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Bottlehead Kits => Legacy Kit Products => Smack => Topic started by: Doc B. on February 15, 2011, 01:13:20 PM

Title: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 15, 2011, 01:13:20 PM
We just did the test firing of a new headphone amp prototype that I plan to take to the Bay Area Head Fi meet this weekend. The amp is designed as a complement to the Crack OTL headphone amp for high impedance headphones. This new design is a WOT (With Output Transformer) design that has been developed for low impedance headphones. I decided to call it Smack. It uses two 5687 tubes. One half of each 5687 is an active loaded single gain stage that is parafeed coupled to an output transformer. The prototype has a single tap of 32 ohms, however we might alter the production transformer design so that it could be configured for 32, 64 and 128 ohms. The second half of each 5687 is used in an active loaded hybrid shunt regulator. The prototype has been built on a S.E.X. amp chassis and uses the same PT-3 power transformer used in Crack, S.E.X. and Foreplay III. The gain stage and shunt reg use the new Soft Start PC board that we use in the new Paramount.

Unfortunately I only have some inexpensive Sennheiser 201s here today to try the amp with. But even with those it's showing promise. It's dead quiet, seems pretty quick and there seems to be pretty good bass for an amp that's about 2 minutes old. Gonna burn it in a bit and we'll see what folks think at the meet. Before anyone asks, I don't have a firm price. But it would probably hit somewhere in the $350-$400 range.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Spinifex on February 16, 2011, 08:10:27 AM
That's great! But what would be the differences between this one and the S.E.X.?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 16, 2011, 08:55:42 AM
Well, we just finished this amp about 20 hours ago so I can only make judgments that may change as we further refine the circuit. Right now we are exploring the best parafeed cap value. We have increased it from 3.3 uF yesterday to about 13 uF this morning and the bass is now about as deep as a SEX with MQ iron, and it seems a bit better controlled. The lower mids seem a little better balanced now too, yesterday the Smack seemed a little too bright to me. The S.E.X. may be winning in the midrange magic category and it might be a little bit more sweet on top. Might also give a little better sense of depth.

From a technical standpoint, of course the S.E.X. is much more versatile in that it can run efficient speakers as well as headphones. The Smack has theoretical advantages for headphone listening in that it is a single gain stage amp and it is shunt regulated. And if we decide to go into production on the output transformer with the higher impedance taps that might make it a little more universally good for both lower and higher impedance cans. All 6DN7s seem to sound equally good so tube selection is pretty easy for S.E.X. The 5687s and 7119s that work in the Smack seem to come in different flavors and it may take some rolling to find a pair you like. Some like that opportunity to play around, others don't want to bother. S/N may be a bit better in the Smack. I will need to cut the HVAC in the building to make a judgment about that, as the noise floor is pretty low in both amps.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: hasafraker on February 22, 2011, 03:53:21 PM
omg you're the devil... I'm working on a little headphone amp for work at the moment but my guess is I might just have to try some smack... if only my speedball would ever show up :(  ...but I must say that my crack is hands down the best sounding headphone amp I've listened to. I might have to offer build services to some of the guys at work after I take my Crack to work and give them a little taste.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 28, 2011, 10:40:27 AM
A little followup here - I took the Smack prototype with me to the Bay Area Head-Fi meet the weekend before last. It was very well received and the general consensus was that the amp did indeed work very well with Grados and other low impedance cans. So I think this one is a "go".  We will start to refine the layout a bit and see just how fast we can bring this puppy to fruition.

One question that was asked a lot was how Smack fit in the line relative to S.E.X. IMO this is a little bit better headphone only amp because the single gain stage and the shunt voltage regulation give it a touch better resolution. Of course the advantage of the S.E.X. kit is that it can run headphones and speakers, so it is quite a bit more versatile.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: xcortes on February 28, 2011, 11:30:16 AM
You said before you were using a pair of Stereomour opts. Those are 4k to 8 ohm, right?

I ask because I have a pair of Nickel Exo 45s waiting for a project (would be drop in!) and two sets of low impedance cans begging for an amp.

No plate chokes, right?

