Hi All,
I have a little SE 6BQ5 amp out of a console that I plan on rebuilding on a new chassis with a 5687 as the gain tube. The little amp uses a 4 section 40uF 350 v capacitor in the power supply. I recently purchased 4 Seimens 330uF/ 385 volt snap in caps that I plan on using in the power supply. The power supply is not a choke input so I think that the new caps will work fine but will the amp sound better or worse with the increase in capacitance? I can just use 2 JJ dual section 40 uF caps. Thanks.
G
I have a little SE 6BQ5 amp out of a console that I plan on rebuilding on a new chassis with a 5687 as the gain tube. The little amp uses a 4 section 40uF 350 v capacitor in the power supply. I recently purchased 4 Seimens 330uF/ 385 volt snap in caps that I plan on using in the power supply. The power supply is not a choke input so I think that the new caps will work fine but will the amp sound better or worse with the increase in capacitance? I can just use 2 JJ dual section 40 uF caps. Thanks.
G
I'm torn between a 5AR4 for the slow warmup or a 5Y3GT which is what came with it. There is not a choke in the power supply. What do you think?
G
G
Gavin,
You'd better not use big caps like that with valve rectifiers. They won't last long at all.
If you want to use valves for rectification, you'll need to use the small cap option.
Cheers,
You'd better not use big caps like that with valve rectifiers. They won't last long at all.
If you want to use valves for rectification, you'll need to use the small cap option.
Cheers,
If the power supply is using vacuum tubes for rectifing you can't use large capacitance capacitors.
For vacuum tubes there's a limit for the capacitance of the first tube. usually this limit is between 32uF-56uF.
One of the problems with high capacitance capacitors is the start-up current and the current peaks during operating.
Vacuum tubes does often have a quite low max current rating, about 1,5 - 2A
For vacuum tubes there's a limit for the capacitance of the first tube. usually this limit is between 32uF-56uF.
One of the problems with high capacitance capacitors is the start-up current and the current peaks during operating.
Vacuum tubes does often have a quite low max current rating, about 1,5 - 2A
LC
Hi Gavin,
If you can get at least one choke for your PSU pls. fit it after the rectifier.
In doing so you can than add a decent amount of reservoir caps after the choke.
If you don't you'll end up with a whimpy PSU and a rectifier that gets hit by the caps charging at switch on thereby risking arc over etc.
Cheers,😉
Hi Gavin,
If you can get at least one choke for your PSU pls. fit it after the rectifier.
In doing so you can than add a decent amount of reservoir caps after the choke.
If you don't you'll end up with a whimpy PSU and a rectifier that gets hit by the caps charging at switch on thereby risking arc over etc.
Cheers,😉
It's not just a question of saving the rectifier, the larger the capacitance, the more VA needed from the power transformer to maintain the charge. Your hum can actually increase with too much capacitance, and you can also shorten the life of your transfrmr in extreme cases.
You can live by this statement: no tube power amp PSU needs any one capacitor to be larger than 40uF.
You can live by this statement: no tube power amp PSU needs any one capacitor to be larger than 40uF.
Hi Gavin;
I'd use something even smaller than 40uF in front (say 20uF) of your choke and finally put in something stouter (e.g. parallel the 40+40uF cap). If money and space in your chassis permits a pair of chokes, you might try a 2pi filter with an even larger value cap as tail end Charlie.
By the way, why not model your PS with PSUD II while you're at it? Depending on your choice of rectifier and the choke(s) you put in you might be able to put in rather more than 80uF after the choke and still not draw too much current from your rectifier.
Also, don't forget current inrush limiting thermistors - they are cheap and they can be switched out of the circuit after turnon, either with a manual switch or a timed relay.
Good luck and all the best,
Morse
I'd use something even smaller than 40uF in front (say 20uF) of your choke and finally put in something stouter (e.g. parallel the 40+40uF cap). If money and space in your chassis permits a pair of chokes, you might try a 2pi filter with an even larger value cap as tail end Charlie.
By the way, why not model your PS with PSUD II while you're at it? Depending on your choice of rectifier and the choke(s) you put in you might be able to put in rather more than 80uF after the choke and still not draw too much current from your rectifier.
Also, don't forget current inrush limiting thermistors - they are cheap and they can be switched out of the circuit after turnon, either with a manual switch or a timed relay.
Good luck and all the best,
Morse
I'm going to use the supply configuration of a Decware Zen amp which basically uses two 32uF/32uF caps and a couple of 3.3uF metallized caps. They have even been so kind as to provide a pictorial on the layout of the amp. Very nice design. Of course I'll be using a 5687 in the gain stage instead of a 6N1P. I'll have to change the dropping resistor values a little and the transformers I'm using are way overbuilt for this application but it should turn out OK. I'll test the transformers out tommorrow and let you know how it goes. Thanks for all of the suggestions. By the way. I'm going to use a 5AR4 rectifier.
G
G
might wanna check out PSU Designer II from Duncan amps website (www.duncanamps.co.uk). very helpful program, have to agree with frank, add a choke, but use a cap input filter (better overall characteristics i think), with a choke somewhere in between the caps following the first one, also dont forget that using larger capacitance caps can increase the voltage segnificantly, and as previously stated by someone increase hum in some cases. my two cents.
How much capacity do I really need?
I have a class A OTL amp non-PP, 200-220V B+ that maxes the triodes for both channels at 540mA so rounded up to 600mA.
Vripple = Iload / 2*50*C
If I target 1V p-p ripple this givens 6000uF in reserve capacitance.
Next in the chain the maida/Christian LT3080 and to finalise a 11Hz RC filter with 140uF with 20ohm before it goes to each of the channels. This almost takes me to around 1mV on LTSpice.
A precharge works but how much do you really need? Would 5Vp-p be ok for regulator input?
I have a class A OTL amp non-PP, 200-220V B+ that maxes the triodes for both channels at 540mA so rounded up to 600mA.
Vripple = Iload / 2*50*C
If I target 1V p-p ripple this givens 6000uF in reserve capacitance.
Next in the chain the maida/Christian LT3080 and to finalise a 11Hz RC filter with 140uF with 20ohm before it goes to each of the channels. This almost takes me to around 1mV on LTSpice.
A precharge works but how much do you really need? Would 5Vp-p be ok for regulator input?
Are you sure it doesn't have a choke? Old consoles regularly used field coil speakers and the field coil was the power supply choke.
NickKUK is bumping a VERY old thread. 18 years ago. NickKUK is not even talking about a console.