[LaserWolf]

I got my hotsub 1 two days ago and I must say that I love it. I'm new to the world of Hi-Fi so I'm not that great at analyzing sounds yet, but I'll post thoughts on the Hotusb as I use it more. so far the biggest thing about the Hotusb 1 is just how quiet it is. when coming out of my laptop sound card I would get all sorts of buzz and whir and other various system sounds. With the Hotusb though it is dead silent, I love it.

 

[gsawdy]

Hi Dave,
Congrats on your success. I stumbled on this thread from a thread on low cost DAC's for notebooks. On your webpage I got really interested in the Digital Volume HiFi headphone amp.

Do you think this would work as a simple vol ctrl/pre for a pair of Dynaudio BM5a's? I want to give them to my daughter and I am looking for a cheap way to drive them and control the vol.

I don't understand the idea of a digital vol control. Can you explain how the vol is reduced? I gather from a prior post there are no resistors, instead there are transistors. Can't transistors degrade the sound? I'm trying to understand this, not be critical. It doesn't sound like what is normally referred to digital volume control which reduces the vol while the signal is in the digital domain.

Thanks for your explanation. George

 

[hotaudio40]

Well that is a very good question

A "Digital Volume" simply means that the volume is controlled by some sort of digital means.

This can be transistors, relays, resistors, pretty much any means of attenuating the signal as long as it is "controlled" digitally.

In computers the signals are digitally controlled through software which in turn controls transistors. Either turning them on and off, or controlling their current output.

Even software will distort an audio signal.

Anything that touches an audio signal will distort it and add noise.

In the case of my digital volume headphone amplifier, the volume is controlled by two devices. A volume control that puts out a digital pulse, and an IC that interprets this pulse and controls volume via transistors, and I'm sure there are some resistors in there too.

The idea being that most of the attenuation (signal reduction) is controlled by the gain of transistors, probably a jfet or some more advanced transistor (I'd have to look at the chip specs, but I know it is good

).

Thus the noise reduction is greatly reduced as transistors have far less noise then do resistors, and carbon volume controls are way noisier then just about anything, and they are the most common volume control in audio equipment, although microprocessor controlled volume is becoming very popular now.

All computers control volume with software that controls a digital control of some type and this is basically the same as what I use, EXCEPT I decided to go with an IC that DOES NOT use a clock or microprocessor.

Thus I believe my digital volume control is superior to those that do use carbon based volume controls or even microprocessor controlled volumes.

Although I have read specs on some chips that use microprocessors and they are quite good

I just wanted to make the purest digital volume that I could.

The chip I use "steps" through attenuation levels.

It does NOT use software of any kind.

And as far as I know, it has NO microprocessor inside the IC.

Back to your question.

Any time a signal is attenuated or increased for that matter, some noise and distortion will be added.

Only by leaving a signal alone will it remain intact fully...

But the purest form of signal manipulation is done with transistors.

And I'm talking about the newest types because they can have noise levels as low as 10 to the minus 12th.

Even though these transistors are NOT linear, with a fancy circuit of several transistors a very linear curve can be achieved.

And that's what these digital volume control ICs do.

My digital volume headphone amplifier will only amplify analogue signals, just so you know.

It doesn't have a DAC inside and does not connect to a USB port or have any digital input.

It has NO resistive or carbon based volume controls and it has NO capacitors in the audio signal path.

Basically it is as pure an analogue amplifier as I could derive at the time I created it.

Are there better digital volume controls.... Well yes there are, but they use micro-processors to control them.... and using them means a more complex circuit and much more chance of noise getting into the system.

Will I use those chips eventually..... Well yes I will

Simply because I like trying all possible combinations.

I hope this helps answer your questions.

hotaudio40

 

[gsawdy]

Thank you for your reply. I did a google search and found this link and the related link the Roland site
Remote volume
and
Jeff Rowland Design Group - Digital Volume Controls

They talk about a micro controller, being a non-engineer type I'm not sure if that is the same as a micro processor. VBG

Anyway those links are primarily for your interest--way over my head, but apparently Roland does or has used them.

You got interested in one of my questions and forgot to answer the one of most import to me. Namely will this unit serve as a vol control/preamp to drive the Dynaudio powered monitors?

Thanks again George

 

[hotaudio40]

Yes, you could for sure use the Digital Volume Headphone Amplifier as a preamp to drive any powered speakers or Power Amplifiers.

Just feed in a line-level signal (~2 Volts RMS) and it will give you a voltage gain of about 3 or 11dB.

It will do quite a good job too, if I don't say so myself

NOTE: One thing to note about using this as a preamp, which may be very important, is that when this headphone amplifier is turned off it resets itself.

Once reset, it will put the volume at 1/2 gain and put the balance back to the middle of the left and right channel.

