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New DIY Altoids Tin Amp - The Class A "Wintergreen Handwarmer" by xrk971 - Page 9

post #121 of 161
Quote:
Originally Posted by stellarelephant View Post

I wanted to post my listening notes for the capacitor options I've listened to over the past few weeks.  I'm including the listening test I did for the last few days with the Nichicon 470uF output caps soldered in place instead of temporarily attached (I believe this cleaned up the signal a bit).  I don't know why I ever bothered using the wires and gator clips.  I found that with them removed and the main caps soldered in, it was much easier to just pressure fit the different bypass caps in place.  I did this from the SMT side of the board, where there was tons of clearance.  I was surprised, but the parts made good contact just placed in the holes.  These impressions were based on listening with Sennheiser HD 598, which have an impedance of 50 Ohms.

1000uF OSCON - no bypass
-bass effortless
-vocals fuzzy
-smooth

360uF OSCON - no bypass
-more treble
-less mids and bass
-smooth

470uF Nichicon AK - no bypass
-sharper transient attacks, most transparency
-most treble details and midbass texture
-most balanced sound

---after soldering in the Nichicons---

470uF Nichicon AK - no bypass
-even treble throughout vocal region
-decent treble clarity, hint of graininess
-I wish there was a bit more HF extension
-tightest, most coherent overall sound

470uF Nichicon AK - 1uF WIMA MKS
-more treble, smoother
-best high treble of all combos tried
-less tightness/coherence

470uF Nichicon AK - 2.2uF WIMA MKS
-more high treble than no bypass, but less than 1uF bypass
-smooth
-vocals full-bodied and pleasantly forward in mix
-still less tightness/coherence

Take it all with a grain of salt.  These are all sighted comparisons.  But after considerable back and forth sighted testing, my current favorite is NO bypass cap.  Even though both bypasses brought forward the treble nicely, I found that they added a very subtle "something funny" or perhaps a null (?) in part of the vocal range.  It almost sounded like a phase issue, where there is cancelling or disagreement rather than coherence.  Maybe I was hearing impedance anomalies at the low corner frequencies of the bypasses...I don't know, or maybe I'm just distinguishing the "hand off" between electrolytic and polyester.  I envy you guys with 250 ohm cans...that puts the corner frequencies of your bypass caps WAY lower, perhaps getting such issues out of the MOST sensitive range of human hearing, the 2-5kHz "vocal presence" range, which is where they occur for me with my 50 ohm cans.

OTHER BYPASS OPTIONS

Larger WIMA MKS
One option for me is to use a larger WIMA MKS.  X already thought of this of course tongue.gif
Even the 6.8uF MKS (14mm tall) will fit in my tin with the way I mounted my board so low!  I'm going to try 3.3uF, 4.7uF, and 6.8uF.  6.8uF would reach down to 470Hz!  I don't think I would hear the subtle "hand off" down that low.  Still, I am a tad skeptical about this strategy, since according to WIMA, the bigger the cap, the worse the dissipation factor at high frequencies. 
See here: http://www.wima.com/EN/mks2.htm  Hopefully this increased dissipation will be inaudible, but I think I can already hear more high treble from 1uF vs. 2.2uF, so we will see if this is a trade-off with higher capacitance.  Have you tried any of the 4.7uF size yet, X?

Smaller WIMA MKS
Another option would be to push my bypass corner frequency above the delicate vocal region, closer to 10kHz.  I could accomplish this with a .33uF bypass.  I could still use a MKT but I'm looking at some other options too.  WIMA themselves do not actually recommend MKS caps in the signal path for audio circuits, though I know that they are often used this way with success anyhow...see pg. 7: http://www.tawelectronics.com/wima/WIMA%20Audio.pdf

Smaller Vishay MKT
This 0.33uF Vishay MKT cap would fit.  Still polyester.  I don't know how these sound compared to WIMA MKS.  If I'm reading the graph on its datasheet correctly, it has a dissipation of 0.01 @ 10 kHz, a smidgen better than the WIMA spec which is .015.  But Vishay also provides more precise measurement data, so it's probably insignificant.  Anyhow, this comparison ranks them a tad higher than MKS: http://www.humblehomemadehifi.com/Cap.html  If fact, he actually mentions good coherence in his impressions.  They are slightly different cap series though.  He compared MKT1822 and MKS4, with wider lead spacings and perhaps other differences.  I'll be comparing MKT370 and MKS2 series.

