Tubelab - Thank you actually for clearing up some things I had questions on. Have you by any chance tried the cascode CCS taking the signal from the mu output instead? I am interested in if this makes any difference as far as performance as the output reach clipping and into very heavy clipping. I wasn't sure though because the 12AT7 seems to be a pretty robust tube, it's no 437A, but no slouch either.
Be sure I was in no way criticizing about the capacitor size. I have nothing but respect for you as a designer, and I am sure there is a reason behind everything. My thinking was that if used as a grounded k with no feedback you could go smaller in order to use a high quality cap that won't break the bank.
I am no "audio extremist" by any means, I just like a solid solder connection myself. I had a vehicle that was acting funny once, couldn't figure out for sure what it was except that it was electrical more than likely. Finally found a beauty of a connector buried down in it that was nice and marshmallow-toasted black. On top of that it had a nice burned plastic + ozone (from arching) smell to it when one got close enough. Bottom line, electo-mechanical connections can fail, not ALWAYS will, but can. I do fully understand the reasoning for the blocks though, I have used them myself. I also agree they save PCB's for repeated soldering. I have destroyed many a solder pad myself in my (short) time.
You are correct sir, and it is a very good point. I did mean motor run cap not motor start. When searching for these buggers they tend to be found in the same general area within a catalog. I should have caught that, I guess I am slipping.
Those super secret 307A's, are they distant (or not so distant) cousins of one of my favorites, the 807? Something sticks in my head that they share some sort of family bond, but I very well could be wrong. You know, looking at the data for the 307A, they seem to share a bit with another directly heated triode. Though the 307A does have a few more girds in the way, that could be fixed...I will say no more...but I would love to know more.
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You had mentioned James, they have some power iron that would work great. There are a few that are 720vct to 760vct @ 250mA or more. Add to that something like the 10H @ 250mA (86R DCR) power choke and either JS-6123HS or JS-6135HSF outputs, and you would have a great set of iron for a great little amplifier.
Cheers
James
Be sure I was in no way criticizing about the capacitor size. I have nothing but respect for you as a designer, and I am sure there is a reason behind everything. My thinking was that if used as a grounded k with no feedback you could go smaller in order to use a high quality cap that won't break the bank.
I am no "audio extremist" by any means, I just like a solid solder connection myself. I had a vehicle that was acting funny once, couldn't figure out for sure what it was except that it was electrical more than likely. Finally found a beauty of a connector buried down in it that was nice and marshmallow-toasted black. On top of that it had a nice burned plastic + ozone (from arching) smell to it when one got close enough. Bottom line, electo-mechanical connections can fail, not ALWAYS will, but can. I do fully understand the reasoning for the blocks though, I have used them myself. I also agree they save PCB's for repeated soldering. I have destroyed many a solder pad myself in my (short) time.
You are correct sir, and it is a very good point. I did mean motor run cap not motor start. When searching for these buggers they tend to be found in the same general area within a catalog. I should have caught that, I guess I am slipping.
Those super secret 307A's, are they distant (or not so distant) cousins of one of my favorites, the 807? Something sticks in my head that they share some sort of family bond, but I very well could be wrong. You know, looking at the data for the 307A, they seem to share a bit with another directly heated triode. Though the 307A does have a few more girds in the way, that could be fixed...I will say no more...but I would love to know more.
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You had mentioned James, they have some power iron that would work great. There are a few that are 720vct to 760vct @ 250mA or more. Add to that something like the 10H @ 250mA (86R DCR) power choke and either JS-6123HS or JS-6135HSF outputs, and you would have a great set of iron for a great little amplifier.
Cheers
James
Sorry if it sounded like I was complaining, I was actually referring to a slam fest that occurred on another audio forum that I am not even a member of. It even got carried over to the Hawthorne Audio speaker forum. I received several emails asking me to go defend my design on those forums, which I am not inclined to do. It would just raise my blood pressure. There have been very few "my kung foo is stronger than your kung foo" episodes on this forum, which is why this forum is the only one I am a member of.
If you are building a Simple SE "by the book" (recommended for all first timers) then I would still recommend a 1000 or 1500 uF cap. Inexperienced users should still build their amp by the book and get it working first, then mod the hell out of it. I do the same thing. I just bought one of Pete Milletts boards. I really don't need or want another 18 watt per channel P-P amp, but I will build it like he designed it, make sure that it works like he states, then proceed to squeeze 50+ WPC out of it. That way if it blows up, I am 100% sure it was something I did wrong. If you build the amp with several mods in it and it doesn't work, then you have a major troubleshooting mess.
There have been a few threads here that dealt with the cathode caps, and the power supply caps. There was a thread where the user wanted to build a Simple SE with no electrolytics in it at all. This was being discussed and someone pointed out some surplus ASC 600uF 500 volt caps for under $10 each. I bought 6, and I believe the poster was going to do the same. I never heard how the amp turned out.