:^)
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 28, 2011, 12:48:23 PM
The Stereomour output transformers can be configured as 4Kohms : 2/4/8/16 ohms, and 8K ohms : 4/8/16/32 ohms.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: xcortes on February 28, 2011, 12:49:47 PM
And in this case you're using?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 28, 2011, 01:11:23 PM
We wired the Smack in the 8K:32 ohm configuration. But I think we will go ahead and shoot for a custom version of this transformer with additional higher impedance taps for the production version.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: xcortes on February 28, 2011, 01:12:29 PM
Thanks for the answer.

Makes sense.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on March 23, 2011, 04:26:50 AM
Dan,

At the Bay Area meet, did anybody try a pair of the audeze lcd-2s with this amp?  Do you think this will be an appropriate amp for the audezes?

Thanks,

Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on March 23, 2011, 07:37:00 AM
I think the LCD-2s need a lot of power. I have posted elsewhere that I have yet to hear an amp that does them justice. I haven't had a chance to try Paramounts with them, but that may be the best bet.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on March 23, 2011, 11:56:17 AM
Dan,

Thanks.  I have seen posts where people say these will work directly from their ipods, so figured that maybe the s.e.x or the smack would work too.  And while they may work, I'm getting that the full-on experience will only be realized with a higher power amp.

Maybe I'll just keep the hd-800s as my cans to shoot for and then the crack will be the best answer ther.

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on March 28, 2011, 01:09:26 PM
I may be misreading something here, but would it be possible to incorporate a switch to easily switch between the 32/64/whatever taps?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on March 28, 2011, 02:13:03 PM
That is the plan.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on May 20, 2011, 03:16:02 PM
Just an update - we got word from our winder that they will be scheduling the winding of a prototype output transformer for testing very soon. This will have, as stated below, 32/64/128 ohm taps. If all goes well we should have a production prototype happening in the next month or so.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Forte on July 23, 2011, 04:27:16 PM
Any more updates on this?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Paul Joppa on July 23, 2011, 05:37:16 PM
Good call! Doc B and I just talked today about bringing that project to the front burner. I have some personal and some medical issues to deal with currently, but I expect to have a lot of time in waiting rooms when I can work on my parts....  :^)
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: InfernoSTi on July 25, 2011, 01:51:04 AM
I'm sorry, Paul, and wish you and your family well soon.  Having a project or two to keep busy with is also a good thing....

John
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 27, 2011, 02:40:27 PM
Just a quick update -

We have tested the 16/32/64/128 ohms transformers in the first prototype and they are really nice. PJ has been puzzling out some PC boards with slide switches that will mount under each output transformer and allow one to choose 16/32/64/128 ohms, single ended output at the 1/4" TRS jack at the front, or balanced output at a pair of XLR jacks at the rear of the chassis plate. At the end of the day today I have what I think is a more or less finalized chassis layout. So we are very close to putting together the production prototype.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on July 28, 2011, 02:28:50 PM
Very cool. Looking forward to this.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 28, 2011, 02:32:11 PM
A bit more progress today - got the power supply filter strip configuration laid out. And I think we're just about ready to sign off on the chassis layout and get a prototype made up.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on July 28, 2011, 04:02:52 PM
Dan,

Are you planning on using full size or mini xlrs at the back of the amp?  Are these outputs going to need a separate single-ended to balanced transformer?

Thanks,

Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 28, 2011, 04:26:20 PM
From what I have seen the people that are playing with "balanced" headphone output (which seems to be more concerned with supplying separate signal cold rails for each channel rather than balancing the output signal with respect to ground) are using a full sized 3 pin XLR connector for each channel. So that is what we are using. Not sure that I grasp the second question properly, but the single ended and balanced outputs are all switched from the output transformer, so there won't be a need for any additional transformers.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on July 28, 2011, 04:38:08 PM
Actually, you answered my second question with your first answer.  Balanced, not differential -- got it -- i.e. individual returns, not balanced with respect to ground.

A little poking around and I see that's what the headphone crowd referers to as balanced, where as the pro world has a somewhat different interpretation/execustion of that idea.

