demented badger

My SumR transformer seems OK. I have not run it under load yet. They seem well built and delivery was under 2 weeks at least to the US.

I hooked my completed kgsshv onboard final version power supply to its SumR transformer this evening and fired it up one circuit at a time. Everything looks good. + / - 453 VDC on the high voltage outputs and + / - 15.0 VDC on the low voltage. I could not measure the bias as my meter only goes to 500VDC. No sparks or smoke though.

I think the device labels on the lower A970/MPSW56 pair are reversed on the ampv15 board. They don't agree with the previous version. The upper pair look OK.

Kevin - In the latest revision, pin 3 of the OP27 is shown as connecting to the 0.1uF cap that previously was to ground. Is this still to ground ? Are you essentially just grounding pin 3 from the previous version? Thanks.

The PCB version that I was looking at only had half the transistors labeled, so I assumed that they were the same in each pair. Good to know not to build it. I removed the schematic so that no one else does either. Thanks for the updated version.

I put together a schematic for the kgss amp circuit using dual transistors in the early gain stages as per Kevins's post a few pages back. I think its correct based on the pcb post and earlier schematics for the single device circuit.

Spritzer - In your experience with this offboard amp, are there areas that are particularly prone to problems ? I am guessing that the high voltage 4686 and 1968 transistors leads would be a problem shorting to the rear of the board or the heatsink where they bend under the board. I was considering slipping some teflon tubing over the leads before soldering them to the pcb to help prevent accidental shorts. Any other areas of concern ? Thanks

I have some blank 2oz copper boards, so I will etch a pair of prototypes and see if they work.

Here it is with a ground plane also with good trace clearances.

What about something like this? With a ground plane of course. A bit larger at 7.5 X 4.5 , but with better clearances for traces. I can get 50 of these made for less tha $20 each with 2 oz. copper on FR4.

Carification, the amp boards would be the offboard variety.

I am considering getting some kgsshv board sets made. To keep costs down, I would like to order in quantity and distribute the excess to the group at my cost. I can get the final version of the onboard mini power supply board in quantities of 25 for about $30 each. I would also like to get 50 of the latest amp board, preferably the one that allows dual transistors, made as well. Kevin, if you could provide the gerber files, I will get a quote on these as well. I anticipate the total cost for the 3 board set to be about $80 plus shipping. To keep the logistics as simple as possible on my end, I would like to limit individual shipments to the US. If someone outside of the US wants to get multiple sets and then redistribute locally, that would be great. Is there enough interest in the group to justify getting 25 board sets made? Please post here if you would be interested so I can decide whether to procede.

Kevin - Are the gerber files available ? The onboard PS version that I have is 8e and looks to be about 7.5 X 9 inches. If a simple voltage divider off of the positive voltage works, that indeed would be much simpler. Thanks.

Here is a KGSSHV onboard power supply board design modified to include both normal and pro bias outputs. I moved things around a bit so that everything would fit on an 8 X 8 board. I have removed the ground plane from the second picture to make the rest of the circuit more visible.

It is big. Five inches in diameter by three inches thick and weighs 9 pounds.

I noticed that Antek has a dual 430V / 0.46 amp toroid model AS-4T430 on their website. It also includes dual 6.3V outputs. It is reasonably priced at $57.00. Does anyone have any experience with this transformer for the KGSSHV ?

Spritzer - It looked OK to me as well,. Thanks for the reassurance.

I have reworked the 450V KGSSHV power supply to provide both pro and normal bias simultaneously. For pro bias I used the circuit as shown in the posted schematic with the voltage doubler and 10M90S followed by the 580V zener string. To add normal bias I tapped the circuit where the 500V option jumper connects and added a parallel duplicate of the circuit from the 10M90S to output, substituting a 280V zener string to get the lower voltage. With a little adjusting, I was able to get everything on an 8X8 board. Does anyone see any problem with this that I am missing? Thanks.

I have a few questions regarding the dual transistor kgsshv board recently posted by Kevin. I am drawing a slightly modified board and putting together a schematic. First, what is the voltage rating requirement for the 1 uF capacitor in the servo ? Does it need to be 1000V ? Second, what are the devices next to the two 2SA1486 ? They do not appear to connect to anything electrically. Also. are the pads next to them just voltage reference points ? Thanks again for your help.

Hello all. I am a new member to this group, but have been following the KGSS threads for a while now and am planning on building a KGSSHV amp in the near future. I have been a user of electrostatic speakers for some time, and have rebuilt a pair of vintage Acoustat 2+2 speakers. I am curious about the board layout picture from Kevin Gilmore a few pages back with the doubled up transistor stages. What are the advantages of this compared to single transistors and has anyone built a prototype of the circuit shown ? The KGSSHV that I have in the works will use the onboard power supply and offboard amp boards. I have built a stepped attenuator (revol3) for 64 step volume control. I was also going to allow both balance and unbalanced inputs. The unbalanced inputs would be converted to balanced before being routed to the volume control. I have not decided whether to put in one or two enclosures. If I use two, I may separate the bias voltage generating on circuitry from the power supply and put it in the box with the amp boards. Less wires to connect between the two boxes that way. I would also incorporate two plugs, one for standard and one for pro bias. Does anyone know a source for boards or a fabricator that does small lots at a reasonable price? I could etch boards myself, but at these voltages I would prefer a professionally made board. The acoustat speakes that I rebuilt were originally powered by their own OTL tube output amplifiers. I stopped using them a while back and converted to a standard amp with a stepup transformer. The 6HB5 output tubes were getting expensive and hard to find and they needed replacing every 2-3 years. Has anyone considered the Gilmore amp as the early stages of a high powered speaker amp with a final voltage stepup via tube at the end? The acoustat amps output 5000V peak to peak as I recall.

I am looking for a board set for the kgsshv amplifier build. I need 2 offboard amp boards and an onboard power supply board. I could etch my own but would prefer a professionally made set. Does anyone have these or have information about availability? Thanks