In such case that both output tubes of the PP circuit produce pure, i.e. non distorted sine signal, then AC current does not exist thru power supply/smoothing capacitor.
Unfortunately this case exisits only in theory. In practical ciruit, even if it is class A PP, there is allways some 2nd harmonic present and therefore some AC-current is flowing thru PS, and smoothing cap is then in the signal path.
But in theory, you are right.
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Ok Theoretically, even those 2nd H distortions should cancel out!
But practically, outside SE (you're correct on that one) PSU capacitors, do not play as big a role as coupling caps.
Provided they are good enough quality to handle stray oddball signals going through them that's not ripple.
There is always a price to pay for any gain in sound quality. I would spend my money on coupling and bypass capacitors first (or avoid them), before I consider an AudioNote cap for my PSU.
Thanx for an educational discussion, perhaps others could pick up a few points from it.
Thanks for the replies, yes I agree with you kentajalli, Nichicon are the ONLY electralytic caps I use, I replaced the Ella's in my Sony 2000f preamp and 3200f power amp.
Will start the build soon, I need to fist find some purlin c section 2mm steel to drill out and get chrome plated first, then get some woodwork done... I would get the chassis made, however in New Zealand the industry is not very good anymore and doing so is highly expensive.
I am looking forward to building a simple, yet warm and unique sounding amp.
I would like to drive the 807's with something that's note commonly used like a pf 86 as I like the sound of pentodes and have a pile of old tv tubes, I have even built preamps using pc900 triodes...
Will start the build soon, I need to fist find some purlin c section 2mm steel to drill out and get chrome plated first, then get some woodwork done... I would get the chassis made, however in New Zealand the industry is not very good anymore and doing so is highly expensive.
I am looking forward to building a simple, yet warm and unique sounding amp.
I would like to drive the 807's with something that's note commonly used like a pf 86 as I like the sound of pentodes and have a pile of old tv tubes, I have even built preamps using pc900 triodes...
IMO The only way a filter capacitor can affect the signal in the audio path is if it fails to adequately do its job and smoothing the DC current. The changes in audio and related harmonics are within the AC path, as this is what is constantly changing a DC supply state should never deviate, that's why this is important to have good coupling capacitors and is also why so many people change them even more often than they do the valves.
At the end of the day my opinion is that exactly my opinion and what sounds good to one person may be different to another and what is important is that your own system sounds right for you...
For me it is not about creating the purist straight through sound but how valve or a capacitor can change the sound and display its own characteristics and behaviour sometimes this is pleasant and sometimes it is not but you only find that out by trying...
At the end of the day my opinion is that exactly my opinion and what sounds good to one person may be different to another and what is important is that your own system sounds right for you...
For me it is not about creating the purist straight through sound but how valve or a capacitor can change the sound and display its own characteristics and behaviour sometimes this is pleasant and sometimes it is not but you only find that out by trying...
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Which to tube is that???
The transformers were built for 12 or so watts max so they will be fine at 10, but this is an audio amp, it won't run it wide open so it will be under ten for 99 percent of its life anyhow.
The transformers were built for 12 or so watts max so they will be fine at 10, but this is an audio amp, it won't run it wide open so it will be under ten for 99 percent of its life anyhow.
Hi Preludefan
This might sound strange at this point in the discussion, but I would never consider pushing a full 10 Watt out of 10 Watt OPT's.
These OPT's might be great for 300b... ok.. kinda expensive tube but there is a nice Teevee tube that comes to mind
Ian
6CB5A is one... 6GE5 is also nice one with a little less power.
Thomas Mayer sometimes discusses them on his blog.
Ok everyone, I have assembled the driver and output stage, am yet to test it properly however, I have tested itwith my high and low voltage bench supplies and the transformers get hot in addition to this one tube is putting out more than the other, I may have bad valves as the supply voltage is 300 V to the plates with 240 V to the screens. The transformers are 5K into end with a centre tap, these measure on a multimeter 600 ohms end to end and around 300 ohms end to tap.... Does anyone know what the issue could be here?
Please post a schematic and some pictures of what you have built.
Have no fear if it is not tidy.
Please post a schematic and some pictures of what you have built.
Have no fear if it is not tidy.
The power stage is identical to this,
http://ryujiwarui.com/data/Schematics/ryuji_807_rev-6.png
One of my transformers got hotter than the other, but at the same time the hotter on seemed to be putting put more power, are my transformers too small and perhaps one of my tubes bad?
They are supposed to be able to deal with 12 W... Ps should I fit a higher resistance cathode resistor?
I kinda agree with MelB... but:
I assume that your 1 ohm resistors are SUPER close to 1 ohm... so you can simply measure the DC voltage off the top of that resistor and calculate current flow (ohm's law). Don't use a higher resitance cathode resistor - it won't help, and if you make it some oddball value, it make it a pain to do your current measurements. (ok so I respectfully disagree with MelB here). Just keep it 1 ohm (or 10 ohm). your choice.
Then you can simply adjust your negative Bias supply accordingly for each tube and regulate the current flow... how many mA's should be flowin' through these lovely 807's?
So you need to adjust bias for each tube individually. I hope you can do this... this is the best solution with this kind of schematic.. its a must. if not, please build it so you can do that.
maybe add a chicken-scratch drawing or photo of what you built.
I assume that your 1 ohm resistors are SUPER close to 1 ohm... so you can simply measure the DC voltage off the top of that resistor and calculate current flow (ohm's law). Don't use a higher resitance cathode resistor - it won't help, and if you make it some oddball value, it make it a pain to do your current measurements. (ok so I respectfully disagree with MelB here). Just keep it 1 ohm (or 10 ohm). your choice.
Then you can simply adjust your negative Bias supply accordingly for each tube and regulate the current flow... how many mA's should be flowin' through these lovely 807's?
So you need to adjust bias for each tube individually. I hope you can do this... this is the best solution with this kind of schematic.. its a must. if not, please build it so you can do that.
maybe add a chicken-scratch drawing or photo of what you built.
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I guess reading the voltage drop at the top of the 1 ohm cathode resistor should be easy with any decent quality multimeter.
Of course 1% or better tolerance 1 ohm resistors are needed.
The transformer Impedance (AC) is 5K ohms while the Resistance (DC) is 600 ohms. These are distinctly different measurements. Impedance can not be measured directly with a multimeter.
Update: I have the amplifier working, however one of the 807's are faulty, so i have ordered a pair of NOS from a gentleman in the Russian Federation, I am looking forward to hearing it once the issues have been ironed out, I did find that using a 120 ohm 10 watt cathode resistor helped the overheating OPT issue and a 1.2k ohm resistor on the second grid to b+ keeps the voltage to it at around 230v.
will update with pictures soon
will update with pictures soon
10 W OT EDCOR is very, very small for 807. You need more than 20-25 W OT.
When I take OT, I use formula P OT = P output x 3-5. You need more than 30 W OT. R primary must be no more 70-90 ohm.
It will give You strong and big bass. /To saturate iron of small OT is very easy/.
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