the discussion started with
http://www.diyaudio.com/forums/analog-line-level/279456-my-b1-buffer-build-4.html#post4734225
That was less than two days ago.
Like I just said, I missed Ammel's post saying he would not use a 100k (whatever reason that may be -- he said about the circuit works well with a 25K or less pot. I don't even know if 10k is too little).
I re-read your technical stuff about the capacitance of the cables and what not.. have to say a lot of it went over my dumb head. So you might of answered the question, but if you did, I'm too stupid to understand the answer.
All I have is a 10k pot now along with the 100k. And I don't know what I should buy to replace it.
EDIT: Re-read what you just wrote for the third time other day; you gave me formulas and stuff if using cables without the B1 Buffer.. and ultimately you said with the B1 Buffer, it can drive any cables -- which is what I understood a few months ago when I bought it. My only question is would the small 10k pot or the large 100k pot work well with the circuit within the B1 Buffer itself. I read Nelson Pass said you could use any pot value you wanted and that that ohm value sets the input impedance. Was thinking a 10k input impedance might of been a bit low for my DAC and it's short 1 foot cable .. I know that if I went with 100k that there would be no impedance matching issue whatsoever between the DAC and b1 buffer.. because as long as the input impedance is sufficiently high enough it's agreeable. But Ammel said that he wouldn't use a 100k pot, but I don't know why exactly. Looks like I need to buy a 20k or 25k pot, but I have no idea what I should buy now.. ALPS only has 20k not 25k if I recall. And I don't know if I should go with a DACT type stepped attenuator instead .. etc..
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Try the 10k vol pot.
Listen for a while, days or even weeks and get used to what you hear.
Then swap to the 100k and hear if there is any difference.
Then decide whether to keep the 100k, or spend time changing back to the 10k.
Don't buy a third vol pot.
Listen for a while, days or even weeks and get used to what you hear.
Then swap to the 100k and hear if there is any difference.
Then decide whether to keep the 100k, or spend time changing back to the 10k.
Don't buy a third vol pot.
Have you read this Thread?
http://www.diyaudio.com/forums/anal...p-amplifier-driving-capacity.html#post4732333
http://www.diyaudio.com/forums/anal...p-amplifier-driving-capacity.html#post4732333
Just did thank you. I understood some of it. (I'll definitely keep the link as a reference.) What I got from it is some formulas and that if the sum of the cable capacitance is too high there might be problems driving multiple amps if the output impedance of the preamp isn't sufficiently low. Fortunately I have the B1 Buffer! I should be able to drive three amps with it fairly easily right, splitting the output three times, instead of twice (another pair of RCA's would need to be added to the 2205 case). Might run the signal to the ACA as well if I do a bi-amp bookshelf speaker setup -- don't know how much that would help the audio but I like tinkering and it was suggested.
I suggest you fit multiple output sockets if you intend driving multiple receivers.
Each output socket should have the resistor that is standard on the B1 for the single output.
Are you using 1k, or 220r?
Then you need two for two outputs, or three for three outputs.
The resistors should be soldered very close to the B1 output node. Then long twisted pair tails to the sockets.
Each output socket should have the resistor that is standard on the B1 for the single output.
Are you using 1k, or 220r?
Then you need two for two outputs, or three for three outputs.
The resistors should be soldered very close to the B1 output node. Then long twisted pair tails to the sockets.
At the moment, I am just using the stock pcb / schematic as is. So I gather I need to add the resistor for the other output. What's happening right now, since it's sharing that resistor?
Here is the schematic I am using -- implemented on the Pass Labs pcb. I am using the exact values and locations in the schematic.
I just drew some in RED .. are these the modifications you want me to make? Looks like 2 resistors per output instead of just one? If one, which resistor?
I just drew some in RED .. are these the modifications you want me to make? Looks like 2 resistors per output instead of just one? If one, which resistor?
An externally hosted image should be here but it was not working when we last tested it.
the 221k (R205 & R105) are there to take leakage current back to source and ensure a minimal output offset. The circuit only needs ONE of these after the 10uF capacitor. Don't duplicate it.
It's the 1k that should be duplicated.
Add a 1k at C201 & at C101 for each extra output.
And remember to take a Return line from that audio ground to each output socket.
It's the 1k that should be duplicated.
Add a 1k at C201 & at C101 for each extra output.
And remember to take a Return line from that audio ground to each output socket.
So like this?
An externally hosted image should be here but it was not working when we last tested it.
Erm.. Nelson has Looong deserved/earned history.
Either Build the B1 ...or Don't.
Ad libbing the Master's design on hearsay.. is.. not clever... imo
Either Build the B1 ...or Don't.
Ad libbing the Master's design on hearsay.. is.. not clever... imo
Adding one extra output isn't much of an "ad lib" now is it? I've already built the B1. Actually, I am not quite understanding what you are getting at.
