HI everyone.. I just wanted to submit for your evaluation an amplifier I found on the internet.
It is manufactured in China, soldered board with Shuguang valves.
The circuit is the follwing:
and finished product:
After extensive research it would seem that the chinese tubes have improved to acceptable levels and can sometimes surpass other manufacturers in terms of realiability and average quality.
I wanted to have an opinion on the circuit and if there is any way to improve output and quality in the signal path.
Thank you!
Alex
It is manufactured in China, soldered board with Shuguang valves.
The circuit is the follwing:
and finished product:
After extensive research it would seem that the chinese tubes have improved to acceptable levels and can sometimes surpass other manufacturers in terms of realiability and average quality.
I wanted to have an opinion on the circuit and if there is any way to improve output and quality in the signal path.
Thank you!
Alex
Is this a 5Z3 rectifier? Can't find 5Z5.
What I'd do with this is replace R6 with a CCS as said and eliminate the first stage with its feedback loop. Take the input direct to one side of the 6SN7 with something like 270K from grid to ground, and ground the second grid. The first stage and the feedback can only make the sound worse. If you need more gain, do it in the preamp, otherwise if you have enough gain you could replace the 270k with a 100K volume pot.
Andy
What I'd do with this is replace R6 with a CCS as said and eliminate the first stage with its feedback loop. Take the input direct to one side of the 6SN7 with something like 270K from grid to ground, and ground the second grid. The first stage and the feedback can only make the sound worse. If you need more gain, do it in the preamp, otherwise if you have enough gain you could replace the 270k with a 100K volume pot.
Andy
Yep sorry for that... 5Z3P
Checking the costs...by eliminating the first stage it maybe actually cheaper to redesign it on a PCB board.
Are there proven applications for th 2A3 I can look at for reference?
By the way andyjevans, thankyou for your input I'll try to redesign it taking out the first stage.
Checking the costs...by eliminating the first stage it maybe actually cheaper to redesign it on a PCB board.
Are there proven applications for th 2A3 I can look at for reference?
By the way andyjevans, thankyou for your input I'll try to redesign it taking out the first stage.
What would be nice is to use plate chokes on the 6SN7. The Hammond 156C are excellent for the price, and even better when two are used in series. This would raise the quality and give a little more gain than resistor loads.
Also think of better coupling caps - the Russian teflon ones are really excellent. FT-3. Need some space in the chassis.
But seriously, since you have to put all this in a chassis anyway and get some transformers, you may be better off just building a 300b SET from scratch. I'm assuming that what you get for your money here is the PCB plus the tubes.
Andy
Also think of better coupling caps - the Russian teflon ones are really excellent. FT-3. Need some space in the chassis.
But seriously, since you have to put all this in a chassis anyway and get some transformers, you may be better off just building a 300b SET from scratch. I'm assuming that what you get for your money here is the PCB plus the tubes.
Andy
yes Andy....the project seems counterproductive since the main goal of somwhat saving on costs is frustrated by the necessary modifications...
I probably would end up spending the same amount of money I would spend bulding 2x Pete millet's push pull monoblocks with KT88 in ultralinear operation. The results would most certainly be better and the cost just about the same (considering what I have at home). The interesting thing about Millet's design is that I can actually use 2A3 (but with slight voltage modifications).
BTW the link to the chinese product is: http://stores.ebay.it/diyaudiokit/P...11689014&_sid=851127124&_trksid=p4634.c0.m322
I just did not want to post it to avoid "marketing and spam issues"
Alex
I probably would end up spending the same amount of money I would spend bulding 2x Pete millet's push pull monoblocks with KT88 in ultralinear operation. The results would most certainly be better and the cost just about the same (considering what I have at home). The interesting thing about Millet's design is that I can actually use 2A3 (but with slight voltage modifications).
BTW the link to the chinese product is: http://stores.ebay.it/diyaudiokit/P...11689014&_sid=851127124&_trksid=p4634.c0.m322
I just did not want to post it to avoid "marketing and spam issues"
Alex
300 euros just for a PCB and tubes is not good value at all. A 300b SET would give you almost the same output. My own 300b SET can be built very cheaply. I get Hammond iron in the UK from Bluebell Audio. It uses a pair of 156C Hammond plate chokes on the first stage (£8.63 + £8.63) and a Hammond 126C interstage (£26 each). For both channels that's a total of just over £100 including VAT. Add a few sockets, a couple of FT-3 teflon caps and some bits and you have over £100 for some tubes. Chinese 300b even sound good!
Andy
Andy
I've never tried it, but if you connect the mid point of the two plate chokes to HT and the ends to the plates this surely performs the same function as the primary of a PP interstage, does it not? You'd then use a CCS and cap output to the next stage.
Andy
If tou configure it as a PP output stage, it should work yes.
But then you need 2 chokes wound on the same core (OR one with a CT)
Thanks for that. Yes, I see your point - it's not something I've tried. But I'm still curious that if you start with two resistors on the plates and then substitute two chokes on the plates this "wouldn't work". What would not work?
Andy
disclaimer: I know nothing about tube amps.
I love the look of the 2A3 tubes. Also the 6SN7 tubes used in the MINGDA MC7R-II preamp .
I built a pair of Dallas II BLH with Fostex FE206E drivers and have been listening to them fro years with mass market SS receivers. First, a RCA ht amp and then a Nakamichi 50W Pass/Stasis receiver. I built a Mauro Penasa My_Ref to power the BLHs from the Twisted Pair kit and HAD a working amp. I then built a Kukabura Pre but hooked up the transformer wrong and killed both the kukabura and My_Ref. Their in a junk box out in the shed.
My Nakamichi was recently struck by lightning and only the power amp works now. I'm considering my options and realize I have never hears the speakers the way they were meant to be heard, with a good tube amp. The idea of seeing glowing tubes above a wood chassis that matches my speakers is just inviting.
Someone else here who is building the Dallas II asked about what to use for a amp and was steered to the Baby Huey design. I'm thinking a integrated amp using 2A3 and 6SN7 tubes would look stunning but have no idea how it would sound. Sorry is this is not the place for a n00bie post but where can I learn more about what I want to do ?
I love the look of the 2A3 tubes. Also the 6SN7 tubes used in the MINGDA MC7R-II preamp .
I built a pair of Dallas II BLH with Fostex FE206E drivers and have been listening to them fro years with mass market SS receivers. First, a RCA ht amp and then a Nakamichi 50W Pass/Stasis receiver. I built a Mauro Penasa My_Ref to power the BLHs from the Twisted Pair kit and HAD a working amp. I then built a Kukabura Pre but hooked up the transformer wrong and killed both the kukabura and My_Ref. Their in a junk box out in the shed.
My Nakamichi was recently struck by lightning and only the power amp works now. I'm considering my options and realize I have never hears the speakers the way they were meant to be heard, with a good tube amp. The idea of seeing glowing tubes above a wood chassis that matches my speakers is just inviting.
Someone else here who is building the Dallas II asked about what to use for a amp and was steered to the Baby Huey design. I'm thinking a integrated amp using 2A3 and 6SN7 tubes would look stunning but have no idea how it would sound. Sorry is this is not the place for a n00bie post but where can I learn more about what I want to do ?
So what did you end up building? I'm looking at Olson's Amity but was geting lazy. I have most of the iron and the tubes so the assembled board looks very interesting.
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