Hi, I’m new to diy electronics and the workings of amps, I have a bsc in physics and am now doing a masters, and I’ve done a bit of electronic here and there but nothing useful.
Basically my ultimate plan is to make my own amplifier so that I can have total control over the specification and sound it produces.
But first I want to do something to warm myself up and my friend has just the thing.
He needs preamp for connection between his Decks and amplifier.
So what I need to do is find a design for a preamp, I have found the following and was wondering if you experts think this is a good idea or if you have anything to add. All help would be much appreciated.
Links:
http://www.mitedu.freeserve.co.uk/Circuits/Audio/gmpre.htm
http://sound.westhost.com/project25.htm
or maybe this?
http://www.paia.com/riaa.htm
#I think this was the right thread to post in#
Basically my ultimate plan is to make my own amplifier so that I can have total control over the specification and sound it produces.
But first I want to do something to warm myself up and my friend has just the thing.
He needs preamp for connection between his Decks and amplifier.
So what I need to do is find a design for a preamp, I have found the following and was wondering if you experts think this is a good idea or if you have anything to add. All help would be much appreciated.
Links:
http://www.mitedu.freeserve.co.uk/Circuits/Audio/gmpre.htm
http://sound.westhost.com/project25.htm
or maybe this?
http://www.paia.com/riaa.htm
#I think this was the right thread to post in#
Unkle77 said:
Audio preamplifier or headphone amplifier
is best 'warm up projects' in amplifier making.
So, your plan is perfect!
- Usual value of voltage gain in preamps is x4 ( +12dB ).
This will take care of most modern sound sources.
- Preamp can have input impedance like 22 - 47 kOhm.
- Good also if it able to drive downto 2.2 kOhm loads, while keeping good sound quality.
- Power supply is often regulated, to give a clean and constant performance.
🙂
please advise what do you want the preamplifier to do
the decks i assume are turntables? if so what cartridfe are you using moving magnet moving coil
do you require tone controls ?
recording facilities ?
what power amp do you think you will use ?
i try to make a wish list and the approach that ideal
will you want a quick lash up on vero or will you want to make it on a pcb
have you any thoughts re ic or discreet devices
regards
trev
the decks i assume are turntables? if so what cartridfe are you using moving magnet moving coil
do you require tone controls ?
recording facilities ?
what power amp do you think you will use ?
i try to make a wish list and the approach that ideal
will you want a quick lash up on vero or will you want to make it on a pcb
have you any thoughts re ic or discreet devices
regards
trev
Thanks for the responses.
Bazukaz – Yeah was looking at them, trying to work out which one best suites me, don’t really have the knowledge at the mo.
Lineup - Thanks could u give me any more info on power supplies
Latala - I think the cartridges of the turntables are moving magnets, don’t really know as I can't find any damn info on this anywhere!! but they are new and from what I could find I’m guessing MM.
The power amp he is using is a Cambridge Audio A5.
I do note require tone controls as they can be done using the power amp.
I will probably make it on PCB (been doing a bit of research into this) may as well get a bit of practice with this before I do anything more complicated.
I’m not sure if I want to use an IC or discreet devices, the IC will be easier but that isn’t really a plus for me. I want the circuit that sounds better/deforms the input less.
He won’t be needing recording facilities either, that will be something I’ll do later
Bazukaz – Yeah was looking at them, trying to work out which one best suites me, don’t really have the knowledge at the mo.
Lineup - Thanks could u give me any more info on power supplies
Latala - I think the cartridges of the turntables are moving magnets, don’t really know as I can't find any damn info on this anywhere!! but they are new and from what I could find I’m guessing MM.
The power amp he is using is a Cambridge Audio A5.
I do note require tone controls as they can be done using the power amp.
I will probably make it on PCB (been doing a bit of research into this) may as well get a bit of practice with this before I do anything more complicated.
