Help with Preamp Design: Seeking Info from Designer

[JohnM24018]

I found a preamplifier (audio) described by the designer on his YouTube video. He posted the schematic with the units of the parts (ie. 3300uf) but he left out the rating, at least I can not find it. Here is what I think I want:
1. The designer is << Website Link Deleted by Mentors >>. there is no contact information. If anyone could supply this
I would simply contact him directly and seek the information.
2. I would attach the schematic he has posted on line and elicit your help but I don't seem to be able to
attach it like I would an e.mail.
3. I like the design because it uses TI5532 (available and cheap) plus I already have the transformer
(25.6 vct). However, I would be open to other suggestions - simple, inexpensive, solid state.
Thanks
John McIntosh

 

[CWatters]

Either post a link to the schematic or save a copy and use the upload button.

 

[donpacino]

do you have a link to the youtube video?

 

[berkeman]

I found a preamplifier (audio) described by the designer on his YouTube video. He posted the schematic with the units of the parts (ie. 3300uf) but he left out the rating, at least I can not find it. Here is what I think I want:
1. The designer is JRMElectronics.com. there is no contact information. If anyone could supply this
I would simply contact him directly and seek the information.
2. I would attach the schematic he has posted on line and elicit your help but I don't seem to be able to
attach it like I would an e.mail.
3. I like the design because it uses TI5532 (available and cheap) plus I already have the transformer
(25.6 vct). However, I would be open to other suggestions - simple, inexpensive, solid state.
Thanks
John McIntosh

Welcome to the PF.

It's interesting that you have the same initials as the website you are starting to ask about...

 

[JohnM24018]

do you have a link to the youtube video?

<< Video Link Deleted by Mentors >>

You will quickly learn I am not the brightest bulb on the tree. I hope this will get you to the video. At the video if you scroll down and click on the "Show More" there is a link to the schematic. Thanks

 

[berkeman]

I found a preamplifier (audio) described by the designer on his YouTube video. He posted the schematic with the units of the parts (ie. 3300uf) but he left out the rating, at least I can not find it. Here is what I think I want:
1. The designer is << Website Link Deleted by Mentors >>. there is no contact information. If anyone could supply this
I would simply contact him directly and seek the information.
2. I would attach the schematic he has posted on line and elicit your help but I don't seem to be able to
attach it like I would an e.mail.
3. I like the design because it uses TI5532 (available and cheap) plus I already have the transformer
(25.6 vct). However, I would be open to other suggestions - simple, inexpensive, solid state.
Thanks
John McIntosh

<< Video Link Deleted by Mentors >>

You will quickly learn I am not the brightest bulb on the tree. I hope this will get you to the video. At the video if you scroll down and click on the "Show More" there is a link to the schematic. Thanks

@JohnM24018 -- please just upload images of the schematic and parts list. This discussion can still proceed without links to what is probably your website. Thank you.

 

[davenn]

He posted the schematic with the units of the parts (ie. 3300uf) but he left out the rating, at least I can not find it.

the two 3300uF caps will be rated 5 or more volts higher than what the DC output is before the regulator chips. ( and preferably 10V or higher than the power rail)
I would start with a 35V rated cap in circuit and then measure the voltage across them.

It's interesting that you have the same initials as the website you are starting to ask about...

indeed, one wonders about advertising

Dave

 

[davenn]

I found a preamplifier (audio) described by the designer on his YouTube video. He posted the schematic with the units of the parts (ie. 3300uf) but he left out the rating, at least I can not find it. Here is what I think I want:

the PSU design is poor, there is no fusing on either the mains side or the DC side.

 

[berkeman]

And there is no output high-frequency decoupling. CN1 and CN2 do not really help...

 

[berkeman]

the PSU design is poor, there is no fusing on either the mains side or the DC side.

And showing just an unpolarized 2-prong AC Mains plug implies a double-insulated transformer (and product design), which I doubt is in the parts list...

 

[davenn]

And there is no output high-frequency decoupling. CN1 and CN2 do not really help...

yup, CN1,2 are useless where they are
1) they are going between rails instead of from each rail to 0V rail
2) and they should be right at the output pins of the reg. chips

And showing just an unpolarized 2-prong AC Mains plug implies a double-insulated transformer (and product design), which I doubt is in the parts list...

tho the video did show an earthed socket
give him 1 point for that

I haven't even bothered to look at the actual pre-amp part of the circuit to see if there are any other issues

Dave

 

[JohnM24018]

Advertising? My name being McIntosh (the apples, the high grade stereo equipment and of course the computer) if I had hit on only one of the three I would be able to just purchase a preamp.

