual impedance of his SS amps.
A good autoformer avoids some of those issues.
And there are many people/reviewers who favour autoformers (MC, Jason Kennedy, Raffa Todes, Jon Honeyball etc.).
Not trying to sell anything just trying to say why some favour autoformers.
Impedance matching is important for resistance attenuators and 'rules of thumb' can be found on the internet although it is not a serious issue for valves ( I was wrong there). Lengths of cables are important due to capacitance effects and the very long cables favoured by our US colleagues could run into problems. Nelson Pass makes a buffer for his resistive passive due to the unusual impedance of his SS amps.
A good autoformer avoids some of those issues.
And there are many people/reviewers who favour autoformers (MC, Jason Kennedy, Raffa Todes, Jon Honeyball etc.).
Not trying to sell anything just trying to say why some favour autoformers.
Arkless Electronics
Trade: Amp design and repairs.
I reckon colouration is why some prefer autotransformers....
Mr Underhill
pfm Member
Can't say I am hearing any colouration with the Allegri, I suspect the EAR868 could be accused of that far more ......but then I thought that was more even handed and detailed than, for instance, the Bel Canto Pre3VB, which was a damned fine pre-amp.
Horses for courses, and you need to listen for yourself.
Horses for courses, and you need to listen for yourself.
Rosewind
Lost in Translation
I have decided to resurrect this old thread because I have bought a directly coupled DIY Pass DC B1 buffer that sounds really transparent and seems to get me a sound that is both detailed and enjoyable. The kind of uncoloured sound you would expect from a passive pre.
Overall I think that the sound is a bit leaner than thorugh various valve kit I have had over the last few years, though not quite as lean as through another Pass B1 I had here briefly, but with the Pass DC B1 I certainly have better defined bass thorugh my EAR 516 and Quad ESL 57s and there is a level of realistic sweetness to the details in the presentation of most music that leaves me thoroughly impressed.
For example, I hear instrumental details in The Beatles recordings that I never heard before, and this without impairing my listening pleasure. The only thing that I am not used to is the use of the power pot beyond 12 o'clock for loud listening.
Still, the Pass DCB1 isn't truly a passive preamp, is it?
Overall I think that the sound is a bit leaner than thorugh various valve kit I have had over the last few years, though not quite as lean as through another Pass B1 I had here briefly, but with the Pass DC B1 I certainly have better defined bass thorugh my EAR 516 and Quad ESL 57s and there is a level of realistic sweetness to the details in the presentation of most music that leaves me thoroughly impressed.
For example, I hear instrumental details in The Beatles recordings that I never heard before, and this without impairing my listening pleasure. The only thing that I am not used to is the use of the power pot beyond 12 o'clock for loud listening.
Still, the Pass DCB1 isn't truly a passive preamp, is it?