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Tascam UH-7000 power supply noise


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I went through the same thing. That is how I found this page. Everyone raves on how quiet this thing is. I saw the same noise profile in iZotope. When I put the supply on an oscilloscope I was able to read the noise. The first thing I am going to try will be putting the supply in a faraday cage and checking it again. Great detective work on your part!

So... I finally got around to it! All I had to do was solder a small cap across the power terminals on the bottom of the power supply that feed the main board. So much quieter. One other thing, I removed the black paint off the screw that has an obvious ground terminal on it. Paint on the screw will prevent it from making a connection. It was a TDK multi layer ceramic cap at 1.5uF. Bought from Mouser for $1.69. Link is here. It worked for me but results may vary as it is a mod and it's the only one I have done.

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So... I finally got around to it! All I had to do was solder a small cap across the power terminals on the bottom of the power supply that feed the main board. So much quieter.

 

Hi ! thanks a lot for the very valuable advice. When you say much quieter does this mean that this shows in a noise spectrum test ?

Because I saw the noise only with tests. The unit is quite silent by ear. But clearly a very low and flat noise floor throughout the band is much nicer than a noise floor with bumps, even if low in level.

 

One other thing, I removed the black paint off the screw that has an obvious ground terminal on it. Paint on the screw will prevent it from making a connection.

 

Also this is very interesting and a really strange mistake by Teac. I see that even in cheap cd player they use copper screws.

I will try to find some fit for the use.

 

It was a TDK multi layer ceramic cap at 1.5uF. Bought from Mouser for $1.69.

Link is here.

It worked for me but results may vary as it is a mod and it's the only one I have done

 

Thanks again indeed. I see on the psu pcb some parts missing and replaced with jumpers.

It is strange. With a electrical schematic maybe some kind of troubleshooting could be possible. Ok to the expert eye also without scheme.

What really amazes me is that replacing the stock even with a very cheap Dell smps 12V the noise floor looks much nicer.

For me extremely low noise floor is the 1st thing. The 2nd one extremely low distortion.

The 3rd one extremely low price ... (joke).

For instance I am amazed when I look at the creations from ExaSound. That is a noise floor

 

e22-RCA-Noise-Floor-USB-Isolation.png

 

Thanks a lot again. I will try the mods you suggest.

Have a nice day, gino

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Hi ! thanks a lot for the very valuable advice. When you say much quieter does this mean that this shows in a noise spectrum test ?

Because I saw the noise only with tests. The unit is quite silent by ear. But clearly a very low and flat noise floor throughout the band is much nicer than a noise floor with bumps, even if low in level.

 

 

 

Also this is very interesting and a really strange mistake by Teac. I see that even in cheap cd player they use copper screws.

I will try to find some fit for the use.

 

 

 

Thanks again indeed. I see on the psu pcb some parts missing and replaced with jumpers.

It is strange. With a electrical schematic maybe some kind of troubleshooting could be possible. Ok to the expert eye also without scheme.

What really amazes me is that replacing the stock even with a very cheap Dell smps 12V the noise floor looks much nicer.

For me extremely low noise floor is the 1st thing. The 2nd one extremely low distortion.

The 3rd one extremely low price ... (joke).

For instance I am amazed when I look at the creations from ExaSound. That is a noise floor

 

[ATTACH=CONFIG]31192[/ATTACH]

 

Thanks a lot again. I will try the mods you suggest.

Have a nice day, gino

 

I replaced my power supply with a custom made linear supply. Fairly easy install but much costlier. Still I'm quite pleased with the results especially when I use it as a dac.

 

 

Sent from my iPhone using Computer Audiophile

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I replaced my power supply with a custom made linear supply.

Fairly easy install but much costlier. Still I'm quite pleased with the results especially when I use it as a dac.

Sent from my iPhone using Computer Audiophile

 

Hi and thanks a lot for the helpful advice.

Other interfaces use a very simple solution, an external smps power brick of decent quality.

 

 

dc socket.JPG

 

In this way the psu is more isolated from the circuits, a nice thing in general.

No RFI or EMI from the psu contaminating the signal.

And it shows in the noise floor spectrum quite nicely. Love that test.

Regards, gino

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Hi and thanks a lot for the helpful advice.

Other interfaces use a very simple solution, an external smps power brick of decent quality.

 

 

[ATTACH=CONFIG]31199[/ATTACH]

 

In this way the psu is more isolated from the circuits, a nice thing in general.

No RFI or EMI from the psu contaminating the signal.

And it shows in the noise floor spectrum quite nicely. Love that test.

Regards, gino

 

Yes. It's seemed more difficult to use an external smps with the Tascam.

 

 

Sent from my iPhone using Computer Audiophile

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Yes. It's seemed more difficult to use an external smps with the Tascam.

 

It's easy to convert it. Just unplug and remove the internal PSU, then attach a wire with a standard barrel jack to the power input on the main PCB. Optionally cover the hole for the IEC power socket with a plate and mount the barrel jack there.

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Yes. It's seemed more difficult to use an external smps with the Tascam.