I’m not sure if I want to use an IC or discreet devices, the IC will be easier but that isn’t really a plus for me. I want the circuit that sounds better/deforms the input less.
He won’t be needing recording facilities either, that will be something I’ll do later
I thought you were going to build an ordinary preamp.
This is an easy project for a starter.
Gain needs only be x4.
If is a phono RIAA preamp you will build, is totally another thing.
A high quality RIAA phono amplifier (or a good microphone amp) is NOT an easy project.
Why?
Because of the high gain needed.
Instead of x4 you will need x100-400 for MM pickup amplifier.
Because of this high gain, also any noise from power supply
will be amplified with same gain!
There are many different RIAA projects to chose from.
They can be from very simple one Op-Amp to very advanced.
I would go somewhere in between.
And I would say, pick a good existing project.
Follow instructions and pay great attention to the practical building directions,
regarding power supply construction and how to wire everything.
I would say you should pick some good documented variation
at ESP sound projects RIAA phono pages.
I think you already have the link in your first post.
Even for me or some other good with amplfiers,
to make an own RIAA project from scratch is a lot of difficulties.
Both good amp circuit, good power supply design and correct practical build
as well as good component quality is needed to get a performance without troubles.
Before and while study and order components, consult other experienced people here.
Most of them will give you good advices on details, what to do or dont, and avoid you going wrong.
Some of the posters however may (and most surely will)
recommend very advanced, complicated and difficult stuff.
These you do not have to listen to. Not too much. 😀
They are in the high end audiophile league,
where you always should have the best and most extreme setup in your home.
Even if they never have proved they have better sound.
Not that one living soul can hear anyway. And this is what counts.
ESP at http://sound.westhost.com/
is down to earth and still very good quality for us more normal DiyAudio Guys.
Most of his stuff is better, than what you can buy for twice the price,
compared to build it yourself.
🙂
This is an easy project for a starter.
Gain needs only be x4.
If is a phono RIAA preamp you will build, is totally another thing.
A high quality RIAA phono amplifier (or a good microphone amp) is NOT an easy project.
Why?
Because of the high gain needed.
Instead of x4 you will need x100-400 for MM pickup amplifier.
Because of this high gain, also any noise from power supply
will be amplified with same gain!
There are many different RIAA projects to chose from.
They can be from very simple one Op-Amp to very advanced.
I would go somewhere in between.
And I would say, pick a good existing project.
Follow instructions and pay great attention to the practical building directions,
regarding power supply construction and how to wire everything.
I would say you should pick some good documented variation
at ESP sound projects RIAA phono pages.
I think you already have the link in your first post.
Even for me or some other good with amplfiers,
to make an own RIAA project from scratch is a lot of difficulties.
Both good amp circuit, good power supply design and correct practical build
as well as good component quality is needed to get a performance without troubles.
Before and while study and order components, consult other experienced people here.
Most of them will give you good advices on details, what to do or dont, and avoid you going wrong.
Some of the posters however may (and most surely will)
recommend very advanced, complicated and difficult stuff.
These you do not have to listen to. Not too much. 😀
They are in the high end audiophile league,
where you always should have the best and most extreme setup in your home.
Even if they never have proved they have better sound.
Not that one living soul can hear anyway. And this is what counts.
ESP at http://sound.westhost.com/
is down to earth and still very good quality for us more normal DiyAudio Guys.
Most of his stuff is better, than what you can buy for twice the price,
compared to build it yourself.
🙂
line preamp
Hi, Uncle77.
i think that maybe you`re trying to make a line level preamp.
That`s a relatively easy task, as lineup and the other members have told you.
ESP projects are really good; the site have a lot of additional info regarding electronics.
My debut was, a pair of years ago, with a very simple preamp based in only one opamp.
That pre was suited for headphones listening, and also good for feeding a power amplifier.
