Hello fellow audio DIYers (although I am novice at this thing).
I am planning to build LM1875 gainclone in stereo setup and I will be using 2 separate transformers 18-0-18 4A. My question probably had been asked and answered but I will ask the most novice question anyway. Can I join together the 0V of these 2 separate transformers in a circuit? And if I can, will it have an undesirable effect to each channel? And can I use 2 separate switches as well or DPDT will do the job.
Thank you in advance.
I am planning to build LM1875 gainclone in stereo setup and I will be using 2 separate transformers 18-0-18 4A. My question probably had been asked and answered but I will ask the most novice question anyway. Can I join together the 0V of these 2 separate transformers in a circuit? And if I can, will it have an undesirable effect to each channel? And can I use 2 separate switches as well or DPDT will do the job.
Thank you in advance.
Remember that the L/R input grounds connect to a common ground in the source.
It's a question of avoiding hum-causing ground loops. You don't have to connect
the two center taps though, or any other part of the two amplifier circuits.
There can be two totally independent mono circuits.
The primary windings are in parallel when connected to the AC line, so a single switch is enough.
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ease of build
Depending on your experience, it is generally easier to build and get mono blocks working than a stereo amp. They are also lighter when tube amps.
Depending on your experience, it is generally easier to build and get mono blocks working than a stereo amp. They are also lighter when tube amps.
Thanks for your reply. 1 last question, does 1 power supply can run 2 LM1875?
Yes, most stereo amps use a single power supply. The grounding with two or more channels can sometimes be prone to hum but is easily remedied
Thanks for your reply. Please note that I only be using transformer with single output center tap 4A 18-0-18 single output only (not dual). Is this sufficient for 2 LM1875? Sorry for redundant question. I am thinking maybe you think that I have a dual output on the second winding.
Thanks. That answer my concern. Perhaps I should build 2 monos with different power supply. Thanks again guys for your input.
Not necessary with those chips, there is enough power available (thanks to Andrew T) from the supply (I didn't check the chip, not familiar with it, left that up to you
Whew... That saves me a lot of time re-arranging my PCB layout.
Say, can you take a look at my PCB design? I'm kind a really don't have the idea of proper grounding. As you can see at the layout, I put a ground plane between the power supply of the first channel and the input components of the second channel. I am thinking that maybe it will shield the input from any noise that comes from the power supply of the first channel.
Thanks AndrewT for your input. I really appreciate it.
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How many of those traces running to a remotely located GND are actually the other half of a signal Flow and Return pair?
Do not split a Flow and Return pair. The increased LOOP AREA becomes an aerial for picking up interference.
And the speaker output is a Signal Flow and Return pair. Keep the Return closely coupled with the Signal Flow, all the way from the PSU through the amplifier to the speaker terminals.
Do not split a Flow and Return pair. The increased LOOP AREA becomes an aerial for picking up interference.
And the speaker output is a Signal Flow and Return pair. Keep the Return closely coupled with the Signal Flow, all the way from the PSU through the amplifier to the speaker terminals.
Uhmm... English please... haha lol. I really don't understand what you said. As I said I'm a novice in this thing.
When you said "split", did you mean I have traces of GND from the amps side at one point and then another traces of GND at the power supply at one different point? Is it just safe to put a one whole ground plane on the entire PCB? I am completely no idea. If you could lay it out for me, I will really appreciate that.
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You mean to say, for every decoupling caps I can interconnect their legs and then back to starground?
Keep the caps and their traces as close as possible to the chip, the 100nF being closest. Connect their 0V together and then back to the power supply. This will hopefully make grounding clearer for you http://hifisonix.com/wordpress/wp-c...re-up-a-Power-Amplifier_Updated-Autosaved.pdf
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