spritzer

Vents above and below the boards to ensure maximum airflow.

My HV doesn't run quite that hot, about the same as the standard KGSS. To lazy to wire it up and test though but I did take a lot of care with cooling the amp boards.

The T2DIY is indeed 100% a Stax design on the amp side. Our version is miles better in terms of noise, stability and is actually run at full power (not 50% as Stax did) but the design is 100% theirs. What's in the PSU box is all Kevin's work.

The internal filaments you are referring to are the output tube filaments? They are referenced to the - power rail so a small trace will not cause any hum issues. The tubes are rated to 1.5A but there is always some variation so I always overspec for at least 10%. I'm using 25VA transformers to drive them in this amp. Each of the front end tubes draws 300mA at 6.3V so 1.3A would be good for the front end. I highly recommend DC for this role though. My Megatron boxes just arrived but I'll probably not get to do any construction for a while. Other stuff to finish first...

Stranded copper wire for me, some is silver plated. I really don't care about this any more...

Great review and I felt compelled to write a bit as to why it's important to open the amps up a bit.

Same here but I've switched to shielded mic cables for input wiring in the last year. The difference is miniscule so no damage at all.

I got some HD650 capsules as a gift from a certain headphone manufacturer (long story) which I've now turned into a HE60 with some reconditioned parts. Not easy by any means and holy hell they are bright off the B-10 amp. I just love how this amp draws out every small annoying characteristic and just pushes it to the front to really annoy you...

I like that one, nice and straight. Are you using plugs to ground the - input for RCA use as I can't spot a switch anywhere?

Should be just fine but I'll report back on any issues. I'll be using the 80mm Galaxy cases so it will be a tight fit.

The potential on the filament is quite high so the transformer has to be close as it possible. Remember that the cathode of these tubes sits on top of the output tubes anode so there is a lot of voltage there.

It sure does.

It's best to ground the input when adjusting offset and balance but in reality it makes little difference. Just turn the volume down and you'll be fine. Input resistance doesn't matter for the amp and you always ground the - input for SE.

Never use Holco in any high voltage circuit and I'd stick with the Xicon's. Mouser has free international shipping if you order for 100$ or more....

I believe the 4-gang can be ordered through the distributors as the new Senn amps use them as well. I didn't want to deal with all that so I went the Alpha pot route.

I wouldn't even think of cramming this into a single box. It can be done but it is a pain to mount toroid's upside down... As for cost, well that's not something we care about at all. North of 1K$ at least, just the tube sockets are 100+$, tubes 2-300$, transformers another 250$ and the list goes on and on. Still this is BH level of performance so it will wipe the floor with pretty much everything out there. It will also look rather menacing...

Matched pairs for everything is just fine. The input tubes are 12AX7's and 12AU7's so matched pairs with closely matched sections. With the EL34's you need two matched pairs for each output stage, output tubes matched together and the CCS tubes matched.

There are 7 different filament supplies for this amp plus 3-4 power supplies needed. I'll be using a BH transformer so that included two HV windings, a winding for the low voltage supply (+/-15V, the + one just for the indicator led's) and two filament windings for the output tubes. That leaves the 4 filaments for each of the CCS tubes which will be handled by two transformers (two windings each) inside the amp chassis, directly underneath the tubes. That leaves the 6.3VDC supply for the front end which will be fed off it's on supply. I'm not going to bother with a separate +300V supply and just use a ~18K resistor to drop the HV line. Nobody said this one was going to be simple to build but this is always the problem when doing tubes properly. Violating the cathode-filament barrier now could make things very interesting on a grounded supply...

All but ready now. Goes to show I have all this HV stuff in stock but no 12V zeners... The forum doesn't allow me to use the linked BB code for some unknown reason... Here is the full version.

I don't think we ever posted a schematic for this amp, I've at least never seen it. It just saves time to do the PCB's directly and we pretty much always know what the other one is thinking. The Megatron won't run any hotter than many tube power amps and all the really hot running bits are outside the chassis. We will probably add some went holes to the board for the final version but I really don't foresee any issues.

Heat will be an issues but all the hot bits are on top of the chassis and I'm in Iceland after all...

I got them from here but I just ordered a large lot directly from the manufacturer in China.

That filament was always supposed to be DC powered but 12VDC operation would have been a better idea in hindsight or even running them at 25V. My plan for this one is to run it off a BH power supply with it and the power transformer in a separate chassis. The amp chassis will also have to have mains running to it as the filament windings for the CCS tubes need to be as close as possible to the tubes. So that will be 4 transformers for this one and all in the largest Galaxy cases. Half the size of the ESX for a far more complicated amp... should be fun....

Hehe, I have a feeling our gifts will be a bit out of the ordinary... You have a PM incoming..

I do have one RK27 sitting here so I might use it but I just got these lovely PCB's for the Alpha pots that I'm dying to use...