Re: Re: Status of first build
I was all set to order new posts, but single pots are unavailable at this time (backorder). An alternative plan is to use a dual pot and rotary switch instead of DPTP switch and single pots. Considering one of the two dual pots below, and the switch. I do not listen to system at high volume, so I want some useable range from pots at lower volumes. I am begrudgingly living with reverse log taper at the moment and find it not suited to my preferences, yielding too much increase in volume at the lower end of the throw. Any opinions or affirmations will again be most appreciated.
Linear taper dual pot (concerned with 10K OHM rating)
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKU1031S28-ND
Log taper dual pot
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKA5031S28-ND
Rotary Switch (very much conjecturing what will work here)
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=GH7102-ND
Nelson Pass said:
Those are perfectly fine.
I was all set to order new posts, but single pots are unavailable at this time (backorder). An alternative plan is to use a dual pot and rotary switch instead of DPTP switch and single pots. Considering one of the two dual pots below, and the switch. I do not listen to system at high volume, so I want some useable range from pots at lower volumes. I am begrudgingly living with reverse log taper at the moment and find it not suited to my preferences, yielding too much increase in volume at the lower end of the throw. Any opinions or affirmations will again be most appreciated.
Linear taper dual pot (concerned with 10K OHM rating)
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKU1031S28-ND
Log taper dual pot
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=KKA5031S28-ND
Rotary Switch (very much conjecturing what will work here)
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=GH7102-ND
Re: reverse taper
Did that, by accident, but only for one channel. So quickly turned volumes clockwise in reaction, elongating the hair-raising experience. Given my preteens often use the system, I'll invest in the correct taper. It was hard enough to teach them to wait for the tube amp before setting the volume.
Lee35210 said:
Did that, by accident, but only for one channel. So quickly turned volumes clockwise in reaction, elongating the hair-raising experience. Given my preteens often use the system, I'll invest in the correct taper. It was hard enough to teach them to wait for the tube amp before setting the volume.
I have already purchased two of the Pass DIY B1 boards with the matched JFET's.
I bought two because I wasn't sure if one of them would comfortably drive my 100K input impedance amp as well as a typical subwoofer plate amp which are quite often 10 to 20K as far as their input Z. My original idea was to set one up with fixed resistors in the stead of a volume pot for the low impedance load and one with the volume control.
Is this wacky thinking? Is one plenty and not to worry about the 5 to 10 times difference in impedance? If this were in fact a good idea what would be the best way to implement it, i.e. wire this mess together. Perhaps wire the fixed unit for the plate amp from a second output or in parallel from the unit with the volume control?
My second question is about the use of stepped attenuators. I have always hated dual volume controls. I also have no need for a balance control in my room, just lucky that way I guess. Part of my plan in the future may be to use a motorized remote control from Bent Audio on a 20K DACT or 20K or 25K Goldpoint.
I am a bit confused about the whole issue of taper and if the stepped units are suitable. I have some experience with comparing a 100 DACT with a 100k "blue velvet" Alps and there was no comparison in my mind as to which sounded cleaner , clearer or more realistic. It was the DACT all the way. I hope not to offend anyone but It made the Alps sound like a toy.
I am not new to audio just new to DIY and have a lot to learn.
I bought two because I wasn't sure if one of them would comfortably drive my 100K input impedance amp as well as a typical subwoofer plate amp which are quite often 10 to 20K as far as their input Z. My original idea was to set one up with fixed resistors in the stead of a volume pot for the low impedance load and one with the volume control.
Is this wacky thinking? Is one plenty and not to worry about the 5 to 10 times difference in impedance? If this were in fact a good idea what would be the best way to implement it, i.e. wire this mess together. Perhaps wire the fixed unit for the plate amp from a second output or in parallel from the unit with the volume control?
My second question is about the use of stepped attenuators. I have always hated dual volume controls. I also have no need for a balance control in my room, just lucky that way I guess. Part of my plan in the future may be to use a motorized remote control from Bent Audio on a 20K DACT or 20K or 25K Goldpoint.
I am a bit confused about the whole issue of taper and if the stepped units are suitable. I have some experience with comparing a 100 DACT with a 100k "blue velvet" Alps and there was no comparison in my mind as to which sounded cleaner , clearer or more realistic. It was the DACT all the way. I hope not to offend anyone but It made the Alps sound like a toy.
I am not new to audio just new to DIY and have a lot to learn.
