Confused with designing

[sleepyeyes]

Ok first things first this isn't the first tube amp I've built but as I've been learning simply building a schematic and designing your own are two VERY different things.

I'm currently in the process of designing my first tube amp. I want to use tubes that I have on hand from previous uncompleted/disassembled projects. I know I want to use 6c33c-b's as the output tubes but currently thats about it.
In terms of other tubes I have on hand 4x 30, 4x 76, 12x 12aq5, and 2x 6e5c (magic eye), 2x GU29 (don't really want to use them as outputs but would love to incorporate them in the design somehow).

Now I don't really want anyone holding my hand through this but I'm pretty much stumped. I picked up Valve Amplifiers by Morgan Jones and read a bunch of stuff online. While I've learned a lot from these sources I feel like they forgot to give a real example of designing a COMPLETE amp from the ground up. Sure they show you how to make a gain stage but never connect it to a power stage and never put any of it into real world context. All in all I feel like the authors know what they are doing but just don't know how to explain it.
The only source I've found online that goes step by step with a complete amp is the Boozhounds one but even then a lot goes unexplained and the author admits himself he doesn't understand certain things.

Basically I want to know 3 things:
How do I know how much gain I need to drive the output tube?
Is it better to work from the output back or from the input forward?
Is there any book or website that goes through the basic process step by step (essentially an idiots guide)?

[SGregory]

Morgan Jones Valve Amplifies is the place to start. Good read and will give you knowledge that you need to start. I was spinning my wheels till I read that, and it is still not far away.

[DougL]

Basically I want to know 3 things:
How do I know how much gain I need to drive the output tube?
Is it better to work from the output back or from the input forward?
Is there any book or website that goes through the basic process step by step (essentially an idiots guide)?

Q1. You create the load line of the output stage. knowing the output stage B+, bias and load, you can determine maximum voltage swing. By knowing Av on the stage, you can determine the input required to get that swing. I use TCJ SE CAD or PP cad, but paper is certainly more manly.
Q2. It makes sense to design from the output. Actually, that's step 2. Step 1 is to define your goals as clearly as possible.
3. As far as I know, Morgan Jones and a site called http://DIYAUDIO.com are about as good as it gets. Check out the writeup for the Red Light District for another design using the methodology from "Designing Valve Amplifiers".

HTH

Doug

[Miles Prower]

Click Here

[DougL]

Very good write up.

Doug

[aardvarkash10]

wow! Good thing Morgan had already written his tomes - you are a definite threat Miles!

[Globulator]

Originally Posted by sleepyeyes

Ok first things first this isn't the first tube amp I've built but as I've been learning simply building a schematic and designing your own are two VERY different things.

Miles's article above is excelent, if a little high bandwidth and complex for a first design. You can use the principles though, also check out this link as it's a nice primer.

If it was me I'd use a simple all triode design for the first go