What Jensen transformer?
What Jensen transformer model did you use? JT11P1 line input - 1 to 1 turns ratio (no gain)
Another option is to use a line output transformer, but this places more demands on the transformer due to higher signal levels after the preamp. Jensen JT-11-BMCF, 1 to 1 turns ratio, bifilar winding, 80% nickel laminations, the best that Jensen makes in this application.
Cinemag is another company that competes at the same quality level as Jensen.
In general, ai always go with the passive transformer option for signal isolation, balancing, bridging and step-up/step down, and polarity reversal.
What Jensen transformer model did you use? JT11P1 line input - 1 to 1 turns ratio (no gain)
Another option is to use a line output transformer, but this places more demands on the transformer due to higher signal levels after the preamp. Jensen JT-11-BMCF, 1 to 1 turns ratio, bifilar winding, 80% nickel laminations, the best that Jensen makes in this application.
Cinemag is another company that competes at the same quality level as Jensen.
In general, ai always go with the passive transformer option for signal isolation, balancing, bridging and step-up/step down, and polarity reversal.
Yes -- 24V gnd and dual supply common (gnd) must be tied together. The schematic image you attached will not work, don't try it.
If you want to go simple and quite good, get a copy of Mark's filter for the Korg pcb from the diyaudio store and add module DLC03B-15 (15V) or DLC03B-12 (12V) from Digikey. This is the module I use for my AA volume control. Make sure you get the "B" version which is appropriate for the 24V supply that will power it. For a temporary test, you can glue the module lightly upside down on the chassis and add some capacitance per the spec sheet at the output pins, and connect to the AA. Should work just fine.
I added Mark's filter to my AA power as well because the module is after all an smps and there's bound to be high frequency trash at the output.
You should look into that. Most of these small smps supplies send noise back through their inputs also. Read the application notes. If you want a small +/- dc-to-dc converter in there for the AA, I think you should have a filter on the B1K pcb. YMMV
I have been listening to my preamp (with the amp camp amp) for a few months. Everything was fine until this evening. I turned off the sonos but left the preamp on to do some reading without distractions.
I heard a pop, then kind of a ring noise. Now the preamp only plays on the left channel. So I pop the lid and look inside and see that the right side of the tube is lit up but the left is dark. I pull out my dvm and get the following at the test points:
T1 - 24.1V
T2 - 23.3V
T3 - 22.6V
T4 - 9.4V
T5 - 9.4V ??
T6 - 0.7V
T7 - 20.6V ??
T8 - 8.7
When i initially set it up T5 T6 was closer to 0.6V and almost the same. I also was adjusting the variable resisters to set T7 and T8 very close to 9.5V
I am unsure what steps I should take to figure out what went wrong and how to repair it.
ps - I used https://cdn.shopify.com/s/files/1/1006/5046/files/DIY_NUTUBE_PREAMP_Revised_2020-07-25.pdf for the trouble shooting.
I heard a pop, then kind of a ring noise. Now the preamp only plays on the left channel. So I pop the lid and look inside and see that the right side of the tube is lit up but the left is dark. I pull out my dvm and get the following at the test points:
T1 - 24.1V
T2 - 23.3V
T3 - 22.6V
T4 - 9.4V
T5 - 9.4V ??
T6 - 0.7V
T7 - 20.6V ??
T8 - 8.7
When i initially set it up T5 T6 was closer to 0.6V and almost the same. I also was adjusting the variable resisters to set T7 and T8 very close to 9.5V
I am unsure what steps I should take to figure out what went wrong and how to repair it.
ps - I used https://cdn.shopify.com/s/files/1/1006/5046/files/DIY_NUTUBE_PREAMP_Revised_2020-07-25.pdf for the trouble shooting.
This is what I came up with regarding inverter circuit and not polluting the B1K power supply...
First time I do this, so if you see anything, please shout!!
Especialy since I took various values as I felt "reasonable"... and wasn't sure about inserting a cap in the (negative) unitary gain loop
Thanks for your help
Claude
First time I do this, so if you see anything, please shout!!
