Nelson Pass B-1 preamp kit

wushuliu · « **Reply #260 on:** 19 May 2010, 04:58 pm »

Gave a couple things a whirl last night with the B1.

1. Battery power does have a very smooth delivery and lower noise. Not sure if it was enough
of an improvement for me to invest in batteries at this time, because I have several AC filter tweaks in place in my system already. For those who don't I think it's worth people's time to give them a listen on batteries. Also, some people have reported liking the way it sounds with only 9v as opposed to 18v, 24v, etc. So there is room for experimentation. I may order a 9v wallwart for kicks.

2. My B1 pcb is actually the one that was sold on ebay (I consider this tutorial my 'penance'). So my fets were regular unmatched from Mouser. Last night I swapped in some matched fets I got from diyaudio. Oops, such have done this sooner! I guess Nelson selling them w/ his boards should have been a hint

I do believe the B1 performs much better. More coherent, lower noise. Smoother, cleaner. So for those of you who did not get matched fets, I recommend it.

3. Output cap size. I threw in 22ufs for kicks just to hear. Little swollen in the low frequencies, but
still sounds good. I have some russian 10uf K73-16 dry polyester caps coming so we'll see how those stack up.

bottom line is there is much to experiment with with the B1.

end o' report

HAL · « **Reply #261 on:** 19 May 2010, 07:32 pm »

Quote from: wushuliu on 19 May 2010, 12:56 am

Do you have a wall wart to compare battery B1 vs. regular? I think I may test that out tonight.

And for the record, if I have to read another 100+ page thread on diyaudio just to build a project my brain will explode. After 2 years I am DONE.

No 9V wall wart, but could always jumper one battery holder to run off a single 9V battery.

The kit here was from Nelson Pass with the matched JFETs.

wushuliu · « **Reply #262 on:** 20 May 2010, 07:07 am »

Well I pulled out the 22ufs. They were too bloated, but hey it was worth a try. I dropped in the 10uf Russian PETP caps that arrived today, and what can I say, I think they sound pretty. freakin'. good. Right off the bat. Not what I was expecting. They're kind of sweet, good detail. Tingly. My B1 has never sounded better. I think it's mainly due to the matched fets and my AC choke filters, those really improved the performance several notches.

I was going to build the DC Coupled B1 on diyaudio next because it's supposed to be better, but I like what I hear so much now I think I'll call it a day. My tweaks on this 'r done.

bigaudioscotto · « **Reply #263 on:** 22 May 2010, 05:21 pm »

Hey Walkern
Did you try the sub out hookup on B1,and did it work.
Thanks Scott

Quote from: walkern on 12 Mar 2010, 05:40 pm

Someone asked Nelson Pass this question at the DIY forum and his reply seemed to indicate that all you'd need to do is connect the second set of outputs parallel with the first, and you'd be good to go. I'm intending to do this myself, (although it may be a little while... I haven't even stuffed my board yet) so I'll let you know if it works.

Neil

Nick77 · « **Reply #264 on:** 22 May 2010, 05:27 pm »

Quote

My tweaks on this 'r done.

Ya right!

Good work, i am using some russian pio's with excellent results also.

walkern · « **Reply #265 on:** 25 May 2010, 09:35 pm »

Quote from: bigaudioscotto on 22 May 2010, 05:21 pm

Hey Walkern
Did you try the sub out hookup on B1,and did it work.
Thanks Scott

Just finished drilling all the chassis holes for my B1... and I've got the board stuffed, so am ready to begin making input and output connections... but it was so hot and sticky in the garage yesterday (my one day off per week) that I couldn't bring myself to solder anything!

I'll keep you posted. Theoretically though, it should work just fine. The unit should drive an amp in a subwoofer just as easily as any other power amp. Fingers crossed.

Neil

1MOR · « **Reply #266 on:** 26 May 2010, 04:51 am »

Finished the board and doing front and rear panel layouts. I should be making chips and mounting pots and jacks by the weekend.

roymail · « **Reply #267 on:** 27 May 2010, 11:35 pm »

Will using a high end stepped attenuator like the Elma/Goldpoint or DACT CT2 in the B1 buffer result in superior sonics as compared to the recommended ALPs blue velvet 25k stereo pot?

I'd rather not tear up my Goldpoint passive if I don't have to...

Anyone know?

poseidonsvoice · « **Reply #268 on:** 30 May 2010, 12:48 pm »

For those interested I have a pair of partially built Nelson Pass B1 boards with matched Jfets, Mundorf and Obbligato capacitors, and Caddock MK132 resistors with an uber power supply for sale here.

Sorry about intruding on the thread, just thought somebody could grab a good deal.

Anand.

wushuliu · « **Reply #269 on:** 30 May 2010, 06:04 pm »

Quote from: roymail on 27 May 2010, 11:35 pm

Will using a high end stepped attenuator like the Elma/Goldpoint or DACT CT2 in the B1 buffer result in superior sonics as compared to the recommended ALPs blue velvet 25k stereo pot?

I'd rather not tear up my Goldpoint passive if I don't have to...