As to Berkman, yes, the video shows a 35 V capacitor after the rectifier. The rectifier, voltage regulator and amps are identified by their model numbers. I can get the correct ones from Digitech. The problems I am having are the capacitors and resistors. I believe that the schematic you have printed is the power supply section. Any thoughts on the rating for CF1 & 2, CD1 & 2CN1 & 2 and RL1?

As to the fuse, yes, it will need one.

I have the schematic that you printed in a PDF. I have also a parts PDF that I have taken from the schematic. These are resident on my PC. If you will give me good instructions I will beam them to you. I would have done that already but I don't know how.

Please, at a time in the distant past I was forced to take Physical Chemistry from the Worlds Self Admitted Smartest Man. He was a PhD from Duke and a complete jerk. When you answer me will you pretend you are dealing with someone who doesn't know too much about this and is in need of assistance. I had assumed you at the Forum were available and inclined to help.

John Douglas McIntosh (It's the internet. Could be fake.)

 

[berkeman]

I have the schematic that you printed in a PDF. I have also a parts PDF that I have taken from the schematic. These are resident on my PC. If you will give me good instructions I will beam them to you.

Use the "Upload" button in the lower right of the Reply window to add them as attachments to a post. Thanks.

 

[JohnM24018]

Here are the schematic and parts list. Thanks John

 

[davenn]

Advertising? My name being McIntosh (the apples, the high grade stereo equipment and of course the computer) if I had hit on only one of the three I would be able to just purchase a preamp.

you didn't get it ... your initials are JM ... the video producer is also JM ... Berkeman and I both wonder if it is the same person and you are just advertising your own preamp

As to Berkman, yes, the video shows a 35 V capacitor after the rectifier. The rectifier, voltage regulator and amps are identified by their model numbers. I can get the correct ones from Digitech. The problems I am having are the capacitors and resistors. I believe that the schematic you have printed is the power supply section. Any thoughts on the rating for CF1 & 2, CD1 & 2CN1 & 2 and RL1?

it was me, actually, not Berkeman

so you already have the ratings of CF1 and 2
CD1 and 2 are already shown as 47uF, they need a minimum of a 15V rating

we have already told you about the uselessness of CN1 and 2 as they are currently located
and where they should be located. The 0.1uF is already stated on the schematic

and the value of RL1 is also already stated on the schematic

As to the fuse, yes, it will need one.

as minimum preferably 3Dave <----- real

 

[jim hardy]

EDIT @davenn 's post appeared while i was typing. Sorrry , didn't mean to butt in, but looks like i did. ...

Here's how you pick electrolytic filter capacitors CF1 and CF2 .

CF1 and CF2 will charge to roughly 1.4(that's square root of two) X transformer winding voltage. Look up 'peak of sine wave' .
That'd be 1.4 X 12.6 (it's 25.2V Centertapped and half that is 12.6) = 17.6 volts. Add 10% for when transformer is lightly loaded, and another 10% for when house voltage from electric company is high. You're up to 17.6 X 120% = 21 volts.

Now - electrolytic capacitors last a lot longer when only used at 70% or less of their rated voltage, so divide 21 volts by 70% = 21 / 0.7 = 30 volts .
You should pick for those two items capacitors rated 30 volts or higher. 35 is a common voltage rating.

Now you know how it's done.
Be aware they're polarity sensitive so pay attention and connect the correct terminal of each to circuit common. One gets its - to common, the other gets its + to common.

If you get interested in filter capacitors here's more than anybody can absorb in one sitting:
http://www.cde.com/resources/catalogs/AEappGUIDE.pdf

Overpriced at 2 cents, as usual,

old jim

 

[JohnM24018]

Davenn: CD1 & 2 at 15V min - Thank you. As to RL1 at 820 ohms what wattage would you suggest?
You said:
yup, CN1,2 are useless where they are
1) they are going between rails instead of from each rail to 0V rail
2) and they should be right at the output pins of the reg. chips

Am I to understand that if they went from one and the other rails (are these b+ & b-?) to 0V rail they would be effective and necessary?
If so and 0.1 uf. what voltage rating? In addition I don't understand what you mean by "output pins of the reg. chips." If you are speaking of right after the Voltage Regulator chips that position seems to be occupied by CD1 & 2. Please understand I am not arguing for one or the other, I am simply after clarification.

Jim Hardy: Thank you, I have wondered how you determined the voltage requirements for filter capacitors.

