mwl168

Holy smoke Jose! This is beautiful! Tell us more about it.

To be safe, you may want to measure the conducitivity of the headphone’s XLR and make sure pin 1 is not shorted to pin 3 and pin 2 is not shorted to pin 4. If the 4 pin XLR is wired with only 3 conductors with one of the conductor being the common ground for the left and right drivers, plugging it into a true balanced amp will end very badly!

Does your PCB also have 18V zener instead of the 12V zener? There appears to be different versions of GG boards with different value parts marked. I don’t recall the differences and their reasons.

No, I think it’s the 120R resistor below, right of the 50K resistor and left of the 12V zener. Need to confirm with the schematic - it’s the resistor between the offset trim pot and B- in series.

The GRHV is fed 350v AC supplies and regulated to 430VDC rails.The GRHV transistors are bolted to the bottom panel of the chassis and that’s enough for heatsinking.

@ Kevin and Kerry; with all these great work and progress being made, will there be a second generation T2 soon that makes use of these advancements and current production parts and maybe a bit smaller in size? I would be happy to organize a GB for it.

On my DAC

I did the same thing with the LEDs but felt something looked amiss on the amp chassis when it's powered on. I happen to have an unused pin in the power connector so I wired the DC supply for the CPC1117N delay to it to power the added LED. Easy peasy! The chassis is 3809H, I ordered it at AliExpress. Here is a link to one of a few that are on AliExpress. https://www.aliexpress.com/item/The-new-small-fillet-decode-Amp-amplifier-aluminum-chassis-1Piece/32620866436.html?spm=2114.search0204.3.223.5dfb374eM3n5KD&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10344_10068_10130_5722815_10324_10342_10547_10325_10343_10546_10340_5722915_10548_10341_10545_5722615_10697_10696_10084_10083_10618_10307_5722715_10059_10534_308_100031_10103_441_10624_10623_10622_5722515_10621_10620,searchweb201603_25,ppcSwitch_7_ppcChannel&algo_expid=e682a1ea-5ec6-4d8c-a5f1-2c4ed26fb865-35&algo_pvid=e682a1ea-5ec6-4d8c-a5f1-2c4ed26fb865&priceBeautifyAB

I made some modifications to my Megatron. Most of them are under the hood. changed the CCS tubes filament supply transformers from 25VA Antek AN 0206 to 50VA AS 0506 (one for each channel). Now the under-load filament voltage is at 6.15v. changed the transformer supplying the front end filament and current sink to 50VA Antek 0512 to accommodate the higher filament supply when using E80CC in place of the 12AU7 and drill some holes on the PSU chassis to help with cooling. added an LED indicator on the amp chassis which comes on when HV supply is on.

It would also be helpful if you can be more specific about what you meant by the "distortion" you are hearing especially on that particular Youtube piece you provided as an example and where the distortion occur (as how many seconds into the piece...).

IIRC, we agreed that the tube unbal-bal boards would be 2mm thick to better handle the mounting/dismounting of tubes. I am fine with 2mm thickness.

Paid. Thanks!

No sure this applies to this situation, but are the inputs shorted to ground when you ran your tests and adjustments?

Thanks Jim!

Switched to matched quads of Svetlana EL34 for the CCS tubes and SED EL34 for the gain tubes and output balance and offset for both channels are all under 3VDC now.