Thanks again. I am really grateful for these tips.
Always brave
Tried that now as well. Tapped everything, pulled on all wires. The channel stays silent. Compared all voltages again. All match the working channel. Same as for resistanse checks. Even shook the entire amp while in operation. No sound is coming out. Guess I'll pull the board on the weekend. Kind regards
Michael
Michael, could this be an issue with the physical terminals of either the RCA or the Speaker Terminals?
Please ensure that there is continuity between:
- the input RCA hot to the PCBs IN +
- the RCAs external connector and the PCBs GND and / or chassis ground
- between the speaker red terminal (anywhere really) and the out + on the PCB (or the centralized ground / earth)
- between the speaker black terminal and the out - on the PCB
Also do the opposite, check there is NO continuity between:
- the outer RCA connector and the hot pin
- the black speaker and the chassis
If all voltages are correct, this may be something simpler like this. Hope this helps,
Rafa.
Please ensure that there is continuity between:
- the input RCA hot to the PCBs IN +
- the RCAs external connector and the PCBs GND and / or chassis ground
- between the speaker red terminal (anywhere really) and the out + on the PCB (or the centralized ground / earth)
- between the speaker black terminal and the out - on the PCB
Also do the opposite, check there is NO continuity between:
- the outer RCA connector and the hot pin
- the black speaker and the chassis
If all voltages are correct, this may be something simpler like this. Hope this helps,
Rafa.
@zimmer64:
I had a similar problem; one channel working fine, one channel silent.
Checked the silent board over and over, re-soldered all components, no change.
Turned out to be a bad connection on the board that was working correctly !?!?!
So, my suggestion is to check the joints on the working board, just to rule everything out.
Good luck!
Laurens
I had a similar problem; one channel working fine, one channel silent.
Checked the silent board over and over, re-soldered all components, no change.
Turned out to be a bad connection on the board that was working correctly !?!?!
So, my suggestion is to check the joints on the working board, just to rule everything out.
Good luck!
Laurens
Hard to tell from your picture, but the middle pins of the MOSFET's might need a little bit more solder.
Also, first melt the existing solder (preheat) before applying more solder.
If soldering while the MOSFET's are on the heatsink, this can take some time depending on your soldering iron.
If you pull the board out, take a detailed picture of front and back and upload those for closer inspection.
Chaps,
Thanks for all the helping advise. I could not spot any faulty joint, even using a magnifying glass....I pulled the board and re-flowed everything from the top and the bottom of the PCB. I works now!
Thank you so much!
Michael
Last week, V1.6 #1 was completed and placed into service as a stereo amp with my Ascend Acoustics CBM 170SE's, and acquitted itself quite well.
Improvement in SQ over the Soundcraftsmen A250 was easily noted, and did not qualify itself after a couple of hours listening, but rather seemed to be getting better, so I wasn't hearing the psychosomatic "I made it from a kit that cost as much as the amp I'm using now, so it must be better." syndrome.
The 94.5db Omegas Super 3XRS's arrived this past Monday, and were of course hooked up promptly. They didn't sound very good at all, however.
Okay, don't panic, they need some break in time. Rigged my laptop in place of the CD transport for source to the DAC and let 'em play for a few hours. Repeated the next day, but 2 sessions of 3-4 hours each. They didn't seem to even develop as much SPL as the 89db 170's did.
Confused, downhearted and a bit angry was I.
Carried on with V1.6 #2, completed and tested yesterday morning, she's working fine. Set up both ACA's for bridged mono, and placed them into service.
The difference was like and day, the Omega's lost the "oversized transistor radio sound" and began showing me what they were hyped to be capable of.
Hallelujiah!
Found myself sitting there grinning like the Cheshire cat as various and delightful, but previously unknown to me tones and textures of sound seemed to come from the air instead of boxes.
The Omega's must have achieved some level of "broken-in-ness" at about the same time as I doubled down on the ACA's, perhaps my ears had done some adjusting, a small difference of speaker placement?
