Cheap and cheerful. Lovely SE Xformers salvaged
Forgive my eccentric ramble here, but: German and Dutch, (radios and recorders, respectively) have fine SE transformers. Most will think of the Telefunkens, but the larger Norelco (Philips) tape recorder SE tube outputs at 5K for EL84/6BQ5s, are the cat's meow! I built a small stereo amp with 2 6Y6GT Pentodes, (not triode connected or with feedback). Driven by a 12AX7s. 12AX7s #1 the #2 section driving the 6Y6GT. (2K 6Y6 plate load rated) into the 5K XFMR with a single 4 Ohm output. Separate chassis power supply with Fisher K100 Power iron @ 200 Volts, (no voltage doubler), WWII GE Pyranol PIO power caps and military Chokes. Separate volume controls for each channel. Played through Tele Radios 4 Ohm speakers in DIY cabinets, or Bell and Howell 12" extension speakers w/DIY cabs + NO crossovers. B&H speakers @ 16 Ohms, but distortion not noticed. I say all this because it was really pleasant, and cheap salvage material. The largest Edcor iron re my present SE outputs most of the time, but 45, 171, 50 type triodes (minus) crossovers and a single 'full range', speaker, are so under rated that I just had to speak up. Engineering is ESL to this music lover with limited skills. A fellow mentioned these ideas a few years ago, no one responded, even to argue. I'm just repeating his info, and my experience. I really love this forum, and the effort you folks make with vacuum tube exploration and education is super. Thank you very much. buffstereo1
Forgive my eccentric ramble here, but: German and Dutch, (radios and recorders, respectively) have fine SE transformers. Most will think of the Telefunkens, but the larger Norelco (Philips) tape recorder SE tube outputs at 5K for EL84/6BQ5s, are the cat's meow! I built a small stereo amp with 2 6Y6GT Pentodes, (not triode connected or with feedback). Driven by a 12AX7s. 12AX7s #1 the #2 section driving the 6Y6GT. (2K 6Y6 plate load rated) into the 5K XFMR with a single 4 Ohm output. Separate chassis power supply with Fisher K100 Power iron @ 200 Volts, (no voltage doubler), WWII GE Pyranol PIO power caps and military Chokes. Separate volume controls for each channel. Played through Tele Radios 4 Ohm speakers in DIY cabinets, or Bell and Howell 12" extension speakers w/DIY cabs + NO crossovers. B&H speakers @ 16 Ohms, but distortion not noticed. I say all this because it was really pleasant, and cheap salvage material. The largest Edcor iron re my present SE outputs most of the time, but 45, 171, 50 type triodes (minus) crossovers and a single 'full range', speaker, are so under rated that I just had to speak up. Engineering is ESL to this music lover with limited skills. A fellow mentioned these ideas a few years ago, no one responded, even to argue. I'm just repeating his info, and my experience. I really love this forum, and the effort you folks make with vacuum tube exploration and education is super. Thank you very much. buffstereo1
I've read a few project articles that sourced transformers from both of the companies below
Amplifier Transformers
Heyboer Transformers - Audio Transformers
The first link is near home for me I may check them out, they appear to be old school using paper insulators making hi fi as well as guitar amp transformers.
Amplifier Transformers
Heyboer Transformers - Audio Transformers
The first link is near home for me I may check them out, they appear to be old school using paper insulators making hi fi as well as guitar amp transformers.
Windcrest 77,
thin aramid paper has a Dk of 1,5-1,8
Teflon, polyethylene and polypropylene have a Dk of 2-2,3
Polyester (PET) has a Dk of 3-3,5
Other isolation materials even higher
Low Dk translates into equally lower capacitance for a given thickness of isolation.
This has advantages and can make the difference between a good and a very good OPT.
If they really use aramid paper (much more expensive) then I would think they know what they are doing.
