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The DIY Tube Head Thread

#21
I'll charge in here if I may. Concerns: This is a bass amp and a powerful one at that. Vibration! You have a lot of parts hanging by their fairly long leads. These are going to vibrate and eventually snap their leads. You need to tie them down physically to prevent this.

By Phase transformer I assume you mean interstage, replacing the phase splitter. As a matter of interest why did you go that route? The only musical instrument amp I know of that went this route was Kevin O'Connor's design in one of his books.

Paul
 
#24
pedro said:
I stand in awe. Honestly, I don't know how anything works and would stand as much of a chance of figuring out the meaning of life as I would of being able to build my own amp.

Congrats.
Click to expand...

Thanks and I have a little modding and rodding to do. I'm going to replace the PT so that I can get the plate voltage of the outputs to about 700V which should get me into the 300W ballpark...

Don't grab the B+ or you'll look like this guy!! :hyper:
 
#25
BassmanPaul said:
I'll charge in here if I may. Concerns: This is a bass amp and a powerful one at that. Vibration! You have a lot of parts hanging by their fairly long leads. These are going to vibrate and eventually snap their leads. You need to tie them down physically to prevent this.
Click to expand...

Good suggestion..

BassmanPaul said:
By Phase transformer I assume you mean interstage, replacing the phase splitter. As a matter of interest why did you go that route? The only musical instrument amp I know of that went this route was Kevin O'Connor's design in one of his books.

Paul
Click to expand...

It's an interstage phase splitting transformer. 6L6-driven SE input, Grounded CT output. It served the same purpose in a Fender 300PS. Why? It's rock solid phase inversion.
 
#26
Seeing as how everyone liked my bass head so much, I thought I'd show you all my other creation. I know it's a little off topic but it might inspire someone into the DIY world...

It's not other than the Audio Augustus Imperator or AAI for short:

P8210136.jpg


ampin.jpg


Made with only the best parts from around the world, it took me 6 weeks to scratch build. It uses the legendary Lance Cochraine circuit, is 60W of the most pure music you have ever heard in your life and weighs in at 105#

The tube lineup is CV1932s, Jan Sylvania 6SN7s, and Gold Lion KT88 outputs followed by Soviet Svetlana 5C3S rectifiers. Ane trimmed up with cocobolo with brass side panels, it looks as good as it sounds. Oh and let's not forget the Soviet mil-spec teflon coupling caps, the silver plated teflon insulated mil-spec point to point wiring, the gold plated tube sockets and the Hashimoto outputs.

I'm satisfied... :hyper:
 
#27
The phase inverter transformer presents a very low drive impedance to the output tubes and allows them to run class AB2. This is why the 300PS can get 300 watts out of four power tubes, the SVT is class AB1 and uses 6 output tubes.

It is easier to get custom torroidal power transformers for some reason. They are a little more expensive in large quantities than E-I (conventional) types. I got two on ebay for a 100 watt amp that uses a single pair of output tubes.
 
#31
Since most of us are under the age of 80, I suspect very few earned a B.S. in Electronic Engineering in the vacuum tube age, so what gives here? I am stunned by the level of knowledge you cats have about this kind of amplification!!!

Ironradio, the tube head is most impressive. We need to hear it.
 
#32
Jim Carr said:
Since most of us are under the age of 80, I suspect very few earned a B.S. in Electronic Engineering in the vacuum tube age, so what gives here? I am stunned by the level of knowledge you cats have about this kind of amplification!!!

Ironradio, the tube head is most impressive. We need to hear it.
Click to expand...

There's actually quite a lot of information about there about thermionic device circuit design, if you dig around a bit.
 
#34
Loudthud said:
The phase inverter transformer presents a very low drive impedance to the output tubes and allows them to run class AB2. This is why the 300PS can get 300 watts out of four power tubes, the SVT is class AB1 and uses 6 output tubes.

It is easier to get custom torroidal power transformers for some reason. They are a little more expensive in large quantities than E-I (conventional) types. I got two on ebay for a 100 watt amp that uses a single pair of output tubes.
Click to expand...

Indeed, but what do you call the 6L6? If you add the sheer cost of the interstage transformer you can easily add another pair of output tubes and still save money. There are trade offs in every design.

You CAN get 100W from a pair of KT88s or even 6550s. Personally I prefer to run my tubes at a less demanding level.

Paul
 
#36
BassmanPaul said:
Indeed, but what do you call the 6L6? If you add the sheer cost of the interstage transformer you can easily add another pair of output tubes and still save money. There are trade offs in every design.
Click to expand...

I may be wrong, but the primary reasoning he used an interstage tranny is that he found a NOS model from a 300PS, along with its OT, for very cheap on eBay.
 
#39
ive made a couple simple guitar amps.

also bought a 200w tube amp (old australian guitar amp, brand has fell off the radar a bit as they went under late 70's so i got it cheap) with the intention of designing my own amp and using the transformers, but the amp sounded good and i dont want to pull apart of musical history, especially when there fairly rare. since bought a second one...

been planning to make a 100w valve amp for bass using my own design, but have some other projects that i should finish first (i make instruments as well). still planning the design though.

my question is reguarding the lack of tone controls. do you use an active bass with onboard eq? how does it sound with a passive bass if youve tried it? does it lack the low end? i like quite a middy sound, but maybe not that middy.

i wish i lived in north america where second hand transformers like that pop up. i could get it shipped to australia, but the price for shipping would be quite rediculous due to the weight.
 

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