Most likely some, or all of the above and maybe other factors that don't occur to me.
Next up is to try the ACA's in parallel mono mode as the Omega's are of nominal 8 ohm impedance. Not in any hurry, though, as my system sounds better than anything I've before experienced.
You can be sure I will get to it, however.
Cheers to everyone.
Improvement in SQ over the Soundcraftsmen A250 was easily noted, and did not qualify itself after a couple of hours listening, but rather seemed to be getting better, so I wasn't hearing the psychosomatic "I made it from a kit that cost as much as the amp I'm using now, so it must be better." syndrome.
The 94.5db Omegas Super 3XRS's arrived this past Monday, and were of course hooked up promptly. They didn't sound very good at all, however.
Okay, don't panic, they need some break in time. Rigged my laptop in place of the CD transport for source to the DAC and let 'em play for a few hours. Repeated the next day, but 2 sessions of 3-4 hours each. They didn't seem to even develop as much SPL as the 89db 170's did.
Confused, downhearted and a bit angry was I.
Carried on with V1.6 #2, completed and tested yesterday morning, she's working fine. Set up both ACA's for bridged mono, and placed them into service.
The difference was like and day, the Omega's lost the "oversized transistor radio sound" and began showing me what they were hyped to be capable of.
Hallelujiah!
Found myself sitting there grinning like the Cheshire cat as various and delightful, but previously unknown to me tones and textures of sound seemed to come from the air instead of boxes.
The Omega's must have achieved some level of "broken-in-ness" at about the same time as I doubled down on the ACA's, perhaps my ears had done some adjusting, a small difference of speaker placement?
Most likely some, or all of the above and maybe other factors that don't occur to me.
Next up is to try the ACA's in parallel mono mode as the Omega's are of nominal 8 ohm impedance. Not in any hurry, though, as my system sounds better than anything I've before experienced.
You can be sure I will get to it, however.
Cheers to everyone.
Just finished my 1.6 build, first ever amp build for me, new to it all. Everything seemed fine, checked and rechecked and power up seemed fine, no blue smoke and two lit led's. When I went to set the bias however my meter shows 24V at Q1 center and pot adjustment does nothing. This is the same on both boards. I'm getting ready to start checking resistances and voltages but I was hoping someone here might know what my problem might be? At least, you know, my problem with this build.
Check the easy things first. Make sure that the zero volt line of the board is connected correctly and not floating. The source pin of Q1 (the right hand one as you look directly at the FET from the front) should have zero volts on it. Check that is so.
Beyond that and it would appear that Q1 isn't being biased on... and here a full set of voltage measurements giving the readings on all four transistors would help.
Is the FET the correct type and inserted correctly ?
Beyond that and it would appear that Q1 isn't being biased on... and here a full set of voltage measurements giving the readings on all four transistors would help.
Is the FET the correct type and inserted correctly ?
Ding ding ding....I was sitting there probing around checking voltages and just really puzzled. I'm a noob at soldering a PCB, but I've built other things and have gotten to know my own mistakes so my reasoning is this is something really obvious, but somehow I missed. The FETs are upside down....ugh. This will take some time to correct, if I can correct. I hope I haven't done fatal damage here.
Nothing that can't be fixed easily and cheaply
The FET's can be removed by snipping the leads (if you aren't familiar with de-soldering practices and have the necessary stuff). You can then heat and remove each 'stump' with pliers and finally clean the hole with a bit of stainless wire and heat. Solder won't stick to stainless. Or use solder braid.
I can't say for sure if the FET's will be OK... although I suspect they will be. The critical thing would be whether the Vgs parameter has been exceeded and if so then by how much in relation to the FET's spec. Power FET's like the IRFP240 are typically -/+20 volts and you have up to 24 volts available.
Without the FET's fitted you should actually end up with close to zero volts at the amplifiers mid point. Its a bit hard to visualise what would happen in your set up with reversed FET's
For what a set of new FET's would cost it might be wise to replace them.
