What do you think of this as a preamp for a pair of QUAD 405-2 clone
Maybe i use it for the JLH-69 i plan to build as well.
It's actually a really nice headphone amp, but i changed R1 & r5 to lower the gain.
Will it work or should i start all over again ?
Maybe i use it for the JLH-69 i plan to build as well.
It's actually a really nice headphone amp, but i changed R1 & r5 to lower the gain.
Will it work or should i start all over again ?
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I think you need to start all over again. Something is mis-connected. You have no feedback loop to the negative input- and it's grounded. I think you meant to connect the negative input to the node between R1 and R5, not to ground. There is a great site of audio projects using op-amps - Elliott Sound Products (ESP). You might find some inspiration there.
BTW- you should try his project 113 Headphone Amplifier- It has lots of power, and is the very cleanest I have ever heard.
BTW- you should try his project 113 Headphone Amplifier- It has lots of power, and is the very cleanest I have ever heard.
Thanks for reply.
Well, i'm gonna go over it again and see what i did wrong.
I only have an old image og a PCB, I try again.
Well, i'm gonna go over it again and see what i did wrong.
I only have an old image og a PCB, I try again.
Please first check what input sensitivity your power amplifier has. Does it need 1V for full output? Are your sources younger than 20 years with 2V rms output level? Think what will happen if your design has a gain of 20x. Then think if you need gain at all. Also think of impedances. What load does the preamp tolerate and do the sources tolerate the preamp? Are the sources perfectly capable of driving the power amplifier? Are they maybe even more capable when connected directly than the preamp design?
Determine if you need a preamp at all. Maybe you can invest in a relay controlled volume controller with relay controlled source selector buit in the amplifier. Saves a lot of possible side effects and a few interlinks too. Maybe what you may need is a buffer after that source selection/volume control. A preamp with a gain of 1.
Determine if you need a preamp at all. Maybe you can invest in a relay controlled volume controller with relay controlled source selector buit in the amplifier. Saves a lot of possible side effects and a few interlinks too. Maybe what you may need is a buffer after that source selection/volume control. A preamp with a gain of 1.
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All really important considerations, and if you don't understand part of it please ask questions.
I think you might enjoy exploring Rod Elliott ESP Project 243 as it is a hi-fi pre-amp that is designed in modular sections, uses a single ended 24V supply which is much easier to find (wall wart) and compares the modern op-amp implementation with the retro transistor based design. It's very educational.
I think you might enjoy exploring Rod Elliott ESP Project 243 as it is a hi-fi pre-amp that is designed in modular sections, uses a single ended 24V supply which is much easier to find (wall wart) and compares the modern op-amp implementation with the retro transistor based design. It's very educational.
No one with a recent integrated amplifier and modern sources needs a preamp. If you decide to insert a superfluous device you get a lot of error possibilities extra. I do this for ages, it works perfectly without a preamp. The urge to insert a totally unneeded preamp is like alcoholism so expect a fallback now and then.
And modular designing is a curse not a blessing. It is developed by software designers that turned to designing hardware and decided to keep their pattern of dividing everything by function.
And modular designing is a curse not a blessing. It is developed by software designers that turned to designing hardware and decided to keep their pattern of dividing everything by function.
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You do need some sort of variable attenuation, and most people can't afford aerospace stepped attenuators or relay anything. The OP is a likely novice (please correct me if I am wrong), copying a circuit from a circuit board. I'm recommending novice and highly educational projects that are appropriately designed for use as a pre-amp. Is it up to your standards, probably not. Helpful, certainly.
Aliexpress sells good kits that cost less than a quality potentiometer. Relay based, original Omron bistable relays even.
Know your stuff. Use stuff you really need, don’t be a clueless consumer buying unnecessary stuff piling up.
Know your stuff. Use stuff you really need, don’t be a clueless consumer buying unnecessary stuff piling up.
Did I go to school with you, dude!?
DIY is fine but better build something really needed. One does not need gain in this day and age.
Post 4 says it all in detail. OP has a Quad 405-2 clone and possibly a JLH69. Probably both with your “DIY” approval. Excellent opportunity to give either one a selfbuilt internal (relay based) source selection/(relay based) volume control board instead of an opamp thingie doing eh … doing what exactly? Also 2 interlinks and 4 connectors less needed.
DIY is fine but better build something really needed. One does not need gain in this day and age.
Post 4 says it all in detail. OP has a Quad 405-2 clone and possibly a JLH69. Probably both with your “DIY” approval. Excellent opportunity to give either one a selfbuilt internal (relay based) source selection/(relay based) volume control board instead of an opamp thingie doing eh … doing what exactly? Also 2 interlinks and 4 connectors less needed.
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Sources do not have 2v present as the level is in the media you play which is just 0.316v RMS. The exception is test CD's that adequately warn of 0DbFS
Your right though that determining if a preamp is needed at all , as one can by matching the sensitivity of power amps to 0.316VRMS , only have to use a passive. Ideally that passive should be capable of adjusting the shunt resistance not to have any adverse loading, which overturns a 100 years of wrongly doing it. The series resistance should at lowest volume for purpose of silence be circa 25 mega ohms, and not rely on grounding the shunt resistance.
We had this discussion before and design parameter is 2V rms for decades. Not that it is 2V rms continuously but that it can be 2V rms. If it can be 2V rms we better calculate with 2V rms and have no troubles. Amplifiers mostly 0.775 to 1V for full output so all is good. It will work OK in 99% of cases without a new thread here or the need for any audio professor/academic creating more intelligent issues to solve.
Make your own way more thought out standard and you will always have something to do. Perfect candidate for the tube section where they like to have such issues. It will also not solve the (future) issue of the OP.
Make your own way more thought out standard and you will always have something to do. Perfect candidate for the tube section where they like to have such issues. It will also not solve the (future) issue of the OP.
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True.
Sources will be CD and BT ( phone & computer )
I dont actually think i really need a preamp, but it would be fun to build.
But as you said, i maybe should put some effort in other thing, like volumecontroll and source-selector.
Thanks for pointing me in the right direction and focus on whats actually needed.
I think i keep the headphone-amp as is, and just use it as a headphone-amp.
Did you figure out the mis-connection? Do you have a final schematic? What is the impedance of your headphones? (an op-amp may not be sufficient to drive them.)
Nah, after Jean-Paul answered i continue without a preamp. I will not do a final schema since i wont use it anyway.
My headphones are AKG K141 Monitor, Imp..= 600 Ohm
My headphones are AKG K141 Monitor, Imp..= 600 Ohm