Best

John McIntosh

 

[davenn]

As to RL1 at 820 ohms what wattage would you suggest?

standard 1/4 watt

Am I to understand that if they went from one and the other rails (are these b+ & b-?) to 0V rail they would be effective and necessary?

yes, as I said in the earlier post

If so and 0.1 uf. what voltage rating?

their standard minimum voltage is usually 50V or 100V

In addition I don't understand what you mean by "output pins of the reg. chips." If you are speaking of right after the Voltage Regulator chips that position seems to be occupied by CD1 & 2. Please understand I am not arguing for one or the other, I am simply after clarification.

I mean just that, right at the output pins of the chips

yeah, well the designer did a crap job of his layout
you can just solder them into place on the under side of the board

 

[berkeman]

Please, at a time in the distant past I was forced to take Physical Chemistry from the Worlds Self Admitted Smartest Man. He was a PhD from Duke and a complete jerk. When you answer me will you pretend you are dealing with someone who doesn't know too much about this and is in need of assistance. I had assumed you at the Forum were available and inclined to help.

Fair enough. since this project involves connecting to the AC Mains, can you say a bit about any experience you have with AC Mains projects? There are several very important things to get right to keep the possibilities of electrocution and fire down as low a possible. We've mentioned/alluded to a couple of them so far, and based on your answer to my query we may need to expand on them quite a bit.

For example, Dave says that a 3-prong power plug is shown in the video. Do you know what you need to do with that 3rd prong (Earth ground) connection right away as the wire enters your enclosure? Are you planning on using a metal or plastic enclosure for this project? Can you Upload the datasheet for that input AC Mains transformer please? Is it singly-insulated or doubly-insulated? (if you don't know, we will be able to tell from the datasheet.

 

[JohnM24018]

Berkeman: My intent is to cut a piece of metal to cover the space left when Dish supplied much smaller components. I would then attach the ground wire from the outlet to the metal plate. I would use 2 potentiometers to simulate a balance. I would then rely on the metal plate to conduct ground. As a Virginia Class A Contractor I am licensed for almost any construction project. In that capacity I do wire my own residential construction. It is always inspected by the local electrical inspector because a second set of eyes is a good idea. That is what I am depending on you for. As for the enclosure, I didn't really consider enclosing it. It will be inside the "cabinet" and not accessible.

As to the transformer I have supplied a picture of it. I looked thru the internet and was unable to answer your questions. This is probably a good time to mention that I considered mounting the transformer remotely - that is located somewhere else in the cabinet and running it's output to the "board." From my perspective that would get a heavy item attached some where else and making removal of the project easier.

 

[JohnM24018]

I have purchased the parts and am about to assemble. I don't understand enough about:
A. Does pin 4 & 8 get powered from +12V & -12V looking at box A?
B. Does pin 4 & 8 get powered from +12V & -12V looking at box B too?
My question is does the OP AMP need this power at both places?
C. & D. Is this the place where input from my [CD player, Dish TV, Cell Phone etc.] enters?
This OP AMP is a Texas Instruments NE5532.
In addition, Vcc- and Vcc+ - what does cc stand for?
Thank you and Happy Thanksgiving
PS This circuit is not mine. I would ask the original author but I can not find out how to contact him.

 

[Tom.G]

A. Does pin 4 & 8 get powered from +12V & -12V looking at box A?
B. Does pin 4 & 8 get powered from +12V & -12V looking at box B too?
My question is does the OP AMP need this power at both places?

Yes, both pins on both OP AMPs. But be sure wire pin 4 to -12V and pin 8 to +12v. They are reversed in your question.

C. & D. Is this the place where input from my [CD player, Dish TV, Cell Phone etc.] enters?

Yes.

In addition, Vcc- and Vcc+ - what does cc stand for?

No short answer for that one! So here is a longer one.
The 'Vcc' denotes the Collector Supply Voltage. This is a carryover from before there were Integrated Circuits (ICs). The voltage measured on the Collector of a transistor was denoted 'Vc', very useful to know when troubleshooting a circuit or figuring out how it was supposed to work. However that didn't tell you what the power supply voltage was supposed to be, again rather important. So someone decided to label the supply voltage as 'Vcc'. Must have been a good idea since it has stuck around for half a century.

p.s. Sometimes the V_CC- is labeled -V_EE or V_EE- or just V_EE to show it is connected to the transistor Emitters in the circuit. In the NE5532 the V_CC- pin IS connected to the Emitters, so could be labeled any of the above and still be 'correct'. You can see this if you look at the diagram on page 7 of the Texas instrument data sheet.