Pass B1

[anilva]

Another distant possibility if in case you'd use solid core internal wiring, then chances are there might be dry soldering somewhere. I have faced this issue often so now I've stopped using solid core.

No, I haven't used a solid core wiring. Used multistrand teflon wires. Thanks.

 

[captrajesh]

I have a strange problem with the B1 preamp.

Everything seems to be working when it was made and tested, but wasn't used much. Now when I started using regularly I noticed that one channel (left) is sounding weak and feeble.

What a coincidence! Exact same situation and same problem with me too.

Capt. If there are two of us, then I have hopes of solving. Let's see if anyone else responds. Sachin /Om any inputs from your side?

Check this out on DIYA seems to be have a similar problem. According to one poster it is how B1 handles a signal if there is improper ground on the input side. I need to check my B1 all over again.

B1 Preamp - Help Me! - Page 10 - diyAudio

Thanks Om. Will check and revert on the PS and the inductors.

Being a technical noob, I couldn't make out much from the link provided by Anilva and was hoping him to come out with a solution.

Any updates Anilva?

 

[anilva]

Being a technical noob, I couldn't make out much from the link provided by Anilva and was hoping him to come out with a solution.

Any updates Anilva?

Capt, I resoldered all the input connectors and the problem did not reoccur so far. Will let you know if anything happens again.

Edit:
I also believe that the problem is not about dry solder, but supply voltage levels to the B1. I did not have enough time to debug. So far it is working well and hence did not pursue further.

Cheers.

 

[john_k_antony]

I am facing an interesting problem. This is kinda similar to the problem faced by anilva recently.

I was doing the latest resistor mods and while doing so, I ended up breaking the original volume pot. I was once pulling the knob hard and ended with the volume pot losing concats inside. I got a new 50k volume pot from Sachin. I really really have to thank Sachin here for sending me a replacement pot as I couldn't get hold of good quality stereo pot anywhere in SP road Bangalore. The original one was LOG based and new one is LINEAR.

The new pot worked like a charm and my B1 was back in action. But the more I listened, I started to feel that something is missing. I discussed this with Sachin and tried to trouble shoot components in my whole chain.

The problems were:

I felt my right channel is lacking details and the balance is shifted slightly to the left when I sit in the dead center. Again after playing the system for 1-2 hours, there was a perceived loss of detailing. For both TT and CDP sources.

I started trouble shooting my power amp and checked for any broken caps / components and everything looked fine there. Then I check power supply of B1 and it was perfect too.

Then while checking the volume pot, I noticed that the resistance for one of the channels were 48K Ohms and for other it was 44K Ohms. Now when I turn the pot, I could see that there is always a difference of 4K Ohms between two channels and the difference was diminishing while I turn the volume to the full max were the resistance was 0 Ohms for both channels.

The difference was around 3.5K Ohms for my preferred volume setting, which was around 10-12'o clock position.

Now I am wondering if this resistance difference is causing one of the channels to sound more detailed and prominent than the other one, that resulted in lack of details for right channel and stereo image shifting towards left. I am thinking that resistance was more for right channel and that could be the reason it was sounding less detailed compared to the left, for a given volume.

I talked to Sachin yesterday and he also agreed with adding a 3.5K Ohm resistance between 'Wiper' or 'W' port of volume pot and corresponding connection point for the same in the PCB. I just added 3.5K Ohm with some spare 1K and 470R resistors I had. I tested this mod with DMM and looks like I am getting a balanced resistance for both channels when the knob is turned.

I have not put my Pre in the main system yet after this mod. I just wanted to get some opinion from experts about this mod. I also wanted to know if 3.5K Ohm difference between channels is significant enough to result in an audible difference that I am experiencing.

Or do you guys think that this is an absolute NO-NO mod and suggest me to get a new volume pot and use that.

Thanks,
John.

 

[anilva]

I am facing an interesting problem. This is kinda similar to the problem faced by anilva recently.

I was doing the latest resistor mods and while doing so, I ended up breaking the original volume pot. I was once pulling the knob hard and ended with the volume pot losing concats inside. I got a new 50k volume pot from Sachin. I really really have to thank Sachin here for sending me a replacement pot as I couldn't get hold of good quality stereo pot anywhere in SP road Bangalore. The original one was LOG based and new one is LINEAR.

The new pot worked like a charm and my B1 was back in action. But the more I listened, I started to feel that something is missing. I discussed this with Sachin and tried to trouble shoot components in my whole chain.