If Mr. Pass thought a 100K pot would've been ideal, then that's what he'd have placed in front of the buffer.
Perhaps you're overthinking this whole "what value volume pot should I use?" thing.🙂
Yes, ALPS has a 20K pot, but channel imbalance is problematic with any carbon volume pot. I've used their "blue" pots in the past and channel imbalance is marginally better than a $1 ALPHA carbon pot from China.
The DACT type stepped attenuators off eBay have much better channel matching(as do most stepped attenuators) and to my ears sound "cleaner" than a carbon pot. If you have $15 to spend on a volume control, then choosing between the DACT type and ALPS is a no-brainer.
The value of a volume pot is determined by several factors like your source's output impedance and how much the pot will "load" your source.
Andrew is more knowledgeable about these things than I am.
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Oh I didn't think about a large pot in the pre loading the source. I figured if it was sufficiently high, it would actually make it easier on the source. Nelson Pass said we could use any pot value, but like you, I'd feel more comfortable using one that is 25k.
I'd love to get a 25k stepped attenuator, with sufficient steps to be able to control the volume level to where I want it to be. If it sounds better than an ALPS that would be wonderful. I'd love a stepped attenuator that uses a separate pair of resistor values for each volume level, keeping the impedance the same throughout the volume/attenuation range. I know some you buy the impedance changes because they aren't using as many resistors.. forget what they call this? shunt?
I could try as an experiment two 12.5k resistors for a voltage divider, for each channel. That's about where I listen to my music : 50%. That way I could see how much the sound quality is impacted going through a wiper/carbon pot vs. directly soldered.
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Jennifer, I think you'll be fine with a stepped 20K attenuator...very close to the recommended value of 25K ohms.
Only problem with some stepped attenuators is the volume may be too low at one setting and too high with the next step up.
I think you'll find the sound a little cleaner through your voltage divider. I typically use Dale RN55 series resistors.
Let us know what you find.
Only problem with some stepped attenuators is the volume may be too low at one setting and too high with the next step up.
I think you'll find the sound a little cleaner through your voltage divider. I typically use Dale RN55 series resistors.
Let us know what you find.
I need like a 48 position switch (or some high number), with the quality of grahyhill, that switches a pair of resistors for each channel at every volume level (i.e. voltage divider for each level ), which would maintain impedance across the range.
That'd be like 200 resistors though hah. If Iused vishay dale that'd be very expensive! I suppose I could use cheap 1/4 watt metal film Chinese resistors for most levels, and then in the range I usually have the amp set, use vishay for those levels.
Hey guys, so do you think there is a possibility of improvement of sound if I built my own linear regulated power supply with antek toroidal and LM317 in a separate case -- using umbilical cord? Or do you think the filter Pass built into the B1 buffer will sound as good with a noisy SMPS wall wart? I just have the wall wart right now and it sounds good.. just wondering if I'd hear any difference with linear is all. He's already using quite large caps in the filter/smoothing power section of the B1 board.
Why oh why didn't you build the DCB1 (also called Mezmerize) ? Sounds better, has no expensive coupling caps (yay!) and it has way better symmetrical shunt power supplies. Same circuit but better implementation. Six relay driven inputs and boards can be bought at diyaudio....
http://diyaudiostore.com/collections/printed-circuit-boards/products/mezmerize-b1-buffer
Your 10 kOhm 41 step attenuator is waiting for you ! If your sources can drive 10 kOhm that is. If not you could use a series resistor but then your output voltage will be lower.
http://www.acoustic-dimension.com/attenuators/attenuators-main.htm
Stay away from switchers as much as you can. They are not evil but nothing beats a simple linear power supply in devices that don't draw much power like preamps, buffers and DACs. Less hassle, less RF etc. Separate cases might be better technically (in a way), you can better build a shielded PSU in the case to void extra wiring, connectors etc. Just an opinion.
BTW just read your first post in this thread and read you use a linear potentiometer....I built many DCB1's and always used log versions as usual in analog audio.
http://diyaudiostore.com/collections/printed-circuit-boards/products/mezmerize-b1-buffer
Your 10 kOhm 41 step attenuator is waiting for you ! If your sources can drive 10 kOhm that is. If not you could use a series resistor but then your output voltage will be lower.
http://www.acoustic-dimension.com/attenuators/attenuators-main.htm
Stay away from switchers as much as you can. They are not evil but nothing beats a simple linear power supply in devices that don't draw much power like preamps, buffers and DACs. Less hassle, less RF etc. Separate cases might be better technically (in a way), you can better build a shielded PSU in the case to void extra wiring, connectors etc. Just an opinion.
BTW just read your first post in this thread and read you use a linear potentiometer....I built many DCB1's and always used log versions as usual in analog audio.
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