n_maher

Heh, we'll have to see about that. In real news I got about 60% of the power supply wired tonight. It's going much better than expected really and I hope to wrap up the majority of it tomorrow night. The amp chassis will arrive Wednesday and I've spent a bit of time working with its layout in CAD. It's pretty hard for me to believe that the amp, which largely consists of a bunch of resistors, is proving to be the bigger layout headache. And that's not even taking into consideration the wiring aspect of the amp, just the physical layout of the bits and pieces. I see some late nights in my future...

I think what Earl was alluding to is the large voltage spike at turn on. Typically all caps in a tube amp are rated for the full power supply voltage plus a healthy margin for start up. At least that's my understanding of the rationale.

What are the current caps are rated for?

Nice job!!!

Steve, I'd poke around www.mcmastercarr.com, specifically under woven wire cloth and see if you can't find what you're looking for.

Congrats Todd! But some of those are screaming for LOLCAT treatment....

You can't use PSUD to model parallel rectifiers but I know that Pete has been using it to semi-simulate the situation here. And your suggestion of the dual core choke is good and noted for future use. Like I said, I may not stop with this initial build and may tear the whole thing back down depending on what my ears tell me when it's done. Yup, this is one of the things that we'll be watching. The cap is currently sized at 40uF and the option exists to add a series resistor if problems arise or change out the cap. Pete is re-running some of the simulations based on actual data that I've given him from the trafo and we'll adjust things as required. I appreciate all the advice and sanity checks, it's always better to have multiple sets of eyes on things. I'll be doing my best to keep things inline as far as wire routing goes but unfortunately some things about this amp are dictated by the physical size of the parts involved. I'm sure that I could have made things a little bit smaller in the PSU chassis I've designed so far but not by much without turning the top panel into worthless swiss cheese that wouldn't have been capable of supporting You're way ahead of me in regards to this so don't sell yourself short.

Ok, so I think part of the confusion is due to an error in something I posted earlier, no surprise there. Each rectifier will be fed 260VAC, not 385 as previously mentioned. Serves me right for posting without the schematic in front of me and after a long day. Hopefully that clears at least part of this mess up, the rest will come from Pete. He's sent me a few simulations of the power supply and we're taking a few more measurements but the long and the short of it is that everything is perfectly within limits with the exception of peak current, which is borderline. We're going to run a few more simulations with updated data and I'll report the full results as soon as I have them.

A Brief History of The Meance So really this started years ago, but if I tell the story that way it won't make a bit of sense to anyone other than myself. And I did say brief history and I swear I'll try to keep it that way. This really got going in late December of this past year when I got a message from a friend (who shall remain nameless) that they had an abandoned project that I might be interested in picking up. The basic gist of the project was that they had taken the Van Waarde project along with the Wheatfield HA-2 design and started to improve upon the general concept. Most notably this involved paralleling the output tubes and increasing the output coupling capacitance to the point where driving low-impedance headphones would be possible. The original HA-2 was technically able to do this but not all that well in my opinion. So me being the unabashed Pete Millett fan that I am and a former HA-2 owner jumped all over it. Quick note - both the Van Waarde and the HA-2 schematic are out there if you know where to look, the Waarde is at Headwize (linked above) and owners of the HA-2 know where to find its schematic. I believe that Headroom still owns the HA-2 design and as such I won't be publishing that schematic, only my revised version. Now the revised design that started this mess had been taken to the proof of concept level but in such a way that things like the power supply still needed figuring. So while I won't be using much of what was done as a part of that project I do owe my friend a huge debt of gratitude in terms of motivation and inspiration, without that initial push I'm sure that this would have never happened. Now I'm no designer, I never have been and I never will be since there just aren't enough hours in the day and honestly I'm completely comfortable leaving that up to other folks. I love building this stuff but typically my interest dies off quickly after that point. To a degree that had to change for this project since there was still much work to be done. So I started doing some basic math along with consulting with a few folks about the power supply. It was initially my hope to simply re-use the existing HA-2 tube-rectified design and tweak it as needed. This was quickly abandoned after seeing that the existing PS design was pretty much tapped in terms of current capacity. It was at this point that I decided to call in the big guns and see if I couldn't enlist the help of the guy who was really responsible for all this. I've communicated off and on with Pete Millett for the past few years, mostly as a result of my dealings with the Low Voltage Hybrid project as well as dealing with the issues that my original HA-2 had. Like I said, I'm a hug Pete fan. But Pete's a busy guy and I didn't really expect to have him launch into it the way that he did but it'd be safe to say that this project may well have died without his help. He continues to be a integral part of the design process and I can't say thanks enough so, thanks Pete! I started talking power supply design with Pete and we quickly came up with a couple of concepts and I elected to go with what seemed to be the simplest from a parts perspective (fewer transformers and bits that I was used to working with). I also elected to have the amplification side of the equation be essentially a tweaked HA-2 that will run parallel output tubes, larger output coupling capacitors and modified heater supplies. This should help some of the issues that the original HA-2 suffered from which were some PS hum and output impedance that wasn't really all that suited for driving Grados. I think I'll stop here and leave the details to later on in the process but hopefully that paints at least a little bit of a picture as to where this came from and where it's headed.