Smaller WIMA MKP
Hey, why stick with Polyester if I can fit a Polypropylene of the same .33 uF value?  I think I can cram this WIMA MKP2 in there, but Mouser calls it a "RF Microwave Film Capacitor" and its datasheet does not mention bypass as an application, nor are they mentioned in the "WIMA for Audio" doc.  Hmm.  What's the difference between MKP2 and MPK4...just size I hope? 

Smaller VISHAY MKP
This is a long shot for me, but I've drooled over the Vishay MKP polypropylene caps a bit, which are very highly recommended in the Humblehomemadehifi resource.  Sadly, I think the only one I can fit would be this puny .12uF cap.  Not sure if I'd hear anything at all, since the -3db point (corner frequency) with my 50 ohm cans would be way above human hearing range at 26kHz. rolleyes.gif   Still, for folks with higher impedance headphones, this could be a worthwhile upgrade experiment.  Corner frequency is down to 5kHz for 250 ohms.

Please share your thoughts if you have experience with any of these caps!


Thanks for the detailed listening impressions of the various setups. Be warned that not soldering in the bypass cap may not give proper results. The HF's being transmitted by the bypass depends on a good solder joint for low impedance. I am surprised you get anomalies with bypass installed and say it doesn't sound as good. This is probably due to improper connection. Think of it as the worst case of a cold solder joint! Bad for sound quality.

I tried the Silmic 100uF and 1uF Wima in controlled AB testing with an AB switch box and could not hear the difference - except for loss of a small amount of bass extension due to 100uF vs 390uF size.

I think you should solder one of the 1uF Wima's in place and listen again. Use the Nichicon AK that you like so much. It should sound balanced with nice mids and highs.

So for now - I am not sold on Silmics vs Oscons.
post #122 of 161
Thread Starter 
You really believe that simple pressure fit contact isn't good enough to judge SQ by? That's how the headphones connect in the headphone jack... is there a difference?

I can't wait for my USB-rechargeable batteries to come. Very cool that you are prototyping a big rechargeable option, X.

No perceived treble difference between Silmic and OSCON, eh? We should see what max value Nichicon KZ Muse would fit. These top-of-the-line caps are known for clarity and seem to be preferred by some folks above all other electrolytic caps, except perhaps the legendary Black Gates.
post #123 of 161
Quote:
Originally Posted by xrk971 View Post


I don't quite know what balanced headphone outs mean. Normally in amplifier terminology, balanced inputs are what pros use for long cable runs of signals where there is a positive and negative so that CM noise cancels out. But it seems like balanced headphone outs mean separate mono block amps with separate cables to each channel? The amps currently share a common power bus and ground internally. If you paralleld the amp outputs you could drive twice the current but same voltage. So for current hungry cans this would be good.

I am testing a prototype with a dedicated LiPo and charging system and dc to dc step up converter to get 16v from the 3.7v 2600mAh LiPo cell.

The kickstarter route is interesting. So is not having a slick looking CNC'd case stopping you guys from getting an amp like this that has superb sound quality? By all accounts, the reviews that have come in so far have been very positive with regards to sound quality and ability to drive a wide range of headphones and do it well.


IMO wrapping it in Altoid does it no favours.

Altoid amps already have the well established image of 'entry-level fun $70 hack amps' even though this is an entirely different topology amp....

Even the Bluebird amp designer is in to solid billets of machined aluminium now at that $59 price-point.

 

External design aesthetics are a strong consideration over $100 mark.

