B1 builders thread

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jleaman

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richluvsound said:
Thanks Marra ,

thats brilliant. I loath to spend big money on something
(based on my track record) thats likely to get killed during my educational exploits :)

Whats the LDR ?

thanks again , Rich
Click to expand...

I have one sitting in my box, never put together never used and balanced ldr's

make a offer or trade :)

J
 
M

Marra

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Joined 2009
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George Stranchef[hope I've spelt that correctly] posted details of his Lightspeed volume control which works extremely well on its own or with the DCB1. Bit of a beggar to match the LDR's for balanced I believe but it can be done; has been done. I swapped in one of these after first using the switched attenuator. Its quite a long read.

http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html

http://www.diyaudio.com/forums/group-buys/153388-optical-volume-control-professional-pcb.html
 
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richluvsound

richluvsound

Member
Joined 2010
J,

I wouldn't want to offend you . I don't know what their worth to make an
offer .

As far as trade goes , I don't have much , except a complete set of caps for the Pearl 2 that I ordered twice by mistake -Elna and Panosonic . Some heat sinks, a couple of Mundorf M-lytic 40vdc 10000uF caps and 2 Audin 10uF 400VDC caps ... I also have one of Owens I/V board Kits for the Buffalo Dac ....

BTW , I used to live in Victoria, lucky man -Gods country . ,
 

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C

CR500

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Joined 2010
Here's my shot at it. Symmetrical B1 running mid / high amp, OPA627 at +6dB for the low frequency to equalize the gain of the amplifiers. Ribbon cable isn't really going to the power supply. Its just stuffed under there during the build. It connects to the IR control board. Caps on the output of the OPA for protection since the low freq amp is DC coupled on the input. Added a pair of switched and a pair of unswitched power receptacles. Noise floor is better than -100 dB re 1v and freq response only varies by 0.2 dB between 10 and 100kHz. The OPA was a tough to stop the high freq oscillations.

Sounds pretty good but I'm very unhappy with the pot (motorized 20k alps RK168 series). The matching between sections is poor and for some reason it seems to be killing the channel separation. If I remove the pot, crosstalk drops to ~-90 dB. In the circuit, it comes up by about 30 dB.
 

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KatieandDad

KatieandDad

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Joined 2011
Listening Impressions

I'm not over impressed with the B1.

In my build the Buffer is Transparent but lacks excitement.

I built it to satisfy my curiousity, I already have a Pumpkin, which when working, sounds so much more Exciting.

Although all the trebles and bass are present, the amp just seems to sound boxed-in or smothered.

I'm using a self built PCB which was copied from the Gerber files on the Pass Website. OK the upper tracks have been partially subsumed onto the lower side and those remaining were made using wire links. The Upper surface is purely a ground plane.

C100, C200 and C3 are 1uF MKS types.
C101 and C102 are 2 x 4u7 Polyester // 1nF Polystyrene.

Although the supply is unregulated, it is supplied with +28V from a Capacitor Multiplier.

I have heard that the DCB1 corrects these issues but I am yet to find details for building one.
 

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KatieandDad

KatieandDad

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Joined 2011
KatieandDad said:
I'm not over impressed with the B1.

In my build the Buffer is Transparent but lacks excitement.

I built it to satisfy my curiousity, I already have a Pumpkin, which when working, sounds so much more Exciting.

Although all the trebles and bass are present, the amp just seems to sound boxed-in or smothered.

I'm using a self built PCB which was copied from the Gerber files on the Pass Website. OK the upper tracks have been partially subsumed onto the lower side and those remaining were made using wire links. The Upper surface is purely a ground plane.

C100, C200 and C3 are 1uF MKS types.
C101 and C102 are 2 x 4u7 Polyester // 1nF Polystyrene.

Although the supply is unregulated, it is supplied with +28V from a Capacitor Multiplier.

I have heard that the DCB1 corrects these issues but I am yet to find details for building one.
Click to expand...

C102 and C102 are actually Metalysed Polypropylene - not as stated above.
 
KatieandDad

KatieandDad

Member
Joined 2011
The genuine B1 doesn't use a regulated supply. It uses a Wall Brick.

Unless of course Nelson is being secretive about the genuine article.