This too sounds to be another great bh product, and I suppose I'll just have to get one. :-)

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 28, 2011, 04:53:19 PM
Yeah, separate signal cold for each channel is what the emphasis is in the HP community. You can do that single ended like we do with separate Paramounts and K1000s. Of course that presumes the L and R signal cold is not common in the source or preamp ahead of the amp - not a very safe assumption. But Smack will be true balanced output with respect to ground, that is, it is transformer "decoupled" and there will be a grounded center tap.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on July 28, 2011, 09:55:14 PM
From what I understand, the cold on each side is an inverted signal from the hot, giving an effectively doubled voltage swing. As such, balanced headphone amps have twice as much circuitry because they're essentially amping 4 channels rather than two.

If you're feeding in an unbalanced source, it could be set up such that the cold on each side is essentially amping zero and the headphone operates as normal. Some balanced amps also have dual unbalanced outputs, with output 1 giving out hot left/right, and output 2 giving out cold left/right (and in a couple examples I've seen, use this as a default then use an adapter to hook up balanced headphones).
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: mrarroyo on July 29, 2011, 12:29:59 AM
Quote from: Doc B. on July 28, 2011, 04:26:20 PM
From what I have seen the people that are playing with "balanced" headphone output (which seems to be more concerned with supplying separate signal cold rails for each channel rather than balancing the output signal with respect to ground) are using a full sized 3 pin XLR connector for each channel. So that is what we are using. Not sure that I grasp the second question properly, but the single ended and balanced outputs are all switched from the output transformer, so there won't be a need for any additional transformers.

Actually I believe there is a shift happening to the 4-Pin instead of the dual 3-Pin connectors. Not only are they cheaper but also use less "real state" and are lighter and simpler to build. I am switching all my headphones to the 4-Pin arrangement. Thanks.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Beefy on July 29, 2011, 01:26:58 AM
Quote from: Armaegis on July 28, 2011, 09:55:14 PM
From what I understand......

That is all for solid state bridged amps, and doesn't really apply here.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 29, 2011, 07:16:44 AM
So are the amp manufacturers going to a single 4 pin XLR as well, or is this primarily a DIY movement? When I Google 'balanced headphone cable' images most shown have two three pin XLR plugs, though there are a couple 4 pin as well. Maybe the thing to do is sell the amp as I have designed it, with the chassis punched for a pair of XLR D type connector jack shells. That way one could use the standard pair of three pin XLRs or replace them with a single 4 pin XLR, or even a pair of TRS jacks in D style shells, depending upon what is on your headphone cable. We could make this an order option.

Looks-wise, imagine a S.E.X. amp but with no plate chokes on top and nine pin miniature 5687s rather than octal 6DN7s. And it will have the XLR sockets where the speaker binding posts are on a S.E.X. amp, at the back. We're going to see if we can cook up a special pre-order price today and let folks start queuing up, as I think we can have this ready to ship in about 4 weeks.

Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on July 29, 2011, 11:26:24 AM
RSA using a large 4-pin XLR for their full sized, and a small 4-pin square thing on their portables...
http://www.raysamuelsaudio.com/

iBasso has some sort of 6-pin connector on their portable balanced amp...
http://ibasso.com/en/products/show.asp?ID=70
and mini6 to large 4-pin adapter: http://ibasso.com/en/products/show.asp?ID=68
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 29, 2011, 11:41:09 AM
Well, as usual the industry has a big gun aimed at their foot when it comes to setting standards that make it easy for the consumer. I'm just gonna go with the most universal mounting holes we can offer. The D style mounting hole allows for XLR, TRS, RCA, Tuchel, Speakon, CAT-6 and probably a bunch of other styles of jacks. I'll let the cable guys make adapters for the oddball stuff.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Spinifex on July 29, 2011, 02:11:26 PM
I have a small question, after reading the page. It is a parafeed amplifier, but is it a SET or a push-pull?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 29, 2011, 03:17:58 PM
It's single ended, just a single very linear triode gain stage for each channel. The other triode in each tube is the heart of the hybrid shunt regulator for the corresponding gain stage. SE is our area of expertise and IMO it sounds better than PP for these low power levels.  You might take a look at the Paramount soft start driver stage upgrade kit. It's basically the same topology on the same PC board driving an output transformer rather than a 300B. But what you will see under the tube sockets will look very similar.

Rather than making a differential circuit the balanced output is derived at the output transformer secondary, a method that allows for great isolation of the left and right signals and, IMO, better retention of subtle spatial cues in the signal.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on July 29, 2011, 03:48:53 PM
I suppose you could always wire two 4 pin xlrs in parallel and plug in two sets of identical cans for his/her listening?  Say a pair of HD-600s?