Anyone know?

Hi Roy, yes, probably. The B1 does not negate the performance of a volume pot. So the better pot, the better it will sound.

roymail · « **Reply #270 on:** 30 May 2010, 06:22 pm »

Thanks AC,appreciate the answer. I assume the need for the buffer is to match with the very low input impedance of the Class D CDA series amps?

wushuliu · « **Reply #271 on:** 30 May 2010, 06:34 pm »

Quote from: roymail on 30 May 2010, 06:22 pm

Thanks AC,appreciate the answer. I assume the need for the buffer is to match with the very low input impedance of the Class D CDA series amps?

While presenting high impedance to a source, yes. Ideally. For any amp for that matter. Or it could be you need a pre with different inputs. Or both. Some also feel that an active preamp sounds better than passive. From what I've read there's no cut and dry answer. The Class D amp doesn't need the B1.

roymail · « **Reply #272 on:** 30 May 2010, 06:41 pm »

My Elma 20K stepped attenuator seems to work great with my amplifier of about 50K input impedance. So I'm assuming that the SDS series amps (47K) would be a better match for my passive than the CDA series amp with their 7K input impedance. Am I right about that?

wushuliu · « **Reply #273 on:** 30 May 2010, 07:09 pm »

Quote from: roymail on 30 May 2010, 06:41 pm

My Elma 20K stepped attenuator seems to work great with my amplifier of about 50K input impedance. So I'm assuming that the SDS series amps (47K) would be a better match for my passive than the CDA series amp with their 7K input impedance. Am I right about that?

Yes, it would be a better match.

walkern · « **Reply #274 on:** 1 Jun 2010, 10:30 pm »

Finished my B-1 today, and it is working like a champ. Went with all the "standard" parts including dual PEC volume controls (not sure if I'll like that, but I do appreciate having a balance control of sorts). And I set mine up with two outputs, one for my main amp (Class D) and another for my sub amp (Rhythmic) and both outputs work just fine together... no hum issues or noise... and plenty of drive.

I installed everything in as small a chassis as I could, and I wouldn't do that if I was starting again from scratch. Although the wiring is very short, getting all the inputs, outputs, and the volume controls and the selector switch wired up and then squeezing the board into the chassis was pretty tricky. If someone can explain how to upload photos I'll do my best to throw some up here.

Neil

Nick77 · « **Reply #275 on:** 1 Jun 2010, 10:49 pm »

Quote

And I set mine up with two outputs, one for my main amp (Class D) and another for my sub amp (Rhythmic) and both outputs work just fine together... no hum issues or noise... and plenty of drive.

Thanks for the update, have you tried the output with and without the sub connected and confirmed no ill effect?

walkern · « **Reply #276 on:** 1 Jun 2010, 11:00 pm »

Yup. Ran the little bugger with only my Class D amp first just to get a sense for the sound, and then ran the second set of outputs to my sub. No ill effects what so ever. No hum or noise from my Class D, and no hum or noise from the sub either. Connecting the sub did not affect the overall volume level either (thought I might notice a decrease... but didn't). I know some subs have grounding issues with some preamps and other amps all wired together in one system, but in my set up I've never had any ground loop hum issues with either the Class D or the Rhythmik. Up 'til now though I've been using a passive TVC, so I was a bit concerned... but without reason.

Really glad it worked as expected. How often does that happen?

Neil

wushuliu · « **Reply #277 on:** 2 Jun 2010, 11:45 pm »

Quote from: walkern on 1 Jun 2010, 11:00 pm

Yup. Ran the little bugger with only my Class D amp first just to get a sense for the sound, and then ran the second set of outputs to my sub. No ill effects what so ever. No hum or noise from my Class D, and no hum or noise from the sub either. Connecting the sub did not affect the overall volume level either (thought I might notice a decrease... but didn't). I know some subs have grounding issues with some preamps and other amps all wired together in one system, but in my set up I've never had any ground loop hum issues with either the Class D or the Rhythmik. Up 'til now though I've been using a passive TVC, so I was a bit concerned... but without reason.

Really glad it worked as expected. How often does that happen?

Neil

So you have 1 B1 and you split the outputs to feed both your amp and sub?

walkern · « **Reply #278 on:** 4 Jun 2010, 10:12 pm »

That's correct. Basically, I daisy chained from each left and right output to the other pair (as was suggested by Nelson Pass in the VERY long thread at DIY audio). I thought about directly connecting each set of connectors (both pairs) to the board with their own dedicated wires, but the holes in the board did not accommodate me... the gauge of wire I was using wouldn't allow me to double up the stripped ends of the wire in the holes in the board.

Neil

walkern · « **Reply #279 on:** 5 Jun 2010, 01:41 pm »

Here are some photos of my B1. The chassis is a "wrap around" style, so the board is mounted to the bottom, all the wiring was done to all the connectors, and then the connectors were inserted into the chassis, and then bottom was secured to the chassis. The second set of outputs (for my sub) were wired to the first set of outputs, and everything else was wired to the board directly.

Neil