Prototypers wanted

[dsavitsk]

TomB and I are ready to start gathering people to prototype our new amp. For those who do not know, this is a CCS loaded, transformer coupled parafeed headphone amplifier. The transformers are custom designed 10K:300 ohm with a 32 ohm tap so they should work well with just about any dynamic phones.

We would prefer people who have some experience with high voltages and or building with tubes. Also, people who can take a few measurements would be nice, though none of that is, strictly speaking, necessary. All you really need is a soldering iron.

Here's how it will work -- we will supply a circuit board, a pair of output transformers, a power transformer, a pair of tubes, and a pair of tube sockets. This will cost about $80 shipped. We will also supply a case, but we don't know the cost yet -- we are still working this out with Hammond, so factor in a bit more than the $80. Everything else (except for the parafeed caps) is available from Digikey or Mouser and should cost in the $40-$60 neighborhood -- the difference being that there are some optional parts, some places to use slightly more expensive parts, etc. For parafeed caps, there are some options for caps with free shipping, or we may see if we can't get a bulk discount somewhere. But, they will cost as low as $6/pair for Solens, about $16 for Clarity Caps which would be our recommendation, or more for Auricaps or whatnot. At any rate, expect between $150 and $200 in the end.

For now, we need 6 to 7 people. Both of the prototypes that have been built went together without any issues so the board is a known working board. TomB's comment to me upon firing it up the first time: "The presence is incredible. The blackest background I've ever heard.

Bass is spectacular." So, we are not anticipating any real problems, but are looking for feedback on the build process, etc.

Once we have people in place, we'll order the transformers and cases which can take a couple of weeks, so this will be late March, early April.

PM me directly if you are interested. Thanks!

[Hopstretch]

Does it have a name yet?

The Anaconda?

[Voltron]

Sarah like.

[luvdunhill]

Depending on the goals of this prototyping effort (i.e. Doug's approval), I'd be willing to build a second for a Head-Caser.

[dsavitsk]

Depending on the goals of this prototyping effort (i.e. Doug's approval), I'd be willing to build a second for a Head-Caser.

Probably depends on how many people are interested in doing the prototype build. Assuming all goes well, kits should be along before too long

Update: Cases will be in the $25 to $30 range.

[n_maher]

Does it have a name yet?

The Anaconda?

The Torpedo, duh.

[Salt Peanuts]

Yet another post that makes me I'm happy (and wee bit sad) I can't DIY.

[Pars]

I might be interested in this for my brother, but I'll need to check with him to see if this is something he might like.

Chris

[Fitz]

am wanting to build this

[TomB]

The Torpedo, duh.

I said "cruiser" or "submarine" the other night, but Doug thought that I was saying the amp was goofy looking.;) Not True!

Seriously, this is very cool amp. I'm not used to having sound this good at volumes this low. It's very quiet, the volume knob is perfectly gained for 32ohm Grados (with the impedance switch set to low) and the bass at low volumes is as if there's a loudness switch thrown in, but it's perfectly attenuated as you crank the volume up (stays flat, iow). High end detail is great with Grados, too - I've been listening with HF-2's, HF-1's, and SR225's - they all sound wonderful with no bite, no hint of sibilance.

The really unique thing that Doug has done is to put all of this on a PCB. The length has a purpose - to separate the power xfmr from the rest of the things that might pick up interference from that and it works. Most important - I've admitted publicly many times that I was scared sh*tless to build a high-voltage amp, but this was a snap. The only wire anywhere on the amp is the little ground wire for the Alps pot. Nothing could be simpler - or safer (considering). Not that I'm saying don't respect it, of course, but it sure let me get over my fear. It was a pleasure to build. :)

[luvdunhill]

as an intellectual exercise, have you given us enough info to guess the size of the parafeed cap? They look rather large.

[cetoole]

You have the OPT ratio, so you can calculate reflected impedance, and use that. Probably you would want 3-10uf.

[luvdunhill]

cool, that's what I figured. I would have guessed 1uF-2uF until I examined the pics more closely.

[cetoole]

That doesnt take into account any rolloff the OPTs may have or LC resonance though, so it is definitely possible to get boosted bass with the wrong (or depending on POV, right) parafeed cap size.

[dsavitsk]

Tom used 3.9u, I used 4u. I think from 3.9u to 4.7u is probably a good spot. Pins are 45mm, so a 41mm long cap is about right. 300V min as unloaded B+ is ~275V or so.

[Beefy]

I sooooooooo want to, but simply cannot afford it right now

[Currawong]

I'm very interested. I'm still due to build my eXStatA but have been busy, so if anyone feels i'm being a bit selfish here I'll pass. It looks also like I'll need to relinquish my RKV for something cheaper and not OTL, so the timing is good.

[Pars]

I'd like to go ahead with this if you have room. Is there an upper limit on cap size (uf) as I have some Erso caps that are actually rather good. Also, what voltage do these need to be? The ones I have are 250V IIRC.

[zippy2001]

Looks like a nice amp, I wish i was DIYer. One day

Good Luck with the project.

[luvdunhill]

300V min as unloaded B+ is ~275V or so.

Also, what voltage do these need to be? The ones I have are 250V IIRC.

..

[n_maher]

..

Mikhail taught me that was plenty, was he wrong?

[luvdunhill]

Mikhail taught me that was plenty, was he wrong?

... so, where does the series cap go?

[luvdunhill]

I've been listening with HF-2's, HF-1's, and SR225's - they all sound wonderful

man, this must be the most amazing, bestest sounding amplifier evar!

[Pars]

That's kind of what I figured, but thought I would ask.

[cetoole]

man, this must be the most amazing, bestest sounding amplifier evar!