Happy New Year DIY Peeps!
I am building like mad and (slowly) learning and this Sakuma 46 / parallel 801A circuit has peeked my interest.
April 1984
Maybe because it is more approachable than some of his other design's?
The tube line up definitely rocks.
Would anyone be kind enough to walk me through this circuit and answer a few questions?
I understand many have had better results with 46 as driver rather than as power tube. It is cheaper than 45, has a higher mu than 45, and it's a "kissin cousin" so I am interested. I love the 45.
Is it considered sacriligeous to alter a Sakuma circuit, or is there some room for improvement?
What input voltage would be required to dump the input transformer?
Parallel 801A's? I thought paralleling tubes was frowned upon by DHT purists?
How much power will this amp provide?
More specifically how do you calculate the power output of this circuit?
5K OPT's with 801A's? Seems quite a low primary for this tube?
Lot's of contradictions but I want to build it!
I finally have a wonderful and very satisfying Thomas Mayer 6N7 / 45 amp in full time service, so I am looking forward to bread boarding MANY different other circuits and approaches, to compare and LEARN.
I have also built 2A3 and 300B amps, but they didn't stick and I seem to prefer less popular, and less expensive DHT's. My 2nd favorite amp, behind the 6n7/45 is the RH84. I know it is a 180' but it is a wonderful sounding little amp, especially considering the low parts cost. Kitic's bigger RH 307A is also on my build list.
Thanks in advance for your comments and help.
Jason
I am building like mad and (slowly) learning and this Sakuma 46 / parallel 801A circuit has peeked my interest.
April 1984
Maybe because it is more approachable than some of his other design's?
The tube line up definitely rocks.
Would anyone be kind enough to walk me through this circuit and answer a few questions?
I understand many have had better results with 46 as driver rather than as power tube. It is cheaper than 45, has a higher mu than 45, and it's a "kissin cousin" so I am interested. I love the 45.
Is it considered sacriligeous to alter a Sakuma circuit, or is there some room for improvement?
What input voltage would be required to dump the input transformer?
Parallel 801A's? I thought paralleling tubes was frowned upon by DHT purists?
How much power will this amp provide?
More specifically how do you calculate the power output of this circuit?
5K OPT's with 801A's? Seems quite a low primary for this tube?
Lot's of contradictions but I want to build it!
I finally have a wonderful and very satisfying Thomas Mayer 6N7 / 45 amp in full time service, so I am looking forward to bread boarding MANY different other circuits and approaches, to compare and LEARN.
I have also built 2A3 and 300B amps, but they didn't stick and I seem to prefer less popular, and less expensive DHT's. My 2nd favorite amp, behind the 6n7/45 is the RH84. I know it is a 180' but it is a wonderful sounding little amp, especially considering the low parts cost. Kitic's bigger RH 307A is also on my build list.
Thanks in advance for your comments and help.
Jason
Yes.
10k for 801a, 5k for parallel 801's.
About 5W.
Output transformer primer swing about 160V (500V-42V/2*sqrt2), OPT ratio 17.67 (5k:16), secondary RMS voltage 9.1V, thus output power 5.17W.
This is too low for PSE 801a. 500V B+ and 18-19mA (458V, -42V bias) is the limiting factor.
Cathode bias IMHO is the most worse choice, I prefer fix bias.
Hi Jason,
of course it is ok to alter the circuit to your preferences. Sakuma designs for tone and not necessarily for accuracy. Your preference might be different than his.
I find the 5k for parallel 801s too low. The 10Y and 801 is often used with 10k transformers. I prefer 14-16k (7-8 for parallel). This heavily depends on the speaker you use. If you have a speaker with very linear impedance and which does not need a decent damping factor, you might get good results with a low primary impedance.
I did not calculate the power in detail. I'd estimate about 5W from two 801 with that voltage. You can bump up to 600V if you want to squeeze out more power. Up to 7W should be possible from two 801.
This circuit has very low gain and will probably not be practical without a step up input transformer or a third stage.
In my experience the 801 will react sensibly to the filament supply. I prefer LCL with these tubes. You might also consider Rod Coleman filament regs which should work well too.
Best regards
Thomas
of course it is ok to alter the circuit to your preferences. Sakuma designs for tone and not necessarily for accuracy. Your preference might be different than his.
I find the 5k for parallel 801s too low. The 10Y and 801 is often used with 10k transformers. I prefer 14-16k (7-8 for parallel). This heavily depends on the speaker you use. If you have a speaker with very linear impedance and which does not need a decent damping factor, you might get good results with a low primary impedance.
I did not calculate the power in detail. I'd estimate about 5W from two 801 with that voltage. You can bump up to 600V if you want to squeeze out more power. Up to 7W should be possible from two 801.
This circuit has very low gain and will probably not be practical without a step up input transformer or a third stage.
In my experience the 801 will react sensibly to the filament supply. I prefer LCL with these tubes. You might also consider Rod Coleman filament regs which should work well too.
Best regards
Thomas
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I believe, if you want to hear what Sakuma intended, that you have to build it as it is and not change it. He did encourage builders to explore their own 'sound', to make changes and listen to see what they prefer, but if you don't build his version first you won't know what he was aiming for. One thing that put me off his designs is the cost - the use of some hard to find and very expensive transformers. The tubes are not the expensive part. He seems to have had access to some esoteric transformers from Tango(?) and I'm not even sure you can buy them very easily. I believe they make a big difference to the sound of the amplifier.
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