Especialy since I took various values as I felt "reasonable"... and wasn't sure about inserting a cap in the (negative) unitary gain loop
Thanks for your help
Claude
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I apologize if this has been covered already but I could not find it when searching. Last night I connect my B1 with Korg up to my Ashly FTX amp and I noticed I would get a hum when I touched the volume pot. I'm assuming its a ground issue but I never had this problem with other amps. This Ashly amp does not have RCA inputs, its either XLR or 1/4in headphone jacks. I have the RCA to 1/4in headphone jack adapters in place.
Bored184....if you're not certain whether your pots' bodies are grounded to the either the signal ground or the system ground, just try mounting a wire to the threaded portion of the pot and the other end to the signal ground tab on the pot. See if that gets rid of the hum when you touch the pot.
Cheers
Cheers
Or use a technique I think Mark Johnson taught me, which is to connect/clip a lead to a solid return path point, and probe with the other end listening (or measuring). Probe around the pot and see if/where the hum goes away.
--Tom
Well, I had my B1Korg kit built for me ( not enough time, and he's a hell of a lot better than me...).
At first I had it hooked up to a NuForce STA200. Now it's hooked up to a DIY F5.
It sounds.... hey, THANKS NELSON! For real.
Anyhow, the first two days, I noticed some ringing in the left channel as it was warming up. If I so much as tapped on the chassis the ringing would go away. This amp was built so the KORG is on a U-shaped ribbon cable.. which allows the KORG to "float"... it's a clever idea. After a while of warming up, the ringing would just go away.
This is a beauty of a preamp ( I got an original B1 as well... ).
Anyways, I have not heard any more whistling ( knock on my woodend desk... knock! knock!). And with the Korg hooked up to the F5... I have not heard my '78 ADS L810 ever sound so clean and great ( I've had them since new in '78 ). The midrange is lyric and the treble is extended ( that F5 needs about an hour to warm up...). Those speakers are efficient enough that the amp will take them to 9.... which is fine for 99% of the music out there and likely more loud that is good for me.... The bass is deep and controlled as well. With the NuForce STA200 this was a Spinal Clock 11 combo! Cleanest LOUD rock you'll hear.
But anyhow, this is not about amps, it's about the Borg... err... the Korg.. which is a very, VERY nice sounding design. I also have a Conrad Johnson PV9 with the full teflon cap upgrade... and those two are head to head. Right now, I'm using the PV9 as phono preamp feeding the Korg. So, yeah, it's sort of Eating a Cake and Having it Too... ;-)
Again.. thanks Nelson. You're most awesome, really, seriously.
The only upgrades I'd wish for is three inputs and a tape monitor circuit. Perhaps individual pots for L and R. Or one of them concentric, ganged controls... However, that might throw some competition with the Pass Labs products... hmmm.... The KORG is really good. Remote? No need, I need exercise anyhow.
Now, if only my wife would let me put some holes in the house to install some El Pipe-O's... as it is, I'd be lucky to install some El Grande Bong-O's. ;-)
Now, I've looked through the forums, but can't find it.. so excuse me for asking here:
Can I get ACA v1.8 back plates for my v1.6's? I want to upgrade them so I can select mono configuration on the fly... 8 watts just don't cut it with my speakers.
At first I had it hooked up to a NuForce STA200. Now it's hooked up to a DIY F5.
It sounds.... hey, THANKS NELSON! For real.
Anyhow, the first two days, I noticed some ringing in the left channel as it was warming up. If I so much as tapped on the chassis the ringing would go away. This amp was built so the KORG is on a U-shaped ribbon cable.. which allows the KORG to "float"... it's a clever idea. After a while of warming up, the ringing would just go away.
This is a beauty of a preamp ( I got an original B1 as well... ).