 

https://www.aliexpress.com/item/2016-NEW-Bluebird-amp-portable-headphone-amplifier-U6-PLUS-OPA2604-5V-USB-charging/32665824920.html?spm=2114.01010208.3.2.a1rk3H&ws_ab_test=searchweb0_0,searchweb201602_4_10065_10068_433_434_10136_10137_10138_10060_10062_10141_10056_10140_10055_10054_128_10059_10099_10103_10102_10096_10052_10053_10050_10107_10142_10051_10106_10084_10083_10080_10082_10081_10110_10111_10112_10113_10114_10078_10079_10073_10070_10122_10123_10124,searchweb201603_13,afswitch_1,ppcSwitch_5,single_sort_0_default&btsid=2447d302-4d31-428b-8860-a46d13e30934&algo_expid=dc789155-f704-4de7-8046-fd814c12bf54-0&algo_pvid=dc789155-f704-4de7-8046-fd814c12bf54


Edited by Lohb - 3/19/17 at 7:52am
post #124 of 161
Lohb,
Thanks for the feedback. I am indeed already working on a prototype for future release as a commercial product that is wrapped in a very nice case. It's still a ways off though but will look very different and be more cool looking than anything out there.

I see your point about the case though and the perceived DIY essence of a hack job CMOY amp even though this amp is much much more.

Never knew about the $59 Bluebird special. Wow, how do they do that for that price? Thanks for the tip.
post #125 of 161
Quote:
Originally Posted by stellarelephant View Post

You really believe that simple pressure fit contact isn't good enough to judge SQ by? That's how the headphones connect in the headphone jack... is there a difference?

I can't wait for my USB-rechargeable batteries to come. Very cool that you are prototyping a big rechargeable option, X.

No perceived treble difference between Silmic and OSCON, eh? We should see what max value Nichicon KZ Muse would fit. These top-of-the-line caps are known for clarity and seem to be preferred by some folks above all other electrolytic caps, except perhaps the legendary Black Gates.

You have a point but headphone jacks are designed for make-break connections with spring pressure contacts etc. here you have pressure or friction fit tinned legs on tinned through hole on PCB. Probably fine but to be sure solder it. You an reverse with a solder sucker.
post #126 of 161
Thread Starter 
I have desoldering braid but that's it...kinda a pain. I think I'll try some other bypass options first and then solder in my favorite. Did you try the bigger WIMAs out yet?
post #127 of 161
You really should get a solder sucker. Critical tool like screwdriver etc. braid won't get solder out of a hole.

I tried 2.2uF Wima's with Nichicon 470uF AK's on the outputs on gikigil's NHB unit. It sounded very nice.

Get these they work well.

https://www.amazon.com/gp/aw/d/B01C70X7V4/
Edited by xrk971 - 3/19/17 at 10:12am
post #128 of 161
Quote:
Originally Posted by xrk971 View Post
<snip>
You really should get a solder sucker. Critical tool like screwdriver etc. braid won't get solder out of a hole.
</snip>

 

Sorry, saw this passing through.  Braid will easily get solder out of a hole, if used correctly.  Use it on both sides of the pad.  If that doesn't work, fold the tip into a point small enough to fit into the hole.  If that doesn't work, add a bit of solder back to the hole and let the wicking action pull it out completely.  Almost without fail, the solder inside of a pad hole is simply a thin film anyway.

 

There is a place for a solder sucker, but most of the time with what we do around here, it's a sledgehammer applied to a tiny finish nail.  I use one, but only in cleaning up horribly soldered repairs for other people.  I made do without one until I started doing that last year.

post #129 of 161
Quote:
Originally Posted by xrk971 View Post
I don't quite know what balanced headphone outs mean. Normally in amplifier terminology, balanced inputs are what pros use for long cable runs of signals where there is a positive and negative so that CM noise cancels out. But it seems like balanced headphone outs mean separate mono block amps with separate cables to each channel? The amps currently share a common power bus and ground internally. If you paralleld the amp outputs you could drive twice the current but same voltage. So for current hungry cans this would be good.

