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Old 30th September 2009, 09:28 PM   #21
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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.
----------------------------
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
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Old 30th September 2009, 10:10 PM   #22
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Be sure I was in no way criticizing about the capacitor size...I am no "audio extremist" by any means, I just like a solid solder connection myself.
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.

Quote:
Those super secret 307A's, are they distant (or not so distant) cousins of one of my favorites
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.
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Old 30th September 2009, 10:31 PM   #23
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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.
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Old 1st October 2009, 01:06 AM   #24
djn04 is offline djn04  United States
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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.
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Old 1st October 2009, 01:41 AM   #25
djn04 is offline djn04  United States
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Tamura seems to make a power transformer that fits the bill

400V-360V-0-120V-360V-400V DC250mA, 6.3V-4V-0 3.6A,
6.3V-4V-0 3.6A, 5V 3.8A, 5V-4V-0 3A, 7.5V-5V-0 3A

But all their SE OPT's are in the 8-10W range.

5K (Single) 0-4-8-16 15∼50KHz 10W 100ma 30H
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Old 1st October 2009, 02:32 AM   #26
djn04 is offline djn04  United States
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Or I could go with James Transformers

9611 Power transformer
primary 115V 110V
S1: 360V-280V-0-70V-280V-360V
S2: 5V
S3: 6.3V-CT
S4: 6.3V
S5: 6.3V

0.3A
4A
3A
3A
3A

6BQ5
6V6 S.E. X2
6B4 P.P.x 4
6L6

5.4kg

and OPT
6123HS 90mA 2.5/3.5/5k 20W 20Hz~60KHz-2dB 2A3/300B F 3.2kg
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Old 1st October 2009, 02:37 AM   #27
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Quote:
This would be to much according to the design.
Yes that one is much too big.

Quote:
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
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.

Quote:
Tamura seems to make a power transformer that fits the bill
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.

Quote:
But all their SE OPT's are in the 8-10W range.
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.

Quote:
So much for scrounging up handfuls of cheap 307A's, lol!
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!
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Old 1st October 2009, 04:27 AM   #28
w5jag is offline w5jag  United States
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My idea of a high end Simple SE would be triode wired 6V6, with some good OPT's, probably Hashimoto, assuming you have efficient speakers, of course.

Win W5JAG
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Old 1st October 2009, 05:35 AM   #29
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Quote:
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.

Quote:
triode wired 6V6
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
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Old 1st October 2009, 02:32 PM   #30
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Quote:
My idea of a high end Simple SE would be triode wired 6V6, with some good OPT's, probably Hashimoto, assuming you have efficient speakers, of course.
Quote:
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!
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.

Quote:
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.
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.
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