Thanks again for the input Alex and George.
I was in a bit of a panic ordering parts to make sure they arrived at my friends place in time for my visit, so I went ahead yesterday and ordered the parts as suggested by Tubelab as I had described. Ended up going for the smaller iron on the outputs as suggested by Mr Tubelab. At $38 for two it saves quite a lot of money (remember, I have active crossover to solid state driven woofer units). The 200mA power tranny was 400-0-400 volts, and quite a bit more expensive!
Ended up ordering JJ EL34s, 12AT7 and 5AR4. Opinion on the Tubelab (and other sites) site seemed to indicate the JJ EL34s were robust, good sounding and value for money. Went JJ on the other parts too, hope this is OK.
I normally don't ask too many questions, I try to research, study and find out as much as I can without bothering people, but in this instance I was working to a bit of time pressure, so thanks guys. After the panic, I think that much of what I asked Tubelab I eventually found on his site, or links on his site - it just took a bit of looking! For those thinking of building this, you have to look at all of the pages on the tubelab site, many are difficult to find! I found this page useful http://www.tubelab.com/Industrial1.htm lists answers to many of the questions I listed above.
One last question to anyone who can help. On the schematic there is listed an optional auxiliary power supply capacitor that is next to the power supply choke http://www.tubelab.com/SimpleSE_schematic.htm
Tubelab mentions he uses a ASC 100uF 370 VAC motor RUN (not start) cap. In Australia we are not spoiled for choice with a lot of these things, so what should I be looking for as a replacement? Any 100uF cap that is rated at greater than B+ (for instance, I can get this one in Australia http://www.thetubestore.com/ca-jj-100uf-500v.html a JJ 100+100uf 500volt.
Thanks again guys, I am in the middle of university exams at the moment (mature age student!), so cannot spend as much time researching as I would like.
Thanks again for all your assistance,
Chris
I was in a bit of a panic ordering parts to make sure they arrived at my friends place in time for my visit, so I went ahead yesterday and ordered the parts as suggested by Tubelab as I had described. Ended up going for the smaller iron on the outputs as suggested by Mr Tubelab. At $38 for two it saves quite a lot of money (remember, I have active crossover to solid state driven woofer units). The 200mA power tranny was 400-0-400 volts, and quite a bit more expensive!
Ended up ordering JJ EL34s, 12AT7 and 5AR4. Opinion on the Tubelab (and other sites) site seemed to indicate the JJ EL34s were robust, good sounding and value for money. Went JJ on the other parts too, hope this is OK.
I normally don't ask too many questions, I try to research, study and find out as much as I can without bothering people, but in this instance I was working to a bit of time pressure, so thanks guys. After the panic, I think that much of what I asked Tubelab I eventually found on his site, or links on his site - it just took a bit of looking! For those thinking of building this, you have to look at all of the pages on the tubelab site, many are difficult to find! I found this page useful http://www.tubelab.com/Industrial1.htm lists answers to many of the questions I listed above.
One last question to anyone who can help. On the schematic there is listed an optional auxiliary power supply capacitor that is next to the power supply choke http://www.tubelab.com/SimpleSE_schematic.htm
Tubelab mentions he uses a ASC 100uF 370 VAC motor RUN (not start) cap. In Australia we are not spoiled for choice with a lot of these things, so what should I be looking for as a replacement? Any 100uF cap that is rated at greater than B+ (for instance, I can get this one in Australia http://www.thetubestore.com/ca-jj-100uf-500v.html a JJ 100+100uf 500volt.
Thanks again guys, I am in the middle of university exams at the moment (mature age student!), so cannot spend as much time researching as I would like.
Thanks again for all your assistance,
Chris
The 1.41 factor that everyone uses is the theoretical crest of a perfect sine wave. You will NEVER get 1.41 * the RMS value in practice. There are resistive losses in the power transformer and filter choke, voltage drop in the rectifier, and the fact that the rectifier only conducts current for a small fraction of the input cycle. The rest of the time the amp is running off of the stored energy in the filter caps. This is why power supplies generate ripple.
The example quoted above shows 380 volts out of the power supply for 300 volts into it. This is a factor of 1.26, which is realistic. This factor will vary with the current drawn from the supply. Applying the same 1.26 factor to a 375 volt transformer will yield 475 volts.
I have the Industrial Strength Amp playing on my bench currently. It has a 375-0-375 volt power transformer in it. I measure the B+ voltage at 447 with KT88's installed and cranked up to almost 100 mA each. I lose about 25 volts in the drop across the OPT, and another 37 across the cathode resistor. This leaves 385 volts for the tube.
