[nirmal]

Hi all,
I am new to this forum, so kindly excuse if I accidentally offend anyone.
My current setup is Marantz PMD340 cd player as transport, Benchmark DAC1, Cambridge Audio DAB 500 tuner, Bryston 4B SST, B&W 602's (changing to PMC IB1's in the very very near future) and all cables and interconnects (balanced throughout) by chord - the best in their range.
I have read on many forums that  having a pre-amp with the Benchmark DAC1 improves the sound quality compared to plugging it straight into the power amp and using the inbuilt head phone amp for volume control.
Is there anyone else with experience with similar setups on the forum who could suggest suitable pre-amps to audition? I would prefer to keep all connections balanced if possible.
The Music First Audio passive magnetic pre-amp is one that crossed my mind. Any comments? Is the silver wired version worth paying for in terms of sound per £ in comparison with the copper wired version?
I dont have much experince with valve pre-amps, and the idea of deliberately adding distortion to an otherwise exceptionally clean setup, along with the amount of time and money needed to keep it happy do not appeal very much, but if it does make a staggering difference, I would be quite happy to buy one. kindly advice.

Cheers
Nirmal.

[KJ]

Welcome to AC Nirmal!

Since you have the Byston amplifier, why not demo the new Bryston BP26?  It has received great reviews from others on AC.  If that's out of your price range, consider a used BP25.  I think you'll find many others have enjoyed the cleanliness and synergy of the Bryston amp/pre-amp combo.

-KJ

[nirmal]

Thanks KJ for your suggestion. I am going to audition the bryston preamp. I dont want to rule out other possibilities which I am not aware of yet, which might be equally good or better. My budget is £2000 or less, and I listen to mainly rock, pop (the good old fashioned 70's and 80's stuff, not the trash being marketed nowadays), reggae, a fair bit of easy listening songs of varying genere and jazz and the occasional classical album.
The preamp stage seems the ideal place to inject a teeny weeny bit of flavour into a neutral setup, and I am curious about what others have used to achieve their sonic nirvanah.

Cheers,
Nirmal

[Rivendell61]

Hi nirmal,
I am not a Bryston owner....but I do use a Benchmark as a pre-amp.  I have been working on some of the same questions you raise.
I am a little confused by your question....are you actually using the headphone outputs (via 1/4" TRS) as outputs to the Bryston?
Not the XLR outs?
1) My sense is that the "better preamp will improve the DAC1 sound" voices are really saying: "I don't like the neutral sound of the DAC1".
It puts out a very high quality signal.  I don't think any other pre will 'improve' it in any 'objective' way.
2) Adding some 'bit of flavour', as you put it, is a different matter.
My guess is that the Bryston pre has sonic design intentions quite like the Benchmark, i.e., not to add any color.  So it may not fill that wish.
One pre not often mentioned is here (from Manley Labs who do lots of pro mastering gear):
http://www.manleylabs.com/containerpages/shrimp.html
It has very low output impedance so it can drive cables with no loss.  And coming from Manley it should be very neutral--but maybe a touch less so than a Bryston?
In the UK you can buy it from Sable Marketings Gary Ash:
http://www.manleylabs.com/images/SWAG/plant.jpg
(Ash on right looking professional--Robert Plant too)
It is not balanced but:
3) Most tube pre amps are not balanced.  Keep in mind you do not need a 'balanced' pre output to have a 'balanced' connection!
Just a differential input on the power amp.
4) With the the various output options on the DAC1 (XLR/RCA/Plug) you could even run both a stright signal cable set to the Bryston--and one via a tube pre-amp.  Which would give you interesting 'flavour' switching options.
5) Have you used the internal XLR attenuation jumpers to adjust the output so you have full use of the vol. pot?
Mark

[nirmal]

