Filament supply: no schematic, just a bridge rect, 100nF, 4700uF, 4R7 and 12AX7 filaments, wired in parallel with the series of the ECC88 heaters (to get 12.6V).
Sorry... no photos yet
I will do the best I can in finding some digital camera to make some shots... it has a black "C shaped" chassis with wooden sides.
Now it's playing
Sorry... no photos yet
I will do the best I can in finding some digital camera to make some shots... it has a black "C shaped" chassis with wooden sides.Now it's playing
Hello Rocky,
I'm very grateful to all DIYaudio members that helped me along this journey
That line stage has its roots in the requirements I had when designing it, it can provide all my goals in a very good way.
It had to be:
- some gain, max 5 not more
- high input impedance
- low output impedance (it has to drive power amps directly)
- low distortion, low coloration
- only one tube, and better if ECC88.
You'll see that with those requirements it cannot be much far than that, maybe a step up trafo and a CCS-loaded cathode follower would do, but I'm cheap I don't have money for trannies
So I developed it thanks also to TubeCAD: that circuit is listed under "Plate Follower" circuits.
Thank you for the interest!
I'm very grateful to all DIYaudio members that helped me along this journey
That line stage has its roots in the requirements I had when designing it, it can provide all my goals in a very good way.
It had to be:
- some gain, max 5 not more
- high input impedance
- low output impedance (it has to drive power amps directly)
- low distortion, low coloration
- only one tube, and better if ECC88.
You'll see that with those requirements it cannot be much far than that
, maybe a step up trafo and a CCS-loaded cathode follower would do, but I'm cheap I don't have money for trannies So I developed it thanks also to TubeCAD: that circuit is listed under "Plate Follower" circuits.
Thank you for the interest!
Here it is
more on my site http://giaime.altervista.org/mypreamp.html
An externally hosted image should be here but it was not working when we last tested it.
more on my site http://giaime.altervista.org/mypreamp.html
You know what?
Those photos were taken yesterday night at a friend's house, we were willing to try my preamp with his wonderful audio chain.
As soon as I flipped on the power switch, smoke come out of the power tranny
This morning I replaced the PT, it was a poorly done solder joint that shorted the B+ on the chassis
Those photos were taken yesterday night at a friend's house, we were willing to try my preamp with his wonderful audio chain.
As soon as I flipped on the power switch, smoke come out of the power tranny
This morning I replaced the PT, it was a poorly done solder joint that shorted the B+ on the chassis
Giaime said:
As soon as I flipped on the power switch, smoke come out of the power tranny
This morning I replaced the PT, it was a poorly done solder joint that shorted the B+ on the chassis
Have you heard of something call'd fuse?
But serious, thats a very nice pre!
Still waiting for my funds to make mine. My SE amp with 6l6 ended up with a much simpler powersupply becouse I ran out of money.
Hi Giaime,
Ah, you are also in the student group... Well, at least your a little higer up in the system. Its a couple years left before I'm going to the univeristy.
Forgot to mention a thing that I also do to protect my circuit and transformers. In preamplifiers and other equpitment that don't use much power or have large resistans in the powertransfomer, I usally put a small value resistor in series with the ht winding, if its center tap'd, one from each side from the tap, if not, one on each side of the winding. The value usally is from 4.7ohm-10ohm. low value for more power full transformer, 1watt metall reistors are fine. That trick saved me once. Only the reistors burn'd. But, of course, you need to solder clean and solid before the resistors...
Oh, sorry, that was mean, couldn't resist. Please forgive me.
Have a nice day!
Best regards,
Magnus Kofoed
Ps, 1 amp is way to much! I have a 250ma fuse in my power amplifer! I live were it is 230v. Double it if your living in a country with 110v.
Ah, you are also in the student group... Well, at least your a little higer up in the system. Its a couple years left before I'm going to the univeristy.
Forgot to mention a thing that I also do to protect my circuit and transformers. In preamplifiers and other equpitment that don't use much power or have large resistans in the powertransfomer, I usally put a small value resistor in series with the ht winding, if its center tap'd, one from each side from the tap, if not, one on each side of the winding. The value usally is from 4.7ohm-10ohm. low value for more power full transformer, 1watt metall reistors are fine. That trick saved me once. Only the reistors burn'd. But, of course, you need to solder clean and solid before the resistors...
Oh, sorry, that was mean, couldn't resist. Please forgive me.
Have a nice day!
Best regards,
Magnus Kofoed
Ps, 1 amp is way to much! I have a 250ma fuse in my power amplifer! I live were it is 230v. Double it if your living in a country with 110v.
Thank you very much Magnus Kofoed for you reply.
I do live in a 220V country, and I must admit that 250mA fuse blows, but I'm using fast ones. I'll get some retarded ones and try. You're right, obviously. On more "expensive" project I'll fuse everything on the back panel (both mains and HV, and if it's an amp I'll fuse EACH output tube).
Money is not too much... I'm now listening to a 1.6W triode connected EL84SE. Sound is good, but frequency measurements show a not-so-hi-fi response...
I do live in a 220V country, and I must admit that 250mA fuse blows, but I'm using fast ones. I'll get some retarded ones and try. You're right, obviously. On more "expensive" project I'll fuse everything on the back panel (both mains and HV, and if it's an amp I'll fuse EACH output tube).
Money is not too much... I'm now listening to a 1.6W triode connected EL84SE. Sound is good, but frequency measurements show a not-so-hi-fi response...
Attachments
Hi,
Haha! I must admit that your freq. response once and for all says that it is the ear that make the final desition. I always trust my ears.
My 6L6 amp has around 1-2w ouput, it is becouse of the opt. I wound them my self. But they are very good. Freq response was almost flat from about 35-23khz. Very little ringing too. But they are very, very ugly. I have no idea how much dist. my amp has, but for me it sounds good.
If you like I can always send you a pic and schematic.
Yes, that 250ma fuse must be slo-blo if it has solidstate rectifier. In my 6l6 that has a toob rectifier I use 250ma fast.
Maybe we should make our one: "We demand a free world!" club?
Best regards,
Magnus
Haha! I must admit that your freq. response once and for all says that it is the ear that make the final desition. I always trust my ears.
My 6L6 amp has around 1-2w ouput, it is becouse of the opt. I wound them my self.
But they are very good. Freq response was almost flat from about 35-23khz. Very little ringing too. But they are very, very ugly. I have no idea how much dist. my amp has, but for me it sounds good. If you like I can always send you a pic and schematic.
Yes, that 250ma fuse must be slo-blo if it has solidstate rectifier. In my 6l6 that has a toob rectifier I use 250ma fast.
Maybe we should make our one: "We demand a free world!" club?
Best regards,
Magnus
Hello there, sorry for forgotting about this thread.
I've since resolved all humming problems, they were caused by bad grounding.
I've made a page on my site to suggest some possible Plate Follower tube candidates, since I recived some feedback from some people who built the PF as a standalone linestage, with very good results.
Here it is, please feel free to make suggestions!
http://www.giaime.altervista.org/plate_follower.html
I've since resolved all humming problems, they were caused by bad grounding.
I've made a page on my site to suggest some possible Plate Follower tube candidates, since I recived some feedback from some people who built the PF as a standalone linestage, with very good results.
Here it is, please feel free to make suggestions!
http://www.giaime.altervista.org/plate_follower.html
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