Korg NuTube preamp board left channel issues
I've attached a sketch of the grounding of the integrated amp. I'm wondering if I should have connected the shielded cable shield to the volume pot and through to the input of the preamp. I didn't as I Ithought it might create a ground loop. Thinking of it now if since the 24VDC in "-" is not tied to ground then the preamp input is "-" is floating and susceptible to noise. I will double check whether the preamp "-" is grounded via the power amp. Thoughts?
I've attached a sketch of the grounding of the integrated amp. I'm wondering if I should have connected the shielded cable shield to the volume pot and through to the input of the preamp. I didn't as I Ithought it might create a ground loop. Thinking of it now if since the 24VDC in "-" is not tied to ground then the preamp input is "-" is floating and susceptible to noise. I will double check whether the preamp "-" is grounded via the power amp. Thoughts?
Hi again.
I just spend 3 hours with the exact same problem you have, one module connected only had no hum, but both connected had a really annoying 50hz hum, so I figured there must be a ground loop between pre and power amp, tried lots of tricks, no change, until I tried soldering two 2k resistors in series with line signal, now it's completely silent.
In your drawing it looks like you have mixed psu ground and signal ground, I'm no expert but I think those should be kept separate, psu ground is considered dirty.
I just spend 3 hours with the exact same problem you have, one module connected only had no hum, but both connected had a really annoying 50hz hum, so I figured there must be a ground loop between pre and power amp, tried lots of tricks, no change, until I tried soldering two 2k resistors in series with line signal, now it's completely silent.
In your drawing it looks like you have mixed psu ground and signal ground, I'm no expert but I think those should be kept separate, psu ground is considered dirty.
The problem was a bad solder joint on the R1 resistor of the preamp. Volume fine on both channels now. I also had a noise issue which for the most part was resolved by running the GND wire for the power supply for the power amp directly between the two. I still have a soft hiss at the speakers. I have tried changing the input signal wiring to shielded wire all the way from the input RCA jacks right to the input to the power amp module. No joy. I tried allowing the 24VDC for the Korg preamp to float by not grounding the minus, No change. Next I'm going to try putting the Korg PCB into a small enclosure to see if the noise goes away. I'm not sure if its the preamp or the power amp causing this.
Ok, this will not work .. 300a1 has too low acceptable supply voltages (+-55v) - it cannot be directly connected to 1200 which has a rail +-65v.
Once I will need the additional channels, I will have to think about the amplifier's...
TA2022 plus tube preamp
I'm a cheap diyer with less money and time to spend on this hobby. Usually buys PCBs and populate them. But for this one I bought completely populated boards
Long time back I bought TA2022 assembled board from Muse. It is really a great sounding amplifier, vocals resolution is really best compared to my other SS amps. Recently bought another tube preamplifier kit from eBay, Matisse PRT06A so want to build a flexible preamplifier/integrated amplifier. When I use it as a preamplifier I don't want to switch on the power amp section. So I used 2 power switches, front one for preamplifier and a rear one for power amplifier. Also have added pre-out and main-in RCA connectors to manually connect to external amp when use it as preamp or to internal amp for integrated amp. I thought of using a relay for this which connects internal amp when power amp is switched otherwise external. But to keep signal purity I decided to go with manual switching.
Volume control and selector switches are from AliExpress EIZZ brand. Looks very well built for the price.
I'm a cheap diyer with less money and time to spend on this hobby. Usually buys PCBs and populate them. But for this one I bought completely populated boards
Long time back I bought TA2022 assembled board from Muse. It is really a great sounding amplifier, vocals resolution is really best compared to my other SS amps. Recently bought another tube preamplifier kit from eBay, Matisse PRT06A so want to build a flexible preamplifier/integrated amplifier. When I use it as a preamplifier I don't want to switch on the power amp section. So I used 2 power switches, front one for preamplifier and a rear one for power amplifier. Also have added pre-out and main-in RCA connectors to manually connect to external amp when use it as preamp or to internal amp for integrated amp. I thought of using a relay for this which connects internal amp when power amp is switched otherwise external. But to keep signal purity I decided to go with manual switching.
Volume control and selector switches are from AliExpress EIZZ brand. Looks very well built for the price.
Attachments
I'm a cheap diyer with less money and time to spend on this hobby. Usually buys PCBs and populate them. But for this one I bought completely populated boards
Long time back I bought TA2022 assembled board from Muse. It is really a great sounding amplifier, vocals resolution is really best compared to my other SS amps. Recently bought another tube preamplifier kit from eBay, Matisse PRT06A so want to build a flexible preamplifier/integrated amplifier. When I use it as a preamplifier I don't want to switch on the power amp section. So I used 2 power switches, front one for preamplifier and a rear one for power amplifier. Also have added pre-out and main-in RCA connectors to manually connect to external amp when use it as preamp or to internal amp for integrated amp. I thought of using a relay for this which connects internal amp when power amp is switched otherwise external. But to keep signal purity I decided to go with manual switching.
Volume control and selector switches are from AliExpress EIZZ brand. Looks very well built for the price.
Whole thing looks very well build.
I would recommend getting in touch w IcePower since the recommend the 300A1 as a hanger amp for the 1200AS2. The same for a 3 way application, see below I did a copy/paste from their site.
Attachments
Yes.. a based mine intention on that.. leter on a checked the datasheet...
Korg NuTube preamp with ClassDaudio CDA-120 Power amp
I put the Korg Nutube preamp in a enclosure with in the amp chassis. I used shielded signal cabling throughout. I moved the DC supply cable for the preamp as far away from the power amp and AC power as physically possible. So I have done a bunch more testing and found that the power amp is creating 50mV of noise (weirdly shaped square waves of high frequency) on to ground (chassis, DC -, everywhere.). The power amp has some residual hiss even when it's audio inputs are shorted. The preamp then picks up the noise and amplifies it creating an audible hiss at the speakers. Unfortunately I think the preamp will need to be moved to a separate enclosure unless the noise from the power amp can be mitigated. This can't be normal for a power amp to create so much noise or am I wrong?
I put the Korg Nutube preamp in a enclosure with in the amp chassis. I used shielded signal cabling throughout. I moved the DC supply cable for the preamp as far away from the power amp and AC power as physically possible. So I have done a bunch more testing and found that the power amp is creating 50mV of noise (weirdly shaped square waves of high frequency) on to ground (chassis, DC -, everywhere.). The power amp has some residual hiss even when it's audio inputs are shorted. The preamp then picks up the noise and amplifies it creating an audible hiss at the speakers. Unfortunately I think the preamp will need to be moved to a separate enclosure unless the noise from the power amp can be mitigated. This can't be normal for a power amp to create so much noise or am I wrong?
Looks like a soft-start switch circuit. The front panel push button switch is going directly into it.
tpa 3116d2. sounds great for what it is. costed me about 40 usd to buid it. the enclosure is made of discarder pieces of wood and aluminum composite panel.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Hi,
I changed the old transformer (on the photo on the right back) for an Antek. According to them, the oval shape is due to double insulation. In addition I had to move the transformer a little because the switch could not work.
With this transformer, the bass is more precise and dynamic with a lot of depth.
I changed the old transformer (on the photo on the right back) for an Antek. According to them, the oval shape is due to double insulation. In addition I had to move the transformer a little because the switch could not work.
With this transformer, the bass is more precise and dynamic with a lot of depth.
A softstart I designed and built so I can use an illuminated push button to power the amplifier on/off.