The problems were:

I felt my right channel is lacking details and the balance is shifted slightly to the left when I sit in the dead center. Again after playing the system for 1-2 hours, there was a perceived loss of detailing. For both TT and CDP sources.

I started trouble shooting my power amp and checked for any broken caps / components and everything looked fine there. Then I check power supply of B1 and it was perfect too.

Then while checking the volume pot, I noticed that the resistance for one of the channels were 48K Ohms and for other it was 44K Ohms. Now when I turn the pot, I could see that there is always a difference of 4K Ohms between two channels and the difference was diminishing while I turn the volume to the full max were the resistance was 0 Ohms for both channels.

The difference was around 3.5K Ohms for my preferred volume setting, which was around 10-12'o clock position.

Now I am wondering if this resistance difference is causing one of the channels to sound more detailed and prominent than the other one, that resulted in lack of details for right channel and stereo image shifting towards left. I am thinking that resistance was more for right channel and that could be the reason it was sounding less detailed compared to the left, for a given volume.

I talked to Sachin yesterday and he also agreed with adding a 3.5K Ohm resistance between 'Wiper' or 'W' port of volume pot and corresponding connection point for the same in the PCB. I just added 3.5K Ohm with some spare 1K and 470R resistors I had. I tested this mod with DMM and looks like I am getting a balanced resistance for both channels when the knob is turned.

I have not put my Pre in the main system yet after this mod. I just wanted to get some opinion from experts about this mod. I also wanted to know if 3.5K Ohm difference between channels is significant enough to result in an audible difference that I am experiencing.

Or do you guys think that this is an absolute NO-NO mod and suggest me to get a new volume pot and use that.

Thanks,
John.

3.5K cannot make such a huge difference. More than that, if at all one can expect reduction of volume but not loss of detail.

Option is to reverse the channels on the pot and see if it has a similar impact on the other good channel. Then you know where the problem is.


Cheers.

 

[spirovious]

Sometimes when channel are not balanced,we tend to hear more details from the speaker which is playing louder.This can be natural.

 

[jls001]

I also had a similar problem like John. One channel of the pot was around 52 kOhms and the other about 48K. I padded the lower one to make them roughly equal, and could hear that the left-right balance had become nearly dead center. BUT, the added resistor meant that at zero position the pot resistance was no longer infinite, and so some sound could be heard. Eventually I removed it. I now use an ALPS Blue pot. Bonus is better bass definition.

 

[spirovious]

BUT, the added resistor meant that at zero position the pot resistance was no longer infinite, and so some sound could be heard.

What if the resistor is connected on ground side?I mean that channel ground can be connected to pot via resistor.Ideally no sound when pot at zero and no one turn volume pot to full level.

 

[omishra]

What if the resistor is connected on ground side?I mean that channel ground can be connected to pot via resistor.Ideally no sound when pot at zero and no one turn volume pot to full level.

That depends on what you want?
if you prefer little volume in one channel at '0' level then put it towards CCW. Mean in series of ground wire over pot pin.

But generally never prefer pot with mismatch towards lower end. It its total difference then adding it from signal input side is preferred.

BTW I moved to 20K SMD resistor stepped attenuation. Peace of mind
Earlier LSA was also better as matched till 12'o position.

 

[john_k_antony]

Thank you very much guys.

I have now connected the resistor between the 'W' lead of pot and the 'W' point on the PCB. When I checked with DMM, the resistance is almost same between 'CW' and 'W'. I think the resistance between 'CW' and 'W' is what matters. Now when I turn the volume knob to MAX, I get 3.5K Ohm resistance between CW and W for the modded channel and 0 for non-modded one, obviously.

I am going to try this today.

Sachin -> if you have spare pot, I would like to get one form you. Otherwise I found some ALPs pot listing in eBay for around $14 with free shipping to India. I assume all the below pots are compatible with B1.

1. PB 1 Alps 50K 'A' Log Potentiometer Attenuator Stereo New | eBay

2. ALPS Japan Dual 50K Audio Stereo potentiometer POT

3. 1 x Knurled Shaft Alps RK27 Series 50K Stereo Volume Control Pot | eBay

Thanks,
John.

 

[hifiramr]

Why you need to buy those stuff from ebay.com it is not always translatable.You will get original from Indian site then why you taking such risk

Please check below websites

theaudiocrafts

Potentiometers

Check above sites for parts

 

[omishra]

Thank you very much guys.

