I'm building one of these too! Started a separate thread for the purposes of documenting my entire process start to finish (link here) but figured I'd use this thread to ask some of my questions since its so full of experts who are familiar with this preamp. Please excuse the ignorance of some of my questions.
If you read through all this and are still with me, I really appreciate it. I know its a lot but these are the things I haven't been able to answer through searching existing threads/posts. I really appreciate anyone who can answer all of this!! So excited to get started building!
- I bought the version without anything soldered to the board as I wanted to do it myself, and source my own components. None of the resistors positions state a minimum spec for current. If I understand electronics correctly, there's no upper limit to resistor wattage but there is a minimum correct? How do I determine the minimum?
- The large resistors behind the tubes state "2K/3K/5W. I understand this requires a 5W resistor but what about 2K/3K, is this a range? Recommendations?
- For sourcing resistors, I'm assuming I want to choose the lowest tolerance value possible for each? Is there any reason to seek out "audiophile" grade resistors, or will I do ok buying name-brand low tolerance ones from Mouser?
- On capacitors, I understand that the voltage stated is a minimum and you can exceed this so long as the capacitance is correct?
- There is a tiny 1µF electrolytic capacitor, but doesn't state voltage. Does anyone know what it is?
- There are a couple capacitors which are polarized and have both a rectangle and circle printed. Assuming this means you can chose to use either a radial or axial cap? Assuming this is correct, any benefit to one over the other?
- For the 6 input relays, would there be any sound/reliability benefit to sourcing name brand ones instead, or should the included China relays do ok as-is?
- I'm doing a slightly alternative assembly for my board, as I'm designing a chassis where the tubes will be exposed outside of the box. For this I'll be soldering most of the components to the underside of the board rather than the top. For most of the non-polarized components this shouldn't be an issue, and the polarized ones just need to flip correctly. Will the relays work properly if put in backwards? I've read they're not polarized and am assuming this to be ok.
- For the board's power supply, most of the images I'd previously seen online show a 12.6V/3A input, but mine states 12V/15V/3A. Similar to the resistor question above, does this indicate a range? I intend to follow (this link)'s modification of adding a 12.6V low-noise regulator circuit, but am wondering if I can get away with using a 13V transformer.
- For both the 7805 and 2N3055 components, I've seen a slight variation between voltage and current ratings of available components. Does anyone have required specs for these?
- I don't intend to install a balance pot, my understanding is that the board works without this and doesn't require any jumpers to be installed to bypass? Please confirm.
- The inputs have both positive and negative terminals which to me suggest they could support a balanced XLR input. Is this true, or is the negative on the inputs just a connection to the board's ground?
- Lastly, the board has 3 LEDs, does anyone know what specifically they indicate, and which is which? I'd like to run wires to mount them in the front panel of my chassis.
If you read through all this and are still with me, I really appreciate it. I know its a lot but these are the things I haven't been able to answer through searching existing threads/posts. I really appreciate anyone who can answer all of this!! So excited to get started building!
Been around the block a few times with the KSL-M77
Yes, quite the list! I'll address it next.
Have been working on mine for over a year now and did something my 61 year old eyes REALLY appreciated. I abandoned my DIY version and went with the fully assembled (and tested) KSL-M77 for $140. a mere drop in the bucket when compared with all the TIMEi spent trying to get the DIY version going properly.
Do I know how it sounds? Not yet. I am currently completing the task of installing the pre-done board on the cabinet which used to house the DYI version PCB. Im waiting for the 18AWG silver plate solid OFC with PFTE insulation hookup wire.
Expectations are high! Ill let everyone know how it goes.
Yes, quite the list! I'll address it next.
Have been working on mine for over a year now and did something my 61 year old eyes REALLY appreciated. I abandoned my DIY version and went with the fully assembled (and tested) KSL-M77 for $140. a mere drop in the bucket when compared with all the TIMEi spent trying to get the DIY version going properly.
Do I know how it sounds? Not yet. I am currently completing the task of installing the pre-done board on the cabinet which used to house the DYI version PCB. Im waiting for the 18AWG silver plate solid OFC with PFTE insulation hookup wire.
Expectations are high! Ill let everyone know how it goes.
Hi JW, please allow me to try and answer a few of your questions as per below, have fun!