I have chased down some rather toasted connectors in automobiles too. I worked in a stereo repair shop in the early 70's in south Florida. Back then many people did not have air conditioning. The connectors in some big name stereo equipment (early Fisher SS stuff comes to mind) would turn green with corrosion in two years. Many times the only economical repair was to hard solder the boards in.
I don't see much similarity with the 807. The 307A is a directly heated pentode. It has 3 wire grids. The 807 is a 6L6GA with a funny base and a top cap. So is a 6BG6. They are beam tetrodes with indirectly heated cathodes. I have dropped a triode wired 307A (also known as a VT225 and an RK75) into 300B sockets with an adapter and had them bias up almost the same and deliver about 8 watts despite that pesky 15 watt plate dissipation rating.
Search this forum for VT225, there are a few other users out there.
No worries, sorry if I made it sound as if I made it sound like you where complaining...hmmm...lol. No I just didn't want to be taken the wrong way myself. You shouldn't have to defend your designs, at least that is my feeling. I personally love watching you take seemingly mundane tubes that make 5 or 10 watts and getting 50 out of them. There is some sort of devilish fun derived from watching sweep tubes hit that toaster over color on their plates, sweat a bit, then smile and take some more.
I stand corrected on the 307A's. Though that was kind of what I was getting at when I said they share a bit of a resemblance with another directly heated triode. I just wasn't sure if I should come right out and say 300B. So much for scrounging up handfuls of cheap 307A's, lol! Yeah that plate (in the tube Mr. Millet broke open) looks like it could handle a bit more than 15 watts.
I stand corrected on the 307A's. Though that was kind of what I was getting at when I said they share a bit of a resemblance with another directly heated triode. I just wasn't sure if I should come right out and say 300B. So much for scrounging up handfuls of cheap 307A's, lol! Yeah that plate (in the tube Mr. Millet broke open) looks like it could handle a bit more than 15 watts.
My reasoning for using Hashimoto transformers are two fold. One I like the sound of Air Tight and other Japanese tube amps and I know Air Tight uses Tamura and Hashimoto iron. Also I like the look of "enclosed" transformers.
If I can get similar performance/quality in another brand and use a transformer cover to get the same aesthetic I'm open to suggestions.
The next step up in the Hashimoto's is:
480V-420V-240V-0-240V-420V-480V: 0.17A
0-6.3-7.5V: 5A ( x 2)
6.3V: 3A
5V: 3A
This would be to much according to the design.
I guess I'll continue the search.
If I can get similar performance/quality in another brand and use a transformer cover to get the same aesthetic I'm open to suggestions.
The next step up in the Hashimoto's is:
480V-420V-240V-0-240V-420V-480V: 0.17A
0-6.3-7.5V: 5A ( x 2)
6.3V: 3A
5V: 3A
This would be to much according to the design.
I guess I'll continue the search.
Yes that one is much too big.
Look at the Hammond 374BXP. It is a 374BX that comes potted in a square can. I have never used one though, don't know what they actually look like. I finally got my first 300 series transformer 2 weeks ago. They are much better than the 200 series.
That one should work. The 360-0-360 winding should provide over 400 volts of B+, but it is hard to guess the exact voltage without knowing how close to spec the Tamura is. All of the Hammonds put out quite a bit more than spec.
There is a large variation in the way transformer manufacturers specify power handling. The Chinese "50 watt" SE OPT's sold on Ebay are really 8 to 10 watt OPT's and the big Hammond 25 watt OPT's will do close to 40 watts. If the Tamura OPT will really do 10 watts from 15 to 50KHz it would be a good choice. Tamura and Hashimoto transformers both have a very good reputation(with prices to match) and I would me inclined to actually believe their ratings. If you are going to use KT88's in triode mode you are going to get 8 to 10 watts. Too big of an OPT can be bad too.
As someone else mentioned and I have explained before there is a universal way to compare OPT's (assuming no cheating has occurred). Weight! Yes, ignoring ALL other specs a proper high end SE OPT for a KT88 should weigh between 7 and 10 pounds. I am basing this on standard unencapsulated transformers. A potted transformer could weigh 1 or 2 more pounds. Anything outside this range should be suspect.
Why? The Hammond 1628SEA weighs in at 11 pounds. The bass it puts out will shake the neighbors walls, but all of that iron and copper eats up energy, so the big guy is the least efficient transformer I tested, it also has slightly subdued highs. The little Edcor XSE15-8-5K weighs in at maybe 2 pounds. It is rated at 15 watts. Well I can crank over 15 watts through it at 1KHz, but it will not handle 15 watts below 140 Hz. It is however an excellent sounding highly efficient transformer in a 2 watt amplifier, where it will cover 20Hz to 45Khz for $30! The One Electron and Transcendar SE OPT's that I have weigh in at 6 pounds. They will just begin to show signs of saturation at 40 Hz with a cranked KT88 in a Simple SE (most music doesn't go below 40Hz).