Just sent in my pre-order by email as I'm still having problems with the shopping cart and my screen reader.

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on July 29, 2011, 04:46:22 PM
I think that the idea could work well as long as both sets of cans are the same sensitivity, like your two pairs of HD 600 concept. Otherwise, only let the person with the more sensitive cans set the volume! I have some 650s on the way so I can test the theory with my 600s and the 650s.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Paul Joppa on July 29, 2011, 04:50:58 PM
I'm still refining the switching matrix, but here's some complicated details:

1) The switches will be on a board that mounts below the output transformer, under the chassis - so it's not for frequent switching, but no soldering requires to change the settings.

2) there are two impedance switches, giving four possible impedances. They'll be labelled LO, ML, MH, and HI, (16, 32, 64, and 128 ohms respectively) so the same switches can be used with the SEX amps and the Stereomour - they all have OPTs with the same topology, though different impedances.

3) There will be a third switch on the board, for balanced or single-ended output.

4) Here's the messy part - there are eight possible settings, and two kinds of output, as you can see. Total 16 combinations! I'll try to summarize - please understand, I'm on my second G&T (see other posts - family distractions going on) so this may not be accurate  :^)

LO and ML impedance, balanced - the XLRs are balanced with 240 ohm resistors to ground from either balanced output; the 1/4" jack in front is IHF standard 120 ohms source impedance, like the stock SEX.

LO and ML impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs, with no extra series resistance.

MH and HI impedance, balanced - the XLRs are balanced with the transformer center tap to ground from either balanced output; the 1/4" jack in front is on one half of the output transformer (half the voltage of the balanced outputs).

MH and HI impedance, unbalanced - the XLRs are grounded on the cold side, same as the 1/4" jack in front. The 1/4" jack sees the full voltage, same as the XLRs

Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: mrarroyo on July 30, 2011, 03:53:40 AM
I can say that Red Wine Audio on the new Class A headphone amp module only uses the 4-Pin version. Also Ray Samuel has included the 4-Pin besides the dual 3-Pin on his units. The new Apex Pinnacle a $10,000 unit includes both versions, the Eddie Current ZDT and Balancing Act have a 4-Pin as well. Hope this helps.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on August 01, 2011, 08:08:55 AM
OK, our production prototype (the one we photograph for the assembly manual) chassis is on order, and after a once over of PJ's design I will be ordering some of the output switching PC boards. These boards are quite versatile in that they will also fit the S.E.X. V2.1 and the Stereomour, allowing for switchable output impedance on those amps as well.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on August 02, 2011, 12:26:03 PM
Did a bit of listening with our prototype today, which we have set up with rotary switches to allow switching between 32, 64 and 128 ohms output impedance. This rotary switch setup is a bit of a kludge that we did before having worked out the more refined and useful slide switch scheme that will be in the production model.

We listened to a range of headphones - HD600, HD650, K701, MB Quart QP400, Skullcandy Aviator and Ultimate Ears Triple Fi 10V ranging from 32 ohms impedance to 300 ohms. The switchable settings really work well, we found that each headphone seemed to work best at the impedance setting closest to its own impedance. The high impedance cans sounded really nice and the low and medium (K701) impedance cans that we more or less came up with the Smack to work with sounded great as well. Unfortunately I don't have an assembled Crack amp handy to A/B, but I think I would still put my money on Crack as the very best bet for 200 ohm+ headphones. For someone with a good sized collection of headphones who wants a single amp to use with them Smack is a great choice, though I think it's criminal to have many headphones and just one amp, myself. Smack and Crack together could give great performance from a whole lot of headphone types.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on August 03, 2011, 08:08:08 AM
Am I allowed to cackle maniacally in anticipation?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on August 03, 2011, 10:29:45 AM
Certainly, please cackle away. Shawn is restoring a Crack that we attempted some genetic engineering experiments on a while ago. Soon we will have the ability to A/B the various headphones in our listening room on all three amps (S.E.X., Crack, Smack) and start to post more detailed reports.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: tdogzthmn on August 16, 2011, 04:15:33 PM
I am interested in how the sound signature of the Smack compares/contrasts from the Crack.  Which of the two would be considered more neutral?  Im interested in the Smack for use with my 100 ohm ER4S and 120 ohm K400/K500 which work well with the Crack but I can easily hear the difference in amp requirements when I have my HD600 plugged in.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: ironbut on August 16, 2011, 10:45:27 PM
I believe that there's a Seattle Headfi meet on the August the 27th. I assuming that Doc will have all three of his headphone amps there.
I think it's always better to get several folks opinion on an unknown amp.
You might think about posting in that Meet thread and get a few guys to agree to do amp comparisons with particular cans before the meet.
I can't tell you how many times I see folks all bummed out and posting in the meet impressions thread that they wished that someone had taken such and such headphones to do comparisons. When it gets to the impressions thread,.. it's a little late to complain about that kinda stuff.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on August 17, 2011, 04:39:22 AM
Actually the meet is this Saturday, August 20th

