Digital Dilemma

Digital Dilemma

After building my 2Pi Speakers I settled down and spent some quality time remembering to enjoy my music collection. Also emerging was the fact that I have hobby ADD. I picked up woodworking in earnest, then photography, wine drinking, etc. All the while buying and loading more music into my collection. Then one day I had the life altering privilege of attending Jamie Cullum in concert. Unbridled passion is the only way I can explain his performance at the 9:30 club.

So is I went home, uploaded my newly purchased album and sat down to listen. Sadly it became overwhelming apparent that my beloved 2Pi’s were simply missing some bottom end. There was no harmony in the bottom octave just one note burping out. So, I went out and bought some Klipsch RF-25’s which quickly solved the bottom end problem.

Alas – what is the digital dilemma? Power.

My tube amp sounds – wonderful – but having attended a number of live shows recently it’s clear that there is room to improve. The bottom end just doesn’t have the impact when using the Tubes. Loud? yes – Deep? yes – keeps your foot tapping? Yes… But the tube just doesn’t deliver “slam.”

So, it’s back to square one. I’m now running music out of my computer to a DAC via a fiber optic cable. From the DAC to a Bottlehead Foreplay Tube Preamp, then to an old NAD power amp. Hello SLAM. And unfortunately hello listening fatigue. Now the bottom end is full, deep, quick, and accurate but the top end is too bright and the sound stage is totally unrealistic.

I wish for the day when listening to music was simple again – when it was about the cool lights and the jumpy indicators not sound stage, energy, dynamics.

Anyone want to lend me a 300B SET? Maybe some electrostats? How about just a live band that does covers of everything I have in my collection. Sigh.

Pi Speaker Perfection

Wayne Parham at Pi Speakers - I think you have perfection on your hands. I used his 2Pi speaker components and his Pi Align Analysis DOS Software to make a golden rule porportioned speaker enclosure. Covered them in Koa veneer. Built them out of baltic birch plywood.

I've been listening to the speakers for just about 2 years now and I think they are as good as an Audio Note speaker. Hands down amazing sound.

Give them a build and see for yourself.

WOW!

http://www.pispeakers.com/

iTunes Tangle

So I have been runnning a perfect blend of technology and old school. I currently use iTunes to store all my music - in lossless format on an external hard drive. I play the music and direct it out via the fiber optic jack on my MacBook to an external DAC where the S/PDIF signal is decoded and then off to the Thick and Juicy amp.

Recently I had a party where one of my guests hijacked my MacBook via their iPhone and set their phone up as a remote.

Doing so put some piece of software in the loop that took the natural brilliance out of the music and made it dull.

I have experimented with rolling back to earlier versions of iTunes to rectify the situation with no success but on re-installing iTunes (current release) after attempting the roll back - the system somehow got restored to it's previous luster.

So thanks for the help Mac Genius - not for solving my problem but for putting me on a path to get it solved.

In the mean time - Apple - don't muck with success and keep iTunes great.

P.S. Don't EVER mess with the volume control in iTunes - keep it maxed out and you should be good to go.

Success is Thick and Juicy!

So it's been a while since I last blogged. Here's why!!

I've been working to complete my most challenging project yet.

A single ended KT88 tube amp. This amp is a variation of the amp schematic from Angela Instruments (www.angela.com) from their how to section - the El34 schematic.

I've changed some parts out as they were called out in the schematic/write-up but it is still essentially the same.

So here's the details of how this project deviates from the schematic:

1. I changed the choke to handle higher current model. Hammond 193M
2. I changed the power transformer to the Universal transformer (also higher current capacity). Hammond 372JX
3. I used a 12ga solid copper ground bus
4. I bypassed the output stage capacitors with a Dayton 1uf polypropylene capacitor.
5. I wired it with Dayton microphone cable on the signal side. (using the shielding as a drain)
6. I used flat speaker wire for the output side.
7. I used Kimber hookup wire (I think it was the 19 ga stuff).
8. I used KT88's from Tube Depot (matched). Currently the Sletvana SED's.
9. I used the Hammond 1627ESE Output Transformer
10. I changed the output cathode resistor to 500 Ohm (with 28 V at the cathode).


Construction Notes:

Since this amp was created from just the write up off of Angela's web site I had to do my own wiring/chassis layout etc. If you're interested in building one - let me know and I can be cajoled into sending you the plans.

Hammond Box - I used a 10x17x4 grey chassis - if you're going to veneer the box - use this one as the black one is textured. If you aren't going to fiddle with veneer then go with the black box. The transformers I used are so heavy the box top caves in (a very little). I choose not to worry about it - if I didn't say anything you wouldn't have noticed.



If you are interested in this project, please email me at (hudsonmiller ampersat gmail period com) and I'll send you the layout/drilling plans for the lid. I didn't do one for the ends so you are on your own there.

Drilling the chassis - use a drill press and a 1 1/8" uni-bit for the tube sockets. Deeply punch the starter holes or the drill bit will walk off center. (it may still). CLAMP your work.