Anyways, I have not heard any more whistling ( knock on my woodend desk... knock! knock!). And with the Korg hooked up to the F5... I have not heard my '78 ADS L810 ever sound so clean and great ( I've had them since new in '78 ). The midrange is lyric and the treble is extended ( that F5 needs about an hour to warm up...). Those speakers are efficient enough that the amp will take them to 9.... which is fine for 99% of the music out there and likely more loud that is good for me.... The bass is deep and controlled as well. With the NuForce STA200 this was a Spinal Clock 11 combo! Cleanest LOUD rock you'll hear.
But anyhow, this is not about amps, it's about the Borg... err... the Korg.. which is a very, VERY nice sounding design. I also have a Conrad Johnson PV9 with the full teflon cap upgrade... and those two are head to head. Right now, I'm using the PV9 as phono preamp feeding the Korg. So, yeah, it's sort of Eating a Cake and Having it Too... ;-)
Again.. thanks Nelson. You're most awesome, really, seriously.
The only upgrades I'd wish for is three inputs and a tape monitor circuit. Perhaps individual pots for L and R. Or one of them concentric, ganged controls... However, that might throw some competition with the Pass Labs products... hmmm.... The KORG is really good. Remote? No need, I need exercise anyhow.
Now, if only my wife would let me put some holes in the house to install some El Pipe-O's... as it is, I'd be lucky to install some El Grande Bong-O's. ;-)
Now, I've looked through the forums, but can't find it.. so excuse me for asking here:
Can I get ACA v1.8 back plates for my v1.6's? I want to upgrade them so I can select mono configuration on the fly... 8 watts just don't cut it with my speakers.
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Resistor Heat
Enjoyed this build to put in front of an Aleph J.
I'm wondering if it's normal to see R1 and the 100 ohm resistor on the right input side putting off a lot more heat than the left (~30c difference)?
It's a stock kit build, with an SMPS filter.
All the voltages are close to what we should see, and sounds great:
T1 - 24.1
T3 - 22.5
T4 - 8.96
T5 - 6.23
T6 - 6.57
T7, T8 - 9.5
Many thanks in advance.
Enjoyed this build to put in front of an Aleph J.
I'm wondering if it's normal to see R1 and the 100 ohm resistor on the right input side putting off a lot more heat than the left (~30c difference)?
It's a stock kit build, with an SMPS filter.
All the voltages are close to what we should see, and sounds great:
T1 - 24.1
T3 - 22.5
T4 - 8.96
T5 - 6.23
T6 - 6.57
T7, T8 - 9.5
Many thanks in advance.
Attachments
If both resistors are the same value and if the voltage drop across them are equal, then there is equal current flowing in each resistor. You didn't mention the resistor value so I have no idea what the current is. However, assuming that the resistors are of the correct value and therefore the current is also correct, the resistors should not be dissipating enough energy to heat up. Were the J113s and R1 resistors part of a kit or did you match them yourself?
So it may be that the 100R resistor is heating up R1. What is the voltage drop across the 100R resistor?
Also check the voltage drop across the corresponding 100R in the other channel. It is located at the lower left of the PCB, below a 332K resistor.
So it may be that the 100R resistor is heating up R1. What is the voltage drop across the 100R resistor?
Also check the voltage drop across the corresponding 100R in the other channel. It is located at the lower left of the PCB, below a 332K resistor.
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The voltage numbers are more or less the same for both channels and they do not look out of place. The 221R for the resistor seems reasonable as that would give I = 1.67V/221R = 0.0076A, which is within the specified range of 4 to 8 mA.
I don't see a reason for the resistors to be that hot. The 100R resistor dropping 1.5V is dissipating 0.023W and the 221R resistor dropping 1.67V is dissipating 0.013W, so they should not be hot.
So except for the hot resistors, everything else seems normal.
I don't see a reason for the resistors to be that hot. The 100R resistor dropping 1.5V is dissipating 0.023W and the 221R resistor dropping 1.67V is dissipating 0.013W, so they should not be hot.
So except for the hot resistors, everything else seems normal.