Plugging JJ EL34's into the same amp allows the B+ to rise to 460 volts due to the lower current draw of the EL34's. Here I get 20 volts dropped across the OPT and 32 across the cathode resistor, leaving 408 volts across the tube.
500 Volt capacitors are used in my amps for this reason, and specified in the parts list.
You know that your web site is a mess, when you can't find your own stuff. It has been almost 2 years since I gave it a facelift. Microsoft changed the rules here, so I have to learn how to do web sites using "Expression Web" now. Front Page is no longer supported. I have been working on a new lavout for the web page, but haven't gotten very far.
The supplemental cap has a purpose. It is there to provide additional filtering, AND it provides a low impedance across the whole audio range. I would use a polyproprylene capacitor since these have a low ESR asross the audio band. Look at this one:
Ebay Item number: 170078126766
I understand what it is to be a midle aged student. I got my bachelors degree at 40 years old, and my masters at 48 .
Thanks again for your help Tubelab! I don't know enough yet to start guessing and experimenting, so I have gone with your recommendation and purchased the cap you linked to above.
I sent an email order and paypal payment for your board. Hope you received it ok. No rush for you to send it as I will not be able to start building for about two weeks. Finish mid year exam tomorrow, visiting friends in LA for a week, then have to study for work exam (get tested 4 times a year on theory and application of job skills to keep licence)! It never ends..... I am just in my first year of 6 year part time degree. Will be 47 when I finish if all goes to plan!
Thanks again to you, and all of the other helpful members of this forum.
Chris
I sent an email order and paypal payment for your board. Hope you received it ok. No rush for you to send it as I will not be able to start building for about two weeks. Finish mid year exam tomorrow, visiting friends in LA for a week, then have to study for work exam (get tested 4 times a year on theory and application of job skills to keep licence)! It never ends..... I am just in my first year of 6 year part time degree. Will be 47 when I finish if all goes to plan!
Thanks again to you, and all of the other helpful members of this forum.
Chris
The simpleSE's have been in circulation for only about 6 weeks. I have received ONE email from someone who completed their amp (in one week). The TubelabSE boards have been out there for over a year. I have received several emails detailing the sound quality that comes from these amps, but NO pictures. I have shipped over 50 boards which have been mostly TubelabSE's. Anyone have pictures of your amp? Construction details? A short story to tell? Email them to me, and I will start a web page of users amps.
I have received many requests for better quality schematics than the ones posted on my web site. The high cost of Adobe PDF software has prevented me from making PDF's. Last week I was in a local office supply store, and there were two non Adobe PDF programs for reasonable prices. I have created PDF's of the TubelabSE and SimpleSE schematic. They will be on the web site with the next update.
George,
You said you use the Allied 6K7VG with the KT88:
But then you go on to say to use a transformer at 175mA or more:
On the Allied website, is states 750V@150mA.
http://www.alliedelec.com/Search/ProductDetail.asp?SKU=227-0013&SEARCH=&MPN=6K7VG&DESC=6K7VG&R=227%2D0013&sid=4675CB002B5617F
Is this enough current for the KT88, 5AR4, and 12AT7? This is my first project and looking to save some dough. Maybe to put towards better OPTs.
And by the way, thank you very much for the fast shipment of the boards.
Thanks,
Earl
You said you use the Allied 6K7VG with the KT88:
But then you go on to say to use a transformer at 175mA or more:
On the Allied website, is states 750V@150mA.
http://www.alliedelec.com/Search/ProductDetail.asp?SKU=227-0013&SEARCH=&MPN=6K7VG&DESC=6K7VG&R=227%2D0013&sid=4675CB002B5617F
Is this enough current for the KT88, 5AR4, and 12AT7? This is my first project and looking to save some dough. Maybe to put towards better OPTs.
And by the way, thank you very much for the fast shipment of the boards.
Thanks,
Earl
The Allied 6K7VG transformer is rated at 150mA but it is also rated for 50Hz operation. It will handle 175mA on 60Hz current. Being a Hammond sourced transformer is will get hot (all of the 200 series Hammonds get hot). The Allied unit is the exact same size as the Hammond 274BX which is rated for 175mA on 60 Hz only.
I have one of these in my Industrial amp which is currently set up with Electro Harmonix KT88's at 100 mA each. That makes the poor transformer groan to pump out about 220 mA. I consider this an accelerated stress test for the entire design, which has passed just fine so far (6 months). I also have one of the smaller Allied 5K56VG in a TubelabSE that runs at about 170 mA on a 125 mA transformer. I have been using that one almost daily for over 2 years.
