B1 Buffer Preamp

TommyLCW

I have just finished DIY PASS B1 Buffer Preamp- My first preamp.
I live in Hong Kong and components are cheap.

My total cost is now US$ 30.

They are:

JFET (4) 2SK117 (not 2sk170) = $ 4.
Aluminium case = $ 6.
19V DC PS = (my spare notebook computer supply $0.) or $6. if 2nd hand)
passive components, sockets and dials -mainly (2) 6,800uf, pots, knobs & .... = $10.+

I am currently listening and waiting for its break-in.
If it is not too sweet in a week or, I have plan to use better 10u & 1 u signal caps and ALPS pot. $15 or so.

But clarity is satisfactory. You will not regret is you do one.

Face

An Alps pot will definitely be a step up from a carbon pot.

maximillian

Somewhat an old thread but still pertinent. I just bought parts from Digikey and the board from:

http://www.passdiy.com/store.htm

Choice of parts came from here:
http://www.audiocircle.com/index.php?topic=78312.0

In a week or 2 I'll put this together and try it out. If it works well I will be looking at an input board, a subwoofer low-pass pre, and even a remote volume control. I have researched quite a bit and it seems like stepped attenuators are favored, but I'm lazy and want a remote. Therefore I'm looking at the PGA2320 chip attenuator. I got a remote control PCB from Ebay and may look at an LED bar graph for volume indication (not VU display since I would think this would add noise). Taking it easy to make sure I like all the pieces first.

strider

maximillian wrote: »

Somewhat an old thread but still pertinent. I just bought parts from Digikey and the board from:

http://www.passdiy.com/store.htm

Choice of parts came from here:
http://www.audiocircle.com/index.php?topic=78312.0

In a week or 2 I'll put this together and try it out. If it works well I will be looking at an input board, a subwoofer low-pass pre, and even a remote volume control. I have researched quite a bit and it seems like stepped attenuators are favored, but I'm lazy and want a remote. Therefore I'm looking at the PGA2320 chip attenuator. I got a remote control PCB from Ebay and may look at an LED bar graph for volume indication (not VU display since I would think this would add noise). Taking it easy to make sure I like all the pieces first.

I'm interested to hear about this as it progresses, def. update if you remember.

TommyLCW

Over the weekend, I trial run about 10 hours of burn-in ( or 'break-in' -as the unit is not even warm), the initial harsh sound went away. My B1 is now leaving better and better clarity. Somehow, the soundstage may not be wide enough -my vintage pioneer preamp is better.
So as Face pointed out above, is Alps pot my next move? Also, I just wonder, the many high cost cap (us$20 + for the 10uf ) -the V DC go to 400V, are they really worth the investment? I am using tantalum drops, 10uf 50V at $0.80 . Which one should I go for wider soundstage?

blehmbo

NP's spec calls for polypropylene caps for c100 (1uF) and c101 (10uf). Considering both caps are in the signal path the least you should do is match the spec. If you believe that different capacitors of the same type have different sound signatures, you can experiment a bit further by using different polypropylene caps.

heiney9

The poly caps for sure. The best you can afford.

Sonicap
Clarity Cap ESA
Auricap

are all great performers.

maximillian

Is Sonicap much better than Jantzen?

heiney9

maximillian wrote: »

Is Sonicap much better than Jantzen?

It sort of depends on where you are using it and which model Jantzen you mean. One should be a little more selective using something in the high pass vs. the low pass. I would choose Sonicaps over the basic Jantzen's in a high pass (tweeter) circuit.

H9

maximillian

Here's what I got:

http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-910&DID=7
http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-932&DID=7

Equivalent Sonicaps would be about $60. Is it worth it?

heiney9

Where and what are you using them in.

IMO, yes they are worth it for a nice speaker that you will get lots of use out of. My rule of thumb is my main rig is basically no expense spared. I used Sonicaps in my 1C's. My secondary rig which is 5B's and RT25i's (swapped in and out) I used Clarity Caps because they sound better than Jantzen, Dayton and Solen and don't cost as much as Sonic Caps.

So you need to decide if what you are using them in is worthy

maximillian

I'm building the B1 as well. These caps are for c100 and c101 as mentioned above.

FTGV

I have a blank PC board in my parts drawer for the DC coupled, bipolar shunt regulated supply version of the B1 .The beauty of which is the elimination of the need for spendy film coupling caps.My current set up needs gain other wise I would have had it built by now.

maximillian

Already bought most of the parts. Also, I didn't want to deal with DC coupled so went with the official NP B1 PCB.

Hopefully my system will have enough gain that I this circuit will work. The hookup will be: Source->DacMagic->B1 buffer->Adcom GFA6000->LSi9's.

The way I'm making this pre is that I could change the audio path to a different pre since the rest is just input switching. I would like somewhat of sonic improvement over my current AVR (Pioneer Elite) which is my current pre for music.

TommyLCW

Thank all for prompt sharing about caps. My question was - the rail B1 is 18-25 VDC and signal path is 2-6 V.
All the caps in the last 10 threads are 400 - 600 VDC. These figures are for tube amp & Speaker cross-over! Do I need them in the B1 ?
BTW, thanks MAXMILLIAN, your parts are very much within my budget.
Well, FYI, the gain is enough for my CDP and Pioneer M1500 Power Amp driving Tannoy Floorstanding DC2000 of 91db.

blehmbo

They will work fine in the B1. They were mentioned for their sound character not their voltage rating.

maximillian

Built the B1 today and listened for about an hour. Even though I am using Jantzen caps and a carbon pot, there is a noticeable improvement over using the Pioneer Elite VSX-21TXH. Again my system is:

Original Xbox reading FLAC and ALAC files from a NAS -> TOSLINK -> DacMagic -> MIT EXP2 Interconnects -> B1 pre -> Signal Cable Analog 2's -> Adcom GFA6000 -> MIT EXPS-2 cables -> LSi9's.

