mwl168

Cannot speak to the USB cable as I believe most of the outrageously priced cables are based on voodoo science and snake oil. I have a dual mono Buffalo II. I went from using SPDIF to the Amanero/Chronos/Rhea I2S and it's a big step up!

I need a bigger house for all the KG ES amps!

I have used Winged C SED EL34 on my latest version of Blue Hawaii and with both 007 and 009 of the later versions. My DAC is a dual-mono Twisted Pear Buffalo II. I also like the sound. Never tried the re-issue Mullard. I should mention my BH has a few differences compared to the BHSE. It has the 10m90/DN2540 cascoded CCS and is powered by GRHV and GRLV.

I have received payment from most. Thanks all for the prompt responses. I will be placing PCBnet amp board order today. The Gerber file used will be the megatron12v.zip with 12.6vac filament for the front end tubes. Board size is (229 X 229 mm or 9" X 9") I will place the Seeed GRHV board order this weekend (it's 9:30pm Friday night in China now). The Gerber files used will be kgsshvpssicfetsinglenewrightfatsws.zip and kgsshvpssicfetsinglenewleftfatsws.zip. These are the boards with the CPC1117N opto relay and the builders can opt to implement a HV delay if desired. Board size is 139 X 99 mm or 5.5" X 3.9"). I will update everyone when I receive order confirmations.

Sorry, I should have been clear from the get go about the version of GRHV. I was just going by the version I've been getting many requests on since the original GB was completed. I am guessing the version you had in mind is the one below.

The mounting options for the switched version should be the same as the non-switched version. I will be mounting vertically with L bracket. Forgot to mention that the CPC1117N relay also provides soft-start and soft-off. For reference, here are images of the non-switched version:

Thanks again Kerry! Also, found a version of the GRHV with switch that Kevin has posted and it is the same size as the regular one - 139 X 99mm. I propose we use this version for this GB. Again, you can simply leave out the CPC1117N opto switch and the 600R resistor if you don't plan to implement a HV delay. Please let me know if there are objections.

Thanks Kerry. Am I correct that we can simply not install the CPC1117N and the 600 R resistor if no delay is desired?

I have a late thought about the GRHV split PSU. Kevin also published a version with CPC1117N switch on the boards (but no control logic). This allows builders to implement a timed delay to the HV supply. You would have to supply you own control/timer unit which is abundantly available on eBay for very reasonable price (less than$10 US). The board is slightly larger (139 x 103mm vs 139 x 99mm) but the cost will be the same. I should also mention I am not personally aware of anyone who has successfully built this version. Maybe Kerry and others can chime in. What does everyone think? Sorry for this late curve ball I throw you but I thought it's worth a debate since most will be using the PSU for the Megatron. EDIT: found a version of GRHV with switch Kevin posted that is the same size as the original: 139 x 99mm

The group buy is closed. Here is what we have: AMP board GRHV split Jose 2 2 PICaudio 2 3 Whitigir 1 1 gwrskien 1 1 Looser101 2 2 gepardcv 1 1 mypasswordis 0 2 Neg. chiguy 1 1 samsie 0 2 sbelyo 1 0 Base on the vote, the amp board will be 2mm/4oz from PCBnet, $36 per board. The GRHV splt will be 2mm/3oz from Seeed, $30 per set (2 boards). Participants please PayPal me the board cost to my Id below before end of day Friday, 5/12. I will place the orders on Saturday. If you choose to not use PayPal gift please remember to add the applicable PayPal fee. Thanks!

Awesome!

I have a hard time giving the review much credit when different amps were used for different headphones during the review. This "trust me they sound the same because I believe so and told you so" thing is beyond me.

