I suspect that he posted here looking for an answer from me, the "Project Owner" of the 845 SE amp seen on my we site. Unfortunately, I have little new information to offer. I ran my 845's at 1050 volts, which is mentioned on the web site. I liked the sound of the amp, but not the 500+ watts of heat it put into my small room, so it didn't see much use. The OPT's were built by a con artist who made some decent OPT's like these, took a bunch of prepaid orders, delivered some junk or nothing at all, then vanished. They are "10K ohm to 4, 8, or 16 ohm, 25 watts SE OPT for 211 or 845."
I experimented with DIY OPT's a few times in 50+ years of DIY tube amps. All of my experiments produced less than satisfactory results, but most were done when OPT winding info was pretty scarce. The 211 and 845 tubes have a pretty high plate resistance and therefore require minimal imperfections in the OPT (primarily leakage inductance and stray capacitance). The OPT's that I have are about 2 dB down at 20 KHz. After making the 845 amp, I thought about making an 833A amp. I paid Gerry from Transcendar Transformers some considerable money for a custom 5K to 4, 8 ohm OPT rated for 50 watts. The results were a bit worse than the 845 amps, so the transformer sits on the shelf unused almost 20 years later. It was used in the 200 watt SE guitar amp seen in my avatar, which only existed for 1 week due to its extremely unsafe nature. I haven't powered up the 845SE in over 10 years, so it will likely get parted out or sold.
I can now get a very nice sounding 30 watts in SE using a $15 tube on less than 500 volts through a Toroidy OPT that sells for under $100, so I will likely never use the 211, 845 and 833A stuff again.
I experimented with DIY OPT's a few times in 50+ years of DIY tube amps. All of my experiments produced less than satisfactory results, but most were done when OPT winding info was pretty scarce. The 211 and 845 tubes have a pretty high plate resistance and therefore require minimal imperfections in the OPT (primarily leakage inductance and stray capacitance). The OPT's that I have are about 2 dB down at 20 KHz. After making the 845 amp, I thought about making an 833A amp. I paid Gerry from Transcendar Transformers some considerable money for a custom 5K to 4, 8 ohm OPT rated for 50 watts. The results were a bit worse than the 845 amps, so the transformer sits on the shelf unused almost 20 years later. It was used in the 200 watt SE guitar amp seen in my avatar, which only existed for 1 week due to its extremely unsafe nature. I haven't powered up the 845SE in over 10 years, so it will likely get parted out or sold.
I can now get a very nice sounding 30 watts in SE using a $15 tube on less than 500 volts through a Toroidy OPT that sells for under $100, so I will likely never use the 211, 845 and 833A stuff again.
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I wrote this a couple of days ago and forgot to post it. Neat that the page remembers it on its own. Probably some repetition now but what the hay:
Somebody who knows more than me will jump in but in an effort to answer your basic question the 845 data sheet gives operating points at plate voltages of 750VDC, 1000VDC, and 1250VDC, so basically an operating range considered by the manufacturer to be optimal of a 500VDC range, starting at 750V. On the other hand, quite a few people have done "low voltage" versions from 450 to 550V. I have no idea how their sonic performance compares with the data sheet variety.
You can wind transformers so you must be knowledgeable. One of my mentors , an EE with people's lives on his design shoulders, taught me that anything above 500V starts to require special high voltage considerations and that anyone attempting it should take the time to focus on learning what they are. He also mentioned that transformers made for high voltages are physically different in internal construction. The wire's insulation rating alone is not enough.
On a very very personal note, I refuse to rely on the advice of anyone who calls transformers "trannys" as if that's their real name and say it like they want to show everyone how knowledgeable and familiar they really are. In my experience, the best engineers have respect for the things they work with and call them by name or conventional acronym .
I hope you don't mind the directness but I have strong feelings about people (not accusing you!) who use language that leads to disrespect , either of people or the subject those people have spent a lifetime learning about and working with.
Here's one of many threads on the subject of winding your own. I'd pay special attention to the comments and links from Yvesm,
and another one Here with good stuff from Tubelab and others.
Somebody who knows more than me will jump in but in an effort to answer your basic question the 845 data sheet gives operating points at plate voltages of 750VDC, 1000VDC, and 1250VDC, so basically an operating range considered by the manufacturer to be optimal of a 500VDC range, starting at 750V. On the other hand, quite a few people have done "low voltage" versions from 450 to 550V. I have no idea how their sonic performance compares with the data sheet variety.