If your speakers don't go this low, or you use a subwoofer, a smaller OPT would be fine. One builder used a subwoofer to deal with the frequencies below 100Hz so the $30 Edcor worked great in his Simple SE.
There was a bunch of whining about availability in the VT225 thread, so Mr. Millett put some of his tubes on Ebay for a fair price, announced their availability on this forum, and nobody bought any!
HAHAHAHA!
If you are willing to shell out some cash for Hashimoto or Tamura you could look at Electra-Print. Jack winds some great iron, best of all, he winds it for you. You can get that power transformer exactly as you want it, within reason. Jack will let you know if the design will not work correctly. His outputs may seem a bit pricey, but they are top notch. I have seen some of the power iron he has wound, beautiful stuff, check it out:
http://www.audiotropic.net/Projects/tadakiEdit1.jpg
Big ol' hunk of iron there in the middle, that is one of Jack's. They will cost a bit more than the Hammond 300 series, but again, great iron.
Love that tube too. I have a small and growing collection of them to pop in and out of a Musical Machine that is slowly under way. Speaking of which, I just picked up a piece of nicely figured rustic Cherry for the chassis. Local woodworking store has it at a promo price of $2.00 / bf, I couldn't pass it up... think I will have to get more. OT, sorry.
Cheers
James
Well not exactly high priced, and quite ugly, but I bet my little 2 watt Simple SE with 6V6's and $30 Edcor OPT's powered by a $40 Allied 6K56VG can stomp a lot of "high end" amps.
The Lexan Tubelab SE shown on my home page runs Electra - Print OPT's. It is powered by another $40 Allied 6K56VG and typically runs 45 tubes. It HAS been compared favorably to some very high priced amps. I got the Electra - Prints several years ago for $100 each. They are very good OPT's. I don't think that he makes potted transformers though.
A few comments about tranformers: I have a One electron BFT-1B and it certainly is a BFT, it's huge.....and not too sexy either, with it's copper electrostatic shield exposed, complete with varnish drips. Mine is actually an ebay special that has slightly skewed laminations, like it got dropped on a corner at the factory before the varnish dried. It looks like it was built that way. Works fine, looks rough.
I have a pair of Trancendar 5K's with UL taps slated for my Simple SE build and a pair of James 6123s slated for my tubelab SE build. When I ordered the boards from George, I decided that I would build the SSE as a middle-of-the-road build that would be fun to tube roll and experiment with and go a little pricier on the TSE build, hence the transformer choices above. The James output transformers are very nice looking and have a good reputation, they are also available in champagne or black finish. The Trancendars also have a good reputation but look fairly conventional. Both of these transformers are available on ebay for reasonable $$.
Trancendar Gery on ebay has recently offered the 5K SE transformers with UL taps for $5 more than the ones without; this allows UL operation in the SSE.
Like JPeitzman, I am also working to complete Poinz' EL34 music machine so my Tubelab stuff remains half finished.
I have a pair of Trancendar 5K's with UL taps slated for my Simple SE build and a pair of James 6123s slated for my tubelab SE build. When I ordered the boards from George, I decided that I would build the SSE as a middle-of-the-road build that would be fun to tube roll and experiment with and go a little pricier on the TSE build, hence the transformer choices above. The James output transformers are very nice looking and have a good reputation, they are also available in champagne or black finish. The Trancendars also have a good reputation but look fairly conventional. Both of these transformers are available on ebay for reasonable $$.
Trancendar Gery on ebay has recently offered the 5K SE transformers with UL taps for $5 more than the ones without; this allows UL operation in the SSE.
Like JPeitzman, I am also working to complete Poinz' EL34 music machine so my Tubelab stuff remains half finished.
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Ok. So I think I'm going with all James transformers at this point.
They've got a 360V-280V-0-70V-280V-360V 0.3A Power Trans, 90mA 2.5/3.5/5k 20W 20Hz~60KHz-2dB OPT's, and a 20 H 150mA 143Ω choke.
Is 143Ω ok? I think George calls for 150 in the choke.
This seems like a good middle point as far as price performance. It's higher than Hammond/Edcor but much less than Tamura/Hashimoto and a good bit cheaper than Electra-Print.
Now onto resistors, caps, tubes . . . ?
They've got a 360V-280V-0-70V-280V-360V 0.3A Power Trans, 90mA 2.5/3.5/5k 20W 20Hz~60KHz-2dB OPT's, and a 20 H 150mA 143Ω choke.
Is 143Ω ok? I think George calls for 150 in the choke.