I plan to close this GB by end of day Sunday, May 7 and hopefully collect payment and get the boards ordered the following week. Here is what we have so far: AMP board GRHV split Jose 2 2 PICaudio 2 3 Whitigir 1 1 gwrskien 1 1 Looser101 2 2 gepardcv 1 1 mypasswordis 0 2 Neg. chiguy 1 1 Please let me know if corrections. Also, we'll take a democratic approach toward the decision of whether to go with PCBnet or Seeed for the GRHV boards. One vote per set. Majority wins

I did not get quote for 4oz copper option for the GRHV split boards from PCBnet. Obviously it will be more than $57 per set. 3oz copper really should be plenty for the PS boards IMO. The reason I suggested 4oz copper for the amp boards is because of those traces for the EL34 filament supply.

that's assuming the manufacture passes the cost saving to the consumer...

I got quotes back for the GRHV split boards and we have a decision to make. For 2mm thickness and 3oz copper GRHV split boards, with the current number of boards people have shown interest for, it will be about $57 USD per set (one positive and one negative PCB) from PCBnet. If we go with SeeedStudio, it's about $30 USD per set. The amp board (2mm and 4oz copper) from PCBnet will be about $36 per set (two channels on one board). We can save about $10 per board going with Seeed but Seeed only have 3oz option for copper weight. The numbers above include my estimated shipping cost from the fab house to me. You'll need to add shipping from me to you for the total cost. I suggest we stay with PCBnet for the amp board. For the GRHV, which option do you all prefer?

Nice collection!

Well, they are the "split" version so yes, it's possible

Looks like most of the interest is in the split version of GRHV. If those interested can respond with your desired quantity I can get a quote from PCBnet. No restriction on number of Megatron amp boards and GRHV boards - any combination is fine.

I stand corrected. I have mistaken the phase line as the impedance line when reading the measurement. Interestingly, I had always remembered the LCD2 impedance to be around 50ohm since I bought my LCD2 5 or 6 years ago. What you said explains the change in Audeze's current specification.

Intersting. Audeze lists LCD 2 as having 70 ohm impedance on their web site which is twice as high as what the measurement says.

Either the split or dual GRHV boards is fine with me. But best to have one version made instead of two - the number of boards effects the cost greatly as is the case always. If people can respond with their interest here we can start to shape the plan.

You got me thinking if my impression of the Focals were "skewed" by the gears I listened to them with. They were driven straight from a DAC which "supposedly" can also drive headphones. My experience with the LCD2 echoes what you said about the Utopia. In my experience, the LCD2 needs an amp with low output impedance and can deliver plenty of current into a lowish load to make it perform. Given the LCD2 is rated at about the same impedance as is the Utopia, they probably exhibit the same demand on the amps.

Yes, I am planning for a two-box build for the Megatron for the reasons you stated. it would need to be a huge chassis for a single-box Megatron with the large amp board, power supply and all the transformers. Unlike the HV Carbon, BH and Grounded Grid, I expect the GRHV will run much hotter for the Megatron with all the tubes it needs to power. So yes, external heatsink for the GRHV for sure. I have most of the layout done in my mental execution But I have one snag I have not figured out - how to get the AC main supply to the two filament transformers for the CCS tubes that need to be mounted in the amp chassis. I love to hear people's ideas.

Yes, one amp board for both channels for Megatron. The PS is a bit of a dilemma. The old Megatron PS is based on the KGSSHV PS, quite big and not as accurate and low noise as the GRHV. I have been exchanging PMs with a few knowledgeable headcasers in the last few days. With Kevin's recent modification to run 12.6VDC for front end filament supply (Thanks Kevin!) this is what I plan to do personally: I will run my Megatron with a GRHV PS. I will use 7812 and 7912 regulators on the LV section on the GRHV board. The 7912 will provide the -12VDC for the front end current sink and the 7812 will provide 12VDC for the front end filament supply. I will mount the 7812 (which need to drop about 3VDC and pass 600mA) under the PCB and bolted to the chassis below to provide proper heatsinking. I will use a drop resistor to get the 300VDC from the 450VDC supply. I can include the GRHV PS board in the GB if people are interested.