For starters, and to get some basic info, check out
http://headwize.com/projects/index.htm.
http://headwize.com/projects/showfile.php?file=opamp_prj.htm
The second URL have good info about particularities, tips and tricks to design headphone preamps. The majority of them can be tweaked to be used as simple line preamps, only with a reduction in gain.
Another Diyaudio popular favourite is a derivative of the Burr Brown opamp-buffer combination -something like a turbocharged preamp, capable of drive long cables and heavy loads-.
Check out http://focus.ti.com/lit/an/sboa065/sboa065.pdf
or http://www.pha.inecnet.cz/macura/buffer_en.html
The design of the later URL has no gain -is a buffer, with gain 1, designed to give a little more ooomph to weak or anemic sources, like some cheap cd players-; with some modifications in the gain it can be transmutated into a very good an simple preamp.
You can check some threads here in Diyaudio related to that specific topology, with various tweaks
I´m using currently something very similar, with very nice results.
Enjoy!
Hi, Uncle77.
i think that maybe you`re trying to make a line level preamp.
That`s a relatively easy task, as lineup and the other members have told you.
ESP projects are really good; the site have a lot of additional info regarding electronics.
My debut was, a pair of years ago, with a very simple preamp based in only one opamp.
That pre was suited for headphones listening, and also good for feeding a power amplifier.
For starters, and to get some basic info, check out
http://headwize.com/projects/index.htm.
http://headwize.com/projects/showfile.php?file=opamp_prj.htm
The second URL have good info about particularities, tips and tricks to design headphone preamps. The majority of them can be tweaked to be used as simple line preamps, only with a reduction in gain.
Another Diyaudio popular favourite is a derivative of the Burr Brown opamp-buffer combination -something like a turbocharged preamp, capable of drive long cables and heavy loads-.
Check out http://focus.ti.com/lit/an/sboa065/sboa065.pdf
or http://www.pha.inecnet.cz/macura/buffer_en.html
The design of the later URL has no gain -is a buffer, with gain 1, designed to give a little more ooomph to weak or anemic sources, like some cheap cd players-; with some modifications in the gain it can be transmutated into a very good an simple preamp.
You can check some threads here in Diyaudio related to that specific topology, with various tweaks
I´m using currently something very similar, with very nice results.
Enjoy!
Heres some questions:
Would a modern turntable such as technics 1210's or and equivalent turntable need a RIAA preamp or just a normal line level preamp.
I believe i need the line level one as what i want is for the signal to just be amplified. I will leave the fancy stuff until i know what i am doing.
So shall i make this:
http://www.pha.inecnet.cz/macura/buffer_en.html
or, this one?
http://www.mitedu.freeserve.co.uk/Circuits/Audio/gmpre.htm
Or
http://sound.westhost.com/project88.htm
In the bottom on i will not be including the balance or volume controls as my future diy amp will do this.
I will probably do the bottom one, do you guys think this is wise?
Cheers again
Would a modern turntable such as technics 1210's or and equivalent turntable need a RIAA preamp or just a normal line level preamp.
I believe i need the line level one as what i want is for the signal to just be amplified. I will leave the fancy stuff until i know what i am doing.
So shall i make this:
http://www.pha.inecnet.cz/macura/buffer_en.html
or, this one?
http://www.mitedu.freeserve.co.uk/Circuits/Audio/gmpre.htm
Or
http://sound.westhost.com/project88.htm
In the bottom on i will not be including the balance or volume controls as my future diy amp will do this.
I will probably do the bottom one, do you guys think this is wise?
Cheers again
Surely the mixer between decks and amp acts as the preamp in this instance? No other pre should be required.
riaa
As far as I know, Technics 1210 has no integrated riaa preamp inside -some other TT`s for dj use have one, thus the only preamplification stuff needed would be a line level preamp-
But in the case of the Technics, the riaa preamp is needed.
Riaa preamp is tricky stuff to make -the very high gains involved highligth every weakness of the design-, but very rewarding...Here in Diyaudio there are some simple and effective riaa preamps, suited to the novice -or not so novice-: VSPS, El Cheapo...
