bdinnev Posted August 2, 2023 Report Share Posted August 2, 2023 11 minutes ago, Pars said: I do recall on the one CFP3 I worked on, half the LEDs were different, so I changed them all out for the correct ones. Later, the builder said he ran out of the normal ones and used what he had. Not the right move. All of the ones in both boards at present are the same (all purchased in one batch from Mouser), but I will try swapping them all out for the ones MLA mentioned above and see if it makes a difference - I am ordering all new PNP/NPN transistors (I think I ordered the batch I have at the height of COVID when stock was hard to come by and although everything else was sourced from Mouser, those may have come from somewhere less reputable) and some new resistors / capacitors to bump up the GRLV's to 30v so tacking on some LED's to the order won't make much of a difference in the scheme of things. Quote Link to comment Share on other sites More sharing options...
audiostar Posted August 2, 2023 Report Share Posted August 2, 2023 Just adhere to full specs and never have issues. Don't rush. Measure and check components if possible prior soldering, make sure nothing is wrongly placed and badly soldered... then everything comes up magically, nothing to worry about. Quote Link to comment Share on other sites More sharing options...
bdinnev Posted August 2, 2023 Report Share Posted August 2, 2023 OK, a bit more testing. The previous tests I did were all with the SS jumpers in place. I have taken them off and jumped all the ZF jumpers and get some different results. In ZF mode, on the board that was reading -2.5v the DC offset comes down considerably - 145mv and -81mv @ ~150mA bias. On the other board that was measuring -500mv it still measures the same in ZF mode, however I need to adjust the 5k trim-pots a fair amount to get back to ~150mA bias - I think I saw a post a few pages back with a similar situation so will go back and read the thread again! 1 Quote Link to comment Share on other sites More sharing options...
Satyrnine Posted August 2, 2023 Report Share Posted August 2, 2023 2 hours ago, bdinnev said: I have noticed that the LED's on the -ve side of the board don't glow as bright as those on the +ve side of the board - is that normal or has anyone else noticed this in correlation with an issue? I will try changing the LED's and see what happens. Not normal, unless they are dif models. Its a sign you’ve got a pretty hefty inbalance somewhere, as your offset is showing. 31 minutes ago, bdinnev said: OK, a bit more testing. The previous tests I did were all with the SS jumpers in place. I have taken them off and jumped all the ZF jumpers and get some different results. In ZF mode, on the board that was reading -2.5v the DC offset comes down considerably - 145mv and -81mv @ ~150mA bias. On the other board that was measuring -500mv it still measures the same in ZF mode, however I need to adjust the 5k trim-pots a fair amount to get back to ~150mA bias - I think I saw a post a few pages back with a similar situation so will go back and read the thread again! This might be a good clue for someone more versed with the ss/zf parts of the cfa3 circuit than I. Quote Link to comment Share on other sites More sharing options...
justin Posted August 2, 2023 Report Share Posted August 2, 2023 (edited) 38 minutes ago, bdinnev said: OK, a bit more testing. The previous tests I did were all with the SS jumpers in place. I have taken them off and jumped all the ZF jumpers and get some different results. In ZF mode, on the board that was reading -2.5v the DC offset comes down considerably - 145mv and -81mv @ ~150mA bias. On the other board that was measuring -500mv it still measures the same in ZF mode, however I need to adjust the 5k trim-pots a fair amount to get back to ~150mA bias - I think I saw a post a few pages back with a similar situation so will go back and read the thread again! measure the DC voltage to ground at every node in the circuit, and write it down on the schematic, will be very helpful also do you have pF caps across the feedback resistor in SS Mode? Edited August 2, 2023 by justin 1 Quote Link to comment Share on other sites More sharing options...
bdinnev Posted August 2, 2023 Report Share Posted August 2, 2023 1 hour ago, justin said: measure the DC voltage to ground at every node in the circuit, and write it down on the schematic, will be very helpful also do you have pF caps across the feedback resistor in SS Mode? I will get probing soon and see what the results are. Is going to take me a little bit to make sense of the schematic and how it refers to the physical board but that is what learning is all about.... On the learning topic - not sure where the feedback resistors are. The boards are fully populated except for the 2 x surface mount resistors on the underside. Here is a picture - Quote Link to comment Share on other sites More sharing options...
JGergo Posted August 8, 2023 Report Share Posted August 8, 2023 Here is a solution for the ZF/SS problem worked out by Mirko. The SMDs on the back side are alternatives to the 47uF caps. 1 Quote Link to comment Share on other sites More sharing options...
justin Posted August 21, 2023 Report Share Posted August 21, 2023 I decided to order some of these, 4oz copper, panelized/scored. Gilmore Purple People Eater, because purple is the most uber color the PCBs will be available if anyone wants a set 8 1 Quote Link to comment Share on other sites More sharing options...