[*] I bought the version without anything soldered to the board as I wanted to do it myself, and source my own components. None of the resistors positions state a minimum spec for current. If I understand electronics correctly, there's no upper limit to resistor wattage but there is a minimum correct? How do I determine the minimum?
>> The supply voltage of this preamp (B+) is 260V or thereabouts, so if you take the voltage readings printed on the PCB, you can calculate the voltage across the resistors (e.g. 260V - 130V = 130V), and with the resistor value from the schematic you can obtain the current. This will give you the power dissipation under nominal conditions, actually quite low in this preamp. But I recommend to go with larger resistors where indicated, and some people really like Mills Wirewound resistors which should fit nicely (2W/3W) for the big ones. For the smaller resistors, I used Vishay Metal Film 0.6W (again, quite oversized) with no problem whatsoever.
[*] The large resistors behind the tubes state "2K/3K/5W. I understand this requires a 5W resistor but what about 2K/3K, is this a range? Recommendations?
>> The schematic says 2K. Higher values will reduce the phono gain a little.
[*] For sourcing resistors, I'm assuming I want to choose the lowest tolerance value possible for each? Is there any reason to seek out "audiophile" grade resistors, or will I do ok buying name-brand low tolerance ones from Mouser?
>> In my opinion, 1% resistors should do just fine. For the 250K big guys, even 3% should be ok. The variations between the tubes might be bigger anyway. However, in the RIAA section you should match the components between the two channels as tight as possible.
[*] On capacitors, I understand that the voltage stated is a minimum and you can exceed this so long as the capacitance is correct?
>> Correct. Higher voltage ratings usually come with larger size, which may no longer fit.
[*] There is a tiny 1µF electrolytic capacitor, but doesn't state voltage. Does anyone know what it is?
This is the cap on the output of the 7805 voltage regulator, it will see 5V continuously so a 10V or 12V cap should be just fine.
[*] There are a couple capacitors which are polarized and have both a rectangle and circle printed. Assuming this means you can chose to use either a radial or axial cap? Assuming this is correct, any benefit to one over the other?
>> Whatever floats your boat. Axial caps tend to be less available and slightly higher inductance and resistance, but that is just my impression. I would suggest radial and did so in my build.
[*] For the 6 input relays, would there be any sound/reliability benefit to sourcing name brand ones instead, or should the included China relays do ok as-is?
>> I used the included relays and they are just fine.
[*] I'm doing a slightly alternative assembly for my board, as I'm designing a chassis where the tubes will be exposed outside of the box. For this I'll be soldering most of the components to the underside of the board rather than the top. For most of the non-polarized components this shouldn't be an issue, and the polarized ones just need to flip correctly. Will the relays work properly if put in backwards? I've read they're not polarized and am assuming this to be ok.
>> Interesting. For polarized components, in many cases the polarity is given on the board so that should be followed. For the relays, if they are non-polarized that should not be an issue, as the contact arrangement is symmetric. But you can try: Use a 5V power supply to try if the relay properly switches with both polarities applied.
[*] For the board's power supply, most of the images I'd previously seen online show a 12.6V/3A input, but mine states 12V/15V/3A. Similar to the resistor question above, does this indicate a range? I intend to follow (this link)'s modification of adding a 12.6V low-noise regulator circuit, but am wondering if I can get away with using a 13V transformer.
>> In my build I am using a 13V transformer and its fine. I have made a slight variation to the cap follower for the tubes (2N3055), turning it into some kind of a voltage regulator, and this will need 14-15V DC on the collector of that transistor to work fine. But with 13V AC that should be ok. I posted this modification earlier in this thread.
[*] For both the 7805 and 2N3055 components, I've seen a slight variation between voltage and current ratings of available components. Does anyone have required specs for these?
>> The 7805 is a regular 1A linear regulator, not sure what the relay current is but anything above 500mA should be more than sufficient. On the 2N3055, the total tube current is 2.4A if I calculated correctly, so a smaller transistor would do as well. In my modification I used the MJ3001 (darlington, 10A if I remember correctly) without any issue.
[*] I don't intend to install a balance pot, my understanding is that the board works without this and doesn't require any jumpers to be installed to bypass? Please confirm.
>> The 100k resistors right next to the "Balance" socket on the board are the bypass. I bridged them, as they do nothing else than attenuate the signal.
