Headphone half-kit

PatOMalley · « **on:** 11 Jul 2007, 04:56 pm »

I saw that you mentioned a Headphone half-kit in the BLOG: solid state so it should be a small footprint. I am interested. opamps? I know just the ones to use.

hagtech · « **Reply #1 on:** 11 Jul 2007, 07:42 pm »

Would you suggest an opamp or a buffer? Discrete? DSL driver? I haven't thought about it much. All I know is that the required output voltage ain't very big, so using an AB output stage might be the wrong approach. In my OBOE I used an opamp. It sounds pretty good, perhaps not spectacular. I found the output impedance had to be kept quite low to maintain bass response with my Grado 32 ohm cans. Ten ohms was really bad. One ohm ok. Prior to that I ran my Hafler into a 20 ohm / 1 ohm resistive pad. That worked pretty well. Took advantage of the huge available signal swing at low distortions, then impedance matched it to the phones. Kinda stupid to run a 100W amp for phones.

I think I might pick up a pair of Sennheiser 600s.

Scary thought for an audiophile manufacturer, but I've completely dissassembled my listening room setup. It's all in pieces moved back to the shop. The room is under major repair/painting/etc. Thinking I might just shift completely to phones. Is that heresy? In the shop I find it is the only way to go. Much easier to analyze noise floor and other anomalies. No room tuning issues to deal with. And I can set up multiple systems (like one right here at my office computer).

jh

analog97 · « **Reply #2 on:** 12 Jul 2007, 12:34 am »

Quote

I think I might pick up a pair of Sennheiser 600s.

Scary thought for an audiophile manufacturer, but I've completely dissassembled my listening room setup. It's all in pieces moved back to the shop. The room is under major repair/painting/etc. Thinking I might just shift completely to phones. Is that heresy? In the shop I find it is the only way to go. Much easier to analyze noise floor and other anomalies.

True. Everyone knows this. The best sound I've ever heard is the Cornet2 driving my Parasound amp directly (has gain controls and a headphone amp that connects to Sennheiser 6's). Absolutely scary!! What better way to hear pure detail, whether it be noise/problems or pure beauty? Problem is, simply put, it's too damn good! Can't hear anyone, can't be done at a vinyl party, etc. That's why you need great speakers.
PS: still working on my Piccolo......darn!! I goofed it up. Very disturbing and my fault, I'm sure. Awfully nice to have a real engineer lend a helping hand to a slow learner. Had to put in a plug for jh.....he's gone an Hawaiian mile for me.

PatOMalley · « **Reply #3 on:** 12 Jul 2007, 12:45 am »

low impedance for the Grados is what I vote for if it is a ss amp. Not discrete, opamps, so that I can tune it over time. "different" is better over the long haul.

but for me a tidy, small footprint tubed amp would be nice. I have not heard anyone complain about loss of bass or detail for any of your kits. Really I would much rather prefer the tubed amp. I already have a nice little Pro-Ject Headbox MKII amp that I have changed the opamp on. I can get busy and change the caps and it sounds very nice now.

... but who doesn't want an affordable kit for a tubed headamp? We ALL want one of those. Tubed headphone amp. YES.

opinion: Sennheisers do not have the thick heart and "hey, I am right here/there" that the Grados have. They are a bit thin, distant to me.

Shifting to phones only? Don't have to worry about big small room issues, can listen to detail all day long, you can hear groove noise and tape hiss real nice. As a lab tool they are as you say. But you won't be able to hold out - You just got to have music in the air.

hagtech · « **Reply #4 on:** 13 Jul 2007, 08:37 pm »

Ok, how about low impedance drive from a tube? I think that would be cool. Just how small of a footprint are you thinking?