http://www.bottlehead.com/smf/index.php/topic,1995.msg15372.html#msg15372 (http://www.bottlehead.com/smf/index.php/topic,1995.msg15372.html#msg15372)

We will try to have the production prototype of the Smack finished in time for the meet and we will also have S.E.X. 2.1 and a slightly tricked out Crack.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on August 23, 2011, 03:44:16 PM
So, how did the meet go and how did the Smack fare?  And the new s.e.x.?

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on August 24, 2011, 08:21:34 AM
It went very well. It seemed like different people had different faves depending upon their taste and the cans they were using. The Smack accounted for itself very well with people giving positive comments using everything from low impedance AKGs and Sennheisers to HD800s and even power hungry LCD-2s. Another LCD-2 owner preferred the power output of the S.E.X. with the LCD-2. I wish I had made up an adapter to run the LCD-2s with the Paramounts.

My initial impression of the Smack vs. Crack with high impedance cans here at BHQ was that the Crack was better on the bottom end, with tighter bass. At the meet where there is a bit more background noise and the Smack had some more play time on the iron there did not seem to be as big a difference in the bass region and the single gain stage voltage amp and transformer combo was really nice in the mids and top end. For me the "balanced" (floating left and right signal cold) vs. single ended (common signal cold tied to ground) comparison with the Smack was a dramatic difference and probably the day's most impressive demonstration of the capabilities of our amps. Folks seemed kind of split on the Crack vs. the Smack, with the guys who had higher dollar cans seeming to like the Smack a little better and guys who were just getting into headphones and having medium priced cans appreciating that the Crack was very close sonically for about half the money.

One cool thing about these meets is that unlike big trade shows where it takes several weeks to find out if you influenced any sales with your presence, we have had several folks buy headphone amps based upon listening at the meet and reading the results posted on head-fi, with all three amp models selling as a result. I suppose folks want to hear there is a clear winner here, but that's exactly why we make three different amps. Different cans, different tastes.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: xcortes on August 24, 2011, 08:42:11 AM
Impressions thread:

https://www.head-fi.org/t/568061/seattle-8-20-11-meet-impressions (https://www.head-fi.org/t/568061/seattle-8-20-11-meet-impressions)
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: xcortes on August 24, 2011, 08:47:37 AM
So it looks like the Smack is a winner. Have you compared it with your Big Headphone Amp? Maybe I don't want to know!

If I ever finish building my Crack, rebuilding my Parabees for K1K use AND building my 437A preamp/headphone amp (oh, and installing the three pairs of soft start upgrades!) I'll have to order a Smack and recable my Sonys for balanced!
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on August 29, 2011, 11:29:54 AM
Xavier,

Thanks for the link to the impressions thread on HF.  I saw that there was one guy there who likked the smack with the AKG K601s, which is exactly what I would intend to do with mine, including a balanced rewiring of the 601s.

Dan, have you settled on a pf cap value yet?  Earlier in the thread you mention that you started with 3.3 and then went to 13, but wonder if this has changed since.  Also, what kind of voltage rating does this cap need?

I'm really glad to see the movvee towards a balanced headphone amp!

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Paul Joppa on August 29, 2011, 11:36:28 AM
10uF / 250v is now standard.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on August 29, 2011, 11:43:59 AM
Thanks, Paul.  Hope you're doing ok.