Sent from my iPhone using Computer Audiophile

 

Hi, when the box is small actually an external smps is the common solution because of the mains transformer size, weight and radiations.

However I am not completely set on the external solution. I am thinking to keep only the transformer out and place inside the rectification and stabilization stage.

Or use a double stabilization stage, one outside and one inside the cabinet.

Not that is really needed all this complication.

Regards, gino

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Hi, when the box is small actually an external smps is the common solution because of the mains transformer size, weight and radiations.

However I am not completely set on the external solution. I am thinking to keep only the transformer out and place inside the rectification and stabilization stage.

Or use a double stabilization stage, one outside and one inside the cabinet.

Not that is really needed all this complication.

Regards, gino

Expensive but fairly simple to install. It fit. Bigger than the original for sure but the guy who designed it also owns the Tascam. This was easier for me. I wanted everything inside the box. I'm not opposed to external supplies but I already have enough of that.

IMG_4238.jpg

IMG_4239.jpg

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I think I need to qualify, "expensive." The linear supply is expensive compared to modifying the existing supply. The cost was $160 plus shipping from Singapore. I felt that reasonable for the supply considering the design work. The designer was very helpful and provided directions. I think the directions actually made it seem more complicated than it was to install. https://drive.google.com/file/d/0Bx_GtKC7_I2HUjVHN0pULXJmZDA/view

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Expensive but fairly simple to install. It fit. Bigger than the original for sure but the guy who designed it also owns the Tascam. This was easier for me. I wanted everything inside the box. I'm not opposed to external supplies but I already have enough of that.

 

Hi ! the result is splendid and i congratulate you for the great implementation. Clearly that will preserve the normal functionality of the unit. But for me is too complex. I agree that for some an external ac adapter could be very disturbing but i have many and some of very good quality, both smps and linear, that i have bought to be used with other equipment like dacs and headphone amps.

But i admit your work is splendid.

Regards, gino

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  • 3 months later...

Hot damn, I was looking to start improving my own Tascam UH-7000, as I bought it to do audio measurements, but saw the noise and unplugged almost everything to get it down, still some spikes of noise. I knew the power board did radiated noise as my hand on top of where the lid sits showed different fft spectrums. So my tascam has been sitting duck since I tried it with AES/EBU to my Schiit Yggdrasil, (it sucked btw) and now the kids wants to record songs and stuff and I want to use the UH-7000 again for audio measurements, and really want to get rid of that noise. Mabye thats the reason why I find AES/EBU out to my Yggdrasil muddy.

 

So now, linear power supply is gonna get installed for sure.. awesome thread!

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Spectrum before I started modding of noise floor, you can clearly see the bumps there, also some really small bumps between 1-2khz.

spectrum nothing connected, noise floor before any changes to the units power supply.jpg

Then I got a 19€ linear power supply, a sugar to connect, cut the power cable and did 2+2 power +/- to the sugar, and conencted 12v to the linear power supply.

Bingo ! Even the tiny small bumps between 1-2khz is gone by the wind.

after linear power supply powering the unit.jpg

A picture of the mod.

2017-03-06 18.06.23.jpg

 

I will use the original power leads inside cabinet, cut the connector and put it on. Then super glue the linear power supply to the cabinet lid, so when it goes on, everything is inside same box and the power on/off will work aswell.

spectrum nothing connected, noise floor before any changes to the units power supply.bmp

after linear power supply powering the unit.bmp

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Now everything is inside the cabinet. even lid is on. The front panel buttons and wheels work, but not the volume meter :( not sure why.. mabye I disconnected something. I havent connected ground - yet.. will do afterwards. Just wanted to listen to this after I got the linear psu in.

 

Before the mod earlyer today, I took a good listen to the tascam unit as a AES provider for my Schiit yggdrasil, and I could clearly hear a big difference that the tascam unit didnt time the packets properly for Yggdrasil.

Then I took a good listen to the Tascam unit as a DAC feeding my V281 amp through xlr3 cables. And the muddy soundstage was there. In the past is was so muddy that I didnt want to use it in my stereo even. This is why I kept it sitting idle for half a year.

 

Now after the mod, the AES is more detailed and instrument separation is quiet good. Not as good as my Intona unit towards the Yggdrasil with USB, I suspect the clock in this unit not to be 1ppm (it says +/- 1ppm). ( I did use intona with the tascam too). But in a few days I will get Gustard U12 to see how AES works with a proper 1ppm oscillator.

 

Then I connected the XLR3 to my V281 amp, and - WOW. that was quiet a big difference. I had to double check if I had all cables right as I thought for a minute I was listening to my Yggdrasil.

I put a few songs on, and I heard definetely a more rumbling in bass reproduction than my Yggdrasil. Also the soundstage isnt as wide and precise as my Yggdrasil. But it is a very pleasat sound coming from the Tascam UH7000 now. Bang for the bucks definetely.

 

The biggest surprise is definetely on the analogue part after I got the Linear power supply. Holy crap thats a big difference. What did Tascam even think about with that power supply they installed in this unit ?