Started some rumblings about this on my blog. For me, it's almost worth turning this into a little more than just an amp. If you're going to put a volume control on it, then who needs a linestage? And why not use it with a computer? It could have a normal analog plus a HAGUSB-type input. And if you need a switch, why not make it two analog inputs? Not a whole lotta cost added, but the machine becomes more useful and flexible. It is now an integrated amp with digital. Really, most of the cost is wrapped up in casework and iron.

jh

analog97 · « **Reply #5 on:** 13 Jul 2007, 10:13 pm »

OK. Low impedance, tubes and ready to drive good cans fed by my Cornet2. I could go for this. Are you also suggesting it would have a DAC and accept a CD input?

BradJudy · « **Reply #6 on:** 13 Jul 2007, 10:43 pm »

Quote from: hagtech on 11 Jul 2007, 07:42 pm

I think I might pick up a pair of Sennheiser 600s.

Grado and Senn are a good combo if you're going to design an amp - both popular, but with very different impedances. For a couple of years, my two main headphone pairs were Grado SR-225's and Senn HD-600's. (I'm a Beyer DT-880 guy these days)

jh - if you ask folks on Head-Fi what they're interested in, you'll get tons of feedback. Of course, it's feedback pulling in 20 different directions, but you can get a lot of interest. There are a lot of people over there that are used to the half-kit idea.

Daverz · « **Reply #7 on:** 13 Jul 2007, 11:16 pm »

Quote from: hagtech on 13 Jul 2007, 08:37 pm

Ok, how about low impedance drive from a tube? I think that would be cool. Just how small of a footprint are you thinking?

Started some rumblings about this on my blog. For me, it's almost worth turning this into a little more than just an amp. If you're going to put a volume control on it, then who needs a linestage? And why not use it with a computer? It could have a normal analog plus a HAGUSB-type input. And if you need a switch, why not make it two analog inputs? Not a whole lotta cost added, but the machine becomes more useful and flexible. It is now an integrated amp with digital. Really, most of the cost is wrapped up in casework and iron.

Sounds like the Headroom Desktop amp with DAC. I really like this idea because I am considering putting my whole CD collection on a terabyte drive as FLAC files. They could then be play over our home LAN.

PatOMalley · « **Reply #8 on:** 14 Jul 2007, 12:23 am »

Quote from: hagtech on 13 Jul 2007, 08:37 pm

OK, how about low impedance drive from a tube? I think that would be cool. Just how small of a footprint are you thinking?

Started some rumblings about this on my blog. For me, it's almost worth turning this into a little more than just an amp.
jh

Low impedance from a tube? You are the engineer and I am a noob. But tubes I want.
Footprint = 4"w x 8"d x however tall it needs to be. I am thinking small enough to fill in a space like this:

that table is an old humidor. The headamp is a Project Headbox MKII. People put their sodas up there so I don"t want to take all the space.

One thought is a switch to change gain/impedance for Senns and Grados. This will widen the market.
I am using Grado's so no switch, low impedance is AOK.

hagtech · « **Reply #9 on:** 14 Jul 2007, 02:19 am »

I don't know about the DAC part. It's just something I would personally like to have, rather than add a HAGUSB box out the back. Also thinking of an iPod connector or small stereo jack input for the front. Maybe that is useless?

Spent all day working out the amplifier portion. Went through a dozen various configurations until I finally came up with the synergy and low cost I wanted (I was all over the map). Won't be very small as it has six chunks of iron. One tube. Very simple and elegant. No transistors. $30 tranny, $10 choke, two $19 plate loads, and two $20 output trannys. Three $12 auricaps.

Maybe 8 x 10 x 3. All iron hidden inside, only the tube sticks out. Output impedance is about 5 ohms.

jh

ecramer · « **Reply #10 on:** 14 Jul 2007, 02:27 am »

ok looks good when can i get one ill test it out i'm kinda of a headphone junky lol

WGH · « **Reply #11 on:** 14 Jul 2007, 03:09 am »

Quote from: hagtech on 14 Jul 2007, 02:19 am

Also thinking of an iPod connector or small stereo jack input for the front. Maybe that is useless?

