My First Amp

[popilin]

Hello All
This is my first Amp ind I need your help and opinion about it
[IMG]file:///C:/DOCUME%7E1/C3PO/CONFIG%7E1/Temp/moz-screenshot.png[/IMG]What do You Think?

Best regards from Argentina

[alejo]

Hello, I´think if its your first amp is very danger amp. The +B at 900V easy can kill you.

[kavermei]

Definitely not for beginners!

[popilin]

Hello Alejo, Hello Kavermei
Thanks for your interest, but don't worry, I am an undergraduate in Phisics and a TV Repair Man, every day I work with 25KV and I know the risk, I had been "footed" by 25KV a few times (From the TV tube changing FBT, AC source disconected, I am not so fool!!!) and believe me, is painfool!!! Errors like this is the proof that I am human, nevertheless I became more and more cautious. But what about the circuit???

[popilin]

Hi again
Is my own design, I plan to make a PCB (Epoxi of course!) I had calculated clearence between tracks, very high at 900V 7.64mm, if not there will be fireworks.
I am working in an upgrade with an EL34 as Cathode Follower to kill Miller of 845 and class A1/A2 operation, I have some problems here with heat, I hate metal resistors but I hate more Transformers, I have all the Math, even I hate them and I want only one in the output.
Cheers

[popilin]

Crick, Crick, ...., Crick.........

[kruesi]

Transformers may be big and heavy but they're sometimes the best way to get the job done. They were put out of style originally because of their expense- and somehow the idea of them causing an expensive amp became the idea that they are just bad components. They are difficult to design- often resulting in a custom transformer to fit a particular application- but I don't know of a better way to couple the output of a class A stage to the output impedance of a typical loudspeaker.

Your amp looks like a good design- mu-followers, well-bypassed cathodes, fixed-bias on the final. Should be a good one- good luck and have fun building!

[popilin]

Hello kruesi
Many thanks for your concepts, for best clarity, I hate transformers, calculations are the easy part, I live in the end of the world and is very dificult to obtain good materials such as GOSS, only E-I are available and the problem is the direction of the Magnetic Field don't follow all the way (In coincidence with the orientation of the grain) in E, and it is necesary a double C Core.
Impossible to obtain in Argentina!
I agree with You only in the case of an Output Transformer because Valves are High Impedance Devises and Loudspeakers Low Impedance, but interstage only add nonlinearity because the inherent hysteresis of ferromagnetic materials.
Best Regards

[ChrisA]

Originally Posted by popilin

Hello All
This is my first Amp ind I need your help and opinion about it
[IMG]file:///C:/DOCUME%7E1/C3PO/CONFIG%7E1/Temp/moz-screenshot.png[/IMG]What do You Think?

Best regards from Argentina

Everyone always wants to build their last amp first. Build something small first. Maybe a single ended amp based on the 6V6 tube running at about 300V B+ It will be a lot less expensive. Find a design with a parts count of about 1/2 to 1/3 the schematic you posted.

900 volts is not easy to work with, first off where are you going to buy wire? Wire is typically rated at either 300v or 600V. You'd be looking a 1KV rated hookup wire. And then the transformes and choke(s) will need to be made of 1KV wire too, mst of them are not rated so high. Even little parts like standby switch that are rated for 1KV are not common parts. Resistors too. Many common resistors have lower voltage specs so you have to use two or three in series.

The power suply is not shown on the schematic. Watch out that the 900V can NOT get into the 600V part even when the amp first starts up and before the tubes conduct. You will blow up those 450V caps. Think about what happens if a tube fails, can it start a chain reaction?

Finally if you need that much power build a push-pull amp. But I bet you don't need it, just get better speakers

[athineos]

hullo to everyone from greece !one year ow iam looking for aperfect mic preamp!!!please help. my e-mail is ilias1duj@yahoo.gr thanks!!!