Passive vs. active preamp- what´s best?

[ecosprog]

I realise that this is a controversial topic but I am struggling to make this decision and thought I´d try and get some third party input.

I have a new tube power amp on its way and need a way to control the volume, and to let me connect my two sources. I have a Yaqin MS-12B tube phono pre-amp which I intened to use as the line stage. However, as I sit listening to Leonard Cohen through my Bottlehead Crack it occurs to me that the simplest solution would be a simple box with a selector and a decent stepped attenuator, or a passive preamp. The more a play with my system the more convinced I a becoming that simple is ultimately the best. Hence my thoughts on going the passive route.

So, having never tried a passive pre-amp the question it - what are the pros and cons of going this route? I have Googled this subject and found a number of threads on other well know forums but, as usual, with much conflicting opinion. I´m somewhat resigned to the fact that the ultimate solution will be the ´suck it and see´ approach.

[willbewill]

Have you read this?

http://www.lencoheaven.net/forum/index.php?topic=1310

But why not just use the Yaqin - that's what I'm doing at present

[ecosprog]

I´m certainly going to try the Yaqin with the new amp but I´m somewhat curious about the effects of adding more gain and the associated electronics to the system. Seems to me that the ideal approach is to keep the path from source to speakers as simple as possible.

It was the damn Crack amp that started this whole thing. Looking at the path from LP through to my headphones I was impressed by how little there was in the way.

[reinderspeter]

It all depends on the input sensitivity of your power amp but often the extra gain is totally unnecassary. Most poweramps need no extra gain from a pre amp to get them to full power.
The biggest advantage of a pre amp is its lower output impedance compared to a passive.
If you want to try a passive I'd go for something like this: http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

[ropie]

If you want to try a passive I'd go for something like this: http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

And here's Pedro's attempt at building that preamp:

http://www.lencoheaven.net/forum/index.php?topic=3569.0

[low pitch]

If you like the idea you should try an autoformer vol control - simple magnetic path plus low output impedance (depending on step you are on).  Look over at Intact Audio.  It works for me very well. I personally think it not the box it's in that counts as a preamp - but everything in the chain that is driving the main output valves / transformer.  Well I guess unless you are driving long interconnect cables which mostly we aren't.

martin

[ecosprog]

Sorry for the silence from me, busy week and struggled to find time to look at the suggestions and get my mind around them.

I think the Lightspeed attenuator looks really interesting. Contacted the guy that designed it and queried the price of a ready made unit. Unfortunately it´s a bit outside my budget at the moment so maybe I´ll have a go at DIYing the thing.

One solution that I had come across in the past but had forgotten about until I started lookingagain was the Pass B1 buffer pre-amp. The PCB and matched JFET´s are really cheap (especially now that the euro is so strong against the dollar). It has a minimal parts count and all the reviews I have found suggest that it works very well.

I think I´ll order the Pass B1 and in the meantime plod along with the Yaqin MS-12B. Malcolm, I don´t mean the latter in any derogatory sense. The Yaqin really sounds good. However, I´m questioning the need for the additional gain stage and if I can remove this it has got to improve things sonically - doesn´t it?

[jloveys]

Hi Reese, no problem as we are mostly all very busy for the moment...
For the passive buffer I have for trial and it will be at the meet a unit made by my friend Xavier and the results are very good, I do not use the flimsy volume control of my Mac amp and the sound is better.
I can also use a remote control with it !

                     

[daiwok]

Sorry for the long over due review of the piles of preamps at my place 

just to recap the situation .........



ok, what kicked this off was the Music First Audio Baby Reference which was on loan here in Hong Kong ..... after some local discussions, we gather also the following preamps :

Music First Audio Baby Reference - Transformer passive
Music First Audio Classic  - Silver Transformer passive
Music First Audio MKII - Copper Transformer passive
Miyajima Laboratory passive
Luminous Audio Technology passive
JOB passive
Cello Etude passive
Khozmo Passive (Vishay Naked Resistors Z-foil)

Three other active pre-amps were at my place as well .....

MFA MC Reference
Gnostic Technology Gemini
DOGE 8

so as you can see I have a bit of an over dose over the summer .....

[daiwok]

ok, lets take a look inside the fundamentals of the Music First Audio which are transformer based passive .....



the transformers are heavy and shielded as well as all cabling is shielded (coating)

attenuator



Balanced is also offered



cap used



these preamps are the most refine out of the lot. Dynamics are good, but what you notice is the background, its just jet black and that can be said with most passive. I had to have the volume control on the max to get my system playing at reasonably loud levels which was not idea in my system, but worked. I can say these amps are very very detailed ! The treble region on these amps is incredible as they do not roll off as quick as most active.

All three MFA sound very similar and the silver transformers are more lean compared to the copper. The new Baby Reference sounds very similar to the MKII. Not sure where the difference is to be honest.

These pre-amps are not cheap either.

[daiwok]

Front of the MFA classic Silver



back



the Khozmo sits underneath as reference.

[daiwok]

Next up is the Miyajima Laboratory



very simple, light weight and compact - volume switch is an ALPS









Straight away I recognise the sound of the ALPS, very musical, it has a body to the sound, but not lean. The sound is not as refine as the Music First Audio, but it has a nice swing and tempo, rather than dry and detailed.

[daiwok]

JOB

this is an interesting amp. I believe it was a spin out of a Swiss University project with the help of Goldmund. So basically this is the poor mans Goldmund. Inside you see the ALPS, computer style PCB and wiring is used. The preamp is small very compact and light.















Sadly JOB do not exist anymore, but they also made some nice power amps. The sound is very similar to the Miyajima Laboratory due to the ALPS pot. The resistors are different and does make the sound a tad different. I would say the JOB is more rich in sound than the Miyajima or less detailed depending on what you prefer.

[daiwok]

Size matters ? 



The Luminous Audio Technology passive is like a packet of cigarettes ! its small and deadly !!!

only a single input and single output







volume pot is a NOBLE - boy does this sound good ! superb swing factor and boogie in the sound. It just gels music. May not be the most refine sounding, but foot tapping. Sadly the current versions use ALPS. While the sound is similar the NOBLE is a more expensive POT. The NOBLE POT is also the choice for ASR amps.

[daiwok]

Cello Etude



This amp was revolutionary when it was made in the way it was designed as a resistor based volume switch. The detailing is superb. The sound is not bad either. To me this is the amp that sits in between the Music First Audio and the ALPS / Noble types. It is refine, but not as dry sounding to me as the Music First Audio. It has a nice balanced body, but not as rich sounding as the ALPS/ Noble. So this sits on the fence then ? 







now the inside













resistors