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Frihed89 on September 04, 2011, 04:01:30 AM
What is the measured power out and current at the different impedance settings?

Thanks
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Paul Joppa on September 05, 2011, 10:00:00 AM
I don't have a Smack here so all I can offer is the theoretical values based on the plate curves and transformer ratio, assuming the load is matched to the nominal impedance setting:


 16 ohms  1.8 volts 112mA
 32 ohms  2.5 volts  80mA
 64 ohms  3.6 volts  56mA
128 ohms  5.0 volts  40mA


These are RMS voltages and currents. Some 6 to 10dB headroom above the IHF standard. The maximum output power is about 200mW.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on September 06, 2011, 06:58:43 AM
Want to give a status update to those who have pre-ordered. We haven't forgotten about you! As happens sometimes the process of getting the parts together is taking a little longer than expected. Our laser cutter has been swamped and it took a while for him to get us a quote so we could order the chassis plates. They are now in the production queue as are the transformers. Should be a couple/three weeks and we will have some kits to ship.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: tdogzthmn on September 07, 2011, 06:01:24 PM
I have several headphones of various impedances so I wondering if the Smack will give me better results across the board since it is more capable with lower impedance cans than the Crack.  It looks like the highest setting is for 128 ohms which I would think is what you would set it on when using 300 ohm HD600. 
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: keto on September 17, 2011, 09:42:49 AM
PJ posted these outputs for the Smack:

 16 ohms  1.8 volts 112mA
 32 ohms  2.5 volts  80mA
 64 ohms  3.6 volts  56mA
128 ohms  5.0 volts  40mA

which would lead to....

256 ohms 7.2 volts 28mA
512 ohms 10.0 volts 20mA

So (smack me if I'm wrong) wouldn't this make an awesome preamp, with 8K:600 OPT's??????
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on September 17, 2011, 09:58:37 AM
To tdog,

We're tweaking up Crack, S.E.X. 2.1 and Smack for RMAF right now. As we fine tune them (experimenting with more current in the Crack and we finally got around to putting a C4S in the S.E.X. 2.1), they get closer to each other sonically. That said, the single gain stage and the shunt regulator seem to give the Smack the advantage in resolution over the other amps. Where it comes up a bit short with respect to the other two amps is in gain. We were running a very marginal level from our DAC this week and we had to turn the Smack up all the way while the other two amps had some room left on the volume knob. With normal output levels it's not a problem. We adjusted the DAC output up a just few dB and that allowed the Smack to show its stuff with some room left to turn the knob- very quick and dynamic with anything from 32 ohm cans on up.

to Keto,

My inclination would be to try the circuit as a preamp without any transformer. The output impedance would still be OK with a lot of amps - though my own search has been for a preamp tube that will have an output impedance down under 1K ohm, without a transformer. My opinion is based upon trying the transformer output circuit as a preamp vs. a low output impedance tube with no transformer, last spring.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on September 29, 2011, 04:49:24 PM
Quote from: Doc B. on September 06, 2011, 06:58:43 AM
Want to give a status update to those who have pre-ordered. We haven't forgotten about you! As happens sometimes the process of getting the parts together is taking a little longer than expected. Our laser cutter has been swamped and it took a while for him to get us a quote so we could order the chassis plates. They are now in the production queue as are the transformers. Should be a couple/three weeks and we will have some kits to ship.

Any status update on the Smack kits?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on September 30, 2011, 04:39:49 AM
Iron has just arrived. Now just waiting for the chassis plates to turn out a quick final prototype for pics for the manual and then we can start to ship.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on October 06, 2011, 12:13:24 PM
Chassis plates finally arrived this afternoon. We should be able to get the final prototype built and photographed for the manual next week before we leave for RMAF. With a little bit 'o' luck we should be able to start shipping kits not long after we get back from RMAF.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on November 01, 2011, 04:59:39 AM
This has obviously taken longer than I anticipated. The good news is Shawn and I are halfway through the construction of the final production prototype and writing of the manual, and all the parts are here. So we hope to start packing these later this week.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on November 03, 2011, 11:00:44 AM
Looking forward to it...
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on November 03, 2011, 11:07:35 AM
Shawn is soldering in the last caps as I write this. Next, on to resistance and voltage measurements. Then I will spend tomorrow processing the last photos and writing like a madman (I'm about 2/3 of the way thru the manual). Hopefully we can begin packing on Monday.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on November 08, 2011, 05:48:56 AM
Manual is complete and proofed, and the gang started to kit up the parts bags yesterday. Should be ready to ship the first kits in a day or two.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Armaegis on November 09, 2011, 05:43:29 AM
Great news. The pics look great. I'll have to start cleaning up the workbench to make room for this next project.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on November 26, 2011, 02:43:40 PM
I think I have an idea for my wife to get me for a christmas present :-).