This seems like a good middle point as far as price performance. It's higher than Hammond/Edcor but much less than Tamura/Hashimoto and a good bit cheaper than Electra-Print.
Now onto resistors, caps, tubes . . . ?
I used a Hammond P-T159Q choke for my Simple SE. It's rated 7H, 150 mA, 100 ohms. I never had any problems with it - it just works. In my opinion, I'd rather have less DC resistance in my choke rather than more. If you're going to be concerned about anything, think about the total current consumption. Each KT88 is going to eat about 75 mA, and each half of the 12AT7 will take another 8 mA or so. That puts your total over the rated current for your choke, but I'm guessing it'll probably be OK.
I was just going to say something too about the current rating. It may be OK, but like I said earlier, if it where me I wouldn't push it. I would look to something like their 10H @ 250mA choke, gives you tons of head room. Best, it will run hot; worst it will vibrate, run really really hot, and eventually maybe fail. I wouldn't worry to much about sizing that choke just right so that you hit about the DCR of what George is using. In the end it shouldn't make a big difference one way or the other if it isn't a DCR of 150R.
Cheers
James
Cheers
James
I thought about the current rating on my Hammond choke. They didn't describe the 150mA rating as "maximum current" or anything like that. I believe the number is simply where the choke will deliver its specified inductance. From their web page, they state "Units will exhibit less inductance at slightly higher currents or more at lower currents."
I don't know what constitutes "slightly" higher currents. I know the Triad C-14X choke has the same weight, physical dimensions, and nearly identical DCR as compared to the Hammond 159P. The C-14X is rated 6H @ 200 mA. The 159P is rated 10H @ 125 mA. Does this mean anything? Probably not, but deep down inside I'd like to believe the C-14X and the 159P are actually the same unit, just rated under different conditions. That suggests to me that a choke rated for a particular current draw can be operated at a slightly higher load, but you won't get as much inductance. That's pretty much what Hammond said.
Contact the manufacturer, and ask them. Or just buy a choke rated for 200 mA or more and don't worry about it.
If it's worth anything, I have run KT88 in my Simple SE. I've heard absolutely no buzzing from my 159Q choke.
I don't know what constitutes "slightly" higher currents. I know the Triad C-14X choke has the same weight, physical dimensions, and nearly identical DCR as compared to the Hammond 159P. The C-14X is rated 6H @ 200 mA. The 159P is rated 10H @ 125 mA. Does this mean anything? Probably not, but deep down inside I'd like to believe the C-14X and the 159P are actually the same unit, just rated under different conditions. That suggests to me that a choke rated for a particular current draw can be operated at a slightly higher load, but you won't get as much inductance. That's pretty much what Hammond said.
Contact the manufacturer, and ask them. Or just buy a choke rated for 200 mA or more and don't worry about it.
If it's worth anything, I have run KT88 in my Simple SE. I've heard absolutely no buzzing from my 159Q choke.
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George is using whatever he finds in the junkbox. My industrial amp uses a Triad C-24X because it is small and I wanted to hide its ugliness under the deck it is 50 ohms DCR. I have used surplus chokes from 70 to 200 ohms. I would use just about any choke from 50 to 200 ohms, 1 to 10 (or more but I haven't tried it) Henries, at a minimum of 150 mA. I would give up a little inductance for a higher current rating, but for a reason not previously stated. Since DC flows through the choke, it can saturate if operated near the spec limit, and when it does its inductance drops to near zero. The inductance does vary with applied current, and drops as the current increases.
Yup. I have breadborded it with hashimoto HW-60-5's and it sounded very nice except for a hummmm problem, which I attribute to the breadboard (I hope). I also have a pr of the budget 8K PP hashimotos to hopefully use in the 6V6 machine when I find some time. Both pairs of hashimoto's were purchased used from another member here (thanks jazzbo!)
djn04: Additional resistance in the choke will tend to lower your final B+ voltage, which may or may not be a bad thing. Download and model the simple SE PS with PSUDII (power supply designer II) from www.duncanamps.com if you haven't done so already. It's free, easy to use, and lots of folks here will answer questions. You will see quickly how your PS transformer, choke and caps will perform.
Edit: Here is the link right to the PSUDII download page: http://www.duncanamps.com/psud2/index.html
Since you will have a CLC PS design, you can vary the value of the first cap (within a range) to dial in your B+ voltage, so if the choke R is high, you may be able to compensate by adjusting the first cap. Also, your B+ voltage needs can vary somewhat depending on what output tubes you want to run and at what current.
Look at the computer sims on the bottom of this page from Tubelab:
http://www.tubelab.com/AssemblyManualSimpleSE/TubesAndTransformers_SSE.htm
The tables have B+ voltage, OT load, cathode R, etc and the corresponding power out and distortion.
One question: What is the sensitivity of your Zaph Audio ZRTs?
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