Not a top-of-the-line system but decent enough.

The most noticeable improvement is that the highs and lows are more pronounced compared to using the Pioneer as a pre. With the Pioneer I use an STF-2 sub to fill in the bass, but with the B1 the bass may be sufficient without it. I was considering adding a sub channel using a circuit like the one mentioned in this thread (second post). But now I am thinking it's not really needed.

http://www.diyaudio.com/forums/solid-state/59782-leach-amp-sub-pre-out.html


I need to spend more time with this thing. So far, it is great for how simple the circuit is. The clarity is very good and it seems that the soundstage may have increased. It is a step in the right direction compared to the AVR, but I need more time to fully compare the two.

The only negative so far is that there is a slight hum when I turn the volume knob almost all the way up and no sound coming out, but that could be due to using a switch mode wall-wart. I will be changing to a linear supply down the road. However, I can't hear it when any music is playing.

I may replace the caps with Sonic caps. Afterward I will be adding a remote control and relay inputs as mentioned in a previous post. Anyone ever try something like the PGA2320 volume IC? Not using a sub circuit will simplify the circuit. One of the initial goals I had for this project was to use off-the-shelf components, so not using custom PCB's was a goal. Eliminating the sub circuit is a step towards this goal. However, I haven't found a good volume PCB so may have to make my own PCB after-all. All I have found is either really expensive kits or cheap, Chinese PCB's that are questionable in quality.

I've attached a pic. It's sitting on top of the AVR; I still needed the AVR to switch on the amp since it's switched via the AVR and a Belkin PF60.

zingo

Since I started this thread, I'm digging it back up!

I just picked up a B1 from a member at DIYaudio, and plan to integrated it into my Luminous Audio Axiom II preamp. My only concern is the preamp enclosure is fairly small, but I won't worry about that until I try to mate them. The seller did included a stepped pot with the board, so I at least could hook-up the board as is until I figure out its final resting place; I also picked up a 19V laptop PS which should be plenty of regulated current. I'm happy to be back with a B1 again after building one point to point three years ago, as I love the NP sound. I'm just sad that my almost complete Zen Line Stage can't be used with my Martin Logans as they don't require any additional gain; I could only use it on the first attenuator step!

My question for other B1 owners since I didn't use any premium parts the first time around, what do you recommend for upgraded 10uF and 1uF caps that's a good match for the sound of the buffer. The seller I'm getting the board from simply populated the board with generic film caps and other decent part, but nothing exotic. It seems that ClarityCaps are a popular choice for the B1?

Face

Cc mr.

zingo

I don't know if I want to put MR money into four caps right now, but I will go ClarityCap. I think the filter caps on the board currently are Panasonic, and I know the resistors are Dale, so the parts should all be pretty good after adding the ClarityCaps.

blehmbo

I went with soniccaps and I've been happy, but I haven't tried anything else in their place. They fit onto the passdiy board nicely after a little lead tweaking.

zingo

Sonicaps would also be a good choice too, thanks for the reminder.

The board I got is not the original NP board, but one from a group buy on DIYaudio, so the layout is a little tweaked to allow easy placement of large film caps as that was the most popular upgrade.

zingo

Got the populated B1 board last night and it looks good. Seller included a 25K, SMD resistor based stepped attenuator which looks pretty decent; I'm really not liking wiper pots these days, even decent ones like the ALPS blue. The down side is the board DOES NOT fit in my Axiom II passive preamp, so I'll have to mock-up something until I decide what my final installation will be.

I picked up a laptop power supply for cheap online; rated at 19V and 4A. When I was testing it last night, I realized it's some proprietary HP DC plug where the outer ring is ground, inter ring is 19V, and pin is 18V. I think I'll just have to cut the plug off, and use the 19V lead and ground, which shouldn't be a problem; I'll just heatshrink the third 18V lead.

zingo

The buffer installed in it's old enclosure:

zingo

Last night, had the time to cut and dissect the power cord from my laptop power supply that I picked up for a few dollars. It has three wires in it; thick black, thick white, and thin white. Making an educated guess, I stripped both thick wires, and sure enough had 19.5v capable of 4A. Now I just need a interim enclosure to mount it all in, and I'll be able to compare the B1 to a completely resistive passive preamp in my system.

zingo

My test last night and everything sounded good! However, I'm surprised that I only need a few clicks of the attenuator to reach a comfortable listening volume; the voltage sensitivity of the Martin Logan Puritys is starting to bother me a little... The good news is the SMD stepped attenuator currently being used has very good stereo tracking and balance at low level, so I am happy running the B1 "low" if that is the reality. I'll be mounting the B1 in some sheet metal in the next few days until I can get a good enclosure.

Face

Since they are compatible with TV and portable music players, it would explain why it's input sensitivity is so high. I believe you can compensate with a higher value attenuator.

zingo

I figured out pretty early with them that they seem to do well with variable output sources as you suggested, and that the 2V fixed sources provide the volume difficulties. Luckily, it's not that big of a deal as sound quality is not compromised, but I'll do the math on a new attenuator and see what makes sense.

FTGV

Due u know the input impedance of the M-L's amp section?

zingo

14Kohm at the RCA jacks