But any ole paper is not the same as aramid paper, even it may look the same
thin aramid paper has a Dk of 1,5-1,8
Teflon, polyethylene and polypropylene have a Dk of 2-2,3
Polyester (PET) has a Dk of 3-3,5
Other isolation materials even higher
Low Dk translates into equally lower capacitance for a given thickness of isolation.
This has advantages and can make the difference between a good and a very good OPT.
If they really use aramid paper (much more expensive) then I would think they know what they are doing.
But any ole paper is not the same as aramid paper, even it may look the same
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buffstereo1,
I love your writeup about the 6Y6GT single ended, Pentode mode, and no negative feedback.
Reminds me of the good sound I got from an old 1938 AM / short wave Philco radio. Not Hi Fi, but very musical.
I think they knew how to match the Pentode, output transformer inductance, and the speaker bass resonant Q and the open back cabinet; as well as the mechanical high frequency rolloff versus the rising response due to the pentode output stage constant current nature, versus the increasing inductive reactance of the voice coil.
I think those engineers knew more than most of us give them credit for.
I love your writeup about the 6Y6GT single ended, Pentode mode, and no negative feedback.
Reminds me of the good sound I got from an old 1938 AM / short wave Philco radio. Not Hi Fi, but very musical.
I think they knew how to match the Pentode, output transformer inductance, and the speaker bass resonant Q and the open back cabinet; as well as the mechanical high frequency rolloff versus the rising response due to the pentode output stage constant current nature, versus the increasing inductive reactance of the voice coil.
I think those engineers knew more than most of us give them credit for.
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gorgon53,
Thanks for mentioning the underhung voicecoil.
But that triggers my memory. The old 1938 Philco had a dynamic speaker magnet;
Yes, the kind that used an electromagnet (which was also the B+ filter choke).
Having a very strong electromagnet meant that they did not have to worry about the underhung voicecoil efficiency, because the field was so strong.
Some speaker manufacturers have been using very strong electromagnet (field coils) again. I started seeing them in the mid to late 1990s.
That is close to 60 years later.
Thanks for mentioning the underhung voicecoil.
But that triggers my memory. The old 1938 Philco had a dynamic speaker magnet;
Yes, the kind that used an electromagnet (which was also the B+ filter choke).
Having a very strong electromagnet meant that they did not have to worry about the underhung voicecoil efficiency, because the field was so strong.
Some speaker manufacturers have been using very strong electromagnet (field coils) again. I started seeing them in the mid to late 1990s.
That is close to 60 years later.
Transformer - One Electron, Output, 4800 Ω to 16/8/4 Ω | Antique Electronic Supply
One Electron can be added to your shortlist as well. I have the UBT-1. They look a bit rough. But that is no issue for me. Little bit of cleaning and sanding...and then respray and they'll look great.
One Electron can be added to your shortlist as well. I have the UBT-1. They look a bit rough. But that is no issue for me. Little bit of cleaning and sanding...and then respray and they'll look great.
Forgive my eccentric ramble here, but: German and Dutch, (radios and recorders, respectively) have fine SE transformers. Most will think of the Telefunkens, but the larger Norelco (Philips) tape recorder SE tube outputs at 5K for EL84/6BQ5s, are the cat's meow! I built a small stereo amp with 2 6Y6GT Pentodes, (not triode connected or with feedback). Driven by a 12AX7s. 12AX7s #1 the #2 section driving the 6Y6GT. (2K 6Y6 plate load rated) into the 5K XFMR with a single 4 Ohm output. Separate chassis power supply with Fisher K100 Power iron @ 200 Volts, (no voltage doubler), WWII GE Pyranol PIO power caps and military Chokes. Separate volume controls for each channel. Played through Tele Radios 4 Ohm speakers in DIY cabinets, or Bell and Howell 12" extension speakers w/DIY cabs + NO crossovers. B&H speakers @ 16 Ohms, but distortion not noticed. I say all this because it was really pleasant, and cheap salvage material. The largest Edcor iron re my present SE outputs most of the time, but 45, 171, 50 type triodes (minus) crossovers and a single 'full range', speaker, are so under rated that I just had to speak up. Engineering is ESL to this music lover with limited skills. A fellow mentioned these ideas a few years ago, no one responded, even to argue. I'm just repeating his info, and my experience. I really love this forum, and the effort you folks make with vacuum tube exploration and education is super. Thank you very much. buffstereo1
What kind of military chokes are you talking about?
