HUM in Maverick D1 DAC tube output...

Hello,

Last night I "discovered" a hum in my Maverick D1 Tube DAC, when I was changing some interconnects, and my 1st thought was a bad cable, but it wasn't.

There is a hum from the TUBE output of my Dac, putting the volume knob of my amp to 11 or 12 o'clock. Using the Solid State output, it's dead silent.

I've swapped cables, inputs, outputs, the problem is the TUBE output, with any cable, with any input. The other output is silent under all the same situations.

I never realized of that, since I never turned the volume pot without music, so I can' t tell if this is something new, or it was always like this. The unit is like 1 year old, perhaps a bit more.

Is this normal? Should I open the unit to try to fix it? I can't send it to the seller, since I'm in Argentina.

try swapping the tube if you have another one. It could be a lot of things, but thats probably the easiest one to test.

I don't know from experience, but my preliminary research suggests the GE black plate, five star 5670 tube is the best for your DAC.

No affliation; http://www.ebay.com/itm/2-Pcs-NOS-G...pt=Vintage_Electronics_R2&hash=item3a8c3176f4

The hum is not normal. I'd try a new tube as the next thing.

BigElCat said:

I don't know from experience, but my preliminary research suggests the GE black plate, five star 5670 tube is the best for your DAC.

No affliation; http://www.ebay.com/itm/2-Pcs-NOS-G...pt=Vintage_Electronics_R2&hash=item3a8c3176f4

The hum is not normal. I'd try a new tube as the next thing.

Click to expand...

Yes. This is! I ran them in both my GF TubeDAC-09's. It'll really take your dac up a notch if your running the stock Chinese tube.

- Woody

I bought the DAC with this upgrade: OPA627 OpAmp & GE5670W Tube

If the hum is not normal, I don't have another tube to try. I need to trace the problem, to be sure before buying a new tube. I'll contact the seller in the meantime, but I trust AK better than any other advice.

I'll open the unit to take a look

I e-mailed Maverick, and they also think that if the Solid State output works OK, probably the tube is bad.

I've got a 2c51 tube, raytheon, made in USA, '50 or '60 according to the owner, never used... I'll pick it up next week and give it a try.

It was the only compatible replacement I could find locally. I don't know how it "ranks" in sound quality.

Finally, got the new tube, and when opened the unit to take a look, found the fail is the Nichicon 150uF - 250 Volt filter is getting bad... So now, I have a made in USA raytheon 2c51 tube for spare part





The bad new... there isn't 150uF caps available down here...

Can I go down to 100uF? I know tubes don't need so much filtering, I've seen old tube amps with just 45uF.

I can go up to 220uF, but I think they won't fit in place, the unit is quite small, and everything fits perfectly now.

Another question: Should I replace this 3300 uF caps, "H." brand?

Mouser AR shows the exact replacement in stock ... I don't know if that just mirrors the same inventory around the world, or where it would ship from, but ...

http://ar.mouser.com/ProductDetail/...9pzH80qHeVGdo2Gh9%2bIHuGtdQIM9ENdOifCjXAHgw==

Don't imagine I'd want to get too loose in the specs with substitutions. DACs tend to be right sensitive to noise issues ... I know shipping on one cap might hurt, but maybe you got some other stuff you need to lessen the pain.

Next step is to figure out what went wrong ... damage to the jacket looks to be heat related. Good ventilation at the top?

I've asked Mouser before, they charge $100 for shipping, whatever you buy. Obviously they don't want to sell down here. I've tried other options, but they are all more or less the same, very high shipping rates, or they charge you 10 times the price of a single capacitor... so no way...

And the local vendors don't sell 1.5uF, 15uF, 150 uF Just 1, 10, 100, 2.2, 22, 220

So you think 100uF could be too low? It seems the 220 uF won't fit (it's too tall).

I see my only reasonable option is: 100 uF, and try, and perhaps add another 47uF in parallel. It's a shame to butcher a so polite unit like this, but I won't spend $100 or $50 in one $1 capacitor ...