DouglasQuaid Posted August 22, 2023 Report Share Posted August 22, 2023 I am beyond behind nowadays and don't even know what this is. I suddenly want one though. 1 1 Quote Link to comment Share on other sites More sharing options...
justin Posted August 22, 2023 Report Share Posted August 22, 2023 UberAmp2. it's like a headphone amp, but with more voltage and current. 4 boards = 2 balanced channels Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted August 22, 2023 Author Report Share Posted August 22, 2023 acually that is 10 boards total for 2 balanced channels. Quote Link to comment Share on other sites More sharing options...
audiostar Posted August 22, 2023 Report Share Posted August 22, 2023 (edited) Full size mono blocks, thats it. With trafo and caps in the middle. And I surely want a set 👍 Edited August 22, 2023 by audiostar Quote Link to comment Share on other sites More sharing options...
justin Posted August 23, 2023 Report Share Posted August 23, 2023 6 hours ago, kevin gilmore said: acually that is 10 boards total for 2 balanced channels. yes but I ordered them as a scored panel Quote Link to comment Share on other sites More sharing options...
MexicanDragon Posted August 23, 2023 Report Share Posted August 23, 2023 On 8/21/2023 at 12:10 PM, justin said: I decided to order some of these, 4oz copper, panelized/scored. Gilmore Purple People Eater, because purple is the most uber color the PCBs will be available if anyone wants a set @justin - Would this be a good project as a first build should I want to bring @cetoole out of retirement for "guidance"? Quote Link to comment Share on other sites More sharing options...
justin Posted August 24, 2023 Report Share Posted August 24, 2023 Colin should build it Quote Link to comment Share on other sites More sharing options...
MexicanDragon Posted August 24, 2023 Report Share Posted August 24, 2023 4 hours ago, justin said: Colin should build it By the time @cetoole would build it, I'd have a job and could afford to pay you to do it. By then, you'll have 2-3 new amps out. Quote Link to comment Share on other sites More sharing options...
Satyrnine Posted August 24, 2023 Report Share Posted August 24, 2023 (edited) I'm hoping to run a sub with my balanced cfa3. The sub only has SE RCA inputs, or speaker level inputs. Would this Jensen transformer (special low freq edition designed for sub inputs) jt-112p-2hpc.pdfbe a good way to get a SE sub output from the cfa3? Was thinking I could tap the signal after the volume control, before the CFA boards. Thoughts? JT-112P-2hpc - 39k:47k - 1:1.10, +20dbu max input. Edited August 24, 2023 by Satyrnine Quote Link to comment Share on other sites More sharing options...
mikeymad Posted August 25, 2023 Report Share Posted August 25, 2023 On 8/23/2023 at 11:34 PM, MexicanDragon said: By the time @cetoole would build it, I'd have a job and could afford to pay you to do it. By then, you'll have 2-3 new amps out. Besides he has to help me rebuild my PSU for my ES1 first.. 2 Quote Link to comment Share on other sites More sharing options...
Thai Tao Posted August 31, 2023 Report Share Posted August 31, 2023 Hi, What's the current stable gerber file for CFA2? There is too many version in the google folder. Thanks! Quote Link to comment Share on other sites More sharing options...
Pars Posted August 31, 2023 Report Share Posted August 31, 2023 I would think cfp2hmt as the latest one. 1 Quote Link to comment Share on other sites More sharing options...
justin Posted September 1, 2023 Report Share Posted September 1, 2023 On 8/25/2023 at 5:19 PM, mikeymad said: Besides he has to help me rebuild my PSU for my ES1 first.. isn't that just a couple of wall warts? 2 Quote Link to comment Share on other sites More sharing options...
mikeymad Posted September 1, 2023 Report Share Posted September 1, 2023 14 minutes ago, justin said: isn't that just a couple of wall warts? It can be based on history... Quote Link to comment Share on other sites More sharing options...
pontif_ Posted September 3, 2023 Report Share Posted September 3, 2023 Just got the first channel of my CFA3 build up and running. Got the bias dialed in at 150mA. Everything seems to be fine, though the Pk-to-Pk voltage of the positive output is about 1V lower then the Pk-to-Pk voltage of the negative output. Is that something to be concerned about? Seems to be slightly frequency dependent. Quote Link to comment Share on other sites More sharing options...
mrjayviper Posted September 4, 2023 Report Share Posted September 4, 2023 can someone please share the link to the schematics/documents? I think it's a good drive link but I cannot find this link. Thank you. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted September 4, 2023 Report Share Posted September 4, 2023 (edited) 7 hours ago, mrjayviper said: can someone please share the link to the schematics/documents? I think it's a good drive link but I cannot find this link. Thank you. look here https://drive.google.com/drive/folders/1r3g2TAtBUaBdiMorTWX7yYgeJ7maQbYW?usp=sharing https://drive.google.com/drive/folders/152thxfZafBmisG0CKCv6X82V-Ch9TjMH?usp=sharing lots of good stuff Edited September 4, 2023 by JoaMat 2 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.