mwl168

Kevin already laid out an indicator LED and its current setting resistors on the PCB. Going by memory, it's the two 2K resistors and the LED at the very front edge of the GR LV PCB. The resistor values may need to be adjusted based on the regulated output voltage and choice of LED.

If Pars doesn't mind doing the heavy-lifting creating Gerbers with slots, I am happy to work with fab houses to get quotes Personally, I like the option of using the TKD CP2500 series. they seem to have a good reputation for sound quality and the cost is not outrageous.

I did not know Kevin already laid out a Gerber for volume pots. Thanks to gepardcv and GeorgeP for pointing it out and confirming it. I did not see an alpsquad2 but found a alpsquad3 Gerber file on Kevin's site and looked at it through a Gerber file viewer and it looks exactly like the photo GeorgeP posted. I second the motion to alter and fit the TKD 4CP-2500 series given that RK27 does not seem to have a good reputation for sound quality.

Thanks Pars! That would be great.

I think we have enough interest to warrant a GB. I am working with MLA to confirm availability and cost. Re: the PCB, I think we should make it versatile in utility, minimizing the board size would be the second priority. Does anyone have the means and know-how to layout the PCB and create the Gerber file? Below is the link to the datasheet which includes the dimension information. http://www.tkd-corp.com/products/att/pdf/cp600as-e.pdf

Are people also interested in having a custom PCB for mounting the volume pot if we proceed with a GB?

I think this will be the way to go if there are enough interest in the US. TKD Japan did not give me the option to buy directly from them probably because they now have an US distributor. According to the US distributor, we cannot even get close to the $42 unit price even with 100 units.

Hi All: I inquired TKD Japan directly about their 4-gang volume pot 4CP-601 and they referred me to their US distributor. Long story short, looks like I can get the 10K pot for $65 a piece plus shipping. The cost may be slightly lower if total quantity is high. I am still working out some detail information. Any interest?

No, except for the 120R tail resistors (182R on V5 board) of the offset trim pot John pointed out. Although I believe I made this update in the V5 BOM in the previous GB already. The 120R provides greater adjustment range that allows for 20mA output device current.

I think I used an Antek AS-0520 with the GR for my friend's SUSY Dynalo build. It's rated at 1.3A. I bolted the pass transistors to the chassis and it worked very well. Although I see it's out of stock at the moment. The GR single board version offers more flexibility in chassis layout but requires one to use dual secondary transformers. I cannot think of other advantage/disadvantage personally but others may chime in.

Two 24v secondaries will work just fine for the desired 20VDC regulated output. You can go down to 20v since the GR's drop out voltage is quite low. That information is in the thread somewhere. To power the balanced Dynalo you'll need plenty of current so I would recommend at least 1.2A for each secondary and make sure you have enough heatsinks for the pass transistors.

If you can post a photo of good resolution of the faulty board it will help spot if something looks suspicious.

Also, double check the current limit resistor is the correct value. Last time I experienced similar problem it was due to the current limiting resistor being 1000 times the correct value (5.1K vs. 5.1R).

I have a later version of the 009 and have used it with HV, Carbon, BH and SRX Plus. I have not purposely compared the pairings in a systematic way, mostly I just enjoy listening to the music. I do like the combo of the 009 with the SRX Plus a lot!

Has anyone built a 15K attenuator BOM that you are willing to share? Thanks!

Thanks Craig! Very interesting history. I had to look up what "dyslexic" means. And after reading the information, it makes me wonder if that's the problem I have

I actually remember the Lynx brand - probably back in the 90's. The dealer I worked with (and I trust his taste for good sounding audio gears) carried it. One of my cousins may have purchased one with his recommendation IIRC. It has not combusted to my knowledge :-)

One thing to consider if you have not already is to elevate the resistors and diodes slightly off the board by 3mm or so. It's a practice used by many (myself included) to prevent leakage or arcing due to the high voltage involved in this amp.

That would be wonderful!

Tried again tonight without the servo engaged. Similar result - offset shot up to about 170 VDC a couple of seconds after power off. Will try leaving the LV supply on and see what happens as JoaMat suggested next - need to rig something up to separate the HV and LV power switches.

Will do. It may be a while before I get around to it - have been working on resolving a noisy I2S connection problem for the past month.

Was listening to my Carbon/009 tonight and before I shut it down I measured the offset. I have the opto servo engaged and the offset was hovering under 1 VDC while the amp is on. Upon shutting down the power, within a second or two, the offset shot up to just under 200 VDC and gradually declined from there. I plan to disable the opto servo and when I do that I will measure the offset again and report back.

To my knowledge, the GB boards I ordered from PCBNet are either made in the US or Taiwan, most likely Taiwan. I did get a few PCBs from China (Seeed Studio and all 1.6mm and 2oz copper IIRC) and the quality is reasonable to me. But once I experienced the PCBNet quality, it was hard to go back. To the point and in all fairness, I also got one shitty batch of PCBs from a Taiwan factory who I would never do business with again.

I am fairly certain I've measured similar effect of my Carbon which I have been listening to on and off for months without issue. I do disconnect my headphone before power on and off.

Yes, you should see 2 test points next to each of the two 50 ohm resistors on each channel.