This may be important as when you turn on this preamp and say you've got music going into it and your power amplifier is ON.

The output may be QUITE LOUD!!!! because it starts at 1/2 volume.

This wouldn't be an issue if you ALWAYS remember to turn your power amplifier on AFTER you've turned down the gain on this device.

It may not be that big of an issue with powered speakers, but could be quite an issue with a Power Amp configuration.

It could be VERY LOUD!!!!

hotaudio40

 

[minusthetom]

Im pretty happy with my SR80's and don't intend to upgrade them any time soon. I was wondering whether there'd be a noticeable improvement using one of these in comparison to plugging my phones straight into the headphone jack on my macbook, bearing in mind I'm a head-fi newbie.

 

[gsawdy]

Quote:

Originally Posted by hotaudio40 /img/forum/go_quote.gif NOTE: One thing to note about using this as a preamp, which may be very important, is that when this headphone amplifier is turned off it resets itself. Once reset, it will put the volume at 1/2 gain and put the balance back to the middle of the left and right channel. . . . . This wouldn't be an issue if you ALWAYS remember to turn your power amplifier on AFTER you've turned down the gain on this device. It may not be that big of an issue with powered speakers, but could be quite an issue with a Power Amp configuration. It could be VERY LOUD!!!! hotaudio40

Thank you for reexplaining it to me--I'll have to think about that. Maybe a push on/off mute switch. The speakers are pro monitors and pretty robust but they don't have built in limiters and tweeters are delicate. As for forgetfulness--what were we talking about??????? VBG

Next and last question: Since these are to be used on a desktop and portability is not an issue, have you tried replacing the battery with a simple 9v wall wart? I'm well aware of the benefits of batteries but also the inconveniences.
Best, George

 

[hotaudio40]

Well I did have wall wart powered units, but they cost much more to make - time wise, (remember these are hand made ), and in my opinion, the sound quality was not as good as with battery power.

I use NiMH rechargeables for testing and listening to the amps. It saves me tones in batteries and the NiMH seem to last forever. The Alkaline rechargeables always seem to either die or explode but not the NiMH batteries...

They keep going and going....

So that's what I recommend.

hotaudio40

 

[stereolat]

hello to everyone, just this week i purchased a hotaudio mark iv and a ultrasone hfi 2200, i hope this combination sound ok.

 

[Paul_in_Maryland]

I've owned my Mark IV for, I think, about 2 weeks. I bought it to drive my AKG K271S headphones at work. But I burned it in at home--along with the K271S--and home is probably where it will stay. Thanks to its two sets of outputs--stereo mini (3.5mm) and dual RCA--the Mark IV serves double-duty, driving my home K271S phones and my M-Audio StudioPhile DX4 powered desktop speakers.

After a 100-hour burn-in, the sound is quite pleasing: rich, warm, and loud, especially through the speakers. The Mark IV makes the speakers sound much larger.

I've also burned in some new AKG K-181DJ phones and run them on the Mark IV. The 181s sound quite nice in this arrangement. However, for me their quality will be wasted, as they'll be used chiefly for listening to recorded books on the commuter train and bus, unamped.

If you buy the Mark IV, please listen to uncompressed audio files and treat yourself to decent audio cables to connect your phones or speakers. Your sound can only be as good as the weakest link.

Eventually, I suppose I'll buy another Mark IV--or whatever may surpass it--to drive my work setup: AKG K271S phones, M-Audio StudioPhile 3 powered desktop speakers, and (any day now) Yamaha YS315 10-inch powered subwoofer.

One benefit of USB amps that I've never seen mentioned: You can use a cheap USB cable for most of the needed length, and get by with a shorter analog cable to finish the path from amp to phones (or speakers). If you're running a cable that costs an arm and a leg per foot, the savings can be considerable.

 

[Wenglish]

Quote:

Originally Posted by minusthetom /img/forum/go_quote.gif Im pretty happy with my SR80's and don't intend to upgrade them any time soon. I was wondering whether there'd be a noticeable improvement using one of these in comparison to plugging my phones straight into the headphone jack on my macbook, bearing in mind I'm a head-fi newbie.

I can't speak about the Macbook headphone jack personally, as I don't use Apple products. However, if you go back a page or two you can see my impressions about the HotUSB1 vs. the headphone out on my D630. I got a bunch of noise from my D630 (could hear the hard drive spin up, etc) and it was pretty nasty at even moderate volume.

If you get no noise from the Macbook headphone out and it doesn't distort at your desired/max listening levels then I don't know what to say (as I haven't heard that headphone out myself). I assume that the the pcm2705 would be a better chip than whatever apple uses--anyone with first hand experience?


