Hi Everybody
I’m planning to start my first DIY preamplifier. I’m a beginner and not really the “engineering” type. So have patients with me. This is what I plan to build:
Figure 18
MI articles
A linestage preamplifier.
My question is: Is this drawing (the first link) for one channel or two? (I said a was a beginner)
I have some basic knowledge about resistors, capacitors and tubes ohms law etc, etc. But not so much that I could deviate from the drawing. Also know this is potential dangerous and will kill me and burn down my house if I’m not careful.
I’m planning to start my first DIY preamplifier. I’m a beginner and not really the “engineering” type. So have patients with me. This is what I plan to build:
Figure 18
MI articles
A linestage preamplifier.
My question is: Is this drawing (the first link) for one channel or two? (I said a was a beginner)
I have some basic knowledge about resistors, capacitors and tubes ohms law etc, etc. But not so much that I could deviate from the drawing. Also know this is potential dangerous and will kill me and burn down my house if I’m not careful.
Nice preamp, but transformers used are quite expensive. Just letting you know. Will not work as good with cheap trannies.
Figure 18 does say "Schematic of one channel". Attention to detail is on of the ways to not die or burn down your house.
Also does not look like a beginner's project, at least not on a beginner's budget. In my humble opinion, a pre should not sound "great", it should sound like nothing - and be priced accordingly. What source? What amp? What cable run? Why not just a pot?
Have fun!
Also does not look like a beginner's project, at least not on a beginner's budget. In my humble opinion, a pre should not sound "great", it should sound like nothing - and be priced accordingly. What source? What amp? What cable run? Why not just a pot?
Have fun!
Thanks.
Next question.
1) I’m sourcing materials right now. The resistors will work with ordinary 0,4W resistors?
No 2W-5W resistors necessary?
Ethermion thanks
stupid me.😱
Next question.
1) I’m sourcing materials right now. The resistors will work with ordinary 0,4W resistors?
No 2W-5W resistors necessary?
Ethermion thanks
stupid me.😱
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No offence but I just have to ask; are you going to use it as a balanced pre-amp or are you just going to ground one of the input and output terminals?
Balanced topology has many merits but it adds on cost and complexity.
/Olof
Balanced topology has many merits but it adds on cost and complexity.
/Olof
No offence taken
I have no idea. What ever works I guess. I do not know how to make balanced pre-amp or what a balanced pre-amp is.
I have no idea. What ever works I guess. I do not know how to make balanced pre-amp or what a balanced pre-amp is.
Anders, are you building this as a fashion statement ("look at me mom, I've got tubes !") or to solve a problem ? The latter we can help you with, but you need to describe your problem.
If your problem is merely first construction of a tube pre-amplifier, there are plenty of circuits floating around, some are also avaliable in kits (check out "Aikido" by John Broskie; no affiliation here and I don't collect % from his sales but he has some good ideas and he knows what he's doing).
If on the other hand you'd like to learn something along the way, then present your problem first (i.e.: "you'd like to amplify your input signal with output impedance of only 1M 42-times and feed it to your amplifier with 47K input impedance") and you will get the best help possible here.
If your problem is merely first construction of a tube pre-amplifier, there are plenty of circuits floating around, some are also avaliable in kits (check out "Aikido" by John Broskie; no affiliation here and I don't collect % from his sales but he has some good ideas and he knows what he's doing).
If on the other hand you'd like to learn something along the way, then present your problem first (i.e.: "you'd like to amplify your input signal with output impedance of only 1M 42-times and feed it to your amplifier with 47K input impedance") and you will get the best help possible here.
My problem is as I have described them.
Maybe I'll try Aikido instead of this. I don't know. But this tread is for the this amplifier.
So anybody have an idea about the resistors?
Maybe I'll try Aikido instead of this. I don't know. But this tread is for the this amplifier.
So anybody have an idea about the resistors?
Stop.
This is not what you want to hear but it needs to be said- if something VERY basic in the design like this is beyond what you know, you should not be working with high (potentially lethal) voltages and very expensive parts. You'll end up with junk, a lot poorer, and soured on building audio equipment. It's time to hit the books (Morgan Jones's "Valve Amplifiers" should be read thoroughly and digested), get a basic background, and cut your teeth on some simpler, less expensive rigs where a bit of smoke won't cost you too much.
Your likelihood of success going down this path is near zero.
Please, take a deep breath. That preamp will cost you around $1000 when it is all done (I know that because I made similar one. For that money you could buy 3-5 decent ready-made preamps). Do you need such a high end preamp? Are your speakers and power amps very high end?
Here is my recommendation (by no means trying to be patronizing):
look at the starter articles at DIY Audio Articles
There are many good projects for beginners and also you will learn some theory to make right decisions.
In a tube amplifier you need resistors that can stand a lot of voltage. Resistors with a higher wattage rating can usually stand more voltage too. I use Dale Mil.Spec. resistors.