I'm only using a 5VA transformer, but, with the huge capacitive multiplier and C1 C2 on-board, I can't see this being the issue.

The BASS is lovely, it is top end that seems, not lacking, but slow, undynamic.
 
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A

AndrewT

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Joined 2004
Slow and undynamic might be in relation to the Pumpkin.
But if the Pumpkin is operating with low stability margins then the Pumpkin will be exaggerating the fast transients (some to massive overshoot depending on the frequencies). This comes out of the speakers as enhanced detail and fast speed. Not accurate.
 
KatieandDad

KatieandDad

Member
Joined 2011
AndrewT said:
Slow and undynamic might be in relation to the Pumpkin.
But if the Pumpkin is operating with low stability margins then the Pumpkin will be exaggerating the fast transients (some to massive overshoot depending on the frequencies). This comes out of the speakers as enhanced detail and fast speed. Not accurate.
Click to expand...


Interesting thought, but yes, I am comparing them with the "Faulty" Pumpkins.

The DCB1 was produced by Salas to overcome some of the "Dullness" of the B1. I'm not sure I like the entirely DC coupled design though.

Might my choice of caps be the problem ?
 
buzzforb

buzzforb

Member
Joined 2010
KatieandDad said:
I'm not over impressed with the B1.

In my build the Buffer is Transparent but lacks excitement.

I built it to satisfy my curiousity, I already have a Pumpkin, which when working, sounds so much more Exciting.

Although all the trebles and bass are present, the amp just seems to sound boxed-in or smothered.

I'm using a self built PCB which was copied from the Gerber files on the Pass Website. OK the upper tracks have been partially subsumed onto the lower side and those remaining were made using wire links. The Upper surface is purely a ground plane.

C100, C200 and C3 are 1uF MKS types.
C101 and C102 are 2 x 4u7 Polyester // 1nF Polystyrene.

Although the supply is unregulated, it is supplied with +28V from a Capacitor Multiplier.

I have heard that the DCB1 corrects these issues but I am yet to find details for building one.
Click to expand...

In theory, The B1 is supposed to sound like nothing. IT is suppose to reveal everything else and just be transparent. I would argue that you could use the pumkin as your pre with the B1 as a volume control and you would find that the Pumpkin sounded as it did as a standalone. This is theory and i do not question anyones listening experience unless it is just way off from normal. BTW, this is what i have found to be true. The DCB1 hotrodded at higher currents, is a noise killer and does tremendous things in terms of bringin out background detail. It doesn't realy change the sound other than removing noise. Perhaps you like noise and distortion. I think I like a little and will be trying to make my FE (B1 and preamp) as quiet as possible. Seems to me that most of the ugly stuff gets introduced in the low level signal area and just gets amplified throughout the chain. I would like to limit my noise and distortion to the outpu stage, where i will play with the harmonics like in Nelson's "Leaving CLass A" article. I have formed this opinion listening to the Ba3 FE, which gives you a good insight into the difference that harmonics make, as well as the DCb1, which showed me how much reducing the noise floor on a single stage can affect the final sound. I have learned more about amps listening to this current setup than any I have played with yet.
 
buzzforb

buzzforb

Member
Joined 2010
With standard nonDCB1, the cap is going to have a direct affect on the sound. What sounds good is muddy water, because opinions differ. You are going to have to try different ones out. Solen is a good inexpensive start. You could build the DCB1 and then you got no cap! I have never heard anyone describe the B1 as muddy.
 
KatieandDad

KatieandDad

Member
Joined 2011
buzzforb said:
With standard nonDCB1, the cap is going to have a direct affect on the sound. What sounds good is muddy water, because opinions differ. You are going to have to try different ones out. Solen is a good inexpensive start. You could build the DCB1 and then you got no cap! I have never heard anyone describe the B1 as muddy.
Click to expand...


Muddy is an exaggeration. It just doesn't seem to be "Alive".

This morning I've added a low noise regulator and ordered some audiophile caps to replace C100,200,101 and 102.

Now it is running at +18V as opposed to the unregulated 28V.

I'll report on any findings - I'm just letting it idle to see if the LM317 needs any heatsinking - it shouldn't B1 (20mA) + 2 x LEDs (10mA).

(28-18) x 30mA = 0.3W. It shouldn't even get warm.
 

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