Theorically, with the output of some of those riaa preamps you should be able to feed power amps directly, but... those phono preamps are based in only one opamp per channel: that opamp is driving a relatively complex equalization circuit (usually included in the feedback loop); that`s not an easy task, so if you have that opa driving an amp too, problems may arouse.
the icing on the cake would be the make of a partnering line level preamp to provide some extra gain -not a lot, only some-, and to act as a kind of ¨shock absorber¨between the delicate and very low level riia stages, and the less demanding line level input stages of the amp.
As far as I know, Technics 1210 has no integrated riaa preamp inside -some other TT`s for dj use have one, thus the only preamplification stuff needed would be a line level preamp-
But in the case of the Technics, the riaa preamp is needed.
Riaa preamp is tricky stuff to make -the very high gains involved highligth every weakness of the design-, but very rewarding...Here in Diyaudio there are some simple and effective riaa preamps, suited to the novice -or not so novice-: VSPS, El Cheapo...
Theorically, with the output of some of those riaa preamps you should be able to feed power amps directly, but... those phono preamps are based in only one opamp per channel: that opamp is driving a relatively complex equalization circuit (usually included in the feedback loop); that`s not an easy task, so if you have that opa driving an amp too, problems may arouse.
the icing on the cake would be the make of a partnering line level preamp to provide some extra gain -not a lot, only some-, and to act as a kind of ¨shock absorber¨between the delicate and very low level riia stages, and the less demanding line level input stages of the amp.
Basically ive decided all i need is a simple line level amp.
So ive been looking at this pdf:
http://focus.ti.com/lit/an/sboa065/sboa065.pdf
and what ive got from it is that the op amp i would want to use in this is opa671, do you guys agree or am i missing something?
I think i'll give the above a try.
why cant all of these design report the noise and frequency response in the same way so i can work it all out, im relying on you guys to tell me if this is good or if this is better:
http://sound.westhost.com/project88.htm
or will i not really notice the difference?
Cheers for the help guys
So ive been looking at this pdf:
http://focus.ti.com/lit/an/sboa065/sboa065.pdf
and what ive got from it is that the op amp i would want to use in this is opa671, do you guys agree or am i missing something?
I think i'll give the above a try.
why cant all of these design report the noise and frequency response in the same way so i can work it all out, im relying on you guys to tell me if this is good or if this is better:
http://sound.westhost.com/project88.htm
or will i not really notice the difference?
Cheers for the help guys
PREAMP
Hi.
I believe that the decision of which preamp is better for you should be based on a evaluation of your priorities.
The ESP project is very good in my opinion, with a nice set of features -balance, input for assorted sources including tape,etc-.
If you need something flexible and reliable, i think that ´s a sure bet.
The one in the appl.note of Burr Brown is excellent as a line preamp, with the bonus that it can drive very difficult loads -capacitive cables, long interconnects, and including headphones-; the cons is that you will have to design all the switching from scratch to provide some flexibility.
I believe that maybe you can take all the convenience features of Rod Elliot`s preamp and use the Burr Brown`s appl. note electronic design -making an hybrid of the two- . Maybe you`ll have to give up the tape monitoring facility to avoid messing up with the output (it depends on your needs), because in the Elliot´s design the tape signal is derived from the output of the first stage, but the BB design doesn`t have such topology: is more of a monolytic and integrated nature.
The opamp suggested in the appl.note-OPA671- is a discontinued part. I have no experience with it; appears to be very good, but maybe a little ¨over the top¨ for audio purposes. The very wide bandwidth of the part make it difficult to tame properly; maybe you`ll get oscillations, or an erratic behaviour. The execution of the pcb and the psu will have to be impeccable to avoid those nasties.