I have now connected the resistor between the 'W' lead of pot and the 'W' point on the PCB. When I checked with DMM, the resistance is almost same between 'CW' and 'W'. I think the resistance between 'CW' and 'W' is what matters. Now when I turn the volume knob to MAX, I get 3.5K Ohm resistance between CW and W for the modded channel and 0 for non-modded one, obviously.

I am going to try this today.

This is not correct. You must not add it on 'W' pin.

You should add either add on CCW or CW pins of the pot.

 

[sachu888]

Thank you very much guys.

I have now connected the resistor between the 'W' lead of pot and the 'W' point on the PCB. When I checked with DMM, the resistance is almost same between 'CW' and 'W'. I think the resistance between 'CW' and 'W' is what matters. Now when I turn the volume knob to MAX, I get 3.5K Ohm resistance between CW and W for the modded channel and 0 for non-modded one, obviously.

I am going to try this today.

Sachin -> if you have spare pot, I would like to get one form you. Otherwise I found some ALPs pot listing in eBay for around $14 with free shipping to India. I assume all the below pots are compatible with B1.

1. PB 1 Alps 50K 'A' Log Potentiometer Attenuator Stereo New | eBay

2. ALPS Japan Dual 50K Audio Stereo potentiometer POT

3. 1 x Knurled Shaft Alps RK27 Series 50K Stereo Volume Control Pot | eBay

Thanks,
John.

I have one 20k unused DACT type stepped attenuator. I will send you tomorrow. There are many fake parts available on ebay, Be aware. I know two known sources for genuine Alps Blue Valuate,a German seller on Ebay, and Partconnexion Canada.

Regards
Sachin

 

[john_k_antony]

One more question with B1.

I got myself a Yaqin SD-3 tube buffer. I was planning to put the tube buffer between B1 and power amp. Then I was going through the thread again and stumbled upon a post from Om where he was talking about the dual B1 configuration where he shorted volume control ports for the first B1 in the chain. Going by the above logic, do you guys think:

1. Adding the tube buffer before B1 would be better

OR

2. Adding it after B1 where the signal has already passed through the volume control and B1 buffer?

If option 1 is recommended, I am planning to make a small change for my B1 input section like the following diagram.



Thanks,
John.

 

[john_k_antony]

This is not correct. You must not add it on 'W' pin.

You should add either add on CCW or CW pins of the pot.

Thanks Om. I will add it at CW and try

 

[john_k_antony]

I have one 20k unused DACT type stepped attenuator. I will send you tomorrow. There are many fake parts available on ebay, Be aware. I know two known sources for genuine Alps Blue Valuate,a German seller on Ebay, and Partconnexion Canada.

Regards
Sachin

Thanks Sachin. I will take it . Please let me know the cost, I will transfer right away.

 

[jls001]

BTW I moved to 20K SMD resistor stepped attenuation. Peace of mind

Locally available? Is it log or linear?

@Sachin, do you have a spare that I can buy?

 

[Hari Iyer]

I used a 22K Log pot for my DCB1 and find the control of attenuation not so good. Earlier i was using a 100K Lin pot which has better attenuation control than the LOG value.

I will be restoring the earlier 100K Lin pot some time later. Mine is a Philips pot which is also very good and available for just Rs.30/- at LR.

 

[omishra]

Locally available? Is it log or linear?



@Sachin, do you have a spare that I can buy?

Its from *Bay, and linear not log.
Sachin also bought from same seller, i think.

 

[john_k_antony]

One more question with B1.

I got myself a Yaqin SD-3 tube buffer. I was planning to put the tube buffer between B1 and power amp. Then I was going through the thread again and stumbled upon a post from Om where he was talking about the dual B1 configuration where he shorted volume control ports for the first B1 in the chain. Going by the above logic, do you guys think:

1. Adding the tube buffer before B1 would be better

OR

2. Adding it after B1 where the signal has already passed through the volume control and B1 buffer?

If option 1 is recommended, I am planning to make a small change for my B1 input section like the following diagram.

View attachment 18255

Thanks,
John.

I think I am gonna try the above mod as I will get "Buffer (Yaqin) -> Volume Control -> Buffer (B1)" configuration.

I am looking at this post from Om as reference : http://www.hifivision.com/diy/21036-pass-b1-148.html#post498322