[*] The inputs have both positive and negative terminals which to me suggest they could support a balanced XLR input. Is this true, or is the negative on the inputs just a connection to the board's ground?
>> The second is correct. This circuit is not symmetric, and the negative connection on the inputs is ground, actually. they are all connected to each other, you can check with your multimeter.
[*] Lastly, the board has 3 LEDs, does anyone know what specifically they indicate, and which is which? I'd like to run wires to mount them in the front panel of my chassis.
>> They indicate the heater voltage of each tube section. This board switches the heaters of the phono section OFF when not in use, at which point that LED will turn off. I disabled this one by bridging the relay, because I do not want so many turn-on/off events on my tube heaters, especially not on the low noise, low microphonics, matched input tubes which cost extra
Hope that helps!
[*] I bought the version without anything soldered to the board as I wanted to do it myself, and source my own components. None of the resistors positions state a minimum spec for current. If I understand electronics correctly, there's no upper limit to resistor wattage but there is a minimum correct? How do I determine the minimum?
>> The supply voltage of this preamp (B+) is 260V or thereabouts, so if you take the voltage readings printed on the PCB, you can calculate the voltage across the resistors (e.g. 260V - 130V = 130V), and with the resistor value from the schematic you can obtain the current. This will give you the power dissipation under nominal conditions, actually quite low in this preamp. But I recommend to go with larger resistors where indicated, and some people really like Mills Wirewound resistors which should fit nicely (2W/3W) for the big ones. For the smaller resistors, I used Vishay Metal Film 0.6W (again, quite oversized) with no problem whatsoever.
[*] The large resistors behind the tubes state "2K/3K/5W. I understand this requires a 5W resistor but what about 2K/3K, is this a range? Recommendations?
>> The schematic says 2K. Higher values will reduce the phono gain a little.
[*] For sourcing resistors, I'm assuming I want to choose the lowest tolerance value possible for each? Is there any reason to seek out "audiophile" grade resistors, or will I do ok buying name-brand low tolerance ones from Mouser?
>> In my opinion, 1% resistors should do just fine. For the 250K big guys, even 3% should be ok. The variations between the tubes might be bigger anyway. However, in the RIAA section you should match the components between the two channels as tight as possible.
[*] On capacitors, I understand that the voltage stated is a minimum and you can exceed this so long as the capacitance is correct?
>> Correct. Higher voltage ratings usually come with larger size, which may no longer fit.
[*] There is a tiny 1µF electrolytic capacitor, but doesn't state voltage. Does anyone know what it is?
This is the cap on the output of the 7805 voltage regulator, it will see 5V continuously so a 10V or 12V cap should be just fine.
[*] There are a couple capacitors which are polarized and have both a rectangle and circle printed. Assuming this means you can chose to use either a radial or axial cap? Assuming this is correct, any benefit to one over the other?
>> Whatever floats your boat. Axial caps tend to be less available and slightly higher inductance and resistance, but that is just my impression. I would suggest radial and did so in my build.
[*] For the 6 input relays, would there be any sound/reliability benefit to sourcing name brand ones instead, or should the included China relays do ok as-is?
>> I used the included relays and they are just fine.
[*] I'm doing a slightly alternative assembly for my board, as I'm designing a chassis where the tubes will be exposed outside of the box. For this I'll be soldering most of the components to the underside of the board rather than the top. For most of the non-polarized components this shouldn't be an issue, and the polarized ones just need to flip correctly. Will the relays work properly if put in backwards? I've read they're not polarized and am assuming this to be ok.
>> Interesting. For polarized components, in many cases the polarity is given on the board so that should be followed. For the relays, if they are non-polarized that should not be an issue, as the contact arrangement is symmetric. But you can try: Use a 5V power supply to try if the relay properly switches with both polarities applied.
[*] For the board's power supply, most of the images I'd previously seen online show a 12.6V/3A input, but mine states 12V/15V/3A. Similar to the resistor question above, does this indicate a range? I intend to follow (this link)'s modification of adding a 12.6V low-noise regulator circuit, but am wondering if I can get away with using a 13V transformer.
>> In my build I am using a 13V transformer and its fine. I have made a slight variation to the cap follower for the tubes (2N3055), turning it into some kind of a voltage regulator, and this will need 14-15V DC on the collector of that transistor to work fine. But with 13V AC that should be ok. I posted this modification earlier in this thread.