B1 and tripath board
I am planning to build a B1 in front of the Sure Electronics Tripath Board with tc2000+tp2050 chips, described here
http://www.diyaudio.com/forums/showthread.php?s=&threadid=143669
There are two issues where I'd be interested in your advice:
1)
The board comes with an input cap. Can I skip it and feed the output of the B1 directly to the input resistor in front of the TC2000?
I'm quite happy with my 2.2 uF MKT in front of my TA2024. Can I go as low with the output of the B1 and how should I choose the resistors x04 and x05 given the design of the input resistors of the board? The schematics are given in Chapter 5 of this document
http://www.sure-electronics.net/download/AA-AB013_Ver1.2_EN.pdf
2)
Will the B1 run off a 29V regulated power supply or how could it be changed to do so?
thx for your help
I am planning to build a B1 in front of the Sure Electronics Tripath Board with tc2000+tp2050 chips, described here
http://www.diyaudio.com/forums/showthread.php?s=&threadid=143669
There are two issues where I'd be interested in your advice:
1)
The board comes with an input cap. Can I skip it and feed the output of the B1 directly to the input resistor in front of the TC2000?
I'm quite happy with my 2.2 uF MKT in front of my TA2024. Can I go as low with the output of the B1 and how should I choose the resistors x04 and x05 given the design of the input resistors of the board? The schematics are given in Chapter 5 of this document
http://www.sure-electronics.net/download/AA-AB013_Ver1.2_EN.pdf
2)
Will the B1 run off a 29V regulated power supply or how could it be changed to do so?
thx for your help
I think you could do both things you are wanting to do. The B1 should not allow DC through the signal path so I dont think you will need the input caps on your Tripath board. Fire up the B1 and measure for DC and you will know for sure.
The B1 may work fine with your 29V but there are some 25V caps spec'd in. The 15000uf ones. Not sure what voltage the transistors can take. Anyway, if you build a tiny LM317 circuit you can regulate that down with probably no sinking. Maybe insulate the LM317 and bolt it to the frame or get one of those tiny transistor heatsinks. Anyway, then use a pot for the resistor that determines the output voltage of the LM317. A few people have said that the B1 sounds best with 10V and if I recall I think Nelson said it could take up to 40V, but it seems you will like it more with less than that 29V. So just step down the supply you have with the LM317 and you can have nearly any voltage you want.
Uriah
The B1 may work fine with your 29V but there are some 25V caps spec'd in. The 15000uf ones. Not sure what voltage the transistors can take. Anyway, if you build a tiny LM317 circuit you can regulate that down with probably no sinking. Maybe insulate the LM317 and bolt it to the frame or get one of those tiny transistor heatsinks. Anyway, then use a pot for the resistor that determines the output voltage of the LM317. A few people have said that the B1 sounds best with 10V and if I recall I think Nelson said it could take up to 40V, but it seems you will like it more with less than that 29V. So just step down the supply you have with the LM317 and you can have nearly any voltage you want.
Uriah
As long as the total impedance is 10K or more, it doesn't matter that the 2 inputs are different. The same voltage will appear across both. the power amps will not interact.
A stereo stepped attenuator is a valid choice.
This is all about adapting the design for your system and tastes.
As for steps, 2 db seems to be the most versatile. However, without the 20 db of useless gain to kill, a 1.5 db step might give you more control.
Personally, I want to try a TVC, buffered by a B1.
Doug
udailey said:
thanks for the responses.
That was my thinking. Even though the tripath chip operates at 2.5V input voltage, it shouldn't matter for the B1. There's only the big cap on the output and some large resistor pulling the output to ground. I guess this is to make sure it doesn't build up unwanted voltages when open.
Feeding the output of the C101/C201 caps of the B1 directly to the input resistors R16/R30 on the board should be OK then, shouldn't it?
The board has trimmers R5/R26 to pull the input to the desired voltage level, so no floating around possible.
(NB I have yet to look at the DIP-switches that seem to choose the input gain of the board amp. But the board hasn't arrived yet).
I haven't built the B1 yet, but of course I will take care the ratings of the caps go with the voltage I apply.
The PSU is regulated itself and I would like to avoid building a little LM317-heater inside my amp.