I used a bottom plate and constructed feet out of cleko's - apparently these are used in the airplane industry to clamp sheet metal together while riveting. I love them - no screws - just a $6 clamp tool and the cost of the feet. HIGHLY recommend these.

I used the parts express speaker posts and RCA jacks. Other IEC sockets, switch, and fuse holder come from either PE or Rat Shack. The speaker posts are to long to work in the chassis without a spacer block. Drill holes into it and put the speaker posts through then make your connections to build up the back a little.


Wiring is a 2 evening affair. Especially if you get me to send you the wiring diagram.

The tough part of a project like this is the box work - cause if it doesn't look good it may sound great but will still be garage junk to the wife.

I choose to veneer the box in burled maple on the sides and red mahogany on the top. I would have done the whole thing in maple but I couldn't find a sheet of burl long/wide enough here to bother. The maple is sanded, tack clothed, 1 coat of clear lacquer, tung oil, then 4 more coats of lacquer. I did this order to control the color the tung oil brought out. I found on my sample piece that if I put the oil down first it got a bit dark for my taste.

For the veneer I used the oil based contact cement. As before with the LP#9's I used the scraper method to apply pressure to the veneer. I did get one bubble - which I subsequently pierced and then ironed flat. This has worked so far.

Copper detail is kitchen door hardware - I had to drill out the volume knob to fit the volume pot shaft. - there's also a set screw in the bezel of the knob.

For wiring - I just started with the transformer wiring and built it up from there. The ground bus I'm very pleased with. Initial power on for this amp had NO HUM. at any volume level. Literally - no tweaks since I turned it on for the first time. I'm thrilled. And I am convinced it's because of the ground bus.

All point to point wiring. Where resistors/caps hit more than one pin on the tube socket I left the leads long and ran the lead through both pins and soldered both down to minimize connections.

The output cathode capacitors are twisted together, then a piece of stranded wire connects the cathode resistor to the pair of output capacitors. I ran the strands into the groves of the first twist, soldered the joint - and then trimmed the leads so one capacitor's lead came out one end and the other cap's lead the other. Then hot glued them all together.

As you can see in the wiring - power for the heaters is on one side - signal on the other. Where the heater wiring is close to signal (in or out) I've tried to cross at 90 degree angles and give some vertical separation tool.

It sounds - well - "Thick and Juicy". The bass is fantastic and the mid's and treble are just there - pleasantly present - not in your face. I'm absolutely thrilled with it and it has matched perfectly with my LP#9's. I've stopped using the Champ for now - it's waiting for a pair of low efficiency speakers next winter...

Lessons Learned
1. DO use Angela. Their service is exceptional.
2. Do use your community for questions. Paul Joppa, David Walters, Luther Ward, and Ray P. have been an immense help. See the Bottlehead forum
3. Do get the tube amp bug by buying a Bottlehead kit and get your feet wet.
4. Do call Steve at Angela and ask him a technical question. After/When he shuts you down "I'm not sure you're qualified to do this project" - you will be pissed and vow never to do business with him again. Then, when you realize he's in business to send you parts and DIY means just that DIY - you'll turn your well deserved insult into a new mantra to learn your stuff instead of trying to take the easy way out and ask him. Angela's service is exceptional - be happy with it.
5. Don't try and cut your power switch with a dremel - I've not found a good way to do this without fixing it with bondo.
6. Do use handles on the front/back of the amp - this thing is heavy.
7. Do buy the GZ37 rectifier tube before they are all gone.
8. Do put considerable time into figuring out what your first album will be - it will be a great experience and should be well planned.... ;-) Enjoy!!!

Too Much Foreplay for a CHAMP

I am currently running a newly completed Bottlehead Extended Foreplay III as a preamp and my newly constructed chipamp as my power stage into the LP#9's. The sound is excellent , however I listen to a fair amount of music as a fairly low volume level. The Extended Foreplay III C4S constant current source leaves behind a hiss - yes you can hear the current passing when it is hooked along side the ultra sensitive chipamp. This is not a problem when playing music at "audiophile" levels but when you are involved in a relationship it's really hard on the "audiophile" ears when the system is at a whisper as all you can focus on is the hiss.

Enter Paul Joppa. PJ is the king of the Bottlehead circuit design(s) and after posting a comment on the bottlehad forum PJ kindly responded with the following suggestion. He said to put a 66kOhm resistor in line with the signal coming from the FPIII just before going into the chip amp, then putting a 22KOhm across the signal input/output. This configuration would yeild a high impedance and about a 12db decrease in signal strength.

I did this initially with carbon comps and it does work. As before with the BSC however it leaves behind a film of yuck on the music. I decided to crack the piggy bank and order some tantalum resistors from Angela and put them in instead. Again - the lesson learned here is that when you want it right the pocket book has to open. The tantalum's did wonders and the music is back to its ultra clear quality, good imaging etc. And NO HISS from the FPIII.

