Sometimes the obvious things are the easiest to overlook. Yes they are 12AT7's and yes, I have added this to my growing list of OOPSes.
The Simple P-P may be a few bucks cheaper since P-P OPT's tend to cost less than an equivalent SE OPT. I will offer another thought. If you can't decide, consider your choices in music.
Do you long for the warm sound and lush midrange of an SE amp, listen to simple music, vocals (especially female) and prefer an accurate soundstage over in your face transients? If so the Simple SE is your choice.
Do you crank Metallica to eleven? Is your Floyd Pink? Do you favor dynamic music over an exact soundstage? Do you like serious bass. Then go for the Simple P-P.
In reality these are the extremes, and the differences between these two amps depend more on the choice of OPT's than abything else, but I have one of each of my amps available by flipping two switches. I listen to the Tubelab SE when I want perfect detail at relatively low volume (only 2 WPC through 87db speakers). The Simple SE was used for everything else until I got the Simple P-P hooked up. The Simple P-P is now used for rock, metal, techno, and most loud dynamic music, while the Simple SE still gets used for music where one or two instruments or vocals are dominant (especially strings, horns, and female vocals).
Not sure how to join in here, I received a PCB from George (thank you!) and have been looking at transformers for 240V mains and an EL84 build. I came up with a list, and only one tranny is exclusively 240V, the Edcor.
Edcor XPWR066, 240Vrms primary, 50/60Hz, 300-0-300 @ 200mA, 6.3V@4A, 5V@3A, USD$63.36 from Edcor.
Hammond 372HX, universal primary, 300-0-300 @ 230mA, 6.3V@6A, 5V@3A, USD$120 Angela.com.
Magnetic Components, 2 x 120V primary, 355-305-0-305-355 @ 200mA (plus a bias tap), 6.3V CT@5A, 5V@3A. Triode Elec P/N 40-18029 for Fender Twin guitar amp, USD$80.
Hammond 372FX, universal primary, 300-0-300 @ 173mA, 6.3V@5A, 5V@3A, USD$105 AES, USD$83 Triode Elec.
Antek 2T300, 2 x 115V primary, 2 x 300V @ 300mA, 2 x 6.3V@4A, USD$35 from Antek.
The Antek is by far the cheapest, but it will require either a dropping resistor for the 5AR4 from one of the 6.3V windings, or an extra handwound winding for 5AR4. The Edcor looks good as a safe bet. Any suggestions or comments appreciated.
I have never owned a valve amp with a tube rectifier, is this close to ball park figures as far as B+ is concerned? 300Vrms rectified gives approx 380V DC under load, minus 15V across the 5AR4 tube rectifier gives approx 365V, minus around 27V across R1 (150 ohms) leaves 338V, minus 10V to 11V from the output tube cathodes to ground leaves around 328V across the tube itself. Is this a close approximation or am I way off?
I spent most of today working out what parts I can get from Farnell Australia (free shipping within Oz), I made up an xls spreadsheet if any Aussies are interested, and I used AES for the JJ 5AR4, the sockets and the coupling caps. Still thinking about power and OPT's.
Ian.
Edcor XPWR066, 240Vrms primary, 50/60Hz, 300-0-300 @ 200mA, 6.3V@4A, 5V@3A, USD$63.36 from Edcor.
Hammond 372HX, universal primary, 300-0-300 @ 230mA, 6.3V@6A, 5V@3A, USD$120 Angela.com.
Magnetic Components, 2 x 120V primary, 355-305-0-305-355 @ 200mA (plus a bias tap), 6.3V CT@5A, 5V@3A. Triode Elec P/N 40-18029 for Fender Twin guitar amp, USD$80.
Hammond 372FX, universal primary, 300-0-300 @ 173mA, 6.3V@5A, 5V@3A, USD$105 AES, USD$83 Triode Elec.
Antek 2T300, 2 x 115V primary, 2 x 300V @ 300mA, 2 x 6.3V@4A, USD$35 from Antek.
The Antek is by far the cheapest, but it will require either a dropping resistor for the 5AR4 from one of the 6.3V windings, or an extra handwound winding for 5AR4. The Edcor looks good as a safe bet. Any suggestions or comments appreciated.
I have never owned a valve amp with a tube rectifier, is this close to ball park figures as far as B+ is concerned? 300Vrms rectified gives approx 380V DC under load, minus 15V across the 5AR4 tube rectifier gives approx 365V, minus around 27V across R1 (150 ohms) leaves 338V, minus 10V to 11V from the output tube cathodes to ground leaves around 328V across the tube itself. Is this a close approximation or am I way off?
I spent most of today working out what parts I can get from Farnell Australia (free shipping within Oz), I made up an xls spreadsheet if any Aussies are interested, and I used AES for the JJ 5AR4, the sockets and the coupling caps. Still thinking about power and OPT's.
Ian.
You can't go wrong with the Edcor. I have nothing but positive things to say about their power transformers. If you are considering their OPTs, then your could combine shipment.
I'm using a Hammond 373CZ on my breadboard and it is way too hot. With the variac adjusted so that I get 600 VCT out of it, I get 350VDC of B+ and about 340V across the tube. This is too much for the Sovtek EL84Ms I have.
I'm using a Hammond 373CZ on my breadboard and it is way too hot. With the variac adjusted so that I get 600 VCT out of it, I get 350VDC of B+ and about 340V across the tube. This is too much for the Sovtek EL84Ms I have.
I might go for a bit less B+ to run cheap Russian 6P14P. Hi Ian,
You might want to look at getting the trannies made locally, postage from the US can be horrendous. I've used SES (below) before, though for industrial iron, not audio, and they were quite good. They can do audio trannies and might be worth talking to, their rates are reasonable. There are probably others.
