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My laptop's "desktop" [now-not-so-portable] speaker/amp system is ready to graduate from "something through which the computer can make noise" to "second system" status.Uncharacteristically--for my recent adventures in audio gear collection, anyway--this new system is in fact, all new. I'm still an enthusiastic proponent of getting used gear whenever possible for "best sound for the buck", appreciation for recycling, etc., but this time around, it just worked out that I wanted certain components, and couldn't find them used (at least not in a price range that might justify no warranties, etc.).
Not too long ago, I was happy to announce my previously "new and improved" computer audio system, and was especially happy that it cost me just $300 USD (mostly used gear). That system did represent a substantial improvement over the previous Creative Labs "2.1 speaker system in a box" I had suffered with for years, but now I've really gone and done it -- spent a bit more (still, very inexpensive in "audiophile terms"), and came up with a sound I can really appreciate as a "second system" (still can't compete "head to head" with the main system, but that's not the point of this system). This is a "near field/desktop" system.
First, the $300 system that just got replaced:
Analog audio output from computer
Integrated amp: Dayton DTA-100A Tripath amp (50 wpc)
Satellite speakers: NHT Super Zero
Subwoofer: Energy E:XL-S8
Then, I got a Schiit Bifrost DAC for the system, which inspired further changes.Here's the *new* new and improved system (around $1450, including cables and one power cord; may be two more power cords coming):
Digital output from computer (via USB)
DAC: Schiit Bifrost via USB input
Integrated amp: Maverick Audio TubeMagic A1 (hybrid tube/SS class A/B - 20 wpc) (2 x NOS Raytheon 6AK5 tubes)
Satellite speakers: Napa Acoustic NA-208S
Subwoofer: HSU Research STF-1
Headphones: Sennheiser HD600 (not included in cost estimate, above)
Tubes in the integrated amp are still burning in (just got started with those yesterday), but already, the sound is, generally, lovely. With this new integrated amp however, there is a bit of hum coming through speakers/headphones (to varying degrees at different volume level settings - see below). I'm wondering if this hum is a result of "noisy tubes"? Will be investigating. In any event, the hum is an interesting issue, as it's variable, as follows (as I wrote to Ryan at Maverick Audio, earlier today):1) At "zero volume" (7 o'clock), the hum is quite audible (this is a
"near field" desktop application, and a hum this loud cannot be
ignored). At low volumes of listening the hum can be heard, therefore
negatively affecting the clarity of the music (which otherwise, sounds
very nice!).2) As the volume is turned up, the hum begins to decrease at around 10
o'clock, until at straight up 12 o'clock, it's just about silent
(black background). Problem is here, that 12 o'clock is already a bit
too loud for most of my "desktop listening", yet this is where
there is the greatest clarity in the music - without the hum.3) As the volume is increased beyond 12 o'clock (beyond 1 o'clock,
especially), the hum then *increases* in volume, becoming its loudest
at full volume (about 5 o'clock). Of course, I doubt I'd ever want to
turn the volume up beyond about 12 o'clock anyway, so while this last
bit is interesting to note, it doesn't really affect me in practical
terms at the moment.I'm already pretty happy with the sound I'm getting, and if I can solve this hum issue with the amp, I'll be very, very happy! :)
Edits: 07/10/12 07/10/12 07/10/12Follow Ups:
First make sure that the AC power for both the Bifrost and the computer is the SAME AC circuit. Same outlet is best.
If that does not fix it, then try disconnecting the subwoofer signal cables.
If that does not fix it, then try same AC power circuit for the integrated amp, computer and DAC.
Steve N.
To me, being of northern european linguistic roots, that DAC has a really unfortunate name.
To understand what I mean in english merely remove the 'c' and one 'i' from it.
Type "Schiit", all by itself, into a search engine (take your pick), and you'll be faced with page after page of information on that one little company and its products. Good products, in fact.
From several angles, they knew exactly what they were doing when they decided upon that name. Nothing unfortunate about it, delicate sensibilities of some aside, of course. ;)
The first step is to disconnect everything from the amp except the speakers and to power down everything except the amp. If the hum goes away you may have a complicated problem to diagnose. If the hum persists then you know it is in the amp.
