This is the chassis that I used Galaxy 2U w/Steel Covers – diyAudio Store
A 2U galaxy, 300 mm x 280 mm, can't beat the price.
The MURs are very fast but the Schottky could have intrinsic softer recovery although there is no specific data to compare the two types for that, I chose the Schottky for bit less power loss i.e. increased long term reliability for small cylindrical diodes in the higher bias builds.
But for more expensive diodes choose TO-220 types with both fast and soft characteristics as well as naturally more rugged. Like those MSR(F)860G I list in the Reflektor-D guide or anything TO-220 of nice spec you fancy. There are alternative pads in the DCSTB PCBs already.
But for more expensive diodes choose TO-220 types with both fast and soft characteristics as well as naturally more rugged. Like those MSR(F)860G I list in the Reflektor-D guide or anything TO-220 of nice spec you fancy. There are alternative pads in the DCSTB PCBs already.
I'm making my own boards to save money and to have some extras. I created my own macros for the diode pads(either plastic or TO-220) very similar to Tea's.
I'll just go with Schottkys since you recommend them. The TO-220s are nice, I would think they would be a better choice for higher current demands.
The Schottkys are rated at only 1A. Are they being stressed from the initial charging of the 2200uF caps?
SB180's IFSM is 25A (non-repetitive peak forward surge current)
http://www.diodes.com/_files/datasheets/ds30116.pdf
http://www.diodes.com/_files/datasheets/ds30116.pdf
Make sure the transistors are actually in the right spot. I did this on the original build because I was having trouble with the mirrored design of it.
Thanks for advise.
You are right! I have the Q3 and Q4 wrong.
So hard to desolder the transistors.
You can cut the leads flush with the PCB and then resolder SMD style, without having the leads go through the holes. Works better then clearing the holes, at least for my sloppy hands
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Here it is! Sans front and top covers but fully operational. Drilling and wiring XLRs is not what I enjoy mostly but I'm glad it works the way I did it. Please refer to the attached schematic. To be honest, I was expecting to have troubles with input XLR pin 1 connected to chassis. This is the way to connect differential amps but DCG3 isn't such. I guess signal passes through the ground lifters. I'll test it with and without SLBs.
At the time being, I've only had a brief test to confirm it delivers sound. I took the risk to connect it directly on my PCM 1792 current output DAC chip with a single 2 ohms resistor for I/V conversion. That means 11mV DC offset at the input of DCG3 but it doesn't seem to bother
It also means that the signal level is too low. I was anxious about that because DCG3 was going to sit in place of a 18x preamp. Well it does thunderus levels as line stage and, of course rather weak as headphone amp on my 600 ohms AKG K180. But neither the 18x preamp could move them in this set up. For this, another DCG3 after the first is needed Did I mentioned that there is not any coupling capacitor or transformer between the DAC chip and DCG3 output?
There will be intense listening seasions during the weekend, I hope!
At the time being, I've only had a brief test to confirm it delivers sound. I took the risk to connect it directly on my PCM 1792 current output DAC chip with a single 2 ohms resistor for I/V conversion. That means 11mV DC offset at the input of DCG3 but it doesn't seem to bother
It also means that the signal level is too low. I was anxious about that because DCG3 was going to sit in place of a 18x preamp. Well it does thunderus levels as line stage and, of course rather weak as headphone amp on my 600 ohms AKG K180. But neither the 18x preamp could move them in this set up. For this, another DCG3 after the first is needed Did I mentioned that there is not any coupling capacitor or transformer between the DAC chip and DCG3 output?There will be intense listening seasions during the weekend, I hope!
Attachments
Here it is! Sans front and top covers but fully operational. Drilling and wiring XLRs is not what I enjoy mostly but I'm glad it works the way I did it. Please refer to the attached schematic. To be honest, I was expecting to have troubles with input XLR pin 1 connected to chassis. This is the way to connect differential amps but DCG3 isn't such. I guess signal passes through the ground lifters. I'll test it with and without SLBs.
At the time being, I've only had a brief test to confirm it delivers sound. I took the risk to connect it directly on my PCM 1792 current output DAC chip with a single 2 ohms resistor for I/V conversion. That means 11mV DC offset at the input of DCG3 but it doesn't seem to bother
There will be intense listening seasions during the weekend, I hope!
So far so good. No drama. What is the expected 0dbV RMS level of the I/V and what gain you set in the preamp?
Tea-Bag, you did great job with the kits! DC offset @ all four outputs is less than 1mV! Of course you can use the pics for your blog. I have them in higher resolution if it helps.
I' ve never tested transformers. Currently I don't face any of the problems that they could address...