You can wind transformers so you must be knowledgeable. One of my mentors , an EE with people's lives on his design shoulders, taught me that anything above 500V starts to require special high voltage considerations and that anyone attempting it should take the time to focus on learning what they are. He also mentioned that transformers made for high voltages are physically different in internal construction. The wire's insulation rating alone is not enough.
On a very very personal note, I refuse to rely on the advice of anyone who calls transformers "trannys" as if that's their real name and say it like they want to show everyone how knowledgeable and familiar they really are. In my experience, the best engineers have respect for the things they work with and call them by name or conventional acronym .
I hope you don't mind the directness but I have strong feelings about people (not accusing you!) who use language that leads to disrespect , either of people or the subject those people have spent a lifetime learning about and working with.
Here's one of many threads on the subject of winding your own. I'd pay special attention to the comments and links from Yvesm,
and another one Here with good stuff from Tubelab and others.
Not sure who you are referring to here, but in my nearly 70 years on the planet the term "tranny" has been associated with three very different meanings, and a transformer is by far the least common. Another has to do with "personal pronouns" and such, and the most common in my past was the association with the mechanical contraption that changes the gear ratio between the engine and the differential in an automobile, AKA the transmission. I blew up several of those in my hot rodding days. Ever wonder what's inside an old school automatic transmission? This one is a mid 70's vintage Chrysler Torqueflite 727 with about 500 HP feeding it. Yes, it went back together and ran just fine.
On my computer the second "Here" is not clickable, maybe the link is missing or broken. Could it be this one?
https://www.diyaudio.com/community/threads/winding-my-own-output-transformers-dumb-idea.389122/
Attachments
I was referring to the page linked in post # 1,219 above. Over time I developed a knee-jerk reaction to web pages where people take credit for stuff that 's just copy and pasted from others' work and then "personalized" to make it look original. I've seen that done with the word "tranny" a few times and this time I reacted to the word alone without taking the time to look very clearly. I knew that and so didn't post when I first wrote it, giving myself time to look later and see if it really should be said. I forgot that I'd left it in when I sent it today just to answer the operating voltage related question. . . . . and edit time was past by the time I came back.
I never heard anybody referring to their 3 on the tree, 4 on floor, Cruise-O-Matic, Power Glide, M20, Rock Crusher, T-Flite or whatever as Trannies that were trying to convince me they were cool guys just because they knew so much they could say it that way. In conversation, "Tranny" just made it easier to flow on and there was no emphasis on the word itself. Hearing someone try to ingratiate themselves by saying the word twenty times in 21 sentences would make anyone's eyes narrow down a bit. In print tfmr, xfmr , etc. make more sense if fewer keystrokes is your real objective. So Tranny seems pretentious. I just got carried away and let the horses run a little.
Ooh, you got it ! I posted it (or meant to) mostly because of your post though there are others there that might be helpful to the OP.
Yes I am experienced, that's a fact. However, I have a strong desire to learn. I will study the article on security, this is very serious.
Thanks for getting back to me.
Yeah, "trans," "tranny" and "dizzy" common in some automotive circles. Somehow seems mentally lazy to me.
The Wolpert paper in the link you posted is interesting. Great when you can find a source that discusses such topics at a high level, and is specific to one's topic of interest. No interest in winding transformers, but the insight should be helpful in making an informed selection from what transformers are available.
Also, just from interest, don't the commercial transformer builders use a winding machine? Seems like it would be hella tedious to wind by hand. Hard on your hands and eyes too. I suppose there's no reason you couldn't, but is it the best use of your time?
I guess that I would have known that if I had clicked on the link, but I get posts, PM's and emails that often ask questions that I can't possibly answer like "which speaker system is best" often with links to each. I have bought exactly one pair of "HiFi" speakers in my life, and they were a pair of Yamaha NS-10M Studio monitors that I selected from room with about a dozen pair at a large music store. My choice was based on price, and the ability to get drum transients "right." I'm guessing most amp builders have different criteria for choosing speakers, tubes, transformers and most other parts of a system. I thought $300 for a pair of speakers in the early 90's was too much, but the Tannoys that set next to them were over $1000 and the NS-10s were near the bottom of the pricing for all the monitors.
