compact tube amps?
I thought I would see pictures of nuvistor amps, but I apparently am the only person with a bin full of 7895's pulled out of the trash in original boxes. I've never seen sockets for sale for them, just one lonely socket on the Triplett tube tester. Your 9 pin tubes are tubas compared to the piccolo trumpets of nuvistors.
You remember, the US was putting tubes in anti-aircraft shells in 1945. What they were was a big secret, but I would nominate the nuvistor.
I thought I would see pictures of nuvistor amps, but I apparently am the only person with a bin full of 7895's pulled out of the trash in original boxes. I've never seen sockets for sale for them, just one lonely socket on the Triplett tube tester. Your 9 pin tubes are tubas compared to the piccolo trumpets of nuvistors.
You remember, the US was putting tubes in anti-aircraft shells in 1945. What they were was a big secret, but I would nominate the nuvistor.
Last edited:
While not terribly compact, it is smaller than at least one of the amps shown here. It is about 12 inches by 11 inches by 7 inches tall and weighs about 25 pounds. 23 of them are iron and copper! The OPT's are Electra - Print. It is the smallest amp that I currently have and the best sounding.
It makes 2 WPC with 45's or 483's and 6 WPC with 300B's
Attachments
Everybody knows there hasn't been a nuvistor amp worth talking about since the "Big Bang" single ended triode amplifier.
My "No Light District" 6CW5 P-P amp will be pretty compact, though not as compact as I wanted. I went to a larger case to make life easier for myself (I have another small amp in the works that's crowded inside and a right bastard to debug), though it's still reasonably small. Output iron is inside the case, as it's old Baldwin stuff that's fairly ugly. There's another SMPS, too, but you knew that, didn't you... Pics to follow after more work has been done.
Last edited:
You mean like leftover transformers from ATX PSUs and such ?
What I'm curious about is how you took care of startup, regulation etc.
Hi Michael, can you tell us more about this little thing. I really like it. Pix, scheems....whatever you got.
Arnulf, the transformers aren't recycled from PC power supply rubbish, but are designed and built from scratch. The basic design uses the ST L6565 quasi-resonant flyback controller, with some changes for each design situation. The chip has provision for startup. You can check out the data sheets and application note on line if you're curious. It'll also answer some of your questions about regulation.
Why not reuse the old parts ? I mean, the bobbin is there, the core is just two pieces (unlike stacked laminations for 50/60 Hz), it's just a matter of rewinding the bobbin to suit one's needs. If these can cater to many hundred watts of computer they can surely handle a couple of dozens of W ?
I'm looking at the appnote of the controller chip you mentioned (which presents an example of STB supply) which looks quite straightforward despite multitude of output voltages which clutter the schematic
This appnote might just encourage me to finally give these a try - I've been longing for a portable & adjustable tube supply for a while now.
I mean, the bobbin is there, the core is just two pieces (unlike stacked laminations for 50/60 Hz), it's just a matter of rewinding the bobbin to suit one's needs. If these can cater to many hundred watts of computer they can surely handle a couple of dozens of W ? I'm looking at the appnote of the controller chip you mentioned (which presents an example of STB supply) which looks quite straightforward despite multitude of output voltages which clutter the schematic
This appnote might just encourage me to finally give these a try - I've been longing for a portable & adjustable tube supply for a while now.
First thing, the transformers in those supplies are generally varnished, so it's hard to get them apart without extreme mayhem. Second, they aren't generally the optimal size for an efficient design that also meets safety spacing requirements. If you want to proceed without looking into that, it's on your own head. You can find suitable cores and bobbins on Ebay if you look diligently, and not have to worry about tearing an existing design apart.
This is smallest amp I have in the house currently, it's not quite as compact as some of the ones I've seen here. This is actually the second most powerful SE I have designed and built to date. (Quite newly finished 6V6/6J7 pentode amp discussed in another thread.)
The smallest stereo amp I own is about half the size of this one and uses 45s driven by 6SL7s, but it has an outboard supply which is significantly larger and quite a bit heavier - and it is on long term loan to a friend.
The smallest stereo amp I own is about half the size of this one and uses 45s driven by 6SL7s, but it has an outboard supply which is significantly larger and quite a bit heavier - and it is on long term loan to a friend.
Attachments
Thanks for sharing. Actually I knew this amp before!
It's a lovely, simple, well-proportion build.I came back to your homepage for refreshing my memory, but I didn't find much information about the filament supplies, but only one sentence about DC supply cures the hum (or the likes).
Do you use 3-terminal reg for it?
I saw really compact units from you, sirs... Partly thanks to the use of hybrid modern circuits and quite low audio output power, which allow extreme compactness.
I wonder If these one would be considered as "compact", but given the fact that they are OTL circuits (built in 1993, 20WRMS@8ohms) monaural amps...
I also wonder if this one would be considered too, but considering the fact that it is a 2x70WRMS stereo amp (built in a dead M&A rescued chassis)...
Needless to say that each weights an anvil...
I am currently working on a compact 300B amp, trying to preserve a "vintage look" amp (see the ULTIMATE 300B topic).
A+!
I wonder If these one would be considered as "compact", but given the fact that they are OTL circuits (built in 1993, 20WRMS@8ohms) monaural amps...
An externally hosted image should be here but it was not working when we last tested it.
I also wonder if this one would be considered too, but considering the fact that it is a 2x70WRMS stereo amp (built in a dead M&A rescued chassis)...
An externally hosted image should be here but it was not working when we last tested it.
Needless to say that each weights an anvil...
I am currently working on a compact 300B amp, trying to preserve a "vintage look" amp (see the ULTIMATE 300B topic).
A+!
Here is mine but it still remains in the UnWired state. Just another winter project. As the weather gets colder, I turn on the system more and more. the fuse on the left is an on/off switch and the fuse on the right is the volume control. I am still looking for VU meters that will fit in the holes.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.