[*] For both the 7805 and 2N3055 components, I've seen a slight variation between voltage and current ratings of available components. Does anyone have required specs for these?
>> The 7805 is a regular 1A linear regulator, not sure what the relay current is but anything above 500mA should be more than sufficient. On the 2N3055, the total tube current is 2.4A if I calculated correctly, so a smaller transistor would do as well. In my modification I used the MJ3001 (darlington, 10A if I remember correctly) without any issue.
[*] I don't intend to install a balance pot, my understanding is that the board works without this and doesn't require any jumpers to be installed to bypass? Please confirm.
>> The 100k resistors right next to the "Balance" socket on the board are the bypass. I bridged them, as they do nothing else than attenuate the signal.
[*] The inputs have both positive and negative terminals which to me suggest they could support a balanced XLR input. Is this true, or is the negative on the inputs just a connection to the board's ground?
>> The second is correct. This circuit is not symmetric, and the negative connection on the inputs is ground, actually. they are all connected to each other, you can check with your multimeter.
[*] Lastly, the board has 3 LEDs, does anyone know what specifically they indicate, and which is which? I'd like to run wires to mount them in the front panel of my chassis.
>> They indicate the heater voltage of each tube section. This board switches the heaters of the phono section OFF when not in use, at which point that LED will turn off. I disabled this one by bridging the relay, because I do not want so many turn-on/off events on my tube heaters, especially not on the low noise, low microphonics, matched input tubes which cost extra
Hope that helps!
OK I have a quick question, guys. First a little background for this phono question. All of the inputs are in a row on the PCB, (LP, CD,AUX and AUX2). It seems as though those are the four inputs as shown in the schematic. And it made sense to me to connect my turntable's output to the PCBs LP input.
But.. there is a PHONO OUT towards the bottom center of the PCB. Where does that get connected?
But.. there is a PHONO OUT towards the bottom center of the PCB. Where does that get connected?
Hi JW, please allow me to try and answer a few of your questions as per below, have fun!
[*] I bought the version without anything soldered to the board as I wanted to do it myself, and source my own components. None of the resistors positions state a minimum spec for current. If I understand electronics correctly, there's no upper limit to resistor wattage but there is a minimum correct? How do I determine the minimum?
>> The supply voltage of this preamp (B+) is 260V or thereabouts, so if you take the voltage readings printed on the PCB, you can calculate the voltage across the resistors (e.g. 260V - 130V = 130V), and with the resistor value from the schematic you can obtain the current. This will give you the power dissipation under nominal conditions, actually quite low in this preamp. But I recommend to go with larger resistors where indicated, and some people really like Mills Wirewound resistors which should fit nicely (2W/3W) for the big ones. For the smaller resistors, I used Vishay Metal Film 0.6W (again, quite oversized) with no problem whatsoever.
[*] The large resistors behind the tubes state "2K/3K/5W. I understand this requires a 5W resistor but what about 2K/3K, is this a range? Recommendations?
>> The schematic says 2K. Higher values will reduce the phono gain a little.
[*] For sourcing resistors, I'm assuming I want to choose the lowest tolerance value possible for each? Is there any reason to seek out "audiophile" grade resistors, or will I do ok buying name-brand low tolerance ones from Mouser?
>> In my opinion, 1% resistors should do just fine. For the 250K big guys, even 3% should be ok. The variations between the tubes might be bigger anyway. However, in the RIAA section you should match the components between the two channels as tight as possible.
[*] On capacitors, I understand that the voltage stated is a minimum and you can exceed this so long as the capacitance is correct?
>> Correct. Higher voltage ratings usually come with larger size, which may no longer fit.
[*] There is a tiny 1µF electrolytic capacitor, but doesn't state voltage. Does anyone know what it is?
This is the cap on the output of the 7805 voltage regulator, it will see 5V continuously so a 10V or 12V cap should be just fine.
[*] There are a couple capacitors which are polarized and have both a rectangle and circle printed. Assuming this means you can chose to use either a radial or axial cap? Assuming this is correct, any benefit to one over the other?
>> Whatever floats your boat. Axial caps tend to be less available and slightly higher inductance and resistance, but that is just my impression. I would suggest radial and did so in my build.
