Ok I set up the voltage multiplier, its a 5 stage. 24vac in and 180vdc out. I also have a tap at 63v to run my 50c5's heater , which I have a voltage dropping resistor. I found If I run a 12xxx tube in series with it the voltages even out perfectly.
Its actually a bit quieter than before with just a bridge rectifier, but that may be due to my 680 uf filter cap too.
I dont think the output is very clean, its clean enough with a big cap like that but Id like to be able to drop the value of the cap.
I found a circuit from headwize for a high voltage regulator using a mosfet. Will this circuit work for me whtout any changes? Its a regulator for 350v, I only need it to regulate 180v.
Its actually a bit quieter than before with just a bridge rectifier, but that may be due to my 680 uf filter cap too.
I dont think the output is very clean, its clean enough with a big cap like that but Id like to be able to drop the value of the cap.
I found a circuit from headwize for a high voltage regulator using a mosfet. Will this circuit work for me whtout any changes? Its a regulator for 350v, I only need it to regulate 180v.
" Is there any real difference between the 50c5 and the 25/17/12c5's? (besides heater current)"
Spec sheet says no, however, rumour has it that the lower voltage versions of the 50C5 don't sound as good. May have something to do with different cathode sleeves? This might be another case of try and see for yourself.
Spec sheet says no, however, rumour has it that the lower voltage versions of the 50C5 don't sound as good. May have something to do with different cathode sleeves? This might be another case of try and see for yourself.
You're thinking of the 35C5, which is a similar but slightly lower powered version of the 50C5. 1.5W vs 2.3W at 10%THD (though you'd never listen to them at that level!). There's also the 11C5, which is the same as the 35C5 except heater voltage/current ratings. These do have a different cathode sleeve.
The 12/17/25/50C5 and the 6CU5 are all identical except for the heater and should work the same in a circuit.
how come I still have a buzz that I cant get rid of in just the power amp? my filter cap is 680 uf.. I even tried a 680uf on the heaters which helped a little bit, but doesnt get rid of it totally. If I reduce screen voltage to around 90v It goes away for the most part, but its still there a little. Is there any way to fix this?
Ok I have revised my schematic. I decided to go with a different tube just for the heck of it, the 6cw5/EL86 appealed to me because of low plate voltage with slightly higher output at less distortion. Here is my schematic, tell me what you think and how I could improve it 
An externally hosted image should be here but it was not working when we last tested it.
Why does it have two volume controls?
Looks like you could remove one gain stage, or replace it with a common plate driver. Might also consider some NFB, and some decent iron for the output xfmr. Also, watch out for power xfmr core saturation. The W-C is half wave, and that means DC through the secondary.
Looks like you could remove one gain stage, or replace it with a common plate driver. Might also consider some NFB, and some decent iron for the output xfmr. Also, watch out for power xfmr core saturation. The W-C is half wave, and that means DC through the secondary.
because its a guitar amp. Pre-gain and post gain so I can dial in distortion!
I took that off a silverface preamp section.
I was wondering about NFB last night, how would I set it up on this? This is a guitar amp and I really dont know if they use any nfb or not, but I wouldnt think so. All I have right now for the OPT is a cheap little thing from a 60's table top radio, although it looks like a 3 watt, which is ok for the 50c5 Im using but I think it saturates pretty easily, as you can really crank high end out of it untill the tube distorts but the bass distorts real easily. Also you can hear any high end like symbols and stuff coming from the transformer.... Am thinking about getting a small 5 watt transformer instead.
I was also thinking about a full-wave WC setup.. Do you think 100uf is enough for the charging caps in it or should I go bigger? All I have right now for prototyping is 4 330uf 200v caps scavenged from an ATX psu, and I would need 6 or more for full wave. They seem to work just fine ( I finally got almost all of the buzz out of my amp now) I did however find that 47uf was too small for the WC and it wouldnt charge enough to get to full voltage.
The reason I chose the WC multiplier is because of size- I designed this amp to be portable for guitar ( I want it to sit on top of my peavy so I can just disconnect the speaker and run it off of this amp at a moments notice)
So for the size I want, I need to keep all transformers small. The power transformer will be a 24vac 2 amp wall wart. Heres some mockup pics for grins
gotta love those sturdy little tins! Im also going to order some of these for it, I think the gold rings will look pretty nice on it: http://www.tubedepot.com/sk-9ping.html
I took that off a silverface preamp section.
I was wondering about NFB last night, how would I set it up on this? This is a guitar amp and I really dont know if they use any nfb or not, but I wouldnt think so. All I have right now for the OPT is a cheap little thing from a 60's table top radio, although it looks like a 3 watt, which is ok for the 50c5 Im using but I think it saturates pretty easily, as you can really crank high end out of it untill the tube distorts but the bass distorts real easily. Also you can hear any high end like symbols and stuff coming from the transformer.... Am thinking about getting a small 5 watt transformer instead.
I was also thinking about a full-wave WC setup.. Do you think 100uf is enough for the charging caps in it or should I go bigger? All I have right now for prototyping is 4 330uf 200v caps scavenged from an ATX psu, and I would need 6 or more for full wave. They seem to work just fine ( I finally got almost all of the buzz out of my amp now) I did however find that 47uf was too small for the WC and it wouldnt charge enough to get to full voltage.
The reason I chose the WC multiplier is because of size- I designed this amp to be portable for guitar ( I want it to sit on top of my peavy so I can just disconnect the speaker and run it off of this amp at a moments notice)
So for the size I want, I need to keep all transformers small. The power transformer will be a 24vac 2 amp wall wart. Heres some mockup pics for grins
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
gotta love those sturdy little tins! Im also going to order some of these for it, I think the gold rings will look pretty nice on it: http://www.tubedepot.com/sk-9ping.html
"because its a guitar amp. Pre-gain and post gain so I can dial in distortion!"