So are there more opinions whether to run the B1 at 29V is a good idea?
sorry is not so simple:
---
The input:
see Tripath's TA1101B Data Sheet:
"Application/Test Circuit" at Tripath.com
There is a 2.2uF electrolytic (C1) on each input because the input amp is biased at something like 2.5V. That cap has a huge impact on the sound. To get rid of it:
Observe static electricity protection rules. Until this circuit is complete, the Tripath input is floating and very vulnerable.
1) Use a floating, non grounded, 12V power supply. They are readily available.
2) Isolate audio input ground from the 12V ground and connect it directly to the TA1101B-pin 14.
3) Connect the audio signal directly to the resistors: R1. Now the audio is connected differentially to the input amps.
4) Bypass the audio ground (now connected to pin 14) to the circuit 12V ground. I use a 22uF electrolytic and 0.1uF ceramic. + connects to the audio ground. This step limits common mode noise which otherwise totally swamps the input circuit.
5) Insert a 7 or 8 volt zener diode between the audio and 12V grounds, cathode to audio gnd, to protect the chip input, esp pin 14.
6) Put big rf beads on all power, input, and speaker wires (you really should do this anyway with this amp). A single bead for each +/- pair is fine .. that's 5 beads total.
That's it. it makes a BIG difference.
Other tips:
1) rf beads (I already said it, but it's important).
2) nice 1.5 amp torroid output inductors
3) nice (mylar or better) output caps. I use .22uF because my speakers
are 8 Ohms.
4) nice 2200 uF electrolytics for VDD1/2 instead of 180uF
--------
This mod can be done to any of the Tripath chips that have access to the non inverting input pin of the input op amps. Just make sure your souce ground is completely floating. You will need good bypassing from the non inverting input to power ground otherwise you will get noise. Doing this will also have an effect the DC offset on the outputs.
---
The input:
see Tripath's TA1101B Data Sheet:
"Application/Test Circuit" at Tripath.com
There is a 2.2uF electrolytic (C1) on each input because the input amp is biased at something like 2.5V. That cap has a huge impact on the sound. To get rid of it:
Observe static electricity protection rules. Until this circuit is complete, the Tripath input is floating and very vulnerable.
1) Use a floating, non grounded, 12V power supply. They are readily available.
2) Isolate audio input ground from the 12V ground and connect it directly to the TA1101B-pin 14.
3) Connect the audio signal directly to the resistors: R1. Now the audio is connected differentially to the input amps.
4) Bypass the audio ground (now connected to pin 14) to the circuit 12V ground. I use a 22uF electrolytic and 0.1uF ceramic. + connects to the audio ground. This step limits common mode noise which otherwise totally swamps the input circuit.
5) Insert a 7 or 8 volt zener diode between the audio and 12V grounds, cathode to audio gnd, to protect the chip input, esp pin 14.
6) Put big rf beads on all power, input, and speaker wires (you really should do this anyway with this amp). A single bead for each +/- pair is fine .. that's 5 beads total.
That's it. it makes a BIG difference.
Other tips:
1) rf beads (I already said it, but it's important).
2) nice 1.5 amp torroid output inductors
3) nice (mylar or better) output caps. I use .22uF because my speakers
are 8 Ohms.
4) nice 2200 uF electrolytics for VDD1/2 instead of 180uF
--------
This mod can be done to any of the Tripath chips that have access to the non inverting input pin of the input op amps. Just make sure your souce ground is completely floating. You will need good bypassing from the non inverting input to power ground otherwise you will get noise. Doing this will also have an effect the DC offset on the outputs.
thx,
but to avoid one confusion:
I am not trying to build a capless Tripath amp. I am rather planning to hardwire the output cap of the B1 to the input of the tripath. To me it seems a bit of a waste to have two caps in parallel if I were to use both tripath board and B1 as they are.
To my feeble mind the output cap of the B1 serves to isolate the AC output from the DC operating voltage inside the B1. It shouldn't matter whether the DC level after the cap is 0 or 2.5V.
So IMHO it would be over the top to completely float the Tripath.
Its just that one cap btn B1 and Tripath should do.
but to avoid one confusion:
I am not trying to build a capless Tripath amp. I am rather planning to hardwire the output cap of the B1 to the input of the tripath. To me it seems a bit of a waste to have two caps in parallel if I were to use both tripath board and B1 as they are.
To my feeble mind the output cap of the B1 serves to isolate the AC output from the DC operating voltage inside the B1. It shouldn't matter whether the DC level after the cap is 0 or 2.5V.
So IMHO it would be over the top to completely float the Tripath.
Its just that one cap btn B1 and Tripath should do.