I would have no problem using the Allied transformer in a KT88 amp that was biased in the "normal" 60 to 70 mA range. I believe that it contains the same core as the Hammond 274BX, which I have also used. If I was building an amp for extreme use (continuous use, or a current happy user) I might look for a heavier transformer, but they are hard to find and expensive.
The big Antek toroids found on Ebay also work well for another low cost option, but these do not have a 5 volt winding, so you must use the solid state rectifier. I have used this one successfully. I have run two amplifiers simultaneously off of the SAME transformer and it doesn't even get warm.
http://cgi.ebay.com/720V-CT-360V-40...11199021QQihZ017QQcategoryZ4660QQcmdZViewItem
I have one of these in my Industrial amp which is currently set up with Electro Harmonix KT88's at 100 mA each. That makes the poor transformer groan to pump out about 220 mA. I consider this an accelerated stress test for the entire design, which has passed just fine so far (6 months). I also have one of the smaller Allied 5K56VG in a TubelabSE that runs at about 170 mA on a 125 mA transformer. I have been using that one almost daily for over 2 years.
I would have no problem using the Allied transformer in a KT88 amp that was biased in the "normal" 60 to 70 mA range. I believe that it contains the same core as the Hammond 274BX, which I have also used. If I was building an amp for extreme use (continuous use, or a current happy user) I might look for a heavier transformer, but they are hard to find and expensive.
The big Antek toroids found on Ebay also work well for another low cost option, but these do not have a 5 volt winding, so you must use the solid state rectifier. I have used this one successfully. I have run two amplifiers simultaneously off of the SAME transformer and it doesn't even get warm.
http://cgi.ebay.com/720V-CT-360V-40...11199021QQihZ017QQcategoryZ4660QQcmdZViewItem
Yes you can, the secondary of this transformer will be elevated to the B+ voltage. Most "filament" transformers can handle this OK. I wouldn't use a small transformer that was made for solid state stuff.
Before anyone asks the obvious question about the Antek toroids, " Why can't I just use the second 6.3 volt filament winding with a droping resistor for the rectifier?" I have investigated the Antek toroids and found that both 6.3 volt windings are wound together (bifilar). This leaves only the enamel insulation on the wire itself to insulate the two filament windings from each other. I don't think that I would trust this not to break down over time. A short in this manner would likely cause Heater to Cathode breakdown in all of the tubes. Not a pretty site.
I have also heard that rule, and the transformer in my Lexan amp comes close. After several hours of continuous use, 5 to 10 seconds is about all you can take without using bad language. The transformer in the Industrial amp does not get that hot.
I have found that transformers (especially black ones) will absorb the radiant heat from the output tubes. This is why OPT's get warm. When laying out the chassis for a power amp, keep a couple of inches between the power tubes and the power transformer.
Other transformer possibilities:
I have also used these transformers. They are definitely NOT a low budget solution though. I got mine several years ago when they were under $100. Took forever to get it too. The sales person said that I placed the first real order for one. I used it in a mega powered push pull amp, which I later dismantled. I tried it in the SimpleSE, and it is total overkill, but works great.
http://www.toroid.com/standard_transformers/rectifier_transformers/rectifier_transformers_tube.htm
One early builder used a "Dyna Clone" PA060 transformer from Triode Electronics in his SimpleSE. I have not tried them. I imagine that any transformer made for a Dynaco ST-70 would work well. As would the One Electron power transformer.
I tend to use the Allieds because they are far cheaper. I have put them in guitar and HiFi amps for the past 10 years. The only one that ever failed was one that got seriously wet during a hurricane. It still worked for a month before it fried. It was full of rust and green stuff when I took it apart. I don't count that as a real failure.
My suggestion is to use a couple of TV damper diodes. They're pretty rugged and take 6.3V, and plus, the cathode isn't connected to the heaters so your bifilar windings are safe. The novar sockets are a hassle to get but that's the main issue. The tubes themselves (6AY3, 6DN3, etc.) are pretty cheap and available.tubelab.com said:
Yes, I have built 2 lower voltage amps. Updating the website takes time, and I have not been at home much. Since I resumed selling the PC boards, I spend much of my time answering email. This forum allows many people to see these answers and cuts down on the repettitive email.
I built an amp that used the Allied 6K56VG power transformer and the Edcor XSE15-8-5K output transformers with 6V6GT tubes in triode mode. The B+ voltage is 325 volts. It has a real nice sound that is near the 45 in detail. Also like the 45, it makes about 1.5 watts. I have plugged 6L6GC's and EL34's into it, but they don't make any more power and the 6V6's sound much better.
