B1 Buffer Preamp

Thanks to Andrew and everyone else who helped with the Jfet problem earlier - my B1 is finally up and running, albiet without a chassis and not the worlds best output caps, but already it's sounding promising. Only been on for 10minutes so I'll give it a few hours of play before I really start to listen carefully. Already sounds nice and 'clean' running into my GB150D - lots of drive, no nasties :D

Time for a beer and some music!

An externally hosted image should be here but it was not working when we last tested it.
 
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Haha well spotted - you know your chassis!! (Is this a new form of audiophile train spotting?! ;) )

Yes it definitely could do with something and I probably will order another of those chassis.

I have a DCB1 Blue Mezmerize PCB on the way actually, but it'll be a while before I get that one built (or can afford to) so I'll get the rest out of the B1 for the time being. Will either get some PEPT NOS russian caps, or indeed the Obbligato caps which I've always liked once I've got used to the sound. Sounds a little too polite at the moment, but it's early hours and I'm hoping it should open up a little after a day or so's playing time.
 
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Just remembered a thread on the SKA audio forum about using the B1 buffer with a GB150D amplifier. In it Greg Ball (designer of the amp) says,

"...the 1K (on the outputs) should become a link, as the GB150D will provide a resistive load."

So I'll try that on my B1 later today. Still sounding a bit 'restrained' and polite at the moment, though I can definitely sense its potential. Perhaps linking out those 1K resistors on the outputs - as Greg suggested for use with the GB150D - will sort this out.

- John
 
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Just linked out those two 1K output resistors, and it definitely sounds better now. More dynamic and treble seems clearer. Not sure if this should be done to any B1, just those that will be used with Greg's GB150D.

What really struck me is how silent the B1 is - absolutely ZERO hiss, hum or any noise at all. Guess that shows what a quiet amp the GB150D is too. When I compare that to the hiss-a-thon that is my Naim 72/140 combination.... well I know which combination I'll be keeping...

;)

- John
 
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diyAudio Chief Moderator
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A big part about the hiss thing is now you got unity gain. Drops noise gain too. You got your system's gain structure better arranged now in other words. Also the Naim pre amps have too much line gain, and the contrast is strong. Even the newer NAC 552 is too much. Have used that pre many times at a friend's and must be around 20dB gain.
 
Yes it's a mystery to me why Naim have yet to address this problem. Surely it must be fairly simple to eradicate, and could be offered as an upgrade on the earlier models.

Having said that perhaps it's part of the 'secret' recipe for the Naim sound - just sounds better that way, albiet with lots of hiss.

I still adore what Naim does with rock or dance music - even though it is pretty artificial in my opinion, with what seems to be an upper bass lift - but the GB150D/B1 combination seem pretty neutral, without sounding bland or dull.

The B1 is starting to sound better now I've removed those 1K's on the output, but I'm hearing a bit of softness on hihats - 'shhhhhh' instead of 'tst!'. I think as the B1 is so simple it might be showing up the sound of the Takman carbon films on the input. I'll wait a few more days then may well replace those with naked Vishays or something similar.

- John

P.S. Looking forward to building your DCB1 once my 'Blue Mez' board arrives from Tea-bag :D
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Naim keeps a legacy. The circuits were set in the 70s by the late JV. Back then they had 100mv-200mV tuners as line level and his MC phono cards were 55dB. About 280mV with a 0.5mV cart. Half that with LowMC. Bextrene coned speakers were in the low 80's for SPL. Gain was dandy. They have a cross era system upgrade ladder, they can't scrap the system structure up the ladder. Their resolution got better but the system gain was not revised, nor their cornerstones of electronic design and parts selection. A Naim is recognizable sonics from any era and slips in tonally in any grade up the ladder. Din connected so not to mix other makes. That is a hard policy IMHO. Tube line stages are sensitive too, due to the adequate valve's usual mu coming from another era. Nelson's mind frame was correct modern system gain structure for digital sources and sensitive speakers when he introduced unity gain line and low gain amps if you read his then articles. Keeping genes is having a marketing identity and being compatible with ancestry but is also being a dinosaur. They have become much more stylish and have nice music servers and CDPs though. Marketing recognizes identity as top characteristic. So quintessentially British ID that got into Bentley car audio. 007 has Linn in his Aston Martin, his boss has Naim.:D
 
Out of interest I'm curious how many are running the B1 with the recommended 1K input resistors, and how many found improvements (not a change, but a genuine improvement) decreasing that to 330 or 220R?

I'm currently running my B1 without the 1K output resistors as it's being used with Greg Ball's 'SKA' GB150D amp, and he instructed me to link out those two 1K outputs when used with his amp.

So that just leaves the 1K inputs for R102/R202. At present my B1 sounds great, but a little too warm and sometimes too polite - music lacks a little 'bite'. Now I'm using 1K Takman carbon films for R102/202. I remember reading a post by 'Nick77' (post #2524 according to my notes) mentioning the same 'dark & recessed' sound and he was using the carbon film Takmans also. So I think the finger of blame lies there.

I have ordered some 1K metal film Takmans instead as they're so cheap. But am now wondering if I should have gone for the 330R value instead as others have done? Then again the 'purest' side of my nature prefers to go with the designer's original intentions. I'm not really into swapping components to experiment when using PCBs as traces often lift after more than a few soldering/desoldering sessions so I'd prefer to get it right straight away.

My source is a Gigaworks 24/192 DAC using UTC A20 output transformers connected directly to the DACs output pins. I assume there's nothing special about that in terms of output impedence?

So, 1K or 330R for the input resistors on the B1?

Many thanks,

- John
 
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Well Greg Ball told me to remove the 1K output resistors if using the B1 with his GB150D amplifier, and that doesn't appear to have caused any negative changes to the sound. I'm happy with that side of things.

As for the input resistors... and without a scope, as you say I really wouldn't know. Best to stick with your 1K resistors from the original design then, to be on the safe side - who am I to question the guru himself ;)

- John
 
The bass level/extension is fine, but the midrange seems a bit closed in, and 'soft'. Music lacks 'bite' for want of a better description. I'll see if things improve if I switch those 1K carbon Takmans for the 1K metal film versions, should be arriving tomorrow.

- John
 
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The 1K Takman metal films arrived today, so I desoldered the carbon ones and replaced with these new ones.

It's only been an hours playing time so far but that sensation of there being a veil over the music, or a certain softness of tone has thankfully disappeared! The sound has the correct amount of sparkle and 'bite' now. Before it sounded like an unserviced Quad II in terms of a somewhat rose-tinted sound! I checked the values of all the resistors incidentally and all were spot on 1K.

All resistors sound the same some say.... yeah..... if you say so ;)

- John