The first brand new guitar amplifier I've ever bought "new" instead of built or repaired! Also my first Chinese amp...LOL! Hand-wired by a family operation.
Really cute circuit:
Most mini-amps are single-ended in the belief they are simpler, but end up inefficient and require a large power supply, filters, and heavy output transformer. They tend to model after the classic Champ.
This takes a different push/pull route. All tubes are dual triode preamp tubes, which actually work acceptably as output tubes when used in push/pull.
The first stage has both halves of a high-gain dual-triode in parallel.
Then there is a one-knob tone control, with the counter-clockwise "bass" setting shunting the pre-volume (right after the coupling cap from the previous plate) treble to ground via a cap, and the clockwise "treble" shunting the treble across the volume pot, like a variable "bright" switch. Not much gain loss.
Then the first side of the second high-gain preamp tube gives gain. The second half of that tube is a paraphase phase inverter.
Then the two halves of a moderate-gain higher-current dual triode are used as the push and pull output stages. Each stage pushes into a half of a 10K - 0 -10K primary on the small output transformer, with a single secondary labeled "8 to 16 ohms."
This is the smallest 3-tube push/pull I've ever seen. I'm still waiting for it to arrive. Judging from the YouTube clips, this thing is killer.
I guess it also shows that Chinese tubes are cheaper in China than Chinese transformers! Otherwise you could build a nice little 2-tube push/pull amp using an interstage transformer as the phase inverter.
Really cute circuit:
Most mini-amps are single-ended in the belief they are simpler, but end up inefficient and require a large power supply, filters, and heavy output transformer. They tend to model after the classic Champ.
This takes a different push/pull route. All tubes are dual triode preamp tubes, which actually work acceptably as output tubes when used in push/pull.
The first stage has both halves of a high-gain dual-triode in parallel.
Then there is a one-knob tone control, with the counter-clockwise "bass" setting shunting the pre-volume (right after the coupling cap from the previous plate) treble to ground via a cap, and the clockwise "treble" shunting the treble across the volume pot, like a variable "bright" switch. Not much gain loss.
Then the first side of the second high-gain preamp tube gives gain. The second half of that tube is a paraphase phase inverter.
Then the two halves of a moderate-gain higher-current dual triode are used as the push and pull output stages. Each stage pushes into a half of a 10K - 0 -10K primary on the small output transformer, with a single secondary labeled "8 to 16 ohms."
This is the smallest 3-tube push/pull I've ever seen. I'm still waiting for it to arrive. Judging from the YouTube clips, this thing is killer.
I guess it also shows that Chinese tubes are cheaper in China than Chinese transformers! Otherwise you could build a nice little 2-tube push/pull amp using an interstage transformer as the phase inverter.
I'm a bit intrigued by Rob Robinette's micro amps that use triode power amps, like the micro-Bassman.
I'm not at home, and I can't remember the tubes, but I got a lot off eBay that included some high current triodes that I think are normally used for triode power amps. At some point (after I complete my 4 or so pending projects) I'd like to do something with those.
I'm not at home, and I can't remember the tubes, but I got a lot off eBay that included some high current triodes that I think are normally used for triode power amps. At some point (after I complete my 4 or so pending projects) I'd like to do something with those.
I just happen to have been perusing his mods last night and I've had the micro-Champ and micro-Bassman in the back of my mind since I got those triodes. It looks like the Wang is OTL. I don't have a good handle on how to do those. I'd love to see a schematic. All the examples I've seen of OTL amps use 500-800ohm speakers.
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This ebay listing shows the inside pcb Biyang Wangs VT 1H Electric Guitar Micro Amplifier All Tube Amp Head | eBay
Looks like red Box Wimas.
Looks like red Box Wimas.
oh god...rip them MKS/MKT's out dude I'm telling you...
none of them box/metalized are that great....have Siemens MKP that's not bad though/a little smoother etc.
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And after reading this thread, it doesn't look like making a guitar amp with them is something I'd want to do.
I assume you saw the output transformer in the picks of the Wang's VT-1H, nor OTL. A push-pull doesn't need much compared to a single-ended amp.
I was unable to find a schematic for the H&K Tubemiester 5. I'm not familiar with a 12BH7 dual triode...but they get a LOT more power out of it!
Thanks for the link to Rob Robinette's stuff!! I just happen to have those power transformers sitting around waiting for a decent project.
The big differences: The Wangs VT-1H uses parallel input stages to drive a volume and single tone control. Like a Fender without much of a "stack"... The micro bassman/JTM circuit has gain / vol / gain / cathode follower / stack / then a similar output scaled up for more power. Oh, and it has some negative feedback on a switch... The Wangs could probably use that...
These are all cute as heck! But...the Wangs is much less power and much much smaller.
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