I ordered these on Jan 12. I got a "pro forma invoice" on the morning of Jan 13 which I promptly paid with Paypal. Shipping for the pair of transformers was $32. I received a paid confirmation an hour or so later, with a copy of the paid invoice. Their web site showed the "estimated dispatch date" of Jan 13.
A week had gone by with no further correspondence, and no updates to their web site. Yesterday I sent an email asking if they were shipped, and what the tracking number was.
This morning I got a very short reply "We will send it today" with a tracking number that UPS shows as invalid.
I will check the number again tonight.
That store is very interesting to visit if you like building things and are in the area. It's been a while but last time I was there, it had a huge assortment of surplus parts on the shelves... I make a point of visiting every time I'm in the Toronto just to poke around the surplus equipment and pick up some parts.
I'd salvage chokes, power Xfmrs, etc. from the lone remaining electronic salvage/junk yard. Something was always wrong with a complete unit but Mullard, Telefunken and amperex 9 pin tubes were often present in USA Military no cost gear, for the most Paaart. I got alot of Chicago Transformer Company, nut also many Raytheon, some Triad, a few UTC, and several made to spec chokes in identical units but with names I was not up on like New York Transformer Co., etc. I used a single Raytheon in this instance It was a gift for a music lover with very cheap gear. Thank you Gideon1990.
Sorry,
Back to my post # 48. I mis-stated the principle.
An underhung voice coil has more efficiency than an overhung voice coil.
A strong magnetic field has more efficiency than a weaker magnetic field.
So, the 1938 Philco with an underhung voice coil, and strong electromagnet field coil has
2 factors that make the speaker quite efficient.
Therefore, the 6Y6 output power was plenty to make the radio play loudly, without even using the maximum output power.
Back to my post # 48. I mis-stated the principle.
An underhung voice coil has more efficiency than an overhung voice coil.
A strong magnetic field has more efficiency than a weaker magnetic field.
So, the 1938 Philco with an underhung voice coil, and strong electromagnet field coil has
2 factors that make the speaker quite efficient.
Therefore, the 6Y6 output power was plenty to make the radio play loudly, without even using the maximum output power.
Glen at A! scrapped like 800 pounds of coils because "nobody builds anything anymore"...
That said, I've found a few transformers and chokes there, There are boxed of old tubes you can sort through if you are looking for oddball TV tubes, too.
That's where I got my stock of 3300uF/450V CDE caps for 6$ each
I pulled chokes and transformers and other parts out of military and industrial scrap for years. The choke seen here in the power supply my 845 SE amp came from some scrap, as did the large oil filled cap with a 1971 date code on the power amp chassis. The choke says "Saratoga Industries" but the cap is a Sangamo, a popular capacitor brand from days gone by. The choke was ripped out of another amp I made, the 300Beast It ate a lightning strike one day that resulted in some dead diodes and caps....it is still waiting for me to rebuild it.
The driver board on the amp chassis was one of the very first two TSE amp prototypes ever made, from before Tubelab Inc. even existed.
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George, sorry to hear about your experience re. TME. Hopefully they will make it good. I have ordered three pairs of OTs from them, directly on their website. Two pairs weighed less than 5 kg and each pair shipped for US$9.90. The largest transformers (KT88PP) weighed 2.8 kg each, and shipping was quoted around what you paid, George. In stead I ordered one OT at a time and paid US$9.90 shipping for each, so $19.80 for two. In every case I received the transformers in central Illinois 3-4 business days after placing the orders.
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