I guess I'm lucky enough to have a friend who when I approached him with the idea ran with it. I guess it's time to explain this whole mess, but I'll create a separate post for that...

That's who I've been getting mine from but I don't go through Ebay, I just buy direct. Heck, there's even a thread about them here - http://www.head-case.org/product_annoucements/cardas_now_has_unterminated_plugs_for_sennheiser_headphone_cables-t3253.0.html.

Oh, I'm interested in the learning part too, all I meant was that if there's a mistake/error/whatever that I'm not interested in defending the design and ignoring the fault.

Hey, my only vested interest in this is making the design work. If there are issues I'd rather know about them now rather than when I flip the switch!

Sorry, missed this earlier, the diodes that we were considering were 6.3V heaters and that still would have meant running an additional transformer. It's my understand that running the rectifier and say the input tube off of the same heater supply is not a good idea at all. Not to mention that in this amp both the input and output tube heater supplies are referenced to B+ and floated above ground. I've run your initial question by the designer and I'll add this information to the query and see what he says. Let's hope there aren't major issues with the PS design as that would put a serious hurting on my hopes of getting this thing running any time soon.

All of those posts are related to a choke input, correct?

Yes, the 193Q is the first choke. Choke input was looked into but given the current requirement (again, this is my understanding) this wasn't possible unless I wanted to get a custom choke made. 300mA? You mean on the downhill side of the first choke? If so I sure hope I can get more out of it than that since the design was intended to produce ~380mA. And while this is a new design a similar one has been used successfully by the designer in the past so we both have a pretty high level of confidence in what has been sketched out so far.

Agreed, that was one of the 3 options that we came up with for the power supply, the reason that it wasn't used is that it would have required yet another transformer (for the heaters). When I post the schematics I'll post that power supply option as well. As with anything DIY this is just one way of doing it and as usual each had their own compromises/sacrifices. The large choke is a Hammond 193Q, the two smaller chokes are Hammond 1193H's. And I just noticed while looking at the schematics that I have the caps mounted in the wrong positions, d'oh!

The way I understand it each rectifier is fed 385V and then the various other stages drop the B+ down to ~300V at the output. While I didn't design the power supply or the amp for that matter I have complete confidence in the guy that did. The B+ requirements are 300V/.4A which made traditional, single rectifier designs impossible and made trafo selection a matter of "can this be made to work" rather than "this one works best".

You know, the first time I read that I saw now instead of not and thought, "Awww, isn't that nice of Vicki to say." Now I'm more like . I'll PM as soon as I have info. There are two heater supplies for the amp (input/output) so that's one set of 4 and there are left and right HV supplies so there are the other 4. What it feels like it needs is a stiff bottom plate to increase torsional rigidity. I've got some 3/4" oak and maple that is high on my list to use. No clue but I also don't care since I'll just be burning it in through use. Somewhere in the 50 to 60lb range. The trafo is 15, the big choke 21, the chassis another 5 then you've got the caps, 2 other chokes and everything else. Justin is mostly correct, they are rectifiers but they are run in parallel rather than separately. The supplies don't separate until after the large primary choke.

I think it's a safe bet that you'll be a fan of the Menace given your main home amp. And I'll check with my supplier and see if he's got any more 6528s, if you're interested. The BFT is a friggen beast, to be sure and can probably be adapted to many a project given the available secondaries. And thanks for the kind words on the aesthetics. I'm not sure it'll win any beauty contests unless you're like me and drool over things like tanks and trains for the shear mass of them. As far as the 6528s are concerned they are somewhat similar to the 6AS7/6080 family of tubes except that they have a 5A heater so they require a pretty non-standard power supply, as Vicki mentioned. I've actually got some pretty cool tubes to roll through this amp including 7236's and some uber rare Bendix tubes that allegedly have titanium in them. I'm sure some of you at this point are drawing conclusions based on the tubes posted as well as other little details I've leaked. You're probably on the right track, I'll leave it at that for now.

Nights 4 and 5: the final PS chassis fab So I got the tube sockets installed last night (I think it was last night...) and after painting a room today finally got back to it and did the panel layout and fabrication. I also tidied up the caps and chokes a bit and removed the labels. I'm hoping that this is the last time that I mount those particular bits. Overall I've very pleased with how things are coming along and hope to start the wiring tomorrow. The PS is really fairly simple as the eventual posting of the schematic will show and does use some nifty bits. My favorite, as already somewhat hinted at is the transformer. It is so unbelievably flexible it's crazy, here's a link to the data sheet. A few pictures and then it's just about sleepy time. Oh, and two more picture to hint at what's coming in the amp section... Imagine these plus these

Yeah, that's kind of what I was thinking as well. The problem being that given the time sensitive nature of this build the priority is to get a basic version working first and add more features later.

This is basically what I was thinking, so the chokes are all rotated 90deg from the transformer. I got the tube sockets mounted last night so I'm one step closer to wiring. Right now I'm going to go mark and maybe drill the holes for the two Lemo connectors, the IEC/fuse module and also the main power switch. I haven't decided if I'm going to have a separate power switch arrangement on the amp side yet, I'm leaning towards no.

Glad to see the amp in another happy home, I still miss it and I'm growing more sure by the day that selling it in the first place was a dumbass thing to do.