All easily fixable though.
The FET's can be removed by snipping the leads (if you aren't familiar with de-soldering practices and have the necessary stuff). You can then heat and remove each 'stump' with pliers and finally clean the hole with a bit of stainless wire and heat. Solder won't stick to stainless. Or use solder braid.
I can't say for sure if the FET's will be OK... although I suspect they will be. The critical thing would be whether the Vgs parameter has been exceeded and if so then by how much in relation to the FET's spec. Power FET's like the IRFP240 are typically -/+20 volts and you have up to 24 volts available.
Without the FET's fitted you should actually end up with close to zero volts at the amplifiers mid point. Its a bit hard to visualise what would happen in your set up with reversed FET's
For what a set of new FET's would cost it might be wise to replace them.
All easily fixable though.
I went ahead and ordered new FETs, just to be sure. I can desolder with no trouble I think. I'm still sort of shaking my head in disbelief. Being my first build I was trying to be really careful. I'm very colorblind so I even had a friend help with the resistors, just to make sure I didn't confuse any. I just didn't notice the orientation on the IRFP240s. Live and learn I guess.
Wanted to type up a follow up post to the one I did a while back. I was able to sort out my issues with the DacMagic, the grounding loop issues were being introduced my Dell desktop machine via the USB connection. Fortunately I had an old USB toslink card lying around, so I switched to optical input and Viola! All my ground loop issues were solved, and I can play 96khz 24bit Tidal masters quality music to boot!
Listening with the ACA has been quite an enjoyment, definitely better than any other amp I've owned. As my first class A amp, I've also been pleased to discover this thing is perfect for warming my hands as the seasonal change turns weather colder. Yet, it also doesn't draw so much electric that I worry about leaving it on. What a sweet spot this amp occupies!!
One modification I'm tempted to add is a volume control. Realistically, I'll probably never use the thing as a monoblock, I'm thinking I might just replace the monoblock switch on the back with a potentiometer of suitable fit/size/quality. Any recommendations?
Listening with the ACA has been quite an enjoyment, definitely better than any other amp I've owned. As my first class A amp, I've also been pleased to discover this thing is perfect for warming my hands as the seasonal change turns weather colder. Yet, it also doesn't draw so much electric that I worry about leaving it on. What a sweet spot this amp occupies!!
One modification I'm tempted to add is a volume control. Realistically, I'll probably never use the thing as a monoblock, I'm thinking I might just replace the monoblock switch on the back with a potentiometer of suitable fit/size/quality. Any recommendations?
Color blind choosing resistors with numbers not colored stripe
I to make many mistakes trying to decipher the colorcode bands on resistors so I found a line resistor that print the actual number right on the side of the resister without color it’s so much easier. Vishay resistors print the Ohm reading right on top of the resister playing in sight easy to read. Ever since I found these resistors use on other projects it was an easy sale I never want to use colored bands again just give me resistors with printed numbers and values on them
Color blind choosing resistors with numbers not colored stripe
I to make many mistakes trying to decipher the colorcode bands on resistors so I found a line resistor that print the actual number right on the side of the resister without color it’s so much easier. Vishay resistors print the Ohm reading right on top of the resister playing in sight easy to read. Ever since I found these resistors use on other projects it was an easy sale I never want to use colored bands again just give me resistors with printed numbers and values on them
Attachments
I'm running my pair of V1.6's as monoblocks.
Is the design amenable to a straightforward modification that would either slightly reduce, or increase the gain of one amp?
Pondering ways to achieve a measure of balance control for my system without changing my preamp, or adding attenuation into the signal path.
Is the design amenable to a straightforward modification that would either slightly reduce, or increase the gain of one amp?
Pondering ways to achieve a measure of balance control for my system without changing my preamp, or adding attenuation into the signal path.
It would help if you could track down your speaker's impedance and sensitivity specs. Also, some idea of the space (dimensions) that you intend to fill with sound will also help.