mwl168

We are ready to collect payments from all GB participants and get the boards ordered. Here are the quotes (in USD) based on the quantities we have: Mini T2: $22 (per pair) GRHVxxx partially assembled: $54 GRHVxxx bare board: $4.5 GRLV78: $4.5 GRLV79: $4.5 PSU Main board: $8 The GRHVxxx bare board quote went up $0.5 due to the reduced quantity. The mini T2, PSU main and partially assembled GRHV boards all went down slightly. I have updated the table in the first post of this thread with every participant’s total payment for the boards. This payment does not include the shipping cost from me to you. Please PayPal me your payment to by end of day Wednesday, April 8. I will place the order with the fab house when I received all payments. Add 2.9% if you are in US and 4.4% if you are outside US if you prefer not to use PayPal Gift. Please remember to include your HeadCase ID and shipping address in the PayPal payment note. It should take about 2 weeks for the boards to be manufactured and delivered to me. I will then package and send the boards to you. I will request for shipping cost from me to you via PM prior to sending you the package.

Table updated.

I did exactly that - built a universal PSU for KGSSHV, Carbon, GG, BH and the CFA. IME, GG and BH are rather similar. Have not heard a full DIY T2 but building one PSU, a BH and a Carbon will not come close to what it costs to build a T2.

me think that God would have given us three hands if we were meant to do SMD soldering.

Waiting for the final quotes from the fab house. Once the quotes are in I will update the table with the total board payment for each participant. At the point I will be collecting payments from all participants using PayPal and PayPal only. More details to follow in a few days. You need to be specific about which boards you want and how many and whether you want the partially assembled or bare GRHVxxx boards. Read through this thread if the difference isn't clear to you - the information is all here - so you can make the right decision for yourself.

Table updated. Construction notes for those getting started to source parts for your builds: R3 and R2 determine the regulated voltage for GRLV. The formula is Vout = (R2 + R3)/R3 * Vref. Vref is the reference voltage of U4 (LT1021). R7, R8, R9, R10 determine the regulated voltage for GRHV. The formula is Vout = ((R8 +R9 + R10)/R7 + 1) * Vref. Vref is the reference voltage of IC1 (LT1021). You want to keep R8, R9 R10 values close so they have even voltage drop across each of them. On the PSU Main board, R22 (100K) and C17 (470uf) set up the delay time for HV. The 100k/470uf combination provides a roughly 45 seconds delay. Increase R22 or C17 to increase the delay time. C17 needs to be rated 5VDC or higher. Also added these construction notes in the first post for ease of access.

A pair of balanced CFA boards? Sweet! Happy to see another CFA being built! It is still my favorite dynamic amp of all time! Keep us posted!

For a complete PSU, you need 2 GRHVxxx, 1 each GRLV78xx, GRLV79xx and the PSU main board. GRLV78/79 can be replaced with 7815\7915 regulators. Each mini T2 set includes a left channel and right channel board for a complete amp. With due respect, with high, lethal voltage, SMD, etc., this is not a good project for a beginner to take on. Please also read through this thread and the mini T2 and KGSSHV build threads for information. Table updated.

Also, check to see if your front end tubes are reasonably matched. If the 2 5K pots are centered (ones you use to balance the driver tube plate voltages) and the driver tube plate voltages of the two sections are more than 10V off then I would consider the tube does not have well matched triode sections. You can center the 5K pots without removing them from the PCB.

Table updated.

A few things: Offset and balance voltage will settle as the amp warms up. Are these voltage measure when the amp was cold or warm? IME, high DC offset usually caused by poorly matched tubes. Swap the 6SN7 tubes between channels. If the high offset follows the tube, replace with better matched tube(s).

Corrected. Thanks!

Table updated. Please do double check and let me know if I have made mistakes. I will tally up the final board counts and get quotes from the fab house. I will then update the table with board costs and the total due for each participant and start collecting payments. I will place the order when all payments are collected. Please note the payment will include boards cost and shipping charge from the fab house to me (shipping evenly distributed to each board) but will not include shipping charge from me to you. The following participants are dropped from this GB due to no response: Marc Edwards stickyjon23 zumac99

Great! Thanks! I thought 1/2W resistors should do too but looking at the SRX Plus shunt regulator PCB, the resistors look to be physically much bigger. That’s why I ask.

@Blueman2, what wattage rating resistors do you use for the voltage divider to elevate the front tube filament supplies? thanks!