You didn't say if the hum was in one channel or two channels. This may provide a clue to someone who knows the circuit diagram of the amplifier and/or has had similar experience.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
'If the hum goes away you may have a complicated problem to diagnose. If the hum persists then you know it is in the amp.'
To see if it is in the amp, you'll need to short the input first; otherwise, an open input can be the cause of additional hum.
You should also see if there are mutiple grounds. There should only be one ground point in the system; perhaps the last component in the chain. If there is no component malfunction, this can cure the problem fast.
If it is the amp, check also induction thru transformer lamination vibration and hum .
An open input won't cause a loud hum with a working amp although there may be slight hum. The hum will be affected by the volume control and the OP had hum even when the volume control was at zero. The nulling of the hum at a certain volume setting indicated something very strange was going on, since it meant that two out of phase signals were being mixed at some point, one of which could be adjusted by the volume control to get the null.
As the subsequent posts indicated, something was seriously wrong. Fortunately, the downside of this electrical fault was only an annoying shock and blown components. It could have been much worse.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
''An open input won't cause a loud hum with a working amp although
there may be slight hum''
Where do you come from? Mars?
Hum should never be assessed with an open input. You don't know what's around it!
I have no use for audio equipment that has hum. I have been there and done that, decades ago.
A decent amp will not have loud hum when the input is open, i.e. not connected. This is pretty obvious. Where have you been all these years? This is even true with some older vacuum tube equipment which tends to be more sensitive to hum because of higher impedance inputs. Your comments might be appropriate when assessing a high gain phono preamp input, but not a line level input as was the OP's situation.
When I select the analog "preamp" input of my DAC I hear no hum, even if I crank the volume control all the way up, which provides 20 dB more gain than it takes to blast me out of the room when the input is connected to my cassette deck. The only time I have ever heard a slight hum on this input is when it was connected to another device. When I got the Mytek I tested all the inputs to see if and how they worked. If there had been hum on the analog input when the connecter was disconnected I would have returned the unit as indicative of a manufacturing or engineering defect.
When the line level input to my powered speakers is disconnected there is absolutely no sound coming out of the speakers, even with my ear one inch away. Had this not been the case, I would have returned these as well.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
to do with the subject under discussion?
Sounds to me like a diversion.
It seems that a bad power cord on the TubeMagic A1 may have caused some sort of short in the Bifrost DAC? Here's how I've come to this speculation (some peculiar things going on here)...
While preparing to unplug everything, I got a bit of an electrical shock when I touched the power conditioner to which both the amplifier and DAC are connected.
I unplugged the USB cable going from the computer to the DAC, and for some reason, this caused the power on the TubeMagic A1 to go off (at this point, A1 was apparently only getting [partial] power via the computer, USB digital cable to DAC, and then via the analog interconnects from DAC to TubeMagic A1; by the way, during this peculiar power scenario, the tubes in the A1 would not power up).
I unplugged the analog ICs from the back of the TubeMagic A1, and received another shock (handling only the IC cables).
At this point, I tried a different power cable with the TubeMagic A1 - and all seems to be well with this unit again (tubes are working, not even any hum at all - just clean sound, albeit now from the inferior DAC of the computer, via computer's analog output. Now however, the DAC seems to be hosed. No computer will recognize it via USB cable, funny sounds are coming from it, and of course, it's simply not working (though it does "power up").
Do you think the A1's original power cable issue, along with the subsequent power the A1 was sucking through the DAC/computer may have contributed to the hosing of the DAC?
Though the amp's cord may be the ultimate culprit here, it seems it's the DAC that got the worst of it. I'll be sending it to Jason at Schiit tomorrow, and he's quite sure he can fix it up for me.
In the meanwhile, I have at least partially solved the problem of having to use the analog output of the computer...
