PP?
As your first to design and build you are doing a PP? I think a simple SE is.........simpler, no?
I have not completed a design of a PP but have done some with SE.
Go for it! I would be interested in following this thread if you are able to post curves, loadlines, schemes, etc. Looks like you have plenty of interest and help!
Best of luck!
Rick
As your first to design and build you are doing a PP? I think a simple SE is.........simpler, no?
I have not completed a design of a PP but have done some with SE.
Go for it! I would be interested in following this thread if you are able to post curves, loadlines, schemes, etc. Looks like you have plenty of interest and help!
Best of luck!
Rick
I've been talking about tubes on here lots. I used to gab with colt45 on tubes all the time, that's how I got to know him. Trust me, I don't "not believe in tubes"! I think they're great. I still like transistors as well though. I have respect for both worlds.
Re: what about this 12b4a schematic?
Ok one point : the power supply . There seems to be a lot of HT wasted in the series resistors to drop from 355V to 200V . Extra heat in both the resistors and the power transformer . I would also recommend a CCS load for the input stage as I find resistor loading to sound 'sludgy' or 'tubey' at times , but all depends on how you wish to flavour the amp . I managed to get away with using a fairly marginal input/driver HT for my 12B4a amp : 220V . I've biased the 6SL7 driver at a puny 1mA using a 1.25V bias point (NimH battery) , holds the anode at about 150V . CCS is a depletion mosfet . Not really enough headroom for my liking but drives the 12b4a into clipping ok
316a
Guiness said:
Ok one point : the power supply . There seems to be a lot of HT wasted in the series resistors to drop from 355V to 200V . Extra heat in both the resistors and the power transformer . I would also recommend a CCS load for the input stage as I find resistor loading to sound 'sludgy' or 'tubey' at times , but all depends on how you wish to flavour the amp . I managed to get away with using a fairly marginal input/driver HT for my 12B4a amp : 220V . I've biased the 6SL7 driver at a puny 1mA using a 1.25V bias point (NimH battery) , holds the anode at about 150V . CCS is a depletion mosfet . Not really enough headroom for my liking but drives the 12b4a into clipping ok
316a
I haven't a prejudice against either the 6SN7 or the 12AX7 tube. As a matter of fact I have a number of both. I'm certain that there are very good designs out there (or in Frank's head )for either. The 12B4A design looks interesting enough and I will certainly put it on the list of good designs to build. 
Are there any other ideas that anyone would care to share?
Any good 6SN7/2A3 designs?
Joe
Are there any other ideas that anyone would care to share?
Any good 6SN7/2A3 designs?
Joe
Re: Re: what about this 12b4a schematic?
Agreed. With a 5k load, you can probably get away fine with lower current and higher voltage. Not the best operating point but it's not the best suited power transformer either, eh?
Given the relatively low mu, using that 6AU6 in pentode mode might be a good idea too, at least if you want some global NFB (a few dB is good practice anyway), which is probably a good idea given the odd operating point mentioned above.
Tim
316a said:
Agreed. With a 5k load, you can probably get away fine with lower current and higher voltage. Not the best operating point but it's not the best suited power transformer either, eh?
Given the relatively low mu, using that 6AU6 in pentode mode might be a good idea too, at least if you want some global NFB (a few dB is good practice anyway), which is probably a good idea given the odd operating point mentioned above.
Tim
Well I wouldn't claim this one is good but it has enabled my sons WAD 2A3PSE amp to equal my little ECL82SE for sound quality. It's a reworking of the WAD design that makes it a little different.
It is still not as good as my 2A3PP designs and they could use a 6SN7 instead of the 6N6P (with a little tweaking) Not sure I'd call it a begineers amp and it uses a cheap lundahl input transformer as that enabled the changes to stay within budget.
ciao
James
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Hi Frank
My speakers are an improved version (a knockoff) of the Klipsch Cornwall. They feature horn high frequency and midrange and a 15" woofer. They are all custom components as is the crossover.
They are extremely flat in response as I have setup a HP plotter and recorded the response using a warble generator and calibrated microphone. Pink noise was used to obtain the 102db 1W 1M response. If there is a flaw in the equipment I can usually detect it with these.
Joe
My speakers are an improved version (a knockoff) of the Klipsch Cornwall. They feature horn high frequency and midrange and a 15" woofer. They are all custom components as is the crossover.
They are extremely flat in response as I have setup a HP plotter and recorded the response using a warble generator and calibrated microphone. Pink noise was used to obtain the 102db 1W 1M response. If there is a flaw in the equipment I can usually detect it with these.
Joe
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