Hi Rivendell61,
Thanks for your reply. I am using the XLR out on the DAC straight into the  power amp. I believe the DAC 1 has a headphone amplifier, which doubles up as a preamp stage unless disabled by the switch on the rear panel. I should have  phrased my statement differently!
I have had the DAC 1 for only a few months and I am deeply impressed by its ablilities. It is by far the best value for money I've spent on audio equipment. My impressions from the specs, and listening are that the preamp stage is a good clean one, but I havent really done a A/B comparison to find out if it can be improved upon.
My interest in this was sparked by reading a review on the Music First Audio passive preamp http://www.mfaudio.co.uk/passive_pre.htm
My reasoning (which might well be wrong) is that using such an amp, or any other design with a minimal signal path, would improve upon the performance (I accept that this may always not be the case) by virtue of less signal processing and a shorter path and injecting flavour in some cases into the system. Also, it would allow me to use an FM tuner instead of the DAB tuner I am now using.
Your suggestion of running two lines to the amp sound very interesting. Someting worth trying definitely!
I havent used the internal attenuator jumpers on the DAC 1, as I find the factory settings okay, and I wasnt sure if it would do anything to the signal other than change its amplitude. I'll get the screwdriver out tonight and have a go. Thankyou for your suggestion of the Manley Shrimp. I will try to see if I can audition the Shrimp.

Cheers,
Nirmal

[PorkpieHat]

I have a BP25 which I am using with a 4BSST and I love it. Very neutral and clean sound. Great soundstage and imaging. Remote with volume control, muting and phase reversal. The latter is very useful with some CDs - I can be listening to a CD that sounds harsh, hit the phase button and suddenly it sounds better. I have no idea why this is. Multiple inputs and 2 outputs also very useful. Now that the BP26 is out you might be able to get a good deal on one of these used. I have not heard the BP26, but I have seen postings which say that the sound is very similar. This is a no-nonsense pre-amp without a lot of eye candy but a very winning sound IMHO.

[James Tanner]

3) Most tube pre amps are not balanced. Keep in mind you do not need a 'balanced' pre output to have a 'balanced' connection!
Just a differential input on the power amp.


I would be interested to know how this is done?
Because --- if the 'send' is unbalanced, you get the possibility of ground loops, because ground is used as half the signal-carrying circuit.

james

[Rivendell61]

Hi James,
Apologies for letting your question hang--I did not get a 'ping' and only just wandered back here....
Now you have put me on the spot!  I only understand this subject from what I have read--and I have limited luck finding things I've 'carefully' filed on my computer.  I can throw up a few things which might, at least, give you something to agree/disagree with.

Definition: We define connection type via impedance.  So, Balanced has two conductors with equal impedance to ground.  Unbalanced does not.
[ref: Bill Whitlock, Jensen AN-003]

Three quotes from the same source:
1) "AES recommendations require the impedance on hot/cold to be balanced, but to actually produce a signal on the cold wire is optional."

2) "Bill Whitlock provides a good expose on what balanced means.
The crux of the story is: you don't need a symmetrical output signal.  The 'requirement' for a symmetrical output signal is one of the longer standing myths of audio.
You need to have identical impedances on the hot and cold wires, and a good differential input.  It means you can make a fine balanced output on an unbalanced pre-amp by simply tying the cold wire to ground through an impedance which is identical to the impedance of the (unbalanced!) output buffer that drives the hot wire.  The differential input does the work."

3) "The most important thing to do is to use the differential inputs to extract the output signal from your pre-amp referencing the pre-amps ground.  Outside audio this is known as Kelvin sensing"

So....following instructions, I (for my DAC to amp—can not assume this is a ‘universal’ formula) wired a 'twisted pair' thus: RCA end: "tie cold lead and shield together to ground--XLR end as appropriate, Pin1 Shield, Pin2 Hot, Pin3 Cold (to ground at preamp)--In this way, ground currents that flow from chassis to chassis do not flow on the cold wire and place no voltage across it"

I hope that gives some rational explanation!
Not sure what the Bill Whitlock citation above is [he is of Jensen Transformers Inc] but there is a Power Point style AES paper from Whitlock titled "Real-world balanced interfaces and other-world myths" which deals with some of these issues, here:
http://www.aes.org/sections/pnw/pnwrecaps/2005/whitlock/whitlock_pnw05.pdf

I’d be interested to know what you think.
Mark