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Houston we have a problem.

 

When purchasing the PSU, the sales guy told me its linear. well its not. Its switcheable. Im still waiting for the ordered linear ones that look like the ones you guys have in these pictures for the linear ones.

 

Even though I got rid of EMI noise, I now have psu switching ripple in my high detail scopes. A friend of mine and I figured the number of milliseconds for good samples measured is 50hz = to the current we use here, so every few milliseconds I get a ripple that destroys the samples. I tried grounding pc and uh-7000 but same issue.

 

So now its just patience for those linear psu's. I hate switchable PSU's now in audio equipment for sure.

 

Learning curve increases even more.

 

6ms perfekte samples, 2 ms råtten samples aes through gustard.png

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Houston we have a problem.

 

When purchasing the PSU, the sales guy told me its linear. well its not. Its switcheable. Im still waiting for the ordered linear ones that look like the ones you guys have in these pictures for the linear ones.

 

Even though I got rid of EMI noise, I now have psu switching ripple in my high detail scopes. A friend of mine and I figured the number of milliseconds for good samples measured is 50hz = to the current we use here, so every few milliseconds I get a ripple that destroys the samples. I tried grounding pc and uh-7000 but same issue.

 

So now its just patience for those linear psu's. I hate switchable PSU's now in audio equipment for sure.

 

Learning curve increases even more.

 

[ATTACH=CONFIG]33881[/ATTACH]

What exactly does that plot show?

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Just a 1 khz square tone at -6.49db. and that is zoomed in samples of the first few milliseconds. you can see the first 5 squares are almost perfect, then 5 squares appear that is not so good. Basically the switching mode of the PSU kicks in creating noise. The cycle goes just like that. I tried it with AES, spdif, coax, usb with and without galvanized, and finally isolated it to the Tascam unit itself disconnecting everything except to my laptop. Then took the unit to my kitchen to connect it to ground (dont have ground lead in my living room), same issue. So it has to be the 50hz switched more ripple noise.

 

I tried to recreate the square measurement stereophile did on the same dac as I have. and they had a tone at around -6.79db at 1khz. Also doing this, calibrating the unit for measurements.

 

Here is the original plot.

 

6ms perfekte samples, 2 ms råtten samples.png

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Just a 1 khz square tone at -6.49db. and that is zoomed in samples of the first few milliseconds. you can see the first 5 squares are almost perfect, then 5 squares appear that is not so good. Basically the switching mode of the PSU kicks in creating noise. The cycle goes just like that. I tried it with AES, spdif, coax, usb with and without galvanized, and finally isolated it to the Tascam unit itself disconnecting everything except to my laptop. Then took the unit to my kitchen to connect it to ground (dont have ground lead in my living room), same issue. So it has to be the 50hz switched more ripple noise.

 

I tried to recreate the square measurement stereophile did on the same dac as I have. and they had a tone at around -6.79db at 1khz. Also doing this, calibrating the unit for measurements.

 

Here is the original plot.

 

[ATTACH=CONFIG]33885[/ATTACH]

And what's the bottom plot there showing?

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Is that a 1khz tone ? If so, can you run it at -6.5db, do a square tone, and take a scope and show 10-15ms and see if there is variation of the square reproduction sequence or not ?

 

I am just a consumer. You might be able to ask the designer/builder of the power supply. I am confused however. Isn't the 1khz tone expected for the dac being used?

 

 

Sent from my iPhone using Computer Audiophile

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I am just a consumer. You might be able to ask the designer/builder of the power supply. I am confused however. Isn't the 1khz tone expected for the dac being used?

Sent from my iPhone using Computer Audiophile

When you feed the tascam unit with a 1khz tone for instance, it goes to the DAC part and then further to the headphone output and the outputs other outputs. Also it is fed to the ADC for recording of the same tone. This means that you can use this unit to play back eg. Tidal/spotify and record it with the same unit.

 

Thats how I could track down the 50hz ripple effect on high detailed tones to the unit itself.

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  • 3 years later...
On 12/1/2016 at 12:04 AM, junkyardawg1 said:

So... I finally got around to it! All I had to do was solder a small cap across the power terminals on the bottom of the power supply that feed the main board. So much quieter. One other thing, I removed the black paint off the screw that has an obvious ground terminal on it. Paint on the screw will prevent it from making a connection. It was a TDK multi layer ceramic cap at 1.5uF. Bought from Mouser for $1.69. Link is here. It worked for me but results may vary as it is a mod and it's the only one I have done.

 

pls. mark on foto of board, where you soldered this TDK multi layer ceramic cap at 1.5uF.

Thanks.

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  • 1 month later...

Good afternoon All,

Many thanks for this highly interesting thread.

I have a UH-7000 and would like to add the TDK multi layer ceramic cap at 1.5u referred to by Junkyardawg1 above.  However, the connector appears to be muti-way, so I am not sure where to connect the capacitor.  Ae you able to clarify please Junkyardawg1?

With thanks and regards, JSB

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