meeskees

Sorry, I feel a bit stupid, but I don't know how to calculate. For the online calculators you need to know the output impedance.For a -10dB what value will suit?

Thank you for the reply. I did not see how this adapter works.The DAC is fully balanced. Would it not be easier to solder some resistors at the input connector of the amp? The only problem is I am not sure about the values of these resistors.

Thanks, but how can this be done with an XLR input?

The DAC is a Schiit Gungnir.According the specs it is maximum output XLR 4.0V RMS

The input of the kgst is very sensitive. I can only use 25% of the volumepot to get deafening sound. Is it possible to attenuate before the volumepot? The pot is a 10k alps (4 gang)

I replaced the 1.5k resistor by an 1.1k one, so there is enough room for adjustments. In the weekend I have time to walk through the process again and make notes. It's really a great amp headphone combination. Much more detail compared to my Hifiman-400.

I set the multimeter at the highest input (1000V) so there is little variation. I just expected the servo immediately to respond. This evening I had more time to listen. It still sounds great. Perhaps I repeat the measurements and set the meter to a lower input, but first I want to enjoy more music.

Without servo the amp had run for three hours. Then adjusted the pots to 0 V and inserted the opamps and closed the headers. When I turned the amp on again I measured in one channel 9 volts and in the other 6 Volts. After an hour I measured 0 Volts in the right channel and 1 V in the left. This is probably normal I guess?

Okay,that's clear, but how long does it takes? In my case it took an hour before 0 volts were reached. Does this mean the servo isn't working correct?

What does the servo do exactly? I can't see or hear any difference with or without servo. It still takes some time before the tubes balanced out.

Today I have finished the amp. It sounds really great, but I think that's always the case after finishing an audio project. First I have to listen for a couple of days. I still have a question about the servo. After running the amp for three hours I adjusted the pots for zero volts, than I turned of the amp, inserted the opamps and closed the headerpins. Is this the correct procedure? The photos' are not very sharp I am afraid. I want to thank everybody for helping, especially Birgir, Kevin and Geoff. Without this forum I wouldn't even considered to build an amp like this. I really enjoyed the project. Thanks! The next project will be a balanced DAC. Perhaps the DDDAC 1794 NOS DIY DAC .

Hi Chiguy, I had the same problem. You can solve it to lower the 1.5k resistor. See post 246,247, 248,381 and 382. My amp is working fine now. I haven't tested with the servo on. After an hour running all the offset voltages are within 1.5 volts, so I wonder if the servo is necessary. I am now ready to build the amp in a case. Good luck.

Fixed! I only had 1.1k resistors by hand. I hope the amp works. I haven't yet a headphone to test it.

Today I have finished the amp. Everything seems to work. The only thing I can't get right is the bias. It sticks respectively at 7 and 16 volt. So I think I have to lower the 1,5k resistor. What value should I choose?

I am not very sure about the transformer. The transformer from AnTek (AS-1T300 - 100VA 300V) seems okay, but in that case I need an other transformer for the 30V. What is better; 2x280V or 2x300V? Or doesn't matter at all?

Hi Geoff, Toroidy, the same as mentioned by Chiguy? "Audio grade transformers with mounting pads: TS 150VA PRI: 2x 117V SEC: > 2x 280V @0.18A > 15 - 0 - 15V @0.5A > 2x [email protected] cost: 75,80 EUR/pc"

Congratulated with your working amp, Headinclouds. Can you send more pictures, so we can learn from you? Which transformer(s) do you use?

What is a suitable pot for volume control? It has to be a 4 gang, 50k, log pot?

http://nos.nl/artikel/690027-code-rood-voor-vulkaan-ijsland.html This is a news item with a video from the Dutch television about the Vulcano eruption.

My wife's grandson lives in Reykjavik, so we follow the news there. About the DIP jumpers. Perhaps I have to try harder, but I found this 571-826646-2 and this one 517-9691020000DA in the Mouser catalogue. Will this do? I can't see in the picture of your boards weather they are open or closed.

Hi, Birger, how is the Bárðarbunga, at the moment?

What is the name of these parts? I can't find them in the Mouser catalogue. I presume they are open with normal use. Sorry for these dumb questions, but I am no technician.

What are those pins on the right part of the PCB? (Servo) The op27 is not inserted, so what is the use of the pins? Perhaps Birgit is willing to explain. Has someone already made a new BOM?

Thanks for the pcb's. They are looking great. Hopefully I can start building within a few weeks.