No affiliation, etc.
Linky
You might want to look at getting the trannies made locally, postage from the US can be horrendous. I've used SES (below) before, though for industrial iron, not audio, and they were quite good. They can do audio trannies and might be worth talking to, their rates are reasonable. There are probably others.
No affiliation, etc.
Linky
Who'd you go with?
I hope you noticed my post in the other thread about the B+. I made an error wiring the board and so my estimates above were off. Bottom line is that 650VAC yields 325V B+, which puts about 310V across the tubes.
http://www.diyaudio.com/forums/tubelab/162387-simple-p-p-beta-builders-thread-4.html#post2114780
I hope you noticed my post in the other thread about the B+. I made an error wiring the board and so my estimates above were off. Bottom line is that 650VAC yields 325V B+, which puts about 310V across the tubes.
http://www.diyaudio.com/forums/tubelab/162387-simple-p-p-beta-builders-thread-4.html#post2114780
Finally got it built. The heater voltages are fine (I rewound both heater windings, 16 turns for 5V, 21 turns for 6.3V). B+ is around 320/325 with the Antek 2T-300 and mains voltage around 248V. Worked straight up, cathode voltages around 11.20 to 11.25V (matched quad JJEL84 from Jim McShane). Using NOS RFT East German 12AT7. Those voltages were measured during the first few minutes, then I had to connect it to some speakers and listen... Running pentode mode, no FB connected yet, been listening a while, sounds very good already. Bass is strong, detail is very good, stereo imaging is very good, no noise/hum, this amp is going to turn out real nice, I'm very happy. 1hr and 15 mins gone by, definitely the best amp in this little house.
Wife is happy with aesthetics and extremely happy (quote: "in love") with the sound quality, and we know the sound quality can only get better from here. The build is a bit "cottage industry" but I'm a newb at woodwork, scavenged the wood from the garbage bin at work, don't know what it is.
http://i198.photobucket.com/albums/aa160/birdy81260/SimplePP2.jpg
http://i198.photobucket.com/albums/aa160/birdy81260/SimplePP1-1.jpg
Thanks George,
Ian.
Wife is happy with aesthetics and extremely happy (quote: "in love") with the sound quality, and we know the sound quality can only get better from here. The build is a bit "cottage industry" but I'm a newb at woodwork, scavenged the wood from the garbage bin at work, don't know what it is.
http://i198.photobucket.com/albums/aa160/birdy81260/SimplePP2.jpg
http://i198.photobucket.com/albums/aa160/birdy81260/SimplePP1-1.jpg
Thanks George,
Ian.
No pics of rewinding, it took quite a few hours, unwinding and rewinding the clear tape. The low voltage windings on this 2T-300 tranny are the outermost windings, in fact one of the "6.3V" windings was originally a 12.6V CT so I removed the other side of the CT. The 6.3V windings were originally 22 turns so I went 21 turns due to 248V mains here. The 16 turns for the rectifier was checked by soldering the output wires to a socket with rectifier tube fitted and got 5.0V. With the amp powered up and tranny loaded I got 4.9 something, close enough. You need lots of patience and time to rewind it, and strong fingers to keep the wire and tape windings tight. I think winding over the top like George showed would be fine but just spread the windings evenly around the core so you can mount it without putting uneven pressure on the wiring. I'm no expert but I think enamelled copper wire would be the go, and wrap some sort of insulating tape over that.
Just a quick question regarding cathode to heater voltage limits for the 12AT7, stated as 90V in the datasheets I have read. The voltage on the cathode of both phase splitters measures 106V and 103VDC under quiescent conditions. The heater cct is elevated to +20V DC by the 150K/10K divider R4/R3. Is this a bit close for comfort?
For info, in the above post, the enamelled wire diameter that Antek used for the heater windings in that tranny was measured at 0.049" (1.25mm).
Ian.
For info, in the above post, the enamelled wire diameter that Antek used for the heater windings in that tranny was measured at 0.049" (1.25mm).
Ian.
The amp sounds excellent, it is clear to me that the PCB design and layout is very good. I guess that comes from George's lifetime experience building tube amps. I had no idea that a tube amp without sand could sound this good. It sounds good on all types of music. I fitted the NFB resistors, that cleaned it up nicely (running with pentode mode). No NFB caps are fitted yet, I need to buy a selection to test. I guess ceramics are not preferred, what type is to be used? I'm guessing a range from 47pF to 470pF would do the job? Maybe I should scope it first and see what the square wave looks like. I think George said to use a 10kHz square wave, but at what power, 1W?
The Antek AN-2T300 power tranny is getting hot, too hot to hold fingers or hand on it for more than a second and a half after about 4 hours, but it seems to stabilize at this temp. I read recently that a tranny that is too big for the application can run hot. In this case it is around twice the required capacity, but when making buying decisions, for some reason I decided the AN-1T300 would be barely powerful enough. I drilled upper and lower holes to allow air to vent through the middle of the tranny and it seems to have made only a small difference. I ran it 8 hours straight yesterday and there were no hot smells, and the tape wrap around the tranny is not discolored. Maybe its nothing to worry about.
The Antek AN-2T300 power tranny is getting hot, too hot to hold fingers or hand on it for more than a second and a half after about 4 hours, but it seems to stabilize at this temp. I read recently that a tranny that is too big for the application can run hot. In this case it is around twice the required capacity, but when making buying decisions, for some reason I decided the AN-1T300 would be barely powerful enough. I drilled upper and lower holes to allow air to vent through the middle of the tranny and it seems to have made only a small difference. I ran it 8 hours straight yesterday and there were no hot smells, and the tape wrap around the tranny is not discolored. Maybe its nothing to worry about.