Dan, any idea on when the impedance switching boards will be available for s.e.x. 2.1 and stereomour?

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: tdogzthmn on November 28, 2011, 04:26:42 PM
I have another question about the smack, and if it would be considered a hybrid tube amp similar to those produced by Cavalli Audio.  I dont not know the differences that separate a "hybrid" amp design from that of a traditional tube amp.

Thanks.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on November 28, 2011, 05:15:58 PM
A hybrid amp typically implies that one of the amplification stages puts the signal through a solid state device. The Smack does not do this. There are solid state devices in the constant current source and shunt voltage regulator, but none in the signal path.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: M^Cubed on January 11, 2012, 06:13:35 AM
Is the input impedance 100k like the Crack?
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on January 11, 2012, 07:04:57 AM
Yes, the volume control at the input is 100K ohms.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: tdogzthmn on January 12, 2012, 07:14:22 PM
Have the Smack kits started shipped yet?  I haven't seen any posts saying the first batch has been sent out. 
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on January 14, 2012, 02:26:14 PM
Yes, there are quite a few in the field and more shipping this week. It just seems to be taking some time for those who have purchased to post their impressions.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Mr. Davis on February 03, 2012, 01:30:00 PM
What happened to all the Smack builders?  Are your kits collecting dust in the garage? 

Looking forward to seeing some build pictures and impressions.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 03, 2012, 01:59:12 PM
Shawn just completed an assembled Smack that shipped today and we just received an order for another assembled Smack this afternoon (thanks John!), so at least two guys won't have to build them in order to gather some impressions.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Jim R. on February 03, 2012, 02:54:12 PM
Yes, mine is still in the box and probably will be for a while yet. Got to get at least one s.e.x. amp and/or stereomour working first and then the Eros.

I'm definitely looking forward to what others say as more people get them built and broken in.

-- Jim
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: M^Cubed on February 02, 2023, 07:05:36 AM
@Doc B. - where can I go to find a build manual for the SMACK WOT.  Also, have there been any design adjustments for 'improvements' ?   I have some M-caps I believe upgraded in there and a TKD pot.

Thank you.

Quote from: Doc B. on February 15, 2011, 01:13:20 PM
We just did the test firing of a new headphone amp prototype that I plan to take to the Bay Area Head Fi meet this weekend. The amp is designed as a complement to the Crack OTL headphone amp for high impedance headphones. This new design is a WOT (With Output Transformer) design that has been developed for low impedance headphones. I decided to call it Smack. It uses two 5687 tubes. One half of each 5687 is an active loaded single gain stage that is parafeed coupled to an output transformer. The prototype has a single tap of 32 ohms, however we might alter the production transformer design so that it could be configured for 32, 64 and 128 ohms. The second half of each 5687 is used in an active loaded hybrid shunt regulator. The prototype has been built on a S.E.X. amp chassis and uses the same PT-3 power transformer used in Crack, S.E.X. and Foreplay III. The gain stage and shunt reg use the new Soft Start PC board that we use in the new Paramount.

Unfortunately I only have some inexpensive Sennheiser 201s here today to try the amp with. But even with those it's showing promise. It's dead quiet, seems pretty quick and there seems to be pretty good bass for an amp that's about 2 minutes old. Gonna burn it in a bit and we'll see what folks think at the meet. Before anyone asks, I don't have a firm price. But it would probably hit somewhere in the $350-$400 range.
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: Doc B. on February 02, 2023, 07:46:06 AM
[email protected]
Title: Re: What?! Another headphone amp kit?! Smack me!
Post by: M^Cubed on February 02, 2023, 01:52:23 PM
Thank you very much!