I also built another amp using the power transformer salvaged from an old HP audio oscillator. It is 660 VCT at an unknown current rating. I get about 360 to 380 volts of B+ depending upon the bias current in the output tubes. I used Transcendar 3K output transformers which do not have a UL tap, so it is a triode only amp. It makes almost 5 watts with EL34's and somewhat less with other tubes. To me the sound is a bit less dynamic than the Industrial amp which used the exact same components except for the power transformer (450 volts B+).
Both of these amps were thrown together in a big hurry. I built the 6V6 amp in about 4 hours from start to finish, and most of that time was spent drilling holes. I did not photograph the construction of either since that tends to add days to the build time. I plan to rebuild both of them (with pictures) in the near future. I will post some preliminary test data with my next web site update. Full construction details will be posted as they are rebuilt.
Sherri and I have been taking adult woodworking classes at the local middle shcool. We are almost done with the last of the mandantory projects (Adirondack chairs). Now we can do our own "Summer Projects" I am planning some tube amps (no surprise) and maybe a guitar. I threw together the two amps described above to have the electronics all sorted out so I can concentrate on the wood.
There are a few damper diodes in octal sockets. The 6AU4 and the 6AX4 come to mind. Neither of these will plug directly into the PC board, so the SimpleSE gets far less simple. Now if you are willing to hack up a perfectly good PC board (I have lots of them) it can be done. I have toyed with the idea of running both channels of the PC board in parallel for double the power out. This requires two boards for stereo. I sliced a few traces, plugged a 6AU4 into each board, and wired both boards up to the same Antek toroid using the two damper tubes to make the full wave rectifier. It works, and I even tried one of the 800 VCT Anteks to make over 30 WPC.
I have made a few other crazy projects with this PC board. They will all make it to the web site eventually. The previously mentioned lower voltage amps will be posted soon. The crazy stuff must wait. I don't claim to be a good web site designer, so it takes me a while to process and post new stuff. My whole web site has become disorganized enough that I can't find stuff, so it needs a serious update. Each new concept or project brings a bunch of new email which takes a lot of time to answer, so I will stick to the TubelabSE and the SimpleSE amps for the summer.
I built an amp that used the Allied 6K56VG power transformer and the Edcor XSE15-8-5K output transformers with 6V6GT tubes in triode mode. The B+ voltage is 325 volts. It has a real nice sound that is near the 45 in detail. Also like the 45, it makes about 1.5 watts. I have plugged 6L6GC's and EL34's into it, but they don't make any more power and the 6V6's sound much better.
I also built another amp using the power transformer salvaged from an old HP audio oscillator. It is 660 VCT at an unknown current rating. I get about 360 to 380 volts of B+ depending upon the bias current in the output tubes. I used Transcendar 3K output transformers which do not have a UL tap, so it is a triode only amp. It makes almost 5 watts with EL34's and somewhat less with other tubes. To me the sound is a bit less dynamic than the Industrial amp which used the exact same components except for the power transformer (450 volts B+).
Both of these amps were thrown together in a big hurry. I built the 6V6 amp in about 4 hours from start to finish, and most of that time was spent drilling holes. I did not photograph the construction of either since that tends to add days to the build time. I plan to rebuild both of them (with pictures) in the near future. I will post some preliminary test data with my next web site update. Full construction details will be posted as they are rebuilt.
Sherri and I have been taking adult woodworking classes at the local middle shcool. We are almost done with the last of the mandantory projects (Adirondack chairs). Now we can do our own "Summer Projects" I am planning some tube amps (no surprise) and maybe a guitar. I threw together the two amps described above to have the electronics all sorted out so I can concentrate on the wood.
There are a few damper diodes in octal sockets. The 6AU4 and the 6AX4 come to mind. Neither of these will plug directly into the PC board, so the SimpleSE gets far less simple. Now if you are willing to hack up a perfectly good PC board (I have lots of them) it can be done. I have toyed with the idea of running both channels of the PC board in parallel for double the power out. This requires two boards for stereo. I sliced a few traces, plugged a 6AU4 into each board, and wired both boards up to the same Antek toroid using the two damper tubes to make the full wave rectifier. It works, and I even tried one of the 800 VCT Anteks to make over 30 WPC.
I have made a few other crazy projects with this PC board. They will all make it to the web site eventually. The previously mentioned lower voltage amps will be posted soon. The crazy stuff must wait. I don't claim to be a good web site designer, so it takes me a while to process and post new stuff. My whole web site has become disorganized enough that I can't find stuff, so it needs a serious update. Each new concept or project brings a bunch of new email which takes a lot of time to answer, so I will stick to the TubelabSE and the SimpleSE amps for the summer.
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