More suited to audio purposes are OPA627 -excellent, albeit a little costly-, OPA602 -not the last rage in specs, but very musical, smooth and stable-; OPA606; OPA604; OPA134...
Analog Devices makes some nice opamps too, but the only extensive experience that I have with them is w/op275, a dated -but very musical- design.
In the BB design, you`ll have to provide some input and output capacitors to make the preamp more reliable -that is, to avoid feeding dc to your preamp-; I always use input caps; output caps can be eliminated if the next stage have input caps, and/or if the output is dc free.
All said, I have no experience with ESP preamp, so I doesn`t know what it sound like. I think that very good.
I´m using currently something very similar to the BB design, and is very good sounding and reliable. Not the most flexible preamp -is more of a ¨purist¨ approach-, but very good.
Cheers
Hi.
I believe that the decision of which preamp is better for you should be based on a evaluation of your priorities.
The ESP project is very good in my opinion, with a nice set of features -balance, input for assorted sources including tape,etc-.
If you need something flexible and reliable, i think that ´s a sure bet.
The one in the appl.note of Burr Brown is excellent as a line preamp, with the bonus that it can drive very difficult loads -capacitive cables, long interconnects, and including headphones-; the cons is that you will have to design all the switching from scratch to provide some flexibility.
I believe that maybe you can take all the convenience features of Rod Elliot`s preamp and use the Burr Brown`s appl. note electronic design -making an hybrid of the two- . Maybe you`ll have to give up the tape monitoring facility to avoid messing up with the output (it depends on your needs), because in the Elliot´s design the tape signal is derived from the output of the first stage, but the BB design doesn`t have such topology: is more of a monolytic and integrated nature.
The opamp suggested in the appl.note-OPA671- is a discontinued part. I have no experience with it; appears to be very good, but maybe a little ¨over the top¨ for audio purposes. The very wide bandwidth of the part make it difficult to tame properly; maybe you`ll get oscillations, or an erratic behaviour. The execution of the pcb and the psu will have to be impeccable to avoid those nasties.
More suited to audio purposes are OPA627 -excellent, albeit a little costly-, OPA602 -not the last rage in specs, but very musical, smooth and stable-; OPA606; OPA604; OPA134...
Analog Devices makes some nice opamps too, but the only extensive experience that I have with them is w/op275, a dated -but very musical- design.
In the BB design, you`ll have to provide some input and output capacitors to make the preamp more reliable -that is, to avoid feeding dc to your preamp-; I always use input caps; output caps can be eliminated if the next stage have input caps, and/or if the output is dc free.
All said, I have no experience with ESP preamp, so I doesn`t know what it sound like. I think that very good.
I´m using currently something very similar to the BB design, and is very good sounding and reliable. Not the most flexible preamp -is more of a ¨purist¨ approach-, but very good.
Cheers
Hi Unkle77,
I came late onto this thread. You have received so much good advice, that I will just suffice with a few general comments.
The problem with many pre-amps is lack of head-room, especially in the pre-volume control stages. For that reason I have steered clear of op-amps with their general limitation of +/- 15V. Thus I mostly use discreets with between 60 - 80V of supply. Feedback stability problems are better handled, and I believe the best discreets are also capable of slightly lower noise than op-amps. (I am not familiar with the whole op-amp scene, but I believe noise figures of -70 to - 80 dB for MC pick-ups are not possible with op-amps. But I could be corrected!)
Still in pick-up RIAA stages using feedback, I found it somewhat of an omission not to include a rumble filter at the same time. A handy cut of 15 dB/octave or better below 25 - 30 Hz can be achieved by simply adjusting the values of components already there. (It seems rather inside-out to pay hundreds of dollars more for to get a good turntable to do what can be achieved with a few dollars of components.)
As someone (Line-up?) said, these comments might pertain to more advanced efforts though, so just offered in general. My main concern would be for headroom of at least 26 dB, especially with the large variation of CD levels (at least in my experience).
Regards.