[*] For the 6 input relays, would there be any sound/reliability benefit to sourcing name brand ones instead, or should the included China relays do ok as-is?
>> I used the included relays and they are just fine.
[*] I'm doing a slightly alternative assembly for my board, as I'm designing a chassis where the tubes will be exposed outside of the box. For this I'll be soldering most of the components to the underside of the board rather than the top. For most of the non-polarized components this shouldn't be an issue, and the polarized ones just need to flip correctly. Will the relays work properly if put in backwards? I've read they're not polarized and am assuming this to be ok.
>> Interesting. For polarized components, in many cases the polarity is given on the board so that should be followed. For the relays, if they are non-polarized that should not be an issue, as the contact arrangement is symmetric. But you can try: Use a 5V power supply to try if the relay properly switches with both polarities applied.
[*] For the board's power supply, most of the images I'd previously seen online show a 12.6V/3A input, but mine states 12V/15V/3A. Similar to the resistor question above, does this indicate a range? I intend to follow (this link)'s modification of adding a 12.6V low-noise regulator circuit, but am wondering if I can get away with using a 13V transformer.
>> In my build I am using a 13V transformer and its fine. I have made a slight variation to the cap follower for the tubes (2N3055), turning it into some kind of a voltage regulator, and this will need 14-15V DC on the collector of that transistor to work fine. But with 13V AC that should be ok. I posted this modification earlier in this thread.
[*] For both the 7805 and 2N3055 components, I've seen a slight variation between voltage and current ratings of available components. Does anyone have required specs for these?
>> The 7805 is a regular 1A linear regulator, not sure what the relay current is but anything above 500mA should be more than sufficient. On the 2N3055, the total tube current is 2.4A if I calculated correctly, so a smaller transistor would do as well. In my modification I used the MJ3001 (darlington, 10A if I remember correctly) without any issue.
[*] I don't intend to install a balance pot, my understanding is that the board works without this and doesn't require any jumpers to be installed to bypass? Please confirm.
>> The 100k resistors right next to the "Balance" socket on the board are the bypass. I bridged them, as they do nothing else than attenuate the signal.
[*] The inputs have both positive and negative terminals which to me suggest they could support a balanced XLR input. Is this true, or is the negative on the inputs just a connection to the board's ground?
>> The second is correct. This circuit is not symmetric, and the negative connection on the inputs is ground, actually. they are all connected to each other, you can check with your multimeter.
[*] Lastly, the board has 3 LEDs, does anyone know what specifically they indicate, and which is which? I'd like to run wires to mount them in the front panel of my chassis.
>> They indicate the heater voltage of each tube section. This board switches the heaters of the phono section OFF when not in use, at which point that LED will turn off. I disabled this one by bridging the relay, because I do not want so many turn-on/off events on my tube heaters, especially not on the low noise, low microphonics, matched input tubes which cost extra
Hope that helps!
Wow Hesener, hats off to you, all really great and comprehensive info. Thank you so much!!
Sorry for my delayed response, was traveling for the Thanksgiving holiday here in the US and am just now getting back to this. Few follow-ups to some of your notes.
___
>> The supply voltage of this preamp (B+) is 260V or thereabouts, so if you take the voltage readings printed on the PCB, you can calculate the voltage across the resistors (e.g. 260V - 130V = 130V), and with the resistor value from the schematic you can obtain the current. This will give you the power dissipation under nominal conditions, actually quite low in this preamp. But I recommend to go with larger resistors where indicated, and some people really like Mills Wirewound resistors which should fit nicely (2W/3W) for the big ones. For the smaller resistors, I used Vishay Metal Film 0.6W (again, quite oversized) with no problem whatsoever.
>>> I ultimately measured the distance between through holes of each resistor and chose the biggest resistor that I could fit. For the smaller ones, most are ~1-2W at 1% tolerance, which I'm guessing is grossly oversized if you're suggesting that 0.6W is oversized for these. For the bigger ones I ended up mostly with 3-5W resistors at 1% tolerance, which again I'm guessing is oversized. Maybe I should re-shop some of these, but bigger is better right?
___
>> The schematic says 2K. Higher values will reduce the phono gain a little.