A 0.5W Mil.Spec. resistor is the size of a conventional 2W metal film. Go to the Dale, Vishey or Welvyn webpage and study the spec sheets. Maybe you get an inspiration. Ohms law helps a lot too so you have to know your voltages and currents. Thin film metal films have low noise and low distortion because of low voltage coefficient. Some people like carbon comp or wirewound in tube amps because they sound more "human". Exchange your Allen Bradleys in an ancient guitar amp and you are in for a big surprise. The magic is gone replaced by a soulless and sterile sound. For High Fidelity i prefer accuracy though.
A 0.5W Mil.Spec. resistor is the size of a conventional 2W metal film. Go to the Dale, Vishey or Welvyn webpage and study the spec sheets. Maybe you get an inspiration. Ohms law helps a lot too so you have to know your voltages and currents. Thin film metal films have low noise and low distortion because of low voltage coefficient. Some people like carbon comp or wirewound in tube amps because they sound more "human". Exchange your Allen Bradleys in an ancient guitar amp and you are in for a big surprise. The magic is gone replaced by a soulless and sterile sound. For High Fidelity i prefer accuracy though.
Then how in the world did you select this design? It is certainly not typical or common or what most people use as a line stage.
The way to select a design to build is to first list out all the things you need the pre-amp to do.
About the resistors. the way to determine the size in watts you need is to computer the current in amps through it and the voltage across it and multiply those then for safety double that value then use the next largest standadr size. In many cases this saya that even 1/4W resistors are OK but some times, typically in the power supply you might just need a 5W. You have to work it out case by case for every resistor.
Also please, if you want thi amp to work study the design until you 100% understand every bit of it because likely you will run into a problem where it does not work and there will be no one but you to diagnose and fix it. So I think the general rule should be not to build something you can't trouble shoot and repair.
There is a common problem with most beginners. They want to built their last amp first. No, start with the simplest thing that can possibly do the job. Then you build another, an so on. In your case I'd recommend a simple design that does not use transformers in the signal path, AC heaters are fine. A single common cathode gain stage followed by a cathode follower driver and a volume control in front. Use the 12AX7 or 6sb7 or the like. This is very simple, low cost and does not sound bad. Parts should cost under $100USD total.
Look Anders, your first post says:
I'm having great patience with you as requested so I asked about details that are key to your decision as to what to build, namely: load impedance, output impedance of the input, voltage swing of the input. These details would help people here to give you answers that would get you on your way towards a successful build. If you don't know any of these you REALLY don't need to build anything. If you just want to build something for the sake of doing so and if this something must include tubes for the sake of including them, then you can't miss with any existhing schematic (even if it is defective), because you're not going to use the result of your labor anyway.
There is no point in wasting your time and money if you don't know what you're trying to accomplish. There is no point in wasting our time if you don't know what to do. If you need help, we're here as volunteers to help you out but you need to make up your mind first on what're trying to accomplish. I noticed you're a member here far longer than I am so I'm sure you must have some idea of where you want to go with this project. Spell it out and people will help you; I know I will as best I can.
Aaah, come on... you're a beginner with tubes. Please listen to these experienced guys.
You do as you want in the end anyway but you can get all the help you need here.
All you have to do is to put in some effort yourself. You can't just ask questions like is it ok with 1/4 W resistors everywhere. Few will think it interesting to go through the schemaitc and calculate this for you but on the otherhand most people here will happily tell you how to do it yourself.
If you just do some background work and try to understand why you want to build this specific amp and are willing to put in some effort yourself, we will all help you along.
Ge inte upp
/Olof
You do as you want in the end anyway but you can get all the help you need here.
All you have to do is to put in some effort yourself. You can't just ask questions like is it ok with 1/4 W resistors everywhere. Few will think it interesting to go through the schemaitc and calculate this for you but on the otherhand most people here will happily tell you how to do it yourself.
If you just do some background work and try to understand why you want to build this specific amp and are willing to put in some effort yourself, we will all help you along.
Ge inte upp
/Olof
Hey Anders,
Dig through the 23 pages of the one below and you will learn a lot. Every component is described. The parafeed amp described uses the same transformer as the one you planned. Build it with 6H30, 6N6P, 417/5842 or 6C45. It is also more suitable for "normal" use as it is unbalanced as is the major part of the sources available.
HiFiForum.nu - Försteg av högsta klass - Lundahl LL1674-byggen!
Lycka till med ditt värstingsbygge😎!
Dig through the 23 pages of the one below and you will learn a lot. Every component is described. The parafeed amp described uses the same transformer as the one you planned. Build it with 6H30, 6N6P, 417/5842 or 6C45. It is also more suitable for "normal" use as it is unbalanced as is the major part of the sources available.
HiFiForum.nu - Försteg av högsta klass - Lundahl LL1674-byggen!
Lycka till med ditt värstingsbygge😎!
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