Quote:

Originally Posted by stereolat /img/forum/go_quote.gif hello to everyone, just this week i purchased a hotaudio mark iv and a ultrasone hfi 2200, i hope this combination sound ok.

I have a set of Ultrasone HFI2200s. From everything I've read they're much more forgiving than the Pro750/2500s, but they still need quite a bit of burning in. I got mine with 10 hours on them and they didn't sound bad, but they were noticeably better after another 40 or so hours. I stopped keeping track after there (they're probably close to 100, if not a more) and they are still improving.

Solid bass, solid mids, good soundstage. Highs are a little bright, but they seem to be calming down as I log more hours on them.

*EDIT*
Read above, was beaten to it by 3 minutes

*EDIT*

I haven't heard a Mark IV, but from my understanding it's a hotusb1 with RCA and 3.5mm buffered outputs (and some extra magic? Dave can specify/correct me). The USB1 sounds good with the 2200s--I'd like it to have a little more juice to really drive them, but it can get them comfortably loud. Adding an amp helps.

Therefore, a Mark IV should do even better, as I doubt it'll need the added amp. When you get both in let us know what you think.

<thread jack>
Oh, and what do you think of the 2200s color scheme? The brown and orange speaks to me--which is odd, cause I own nothing else in those colors . I really dig the different looks.
</thread jack>

 

[hotaudio40]

Yes the MARK IV is a buffered version of the HOTUSB1.

Simply put, the MARK IV can output 75mWatts into 32 ohms and the HOTUSB1 can output 12mWatts into 32 ohms.

So pretty much the MARK IV does not need an extra amplifier, but nor does the HOTUSB1 if your headphones are efficient as most are.

But of course, it is nice to have the extra power

A little extra "MAGIC" in the MARK IV... of course....

But there is plenty of magic in the HOTUSB1 as well

I just scoped the MARK IV driving 32 Ohms headphones and it was able to produce 4 Volts peak to peak output swings, which is pretty good considering it is running off a 5 Volt power supply.

Almost rail to rail, and maybe it would do rail to rail, but I didn't push it to clipping.

The advantage of the HOTUSB1 though is that your getting pure PCM2705 Burr Brown DAC and then you can add any kind of headphone amplifier you wish on top of that.

You could do that with the MARK IV as well, but it really would be overkill.

NOTE: Remember that adding amps does NOT necessarily increase the power output. The maximum power output is determined by the last power output stage. So if you are using a MARK IV with 150mWatts output power and you add another amplifier afterwards that runs off a 5 Volt power supply you WON'T be getting any extra power output! Because the most it can deliver is the same voltage as the 4 Volt swing of the MARK IV. The HOTUSB1 could benefit from an amplifier as it has a smaller voltage swing.

hotaudio40

 

[PortaDiFerro]

Looks like this little DAC is getting lot of praise, and with the price it's sounding really appealing.

Originally I was considering buying some 24/192 sound card, but external DAC sounds handy so I could use it on laptop and on school computers too.

I gather from this thread this is 16bit device, so being a noob and all, I'm wondering how would it compare against the 24bit soundcards such as some cheaper M-audio models or even the Chaintech?

Also looks like the hotUSB1 has an amp in it, but I already have RSA Hornet M which I love. Would the DAC benefit from another amp such as that?

 

[ddoingwell]

My HotAudio40 TPA6120A2 Based Headphone Amplifier with a 32 Step Digital Rotary Encoder Volume/Balance Control arrived today and I've been listening to it for a few hours of real joy. I'll do the respectful thing and give the amp 100 hours or so before commenting in detail for fear of putting my Size 13 firmly in my mouth. Suffice to say that initial impressions are very good and I'm using the amp to drive my uber-fussy AKG K501s too! Surely things will only get better.

One little thing to note: delivery over Christmas/New Years took 14 days total from Winterpeg...I mean WINNIPEG...to Cairns Queensland Australia, despite the annual Christmas postal rush, public holidays et al. Impressive. The packaging was truly bullet-proof and Dave even supplied a lead, new battery and a little intro letter with that info quoted earlier in this thread about the digital volume pot.

More soon.

Happy New Year of listening goes out to everyone!

Don

 

[ddoingwell]

OK: 24 hours of run-in later and I'm very impressed with the clarity and general sound quality of my new HotAudio40 TPA6120A2 Headphone Amp. I'm using it with my tired little iMacG4, a SuperPro DAC and three different headphones so far. My fussyfussyfussy AKG K501s really have never sounded better to me and wonder of wonders: the K501s have a delightful new tight bass sound that I have never heard in them before. The 9V Duracell Dave provided with the amp is still going strong so there's going to be life in it yet. I'll run it dry to get an idea of battery life and report back.

Stay tuned.

Don