OIC
"I was wondering about NFB last night, how would I set it up on this? This is a guitar amp and I really dont know if they use any nfb or not, but I wouldnt think so."
With that circuit, you can't use NFB (unless it's strictly local to the final). Probably best to not include it.
For a guitar amp, isn't core saturation part of what contributes to the overall sound? Not really sure how much better a five watt OPT will be here.
The W-C operates by charging the capacitors in parallel, and discharging them in series. With a six stage W-C and 100uF capacitors, you really have 16.67uF for ripple filtration at the line frequency. And, yeah, the 47uF units are inadequate. The 330uF units would give an effective 55uF. That may, or may not, be enough. Is the hum tolerable?
OIC
"I was wondering about NFB last night, how would I set it up on this? This is a guitar amp and I really dont know if they use any nfb or not, but I wouldnt think so."
With that circuit, you can't use NFB (unless it's strictly local to the final). Probably best to not include it.
For a guitar amp, isn't core saturation part of what contributes to the overall sound? Not really sure how much better a five watt OPT will be here.
The W-C operates by charging the capacitors in parallel, and discharging them in series. With a six stage W-C and 100uF capacitors, you really have 16.67uF for ripple filtration at the line frequency. And, yeah, the 47uF units are inadequate. The 330uF units would give an effective 55uF. That may, or may not, be enough. Is the hum tolerable?
OH thanks for pointing that last part out, I forgot about series capacitance! 
Actually, I have a 680 uf filter cap between the two rails, and you cant really even tell its on untill you put your ear next to it. I'm sure with the buzz of the preamp you wont be able to tell anyways since its for guitar and a little bit of thats allowed.
What would my capacitance be if I built it as a full wave?
Well.... Im sure glad I did the NFB right for my 50c5... I kinda guessed at it and only looked it up now, and I did it right. I ran the secondary through a 100k pot ( so I could adjust it) and into the input of the tube. Ran the other side of the secondary to ground. It was louder and clearer and sounded much better, well for music anyways, it doesnt make much of a difference for guitar. RIght now I'm just running my preamp out from my peavey into the 50c5 amp and then into the peavey's speaker. Its very loud for only a watt and a half!!
I also noticed that with no bias capacitor it sounds much clearer, although with not as much gain. It seems theres a lot more bass to when I increase the size of the cap, but that bass only comes out very distorted at high volumes, at lower volumes its perfect. Since this is a guitar amp I think I'll just play with that since I dont need much bass below 80hz or so.
Im not sure about the opt, Like I said I wanna keep it small. Do you think the one I have in the pic will suffice for the EL86?
Actually, I have a 680 uf filter cap between the two rails, and you cant really even tell its on untill you put your ear next to it. I'm sure with the buzz of the preamp you wont be able to tell anyways since its for guitar and a little bit of thats allowed.
What would my capacitance be if I built it as a full wave?
Well.... Im sure glad I did the NFB right for my 50c5... I kinda guessed at it and only looked it up now, and I did it right. I ran the secondary through a 100k pot ( so I could adjust it) and into the input of the tube. Ran the other side of the secondary to ground. It was louder and clearer and sounded much better, well for music anyways, it doesnt make much of a difference for guitar. RIght now I'm just running my preamp out from my peavey into the 50c5 amp and then into the peavey's speaker. Its very loud for only a watt and a half!!
I also noticed that with no bias capacitor it sounds much clearer, although with not as much gain. It seems theres a lot more bass to when I increase the size of the cap, but that bass only comes out very distorted at high volumes, at lower volumes its perfect. Since this is a guitar amp I think I'll just play with that since I dont need much bass below 80hz or so.
Im not sure about the opt, Like I said I wanna keep it small. Do you think the one I have in the pic will suffice for the EL86?
Looks good so far as the impedance is concerned, however, the EL86 can output almost twice the power that a 50C5 can do. If you really crank it up, you'll exceed the power rating of that xfmr, and a five watter would be best. Not sure that you can get one that'll fit on the proposed chassis. May just have to be careful not to exceed the ratings too much.
"What would my capacitance be if I built it as a full wave?"
That would stay the same. The main reason to go with a full wave W-C is to eliminate the DC magnetization in the core. Of course, each half of the W-C would be supplying current, so that the demand on the filter capacitors wouldn't be as great. It would be the equivalent of doubling the capacitance of a half wave W-C.
http://cgi.ebay.com/DIY-Tube-Amp-NO...376506796QQcategoryZ43375QQrdZ1QQcmdZViewItem
that might work for me as far as size.
Im glad to hear that about the full wave wc, means I can keep the caps smaller right?
About regulation/noise filtration.. Will it be any better than a half wave? I don't particularley want to use a huge 680uf cap between the rails, I would like to go smaller if possible.
Do I really need NFB with a guitar amp? I gues I can always play around with it, I'm modding a friend's peavey classic 30 and I noticed in the shcem that it uses nfb. I played through one at a music store and it sounded VERY nice...
I guess my biggest concern is the power supply on this thing.. I know the wc will work I just need to figure out how to properly regulate it and filter noise and hum.
that might work for me as far as size.
Im glad to hear that about the full wave wc, means I can keep the caps smaller right?
About regulation/noise filtration.. Will it be any better than a half wave? I don't particularley want to use a huge 680uf cap between the rails, I would like to go smaller if possible.
Do I really need NFB with a guitar amp? I gues I can always play around with it, I'm modding a friend's peavey classic 30 and I noticed in the shcem that it uses nfb. I played through one at a music store and it sounded VERY nice...
I guess my biggest concern is the power supply on this thing.. I know the wc will work I just need to figure out how to properly regulate it and filter noise and hum.
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