Various levels of design classed as balanced, true end-to-end input to output....Some take single-end input and output balanced to the likes of 4-pin XLR with no shared ground like speaker output

So in the case of iBasso PB2 the voltage goes from 16v to 32 volts running balanced out over the 3.5" out.

 

Planar magnetic headphones seem to get better sound-staging/instrument separation/dynamics over single-end though not always.

SE can be as good or better than balanced, it just depends on topology but I'm rabbiting here to an amp designer, so you'll know best.

post #130 of 161
I just read up on balanced drive headphones. The closest thing in pure Class A with speakers is what is known as a circlotron. You need two power supplies and the ground is floating with the speaker voicecoil perched between the two amp MOSFETs pushing one way or the other. DC offset is critical here or your cans are toast. I like the built in safety of an output coupler cap. Of course you can only do balanced drive with a DC coupled amp and headphone.

This would make a good balanced headphone amp for an HE6.

https://www.passdiy.com/gallery/amplifiers/the-amazing-fet-circlotron-construction-continued
post #131 of 161
Thread Starter 
Quote:
Originally Posted by bogde View Post

you guys are probably aware of this, but i thought i should post it anyway, maybe it will help somebody. for the led hole something like this works out great: http://www.ebay.com/itm/Fiskars-Crafts123740-1001-Teresa-Collins-Hand-Punch-1-8-Inch-123740-1001-/262816786454
the 3mm led fits perfectly through the 1/8" whole. and, just like with the 1/4" model, the parts that may stand in the way, like the paper holder (see image), can easily be removed.

Great find, Bogde. The perfect tool for the job!
post #132 of 161
Quote:
Originally Posted by xrk971 View Post

I just read up on balanced drive headphones. The closest thing in pure Class A with speakers is what is known as a circlotron. You need two power supplies and the ground is floating with the speaker voicecoil perched between the two amp MOSFETs pushing one way or the other. DC offset is critical here or your cans are toast. I like the built in safety of an output coupler cap. Of course you can only do balanced drive with a DC coupled amp and headphone.

This would make a good balanced headphone amp for an HE6.

https://www.passdiy.com/gallery/amplifiers/the-amazing-fet-circlotron-construction-continued


This also - https://diyaudiostore.com/products/amp-camp-amp-kit

But there are so many portable balanced amps on the market already that its not as complex as the above, or appears not to be.

post #133 of 161
Quote:
Originally Posted by Lohb View Post


This also - https://diyaudiostore.com/products/amp-camp-amp-kit
But there are so many portable balanced amps on the market already that its not as complex as the above, or appears not to be.

I have the Pass ACA - it's a single ended Class A design that is very simple - almost as simple as mine. They are not DC coupled so I don't know how you would use cap coupled amps to drive a balanced voice coil.

They are quite simple one doesn't even need a PCB. Here's my everyday office amp for powering a mini Karlsonator speaker.

post #134 of 161
Thread Starter 

I found the same 1/8" hole punch (for LED hole) that Bodge found on eBay, on Amazon for only $4, with free Prime shipping.

Fiskars 1/8 Inch Hole Punch

 

Also found this 5/16" punch that can be used for the volume pot (no more filing!) for $8, also with free Prime shipping.

Darice 5/16 Inch Hole Punch

 

But this is what I finally bought.  A 3 Pack that includes 1/16, 1/8, and 5/16" punches for only $6!

Darice Hole Punches Value 3-Pack

 

The 1/16 will be useless, but what a bargain, with free shipping as an add-on item.  I believe you have to spend $35 to even be able to purchase an add-on item.  I had to buy a baby shower gift already so I just threw this in the cart before checkout.  FYI I already own a standard 1/4" hole punch, which works perfectly for the two audio jacks.

 

I'll report back on my next tin punching experience when this arrives.


Edited by stellarelephant - 3/20/17 at 8:22am
post #135 of 161
Is it bad if c4 and c5s solder is touching each other?
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