The unit is well ventilated, I think the part just failed, perhaps the 250V rate was too close to the max working voltage. Again, a higher voltage cap won't fit... I'll check the soldering, to see if some cold solder could be overheating the part.

well reducing filtering that much doesn't sound like a good idea never a good idea to go lower...Ironic it was the nichicon that is/went going bad when you got some cheaper junk caps next to it that look alright those might not be too far from going either who knows I would load it all up with some new panasonic's or CDEs or something like that Chemicon etc, I seen more of those older rubycon and Nichicon stuff blow up/melt leak/short you name it as well as the junk no name korean/chinese caps.....sucks when you can't get what you need though... doesn't look like you got much room but yeah could butcher it and just rig up some parallel combo to get you that capacitance.

Just another thing to think about is perhaps what caused that component to fail prematurely, as Nichicons are generally good caps... I'd check working voltages and ripple before randomly replacing that specific cap alone...

Those chinese caps are working at 25 V, and the "nichicon" (what could be a fake nichicon...) is at 250Volt...

There is a rectifier right beside the cap. I'll replace that too, just in case, and verify the working voltage.

All what I have down here are EPCOS caps, so I agree, I could upgrade all that no-name caps, if they fit...

Never used EPCOS stuff but heard people say they are not half bad...

$100 to ship a cap ... wOw ... just ... wOw ...

OK then ... the infamous PLAN B ... how about stacking caps? One 100 uf and two 22uf. Maybe even throw in a 10uf. That gets you into the range of the original 150uf +/- 20% rating. Stretch the leads, and there should be plenty of room in front of the transformer?

Probably wouldn't hurt to increase voltage ratings also - assUming you have larger ratings available, and the larger ratings fit. The box shouldn't have any issues with up to 600v.

I'd run all this thru Ryan at Maverick first though. Open a ticket and maybe he can even figure out a way to get a couple spare caps heading your way ...

Excellent DAC by the way ... I love my D1+ ...

PS ... just noticed you already mentioned stacking caps ... never mind! I wouldn't worry about "butchering" the DAC ... you do what you gotta do ...)

elnaldo said:

I've got a 2c51 tube, raytheon, made in USA, '50 or '60 according to the owner, never used... I'll pick it up next week and give it a try.

It was the only compatible replacement I could find locally. I don't know how it "ranks" in sound quality.

Click to expand...

Stolen from the web ... pretty popular list and a good place to start:

1st class,
WE396A (D getter)
WE2C51 (D getter)
Bendix 6385 (toooo expensive)
Tesla 6CC42 (rare but sometimes will show up in the market)

2nd class,
WE396A/2C51 (O getter)
Tung-sol 2C51 (they invent this tube, 1950s, D getter)
Raytheon CK5670 (1950s, D getter)
* Raytheon CRP 5670 windmill getter
RCA 5670 (1950s, D/Plate 2 supporting rod getter)
* RCA Command Series 5670
GE 5670 (3 mica structure, mostly 5 stars tube)

3rd class, (after 1960s)
GE 5670
RCA 5670
Tung-sol 5670
Sylvania 2C51
Sylvania 5670 (sometimes marked Mullard)
RTC 5670
Philips 2C51

4th class,
Russian and Chinese 6N3P, -E, -EB, -EV

I've already opened a ticket at Maverick, just to keep them informed about the failure rates of their units, since sending it for repair is not viable.

I think I can fit a 100uF and a 47uF, the 100 being vertical, where the 150 is now, and the 47 in horizontal position, bending the leads, with the top pointing to the front of the unit.

I've got a Raytheon 2c51, military specs (supposed) in it's box. I can post a pict later. But I think I won't use it, if the cap was the fail.

Well, PLAN B is not possible by now... Not 100uF 250V available....

I'll keep looking...

I did the recap yesterday...

To me, this could be a fake nichicon...

Last pict, the 2 caps I had to parallel: 2 x 68uF, to get 136 uF replacing the original 150uF.

I replaced some other caps too, some "GOUGID" and "HLSC" caps. Replaced with Epcos caps.

... and?

(Don't keep us in suspense ... humm gone?)

yes! ! hum is gone, it's performing perfectly! !

Now I'll know where to send mine if it needs fixing ...

Let me see ... if shipping an ounce of caps is $100, that would make a DAC ... er ... um ... a LOT! <G>

PS ... I take it you did pick up that other tube? Good to have a spare, and the variety is nice. Surprising how much difference one little tube can make.