>>> Ok, wondering if I should go down to 2K then... Looking at the pictures of the pre-populated board on Aliexpress they all have 2.4K, so that's what I currently have spec'd. Will this make much of a difference?
___
>> In my opinion, 1% resistors should do just fine. For the 250K big guys, even 3% should be ok. The variations between the tubes might be bigger anyway. However, in the RIAA section you should match the components between the two channels as tight as possible.
>>> Sounds good, I have spec'd all 1% or lower resistors, except for 2 5.1kΩ 5W resistors, which I could only find in 5%.
___
>> The 100k resistors right next to the "Balance" socket on the board are the bypass. I bridged them, as they do nothing else than attenuate the signal.
>>> Would I be wise then to bridge these rather than putting in 100k resistors?
Also, to follow up on my last post, here's a link to my current specs spreadsheet in case anyone's interested in critiquing some of my choices. Or alternatively in case this becomes helpful to anyone else completing this build. So far I've only ordered the film capacitors (Black Friday sale). Doc is active at this point so things may change yet.
Specs Spreadsheet here
Specs Spreadsheet here
I got my amp going. But after quite a fight with cold solder. And I need to replace the 7pin socket from which my 6X4 slowly escapes.
But all in all? Not bad!
And built a super compact model which only has room for the PCB inside. I put the transformers and choke on the outside of the case.
And speaking of chokes, how close does the choke need to be to 20H? I have a beautiful NOS choke which would fit this amp perfectly but its only 15H...
But all in all? Not bad!
And built a super compact model which only has room for the PCB inside. I put the transformers and choke on the outside of the case.
And speaking of chokes, how close does the choke need to be to 20H? I have a beautiful NOS choke which would fit this amp perfectly but its only 15H...
I don't have a resistor in this position on mine. I just assumed it shouldn't be installed when using a choke.
Trond
Also I brought the input and output line cables through the sides as opposed to strictly the back. Makes for a much cleaner setup and internal connections to the PCB from the Rhodium plated RCA connectors.
Which reminds me. The truth? The 7-pin rectifier is a piece of ... trash. Does anyone have a nice PCB-mount 7-pin porcelain tube socket they'd sell me? I didn't want too make a quantity 1 part number order...
Thanks!
Which reminds me. The truth? The 7-pin rectifier is a piece of ... trash. Does anyone have a nice PCB-mount 7-pin porcelain tube socket they'd sell me? I didn't want too make a quantity 1 part number order...
Thanks!
Member
Joined 2009
Paid Member
Hi Rodango, sorry to reply to you only now, it has been a busy few weeks... Your idea to have the inputs on the side is good, Kondo san actually did a similar thing with an integrated amplifier, if I remember correctly.
In some places, the cables seem to touch the tubes, remember they get hot so the isolation may be melting, best to keep some distance.
Obviously all parts are in place, so my comments may come a little late ;-) In any case - On the 2k cathode resistors, 2.4k should work, with 2.2k being the next closest standard value. You could also put two resistors of 3.9k in parallel. Tolerance should be 1%, but don't worry, the tube tolerances may be bigger....
On the 250k resistors, yes bigger is better IMHO as long as they fit nicely. A friend has put boutique resistors from AudioNote (Tantalum, $50 each!) and believes it sounds better, proceed at your own risk and pleasure....
On the trimpot and tube supply voltage, check out the little mod posted in this thread, replacing the 2N3055 with a darlington (e.g. MJ3001) and putting a zener diode at its base (14V), and the trimpot to maximum resistance. Worked very nicely!
In some places, the cables seem to touch the tubes, remember they get hot so the isolation may be melting, best to keep some distance.
Obviously all parts are in place, so my comments may come a little late ;-) In any case - On the 2k cathode resistors, 2.4k should work, with 2.2k being the next closest standard value. You could also put two resistors of 3.9k in parallel. Tolerance should be 1%, but don't worry, the tube tolerances may be bigger....
On the 250k resistors, yes bigger is better IMHO as long as they fit nicely. A friend has put boutique resistors from AudioNote (Tantalum, $50 each!) and believes it sounds better, proceed at your own risk and pleasure....
On the trimpot and tube supply voltage, check out the little mod posted in this thread, replacing the 2N3055 with a darlington (e.g. MJ3001) and putting a zener diode at its base (14V), and the trimpot to maximum resistance. Worked very nicely!