Hi
piero7 please tell us more about the amp , the sound the speaker that you use
For me the most important thing is the sound not the power. Most of the time we use an amplifier at 2w or 3w when we are listening music. I found something interesting here using 6c33c 15W SE Tube Power Amp and Power Supply and here www.borbelyaudio.com/adobe/15wse.pdf
.
Regards
piero7 please tell us more about the amp , the sound the speaker that you use
For me the most important thing is the sound not the power. Most of the time we use an amplifier at 2w or 3w when we are listening music. I found something interesting here using 6c33c 15W SE Tube Power Amp and Power Supply and here www.borbelyaudio.com/adobe/15wse.pdf
.
Regards
Yes I´d like to hear more as well. Does it sound SETísh or less twangyPP. how does the 6c33c fare in these conditions, with positive grid (class A2)?
I see that high tension is up to 600V, so this is probably not the amp for me. My ideal would be something that drives a 4 Ohm speaker with 10-20W with sub 400V
I see that high tension is up to 600V, so this is probably not the amp for me. My ideal would be something that drives a 4 Ohm speaker with 10-20W with sub 400V
I used it with Sonus Faber Minima Amator, not the best due low efficency, very good sound. Warm sound with the Sovtek tubes. Much better with old Telefunken/ITT (ECC83&EL34). I plan to rebuild it with the new E813CC by blackburn
trondareo, my configuration was this SE driving the Minima Amator (4ohm) directly and a selfmade pushpull sub (cutted with an electronic crossover at 60/80hz) drives by a Pioneer M90.
trondareo, my configuration was this SE driving the Minima Amator (4ohm) directly and a selfmade pushpull sub (cutted with an electronic crossover at 60/80hz) drives by a Pioneer M90.
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Right now I´m running a single ended triode with FU13s (813). I am very happy with the sound in every way. But I want the challenge of building an amp and I want to reduce the threat to my family and the neighbors kids. The FU 13 is running on 900V dc
If you are looking for a safe amp then any "classical" one - with exposed tubes - is potentially dangerous no matter what anode voltage you are using. 300V is dangerous as well.....
The only way is to build it in a closed chassis, like a SS amp!
Like this:
http://www.webalice.it/jlc891/fotopraseto2.htm
Yes, there is obviously danger involved in any tension high enough to use our bodies as a short to ground. (in principal, all voltages). However reducing voltage by half or two thirds does reduce risk of arching. Loosing the anode cap on FU13´s reduces risk of contact with HT. And with good design one might look at the tubes, cool them and keep them behind glass or bars at the same time. This whole hobby of ours includes risk, I drive a motor cycle and go sailing as well, its risky, but fun!
Of course there is a small DC offset across the speaker. The loop defined by rdf in post #45 is clear and obvious. To deny it does not stop it being a fact.
No, I am not denying anything. Maybe you should look carefully at the whole circuit.......
The picture you show is just the grounding.
You are missing the primary of the OPT and the decoupling cap. It is a para-feed. This why they are not in that scheme!!
When you put them there can be no dc loop into the oputput transformer once all the regulations are ok.
The actual starting configuration of the output is figure a:
http://www.audiodesignguide.com/ba/msb_output.jpg.
When you buy the kit you have all the necessary info. It's not improvised chinese stuff!
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and more....Aloia is not a diy'er! He is a professional. He produces amps in any technology since 1980: valve, hybrid and solid state. His non-switching class-A solid state design is one of the best around. You can buy the output modules as well....
He is the only one who uses choke input supplies in his solid state amps! I have not seen this solution in any commercial SS amp until now
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On the contrary, it is you Mr. 45 who needs to look again. The parallel feed part is the primary winding of the transformer. The secondary winding of the transformer is in SERIES with the cathode and the cathode resistor. The cathode resistor forms a voltage divider with the parallel combination of the secondary winding and the speaker impedance. Therefrore a dc voltage is presented at the junction of the voltage divider.
The circuit diagram shows 1.6V at the cathode therfore by action of the voltage divider there will be approximately 30mV at the junction of the divider, i.e. 30mV across the loudspeaker. It may not cause a significant problem, but it exists as a FACT.
Gordy that connection is the second stage only. First you must start with the classical connection (figure a) without loop feedback.
If both ends of the opt have the same potential there will be zero DC current. This issue is an old one and was the object of a letter in an Italian review. Obviously Aloia is not stupid and does not reveal the details. Otherwise he would not sell so many kits!
There is a number of operations you have to go through before going to that connection. Buy the kit if you want to know how to do it.
If you look at the complete schematics maybe it is more clear (you have to consider the DC feedback, too):
http://www.bonavolta.ch/hobby/en/audio/6c33c_3.htm
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The circuit diagram shows 1.6V at the cathode. I am pretty sure in the article it is stated that all those numbers are referred to a current that is precisely 160 mA. 160 mA x 10 ohm = 1.6V! So the voltage drop across the opt is zero....
The opt has no gap. 30 mV across the secondary (that is in parallel with the speaker) would mean saturation at any output level.....
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Please understand that the (conventional) current flow MUST return to ground. The 160mA flows down through the resistance of the 10R resistor and then down through the resistance created by the parallel combination of the transformer secondary and the speaker impedance. It is the only available low impedance path. The electrons MUST follow this path!
The current flow through the parallel combination of the transformer secondary and the speaker impedance MUST create a voltage drop.
Why can you not recognise this? Why can you not admit that there is a small DC offset across the loudspeaker? Do have a psychological need to defend the designer?
To others reading... there will be a low DC offset across the speaker if you use this design. It may not be a problem for you, just make sure that your transformer is rated for a DC current in the secondary.
The fact is that amplifier is NOT conventional!
I am not defending him, just reporting some facts. He does not need my advise.
The point is: that connection is only with DC loop feedback and when both ends of the secondary are at same potential (of the ground) there will be no offset. In principle there is no offset, in practice I cannot tell because I just read the article and listened to the amp and it was dead silent when there was no music. The result depends very much on the correct implementation; for sure it is much less than 30 mV, maybe 3 mV maybe zero! I don't know.
For sure this issue is inexistent among those who bought the kit.....
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45, There IS around 30mV across the speaker. Work it out its simple Ohms Law. If you dont believe it, measure it. IT IS THERE.
30mV is hardly going to take the transfomer anywhere near saturation though and I dought if it would cause a problem with most speakers. Maybe a bit of a click at turn on if that.
30mV is hardly going to take the transfomer anywhere near saturation though and I dought if it would cause a problem with most speakers. Maybe a bit of a click at turn on if that.
Yes I know the law and it also states that if the two ends of secondary have the same potential (i.e. zero offset) there is no current through. Have you considered the full loop including the feedback network, currents, nodes etc. in your calculation?
The author states that the exact current through the 10 ohm resistor in that schematics is precisely 160 mA. The ground is at 0 V as you can read on the cathode of the EL34. So the offset is zero.
Also many people don't fully understand how that amplifier is able to give 30 W RMS (THD 5%) before clipping with an anode dissipation well below 60 W, yet!
If you don't believe you can write to him. He is very friendly.
email: bartolomeo.aloia@tiscalinet.it or aloiabartolomeo@tin.it
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