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Old 27th August 2013, 05:31 PM   #141
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Quote:
Originally Posted by max29 View Post
If an older tube amp or others on 220vdc you can use a bucking trafo.

Take a 15 or ...vdc trafo f.e. (printer ..scanner.. phone ...loader ..a.s.o..) peel off the black cover and connect in phase opposition in series with the 220vdc

That extra transformer: its primary to the mains and secondary in anti-phase with the primary of the transformer to tube amp
That is what I have done with my SETs, 18v toroidals. And for my friend, a 23v toroidal, as his PS Audio pre transformers buzz, so we are dropping the voltage, even though they should work OK on 240v. I suspect they don't like 50Hz.
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Old 10th October 2013, 07:30 PM   #142
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6L6G power tubes and 5V4 rectifier. I have the same amp with a 6SL7 amplifier tube and a few other changes. It was supposed to come as a kit, but arrived pre-built. I don't think this thing has the nuts to handle EL-34s and 6550s, but the 6L6Gs sound fine to good depending on brand and condition. No balance so you need to have matched tubes. I am running a pair of Straight 8s for center in HT with it right now, but have had it on Altec 416s/Heil AMTs and it did very well for size of OPTs.
I'd leave the feedback in there, it ain't that good, besides unless you can do a variable feedback that can go to zero, best go as designed, or put a switch in it to go zero or 10 ohms.

Thatch
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Old 12th October 2013, 04:41 PM   #143
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Quote:
Originally Posted by Thatch_Ear View Post
6L6G power tubes and 5V4 rectifier. I have the same amp with a 6SL7 amplifier tube and a few other changes. It was supposed to come as a kit, but arrived pre-built. I don't think this thing has the nuts to handle EL-34s and 6550s, but the 6L6Gs sound fine to good depending on brand and condition. No balance so you need to have matched tubes. I am running a pair of Straight 8s for center in HT with it right now, but have had it on Altec 416s/Heil AMTs and it did very well for size of OPTs.
I'd leave the feedback in there, it ain't that good, besides unless you can do a variable feedback that can go to zero, best go as designed, or put a switch in it to go zero or 10 ohms.

Thatch
6L6 family power tubes is about the upper limit here. The limiting factor with this amp is the power supply. You are at ~300v after the rectifier, and of course the capacitors etc are sized accordingly. SE - 1 output tube per channel no need to have matched tubes and matched tubes don't stay matched after being used .... On the feedback resistor you should be using 10-15K ohms there attached to your output transformer and feeding back to your driver tube. I've tried this amp without feedback and it sounds better with feedback.

Cheers,
Bob
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Old 2nd January 2014, 06:48 PM   #144
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Hi guys, I finished up building the 6p3p kit and I wonder why I mesure 150V ac on my powertubes filaments!? When I mesure the black-black unhooked I have around 7V ac. I have look for bad connections but everything looks ok. Could the PT be bad ?

Any suggestions ?
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Old 2nd January 2014, 07:48 PM   #145
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Solve, sorry, I made a mistake measuring the voltage, voltage are all ok. But I still have a very low volume coming out of the speaker.

any ideas why ?
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Old 30th January 2014, 05:36 PM   #146
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Hi marmot
Did you solve your speaker output problem/issue?
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Old 31st January 2014, 02:46 AM   #147
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Quote:
Originally Posted by Inductor View Post
Hi marmot
Did you solve your speaker output problem/issue?
Hi Inductor, I have not solve the clue and I have start a new thread right here :

http://www.diyaudio.com/forums/tubes...-new-post.html
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Old 2nd February 2014, 07:53 AM   #148
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Default 6p3p bass improvement?