Maybe not. Two of my friends are never without their iPod's, they both are around 50 years old and I don't think either own a stand alone CD player. CD's go into the computer CDROM, ripped and then stored in iTunes waiting to be put into the iPod. I know, it is sad what they do to the music.

One buddy has 24 GB of mp3's on his iPod, the other buddy really, really wants a good tubed headphone amp kit he could build.

BradJudy · « **Reply #12 on:** 14 Jul 2007, 03:44 am »

Looks interesting Jim, and different from some of the other popular headphone kit options like Bottlehead or Mapletree (of course, Mapletree seems to be moving away from kits).

PatOMalley · « **Reply #13 on:** 14 Jul 2007, 03:53 pm »

Quote from: hagtech on 14 Jul 2007, 02:19 am

Spent all day working out the amplifier portion. Went through a dozen various configurations until I finally came up with the synergy and low cost I wanted (I was all over the map). Won't be very small as it has six chunks of iron. One tube. Very simple and elegant. No transistors. $30 tranny, $10 choke, two $19 plate loads, and two $20 output trannys. Three $12 auricaps.
Maybe 8 x 10 x 3. All iron hidden inside, only the tube sticks out. Output impedance is about 5 ohms.
jh

Nice. Castanet, huh? No horns? 6H30 looks like it has current Sovtek production(Sovtek 6H30PI) using legacy equipment that was used to make 6H30P-DR. Physically they look the same. There is no swapping other than deciding to go NOS or new: single source several brands, so that neurosis is avoided.

.

new on left, NOS on right.

I can get a bigger table, no sweat. Or an extension cable. I'm in.

hagtech · « **Reply #14 on:** 14 Jul 2007, 06:41 pm »

I'm wondering if just having one of those RCA-to-2.5mm cables will work for the iPod. Use the headphone output jack? Or maybe they make a cable that connects to the line outs on bottom? That would be better. Trying to DIY a clean and professional looking dock by hand might be asking a bit much. Or does somebody sell such a thing? A panel mount dock?

jh

BradJudy · « **Reply #15 on:** 14 Jul 2007, 06:59 pm »

While a dock-side ipod connector is neat, they are somewhat difficult to source (I think some of the custom cable guys on Head-Fi has sourced cable-mounted connectors) and they only work for iPod owners (while iPod dominates the market, a general purpose 3.5mm or RCA jack has a broader audience).

dnewman · « **Reply #16 on:** 15 Jul 2007, 03:05 am »

I too am very interested in such a tube headamp DIY kit. FWIW, of the three tubed headphone
amps I've built, I definitely preferred the 6H30 based single ended, single-tube design (SESS) of
Andrea Ciuffoli (http://headwize.com/projects/showfile.php?file=ciuff4_prj.htm). My other two
headphone amps were OTL designs, but the simplicity of using a single tube with output transformer
in place of two (per channel) power hungry tubes produced more pleasing results.

Dan

PatOMalley · « **Reply #17 on:** 15 Jul 2007, 03:03 pm »

Been reading the blog and the rolloff at 18k is not a detriment in my view, it's a plus. that rolloff may save some ear life. That high pitch will kill you sometimes.

hagtech · « **Reply #18 on:** 15 Jul 2007, 06:44 pm »

I meant the rolloff was 18Hz in the bass. Or likely a total -3dB of somewhere in the 20Hz to 25Hz reagion. I bet I can get at least 30kHz on the top end.

Here's a question: Which chassis orientation do you prefer? Narrow and deep, or wide and shallow?

jh

BradJudy · « **Reply #19 on:** 15 Jul 2007, 08:01 pm »

I'd vote narrow and deep, as long as the depth stays inside of typical rack shelf depths.

Either way, I'd vote for board layout that don't prevent the ambitious DIY'er from building either form factor (if they wish to mount I/O and controls off-board). I always find it interesting when people do something non-standard with boards like rotating or flipping them from their intended use.

For example, with an amp with this much iron, I think it would look killer if someone potted all of the trannies and top mounted them. Six shiny cans and one tube.