My hearing has been degrading over my lifetime due to Meniere's Disease. I was told that I would be deaf before I hit 60 years old. I will be 70 in a few weeks and would likely be judged "deaf" today if tested again. I got a set of really expensive hearing aids a few years ago that only offer a little help in some conditions, but my hearing is anywhere from 20 to 40 dB below normal and changes daily. When I built the first TSE, I got a pair of Electra Print OPT's along with several other popular brands, and the usual Hammond and Edcors. At that time the EP's were the obvious choice for the TSE and they are still there. The One Electron's were sold first. The sounded good, but the others sounded better. I had 12 pairs of Transcendars, and sold most of them. I still have a few and will likely keep them. Ditto the Hammond 1628SEA and the big Edcors.
I'm not sure I could be so discerning today due to hearing issues. I have played a bit of "OPT rolling" with my UNSET board. Oddly, I keep coming back to the 1628SEA wired for 2500 ohms and the Toroidy 1500 ohm KT88PSE's wired for 3000 ohms. When I get tired of one, I switch to the other. The Hammonds are notably lossier, but have awesome bass for an SE amp. For most the choice will come down to priorities, listening tastes, and speakers. Want to crank Pink Floyd through 15 inch speakers, Hammond! Want ultimate detail and imaging for less money, Toroidy!
I "made" power transformers by ripping the secondaries off of an old TV transformer and winding a new one on. They were successful. My attempts at making OPT's usually resulted in lumpy frequency response, excess loss, dull lifeless sound, or all of the above. I used laminations salvaged from dead OPT's. I have not tried to make an OPT in at least 20 years, probably longer.
Please understand that the peak voltages seen by the transformer in normal operation are at least twice the B+ voltage. I have seen 2500 volts on the plates of an output tube in an over driven guitar amp with a 430 volt B+. A member of this forum built an SE amp with a large triode running on a kilovolt level B+ voltage several years ago. He paid a well known European transformer builder a lot of money to make his custom OPT's. The amp worked fine on first power up but one OPT burst into flames as soon as he cranked up the volume. His user name was Alex on the rocks, but the account was disabled before we ever heard what happened. I can't find it today. There have been threads discussing OPT's and the possibility of external protection from excess voltage scattered throughout the "tubes" forum. It might be worth a search or two.
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Are there any TSE II boards currently available for purchase? My DiyAudio account email adress was blocked. I now have got it working again. I am not able to send any PM's..so unable to contact George through PM.
Yes, the boards are available. I just replied the details to your email. Yesterday was my 70th birthday and I got a new low cost smartphone, so I spent the day wandering about outdoors exploring the "50 Megapixel" camera.
Is it feasible to build mono block amps using the stereo TSE II boards? one per chassis? I am thinking the power supply voltages may end up a bit too high considering the lower load placed on the supplies with only one output and one driver tube per chassis? Any other potential problems with doing this? Has anyone tried this? seems as though others in the tread that built monos have done point to point builds. I am planning a 300B build.
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Decided to restore an SSE board with parts from the bin and wonder if a 47uF 650 vDC Cap is meaningfully inferior to the full 100 uF spec'd for the power supply. I have an 100 but 400 vDC. I also have another 47 uF 400 vDC. All three are Solens and about 15 years old.
A 47 uF part might not be large enough to kill all hum if efficient speakers are used. It would be fine in applications where an auxiliary off board cap is used. one could also add a second 47 uF in parallel with the first if you have two and there is room to hide one under the board or externally mount it.
I didn't read your original post carefully enough. Since this is a TSE / TSE-II thread I assumed the amp was one of those, which tend to operate at or below about 400 volts.
The power supply caps see the full B+ voltage. The 5AR4 usually warms up a bit faster than the typical audio output tube so the power supply caps can see well over 450 volts during warm up. I usually use 500 volt electrolytics in an SSE but my current residence and my old place in Florida both had pretty wide fluctuations in line voltage, but at opposite times of the year. If I remember correctly Solen's are polypropylenes which can handle momentary overloads better than an electrolytic, but even I wouldn't use a 400 volt cap on 435 volts.
Moving along to the Diodes...my 2006 copyright board never had the Diodes installed or any jumper on the switch eyelets. No reason to change that, yes? There used to be something in the assembly manual in regard to using the tube capacitor only but I can't find it now. I use a 5AR4.