I came late onto this thread. You have received so much good advice, that I will just suffice with a few general comments.
The problem with many pre-amps is lack of head-room, especially in the pre-volume control stages. For that reason I have steered clear of op-amps with their general limitation of +/- 15V. Thus I mostly use discreets with between 60 - 80V of supply. Feedback stability problems are better handled, and I believe the best discreets are also capable of slightly lower noise than op-amps. (I am not familiar with the whole op-amp scene, but I believe noise figures of -70 to - 80 dB for MC pick-ups are not possible with op-amps. But I could be corrected!)
Still in pick-up RIAA stages using feedback, I found it somewhat of an omission not to include a rumble filter at the same time. A handy cut of 15 dB/octave or better below 25 - 30 Hz can be achieved by simply adjusting the values of components already there. (It seems rather inside-out to pay hundreds of dollars more for to get a good turntable to do what can be achieved with a few dollars of components.)
As someone (Line-up?) said, these comments might pertain to more advanced efforts though, so just offered in general. My main concern would be for headroom of at least 26 dB, especially with the large variation of CD levels (at least in my experience).
Regards.
Unkle77:Johan Potgieter said:
This is the part where somebody tries to talk you into something more complicated than you need (they missed the part where you said you wants a line-level amp).
The ESP is easiest because you can buy the PCB. The TI is more advanced and you may have problems if you lay out your own PCB (unless you've done this sort of thing before).
But stay with op-amps, for sure.
Shame, Paulb,
I did say these were general comments; someone did bring RIAA into it and one reference given by Unkle 77 was of RIAA pre-amps.🙂
Seriously, thanks for your honesty. No, I did not try to talk Unkle77 into something he does not require; but the discussion did open up, so I just added what I would use plus reasons, coming from my experience - I did momentarily forget about the requirement for line-level only, with all that.
It is certainly a good principle not to over-design, though also to take the future into consideration - sometimes a difficult decision.
Regards.
I did say these were general comments; someone did bring RIAA into it and one reference given by Unkle 77 was of RIAA pre-amps.🙂
Seriously, thanks for your honesty. No, I did not try to talk Unkle77 into something he does not require; but the discussion did open up, so I just added what I would use plus reasons, coming from my experience - I did momentarily forget about the requirement for line-level only, with all that.
It is certainly a good principle not to over-design, though also to take the future into consideration - sometimes a difficult decision.
Regards.
Well, you did say yours were general comments. Sorry if I offended you. My comments were just making fun of the earlier post by lineup where he predicted someone would recommend a complicated solution. I try hard not to sound rude but sometimes it still comes across that way.
It's difficult to tell sometimes, when a question is asked, as to how much an individual knows about the topic. Not many beginners would know the difference between an RIAA phono preamp and a line-level preamp.
It's difficult to tell sometimes, when a question is asked, as to how much an individual knows about the topic. Not many beginners would know the difference between an RIAA phono preamp and a line-level preamp.
No offence at all, Paulb!
My smile was honest; if one does not use humour in this game quite often, one will perish of depression over ... well, I am sure you will know. It is exactly as you "say" in the rest of your post. Unfortunately narrative does not allow a humourous facial expression to come across (well now, digital photography is not that inaccessable - but then do allow me some dignity at my age!)
Regards.
My smile was honest; if one does not use humour in this game quite often, one will perish of depression over ... well, I am sure you will know. It is exactly as you "say" in the rest of your post. Unfortunately narrative does not allow a humourous facial expression to come across (well now, digital photography is not that inaccessable - but then do allow me some dignity at my age!)
Regards.
One thing I love about this site is that it allows me to say, for example, "Hey, I was chatting with somebody in South Africa today..."
Cheers,
Paul
Cheers,
Paul
Thanks Paulb, I will take that as a compliment. Also, depending on where you are and with my limited knowledge of geography, we might be "balancing" the earth from almost opposite sides!
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