As it turns out, one of my little DAC/headphone amps also offers a pair of RCA analog outputs! (Audioengine D1). So, I plugged that into the computer, and I'm using the analog outputs to go into the TubeMagic A1 amp. Not quite so stunning as the D/A conversion usually coming from the Bifrost, but certainly still a marked improvement over the computer's internal DAC! :)
The repaired Bifrost just arrived a little while ago, and now it's back in the computer's sound system. Everything is working as it should, and sounding wonderful! No hum, no electric shocks, etc. Just good sound.
I can now enthusiastically endorse the following "desktop" computer sound system:
USB digital output from laptop computer (DH Labs Silver Sonic digital USB cable)
DAC: Schiit Bifrost (w/USB input option, of course)
Integrated amp: Maverick Audio TubeMagic A1 (Audio Art IC-3 analog interconnect pair from DAC to amp)
Speakers (monitors): Napa Acoustic NA-208S
Subwoofer: HSU Research STF-1
Headphones: Sennheiser HD600 (pure tube headphone output section from amp)
Power cords: Pangea AC-14SE for DAC, amp, and subwoofer
Still doesn't compete with main music system, but for a near field desktop system, it's sounding very nice (more "burn-in" time still expected for both Bifrost and hybrid tube/ss class A/B amp).
It may be worth your while to buy one of these plug polarity check units (cheap). If someone had invertantly transposed live and neutral (may be even on cable connectors), this is not only dangerous but can cause real problems.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
bot, i'm thinking that the opamp you are pointing to is a dual, not a single, and that the bypass caps near it may prevent using a 2 single-dual adaptor into the socket.
> > > > bot, i'm thinking that the opamp you are pointing to is a dual, not a single, and that the bypass caps near it may prevent using a 2 single-dual adaptor into the socket.Ahhh, thats a good point.
Maverick makes an optional opa627 board to fit into the sockets. I'm not quite sure how big it is, but if it can fit in the ones next to the tube I should have enough room for the bypass caps.
The Mundorfs I plan on using are 25mm or about 1" in dia. This is pretty close to the large square size around the WIMA cap. It might be a snug fit, we shall see....
I also plan on making a shield to go between the R-Core and the board, this might be a bit of a challenge. I think for sure the Shinkoh resistors will be larger than stock.
Here is a pic of a Havana Dac I modded. The Maverick will be modded with similar parts.
Upgrade Summary - Total 54 parts upgraded
-PCM56P-K grade chips x2 - classic NOS Dac sound and increased extension
-R-Core x1- increased impact and clarity across the spectrum
-Jupiter Caps x6- incredible lush textured sound but still clear presentation throughout
-ELNA Silmic and Silmic II x25 - electrolytic caps throughout - sound stage depth/width
-Shinkoh Tantalum resistors x6 - transformed the Dac into a different beast, now I can hear the harmonics of the tube. The music swings as it should, shimmer and sheen without glare. Shinkohs seem to remove the electronics from the music.
-Schottky Diodes x8- enhanced the character of the Shinkoh resistors a must have to get the full potential of Shinkoh
-Auricaps x5 - improved texture throughout the frequency range
-Hi-Fi Tuning Supreme fuse x1- provided more energy and impact
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
Edits: 07/11/12
actually the caps i was referring to are the really small film caps, they look light green in the picture you posted, and they are on either side of the single opamp (not one of the opamps that are next to each other).
they may be just a little too tall for a browndog adapter to fit
Oh okay...well I don't know what Maverick is using but I am sure they worked out the ergonomics. The OPA627's will come from them already installed as an option.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
OPA627 - I personally don't like the dry, analytical sound. They also cannot drive capacitance.
I tested/used a bunch of different opamps in the D1 when I had it. I liked the 627 best because it was the most extended and yes analytical. It contrasted the tube character good. The Mundorf caps are on the lush side as well so I think the analytical nature of the 627 would be a good match. Personal tastes I guess. Either way I am modding it as a gift so I will probably give a few other opamps and tubes with it in order to change.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
If you bias most opamps towards Class A with about 5mA, they sound better, especially the 627.
Thanks for the tip!
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
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