First Project, need some help

[almightyzappa]

I guess I posted this in the wrong forum... Reposting here.

I've decided to start on my first tube amp project. I've had a little experience with solid state but this will be my first go with tubes. I have access to a gentleman with some experience with Tube amps who's agreed to help me with construction. He's not wanting to do the math though, and I'm not quite knowledgable enough to figure out what exactly I need.

The amp I have my eye on trying to replicate is the Audio Innovations 500 integrated amplifier. 25W per channel output, has a phono stage in it. I found the schematics here: Audio Tube Amp Schematics

The questions I have are, what kind of transformers will I need for this? I see some voltages, but I'm not sure of the exact specifications on this one.

Also what kind of capacitors (pio?) and resistors would be best to use?
I want to try and get a parts list together so I can figure out price and a plan for purchasing parts. Any help would be much appreciated.

Thanks in advance!

[Eli Duttman]

The schematic info. in question can be found here. OP, please provide URLs in the future.

A word to the wise, "stock" AI preamps are notorious tube "eaters". Draw your own conclusions.

As for power "iron", the RMS voltage of the rectifier winding should be approx. 300 VAC. Practical considerations suggest a DC yield of 1.3X the RMS value. Now, the current rating of the rectifier winding should be 2X the total DC draw.

[almightyzappa]

Sorry about that. I copied and pasted from before and my URL didn't carry over. Thanks for posting the link.

[almightyzappa]

Also you mention "Stock"

Since I'm just using the schematic as a baseline, do you have any suggestions for what to change to stop it from going through tubes like crazy?

Also I'm just using this schematic because it has the output I want as well as the phono stage. If there are other better schematics I should be working from I'm very open to suggestions.

[scott17]

Just a suggestion, but you might want look into building a separate amp and phono preamp. Take a look at this thread:
Posted new P-P power amp design

Many folks are building this amp so it would be very easy to get support seeing as this is your first tube amp build.

Another kit that would meet your requirement for 25 watts/channel:
Triode USA Dynaco ST-70 Tube DIY Amp Kit

I don't have any recommendations for a phono preamp but I'm sure many folks here can offer suggestions.

Good luck.

[rvrazvan]

I think you should star with an basic schematic. I would suggest a simple PP amp with el84. Have a button for feedback, so you can turn it off when you want.


this is what i am using on my 6c33 SET build
Conectors-Neutrik
Resistors-Royal ohm
Capacitors(coupling)-Russian teflon(cheap and they sound very good)


Here is a cheap chinese shop that has alot of goodies.
HiFi DIY Site - VT4C/211 Power Triode

[almightyzappa]

I was thinking of something a little more advanced since I have access to an electrical engineer that has a backround in tube stuff. He's going to be heloing me construct the project. I just want to do my due diligence and research on parts and the correct transformers before going to him for help.

So if anyone has details or can link me to the transformers that would work for the AI 500 that would be great.

I'm going to check out these other links provided as well, thanks for the help everyone!

[rvrazvan]

then go pro!
Try gm-70 or 6c33c. You will have something exotic this way.
I can help you with the 6c33c. gm-70 ...maybe next year.
if you want the best out of tubes stick to an SE configuration. It will blow you mind.

[ChrisA]

Originally Posted by almightyzappa

...
The questions I have are, what kind of transformers will I need for this? I see some voltages, but I'm not sure of the exact specifications on this one.

Also what kind of capacitors (pio?) and resistors would be best to use?
I want to try and get a parts list together so I can figure out price and a plan for purchasing parts. Any help would be much appreciated.

Thanks in advance!

I don't know why they call these "tube amps". Yo will find that the biggest and most import and and by far most expensive part are the transformers. The quality of the result will mostly be which output transformers you select. In fact you might even select the amplifier based of the which transformers you can get good deals on.. Seriously, they cost well over $100 each and you will need three of them.

Which brand of cap to buy is so far down on the list of what matters that I'd wate until I had a working amp to decide. Built it using generic film caps. You may have to fine tune the frequency response by changing values. Do that with 80 cent caps. Tune? why? Because you are not going to find the same transformers the designer had and will have to substitute current production parts.

Find output transformers you like, then hunt for a schematic or design. You may have to repeate these steps a few times. Then look to see if there is a power transformer that is a good match. Then get a blank chassis that tis larger than you think you need and see if you can come up with a layout that fits. You may find you need a different size chassis.

Want to avoid all of this? Build a clone of common amp. The Dynaco ST70 is lie that. You can buy custom chassis with holes punched to match the transformers and the design layout is already done for you. But maybe this is to easy and you don't learn anything just doing screwdriver work? Sodo the above, but don't even think about caps yet, just buy a handful of reasonable values and stock your parts drawers

I would not try andbuild one big integrated system. Break the system up into more and simpler projects. Get one to work then move on.

[aardvarkash10]

+1 for Chris

worrying over the caps and resistors is like getting fretful over which brands of salt and pepper you will sprinkle on a great meal in a restaurant...