Stereo 100w Valve Amp

[tiv48]

i used to drive a pair of mission 780 from a beam echo advantic valve amp .the output of this amp was app 8.5 watts.
in a 13x12 foot room you would not want to turn the volume full up.
the trouble is that you want massive power (for a valve amp ) and high quality . to get the high quality the output stage needs to baised towards class A this means big high quality output transformers.
another idea you may want to investigate is say a 30 watt valve amp and high efficency (102 db/watt ) speakers.
or how about bi amp say a high quality valve amp for mid and trebble and high power solid state for bass.
just ideas
rob t

[Mr Clock]

Thanks for your replys,thats the sort of advice I,m looking for before I go farther. if we stick to PA/Guitar amps for a minute heres a link to a 1000w amp using 807's. Having said that there hasnt been an update since the writting of the article. I think someone said Johns Mum hadnt been well. http://www.chambino.com/construct/const17.html . There are other 807 related projects on his site,including a 200w (CBA225) using 8 807's.

Looking at the data sheet 807 in class AB2 gives approx 30watts. The Geloso G272A uses two to give 75-100w. I,ll send the PDF,Andy.

[Joe]

That link's a duffer. Chambio.com seems to be a Portuguese clinical laboratory!

- Joe

[Nick]

It should be http://www.chambonino.com/ and if you look at the 1000W mono amp I rest my case WRT getting a hernia thrown in ! (see http://www.chambonino.com/construct/const13.html)

FWIW, Morgan Jones used to carry his "Crystal Palace" amp blocks around in a wheelbarrow...

[Joe]

That is indeed a beast of a thing! Just imagine what it would be like if it was stereo.

- Joe

[Joe]

Here's the Geloso circuit refereed to above:-


  Document0.pdf (Size: 111.31 KB / Downloads: 56)

- Joe

[Mr Clock]

Thanks Joe.This the sort of amp I want to build. I want to build a stripped down version.With less inputs,and a simpler OPT. I would appreciate your thoughts. The PSU seems to me to overly complex with two transformers. I,m unable to fathom wether this is a PA amp or a HiFi amp. The bumf I,ve read so far,on various forums etc is mixed. The consensus is, its a good design/amp. The translation of the full text,is ambigouous,Andy.

[Nick]

I believe that most audio types prefer 807's triode-strapped...

Consider: http://www.tubeaudio.8m.com/807/807.html - seems to be well regarded, and its an SE amp, so you can join an exclusive crowd !

There are many 807 amps out there - its a commodity tube that was produced in the 100s of 1000s, and its as tough as old boots.

[pwdrive]

Thanks Joe.This the sort of amp I want to build. I want to build a stripped down version.With less inputs,and a simpler OPT. I would appreciate your thoughts. The PSU seems to me to overly complex with two transformers. I,m unable to fathom wether this is a PA amp or a HiFi amp. The bumf I,ve read so far,on various forums etc is mixed. The consensus is, its a good design/amp. The translation of the full text,is ambigouous,Andy.

Hi there, judging by the pictures and the standby switch I would say it was designed as a PA amp.
The second transformer supplies the valve heaters and the seperate standby bias, the bridge supplying the preamp valve heaters is self explanatory.
Why two transformers? Better overalll regulation/spreads wattage disipation/better regulation on grid bias as unaffected by standby switch position, my thoughts, someone might know otherwise or have other ideas. Looks a well thought out design.

Lawrence.

[tiv48]

because it has mic inputs i would say its a pa amp .
not shure i have come across a seperate -36 volts switched to the screen grids of the output valves to bring about standby before.
it does not give any bias setting but iam guesing it will be biased to ab1
another nice touch is the seperate secondry winding for feedback on the output tx.
i cant see the output being more than about 30 watts.
rob t