Hi chaps,

Just finished putting my silicon ray 6p3p kit together (after a lot of work learning elementary Chinese and reading this forum, especially Bobrown - thanks Bob) and it works perfectly first time.
Sound is excellent in mids and top but could do with a bit more bass. Do I just need to burn it in?
Anyone any suggestions. Speakers are 30year old Celestions which are usually fine for this.
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Old 3rd February 2014, 02:40 AM   #149
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Hardwork,
Feel free to join us at the multi-way forum where we can check the model driver you are using for woofer and related alignments, this if you feel it's speaker related (plus the size/type of your room).
Have time to detail the complete crossover and multi-way drivers, with pictures if you can (for the components/type of the crossover, plus the model speaker you are working with for complete feedback (if you feel like it). I'm not used with amps but can certainly help, or other members. I will remember U, this if the/your option are acceptable. Have fun.
Note: First check from this thread what you can do (with the amp), then address to new multi-way forum, if needed.
Multi-Way - diyAudio

Last edited by Inductor; 3rd February 2014 at 02:43 AM.
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Old 5th February 2014, 06:24 PM   #150
Pdwhitt is offline Pdwhitt  United States
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Default Finished 6P3p a few months ago

I finished the build of my Siliconray 6p3p tube amp, and it has been a fun experience and the amp sounds great! The stock components that came with the kit all were good quality, and sound good. This was my first project of this size and complexity, and with the schematic diagram, wiring diagram, and help from Bob (bobrown14) of diyaudio.com, the amp worked the very first time I switched it on.

Here are my build notes. Be careful! I know everyone that writes about tube amps says this, but so will I. Be sure to safely discharge capacitors, make sure electrolytic caps are wired the correct direction, triple check your work, and do your initial fire-up in stages.

I used the advice from Chung at skycoral.com/building-low-profile-amplifier/ as a step by step guide. I checked all of the resistors and they were within tolerance. I wanted to add a power on indicator lamp, and move the volume control to the center of the front panel, which required drilling the chassis. Let me tell you, this steel chassis is hard! Make sure you have hardened bits for steel. I wired the lamp to the 6.3 volt heater pins 2 and 7 from the right 6p3p's, and added a rheostat to the front panel to allow dimming of the light.

I ordered an Alps blue velvet volume pot, but unfortunately one of the channels tested bad, so I ended up using a 100k from Radio Shack. I initially wired the pot wrong. Fyi, correct wiring when looking at the rear of the volume pot: left pin is input, center is output, and right is ground. Topped it off with a new volume knob. The RS has a little noise with turning the knob, so I may try another Alps.

Two IN4007 diodes were added to the rectifier as recommended by Bob, 6p3p tube amplifier kit

Capacitors replaced were the FOAI 22uF with Illinois TTAA, LXV 470uF with Panasonic, and the Bennic .33uF filter caps with Cornell Dubilier. But I'm not sure I noticed any difference in sound.

I replaced the preamp tube with a Russian 6n1, but the replacement tube caused a significant hum, so I went back to the Chinese tube which came with the kit, and it works well and is very quiet.

I replaced the power amp tubes with Golden Lion KT66, which sound a little louder and clearer than the original 6n3p Chinese tubes, and the KT66's look impressive!

The biggest change was the 10k feedback resistors from the 8 ohm outputs to pins 3 and 8 of the 6n1 preamp tube. The amp initially sounded dull and lacked high frequency clarity. I changed the value of the .33 uF filter caps but this didn't change the tone. Removing the feedback loop added both volume and clarity, but the sound was too bright. 330k feedback resistors made the amp sound much better. I finally ended up removing the feedback resistors altogether, and instead wired in a rheostat to the front panel, allowing me to dial in just the right amount of feedback resistance. This acts as a poor mans tone control.

Overall impression: This can be a very good first diy tube amp if you study the schematic and wiring diagrams. The stock amp looks awesome, is quiet, sounds good, and with a few simple mods (rectifier diodes, new power tubes, and feedback resistors) is plenty loud enough and sounds great!

PS.... I have used the amp for several months, it has worked flawlessly, it's quiet, and i am still very happy with it.
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