Chip Amp - Project Notes

A Chip Amp in a Humidor - The Huma-Champ
Another experiment in Audio Addiction...


The Huma-Champ
So this story begins at http://www.audiosector.com/ and the LM4780 Kit. "Kit" is more like it (emphasis on how kitty the kit is). It is an excellent printed circuit board and parts to put on it. No wire, No enclosure, No Heat sinks, No Mounting Parts, and dam near no Instructions. So the challenge was on. Could I make this diminutive bag of parts come alive.

I don't like to bring my table saw out of the basement. I don't have anywhere to store it, sawdust goes everywhere and I am concerned my neighbours will get pissed. So my first concern was what to stick this amp project in.

One day while walking aimlessly through the mall I saw out of the corner of my eye a Cigar humidor. And the idea was born. I would buy a humidor and use that as the enclosure. I did some surfing on e-bay and found a winner - new glossy black for just over $40.

Next was the heat sink. I don't' do thermal calcs. I studied the LM4780 design guide for days trying to make sense of the math and finally gave up. The calculation said I needed a heat sink with a 1.5 C/W heat transfer (what ever that meant). So then I started cruising the web for heat sinks. I found a vendor that seemed to have a wealth of heat sink material that fell into that category of heat transfer and gave them a call. HA! they asked how many feet I wanted. I only want 2 3" pieces. The guy actually laughed. Then I hear the rapid strokes on his 10 key and I get a blunt - that will be $89 not including shipping. This project was beginning to piss me off.

Back to e-bay - typing in heat sink I land my prey. A fine gentleman is selling heat sink that appears to have turned up on his kitchen table after working second shift at a aluminum extruding shop. He was happy to saw it to size for me and ship for under $30. Now we were talking.

My final stop was on the transformer. Since the "kit" did not include any power transformer, switches, wire etc. I went to Parts Express and picked up one of their torrodial's. As far as sizing goes - the LM4780 wants somewhere in the neighbour hood of 20-28 Volts - pre-rectification. I ended up selecting a 22V, 22V model at 160VA. I think this is working out fine although I'm sure some people will say that I'm underpowered and should have gotten the 22V, 22V at 320VA'ish. Bla Bla. I doubt I'd hear the difference. Besides - I did a little more upgrading.

Enter Mouser - I decided to implement the snubber configuration on the boards from audio sector and I think it worked out well. I purchased some 15,000uF capacitors from Mouser along with the resistors and a couple of orange drops to complete the setup. Although the capacitors don't fit in the top of the board they plug nicely into the underside. This will give me a "nearly dual mono" configuration and the extra juice from the caps will probably make up for the partly anemic transformer.

As you read the web on implementing the LM4780 you will learn about the backside of the chip carrying -35V. It does - insulate against it. I ended up with the sil-pad. That was a lesson learned.

So - here's some pictures of the final Huma-Champ. My first un-kit DIY project. I'm thrilled with it. It sounds wonderful, is dead quite, and packs a punch. Enjoy!

Note the stand off and break in the RCA cable is for a Line level L-Pad to absorb a hiss from my preamp. If you are going to give this project a try. Do so without this correction unless you have the Bottlehead FPIII with the C4S upgrade.

Lessons Learned

Coming from the rear - Figure out how to integrate RCA jacks in the rear. I wired directly to the board but it would be better if I figured out how to put in room for the RCA jacks. Problem is none of them come long enough to simply drill a hole in the rear of the unit. The speaker posts work because I found some that are threaded and are long enough to fit.

Blue Tape - I covered the box in Blue Tape the moment I got it. I believe it helped keep the finish throughout the construction - I'd do it again.

Grounding - This was my first attempt. Seems as though I needed to maybe take some electronics classes. You can see in the photos above that I have a "star" ground fabricated out of a terminal strip. All ground leads go here. It was how I eliminated the buzz.

Fiddle, Spark, Boom - Don't try and diagnose a grounding problem while the unit is on. I bought a new kit from audio sector by trying to see if I could eliminate a ground loop problem before I made the star ground above. Lucky I'm alive. Ruined a speaker driver the in the process.

Tapping the Heat Sink - When tapping very small holes like the #4-40 screws I used to secure the chip to the heat sink I wasted two taps and countless holes. Go SLOW and back out often and clean the tap. I tried to force the tap through the metal and ended up snapping the tap off in the handle.

Baffle Step Correction Clarity!

Ok - so anyone who may have been keeping track of my angst with my LP#9's will have determined that I've been struggling with a rising response. The Martin-King site recommends a baffle step correction circuit. I tried the circuit and was not thrilled.

NOW I'm Thrilled. I replaced the components of the BSC with cement clad wire round resistors and presto - no more film - the highs were still clear and the bass came out just as it should. I also replaced the solen caps. with some dayton polyprop.

So if you want - go for the LP#9 design. It's done. I'm happy.