mwl168

Thanks JoaMat and Kerry. I figured as much - the Volumite may work but will need to reprogram the ATtiny85.

Hi Kerry: Not sure if you are familiar with Twisted Pear Audio's offerings but is this similar to the Volumite they offer for their Buffalo DAC?

I power my SRX Plus with my old KGSSHV PS tuned for 340VDC rails. It works great and I like the combo a lot! My SRX Plus costed me more than $1K to build but I used some fancy tubes and pricy coupling caps

Grounded Grid - probably falls somewhere between KGBH with 6CA7 tubes and KGSSHV carbon in the list.

If you have to buy all parts from scratch, I don't think a KGSS will be any cheaper than say a KGSSHV Carbon to build. And I do believe you can build a Carbon for under $3000 not counting labor.

To second congo5's point, the input should be shorted when you test and adjust DC offset. This is something I often forget to do too.

Nice build George! Congrats! How much output current are you running and what's the temperature on the heatsink upon full warm-up??

The 3 trim pots on each channel adjust the output DC offset. You want to get the offset as close to 0V as possible reference to ground. The adjustment needs to be made without the servo engaged. If you are using the TO92 version boards, the pot next to the LED by the power connector affects the output of both phases while the 2 pots in the middle of the board each adjust one phase of the output. I first adjusted the pot next to the LED so that the inverted and non-inverted output offset are fairly evenly spread in reference to ground, I then adjusted the pot on each output phase to bring the offset close to 0V. The goal, when you done adjusting, is to get the DC offset between the two output phases as close to 0V as possible. This is very tricky work due to the constant thermo drift so experiments and patience will be needed. There are quite a few related discussions in this thread if you have not already read them.

Update: the PCB orders have been placed with Seeed. Pars and I have been working with Seeed on the plated-through slots so I prefer to stay with them. As it turned out, the problem I encountered during ordering relates to the optional message I wanted to attach to the order about these slots. I ended up sending the message as a separate e-mail to Seeed to circumvent this issue. Thanks John. I checked PCBwin out. Their quote process does not allow for PCB that's smaller than 10mm x 10mm and ended up calculating out to be more expensive than Seeed although I am not sure I did it right. Will check it out again in the future.

Very very nice builds. Congrats! Do those L shaped brackets come with the chassis or something you added on your own?

Quick update; I tried placing order with Seeed 3 times over the past two days and kept running into problems. I have e-mailed Seeed's customer support and hope they can resolve their web site issue soon. Will continue to try and keep you all posted.

I have received response from Seeed and ready to place order. For those that have not submitted payment for the boards, please check and update your entries in the GB spreadsheet below if you decide not to participate so we have correct counts for each boards. Thanks! https://docs.google.com/spreadsheets/d/1O_LNaSDBViihkC0dNcYe46SqjOwteiTFmRmuXMRY4fA/edit#gid=893748295

Pars has sent me final versions of the three boards (4CP601-only, 4CP601/4CP2500 and 4CP601/4CP2500/Als RK27). We are both waiting for Seeed's response to our inquiries of the rectangular plate-through holes. I plan to place the order for the boards to be made next week. I am opting for the 1.6mm thick and 2oz copper boards as previously stated. Pars shrank the board size since early on so now all the boards will be $3 USD each. Please update/finalize your board quantities on the spreadsheet before end of this coming weekend. I will be placing our order next week. Please PayPal me the board cost using the account below and remember to include PayPal fee if you choose not to use the PayPal gift option.

Paid. Thank you!

Update on the PCB part of this GB: Pars has sent me final versions of the three boards (4CP601-only, 4CP601/4CP2500 and 4CP601/4CP2500/Als RK27). We are both waiting for Seeed's response to our inquiries of the rectangular plate-through holes. I plan to place the order for the boards to be made next week. Please use the spreadsheet in the 2nd post on this thread from MLA to specify your interest. below are the images of the boards:

Thanks Kevin and Craig! I plan on using exactly that - 18AWG wire, 600V rated, PTFE stranded wire I bought from Apex Jr. I will be using a star-schema grounding tying the IEC ground and the regulator ground to the chassis. In this case, should I still tie the 7th wire to the chassis on both sides? On the amp side, how should I handle the grounding? Will tying the 7th wire to the chassis be sufficient? I did not go into all details - I am actually planning to use the same PS unit for my Blue Hawaii and, in the future, the Grounded Grid. I plan to have a separate 4 pin connector and wires for the 6.3 vac filament supply which I will twist the wires. I also plan to install a separate switch (together with thermistors) for the transformer secondaries for the HV. This switch will function as a manual delay for the HV supply for the BH and GG. I'll leave this switch in the "ON" position when I use the PS with Carbon and HV. When I use it for the BH and GG, this additional switch will be in "OFF" position when I turn on the main power switch and be flipped on after 30 seconds or longer. EDIT: I forgot to mention that the reason I am doing the HV delay this way is because I use the off-the-shelf Antek transformer (AS3T-325) which has the 6.3vac and 325vac secondaries on the same transformer.

I need some advice with the construction of a power cord. I am ready to case my Carbon finally and it will be a two-chassis layout; one chassis for the power supply (GR HV, LV and transformers) and one chassis for the amp. The power supply connection will be through a 7-wire cable (ground, +580 VDC, +400 VDC, -400 VDC, +15VDC, -15VDC and one wire will be unused for now). I plan for the cable to be about 3 feet long to provide flexibility in placement. My questions are: 1. Is 3 feet too long? If so, what's the appropriate length without causing problems or degradation in power supply quality? 2. Should the 7 wires be braided, twisted or just leave them parallel to each other? Thanks in advance for your thoughts and advice!

I am in for 5 Alpha/Song Huei pots.

To clarify, is the price quoted for a balanced stereo pot or single-end stereo pot?

Will do. Hopefully Seeed will respond to your e-mail now that weekend is over.

Thanks to cspirou for your rational. Interestingly Song Huei's web site mentions collaboration with TKD but not Alpha. I can visit the factory next time I visit home and maybe even strike a deal of some sort for a batch. But the nearest plan I have won't be till November time frame.

Care to elaborate?

We will offer this new board along side the 4CP601-only and 4CP601/4CP2500 boards as a third option if there is enough interest. Please state your interest here in the thread and I'll ask MLA to add another column to the spreadsheet if necessary.

I am also interested in how the Elear compares to the Utopia being at 1/4 of the price.

Can confirm UFN's answer based on my own builds - 1.7V red LEDs on my KG designed Dynalos and ES amps.