nikongod

They serve sort of the same function in a different way. Sorry to be the language-police on it. Filaments are in directly heated tubes. 300B, 45, 307a etc Heaters are in Indirectly heated tubes. 12au7, 6sn7, 6dj8, etc The cathode of the tube must be heated for the electrons for flow through the tube. A filament is BOTH the heating element, and the cathode in 1 part. this allows for greater heating efficiency than the heater which was very important when everyone used batteries to run their junk. All of the power to heat AND the audio signal goes through the filament. The problem is that the audio signal mixes with whatever noise is on the filament power supply. Everyone loves DHT's though, so we come up with interesting ways to get around the problems. A heater is electrically insulated from the cathode. This is not as efficient as the filament arrangement but the heater does its thing by its self, the cathode does its thing by its self. There is a TINY bit of interaction between the 2, but by and large they are different parts so noise pickup between the 2 is GREATLY reduced. Separate heater/cathode also allows the heaters and cathodes to be at different voltages which makes pretty much everything easier and less expensive.

I would keep the tube heaters/mosfet source loads the way they are now. They are heaters, not filaments. Within reason you can do whatever you want to a heater, nothing happens. The tiny bit of signal running on the heater does nothing. If you want to cure everything in the Melos easily, I would modify a Cavalli EHHA to be more like a Melos. Good stuff for upgrading the diodes and caps. Separating signal and power is going to be a BIG task: Aside from the left channel mod its not *that* bad. I tried putting a choke in the PSU. It caused my amp to randomly oscillate so I took it out. I think Doug tried it too and had the same poor results.

There are lots of wires under the PCB. its icky. All the nastyness on the top of the PCB is pretty much the same on the bottom, plus the wires for stuff they forgot to put in. The left channel mod is a wire from one of the jfets between the tubes to one of the mosfets. The trace near it (the trace is kind of S-shaped, and wraps around the power supply wires ) should be cut at both ends. The mystery wires may go to one of the rear preamp outputs. The original SHA-gold used the photentiometer as a buffered passive preamp, and sent that signal to both the tubes, and the outputs in the back. The stock transformers were all over the map I think Stuarts melos does have one of carlos's realllllly nice custom would transformers though. IIRC they had white tape around them rather than the common clear plastic tape. Ideally the transformer should have: ~120v @100ma for the B+ supply 2*9-12v@~1a for the LV supplies.

In the unlikely event anyone STILL needs a plane ticket jet blue is having another 1 day sale.

A 12au7 will fit with 1 trace cut & 2 splices to run the heaters differently. The original prototypes of the Melos used a 12au7 as both a simple lame common cathode (lame) and as a LTP. I am pretty sure that the 6dj8 runs better with ~40V & 0.75mA across each section than the 12au7 does... I would not try it myself. Most of the noise on the sha-gold comes from the B+ supply which crosses the PCB straight through the middle of the audio supply twice. I suspect there is a fair bit injected by the op amp DC servo, but have not tested this. The heater supplies are regulated DC, Ears I trust say filaments should be heated by CCS supplies or full level AC. Nominal levels of signal on a heater separate from the cathode isn't going to hurt anyone, people use full AC with no hum! Most weak attempts at DC heaters with a single big cap after a rectifier have more noise than the signal used to run a headphone. and its nasty spiky noise too. Im not sure if Stuart's Melos was moded before or after the left-channel mod was "created" It didnt sound like it needed it when I heard it.

The stepper was dirty when I saw that one. The channel balance should return to normal when the stepper is cleaned. I used a pre-attenuator on my melos. I forget how much gain they have stock. I think its voltage gain=7 aka a lot link to pre attenuator

Happy Birthday!

Happy Birthday Alex!

Jet blue is running a 1-day sale. Does anyone have a couch/bed available for me?

How else would you grid bias a tube with top caps?

Happy Birthday!

I want to listen to BA goodness, and will try to get you to run this with the HD800.

I bought tickets a moment ago. Im flying in On jet blue Thursday, landing at ~7pm Flying out Sunday evening, take off 630PM

In.

The Behringer DEQ2496 has parametric EQs. I set it based on this thread on the 'fi link I am also interested in building a standalone clone of the stock filter in case I ever sell these.

If anyone has an inductance meter handy (that can measure what may be a LOW value accurately) you are welcome to my K1000 PCB's in the name of science. One of them didnt survive my re-recabling efforts... and I do the notch digitally now.

Jet Blue goes to tampa from newark airport. bonus round! double bonus round!

It is very possible for a speaker to blow an amp. Check the web to see if you can find the "impedance VS frequency" response graph for the speakers your parents have. If it dips much below 4ohms anywhere some amps will go poof. If it dips below 2ohms many amps will go poof. Regarding cutting in and out: I dont know. Id try to clean the binding posts first. Solves ooh so many problems. Replace the drivers & cabinets with horns? I like!

Happy Birthday!

Happy Birthday!

Sorry to hear Shelly I found the first girl I kissed on facebook.

Happy Birthday Guys!

Happy Birthday! I hope you both have a great time!