Hello everyone.
Here is the Amp I just finished.
It was made for my mother, and I will be adding lighting per her request.
The Chassis is made of Goncalo Alves. It is a tropical and sustainable hardwood from south and central America. Tough to work with, but the bare wood will last at least 30yrs. for decking. I have left the wood bare. You cannot glue it due to the oils in the wood. It has a very high fire resistance rating.
The top caps are vintage ceramic attached to copper tubing, which goes through a collar attached to the wood. The tube goes all the way through the chassis. The plate wire is fed through the tube, into the top cap with the stripped part of the wire sandwiched between the top cap and anode cap. (I took the clips out of the top caps). It is then locked down with a set screw in the collar.
The contact is firm and the tube, cap and tubing does not move when I try to wiggle it. This was the safest way I could think of to have the top caps... plus, no clips means that it wont pull off the anode caps on the tubes, which frequently happens.
The circuit is simple. I used Regulator tubes to regulate the pre-amp voltage.
The time delay is done via a relay tube shown in the post below.
The Pre-amp tubes are 6ER5's with the power tubes being 1625's. 3DG4's are the rectifier tubes arranged in a voltage doubler configuration. It is in triode mode with 512VDC B+ and 460VDC plate voltage. The OPT impedance is 14K. Magnet wire is mainly used for hook-up wire. Solid, and a high voltage rating... a pain to strip, but great to work with.
Each channel has it's own volume control.
I also used some 837's and 802's with good results, but the dissipation was higher than the 12W (837) and 10W (802) maximum.
Basically, this amp is the most transparent I have made to date. It is also snappy and precise with a tight and low bass. I still has a nice warmth without sounding veiled, mushy or bloated in the bass. There may be some harshness, but I can alter that with changing the coupling capacitor.
The owner (my Mother) likes the sound, and feels that it is not harsh...time will tell.
Comments/ questions are welcome.
Here is the Amp I just finished.
It was made for my mother, and I will be adding lighting per her request.
The Chassis is made of Goncalo Alves. It is a tropical and sustainable hardwood from south and central America. Tough to work with, but the bare wood will last at least 30yrs. for decking. I have left the wood bare. You cannot glue it due to the oils in the wood. It has a very high fire resistance rating.
The top caps are vintage ceramic attached to copper tubing, which goes through a collar attached to the wood. The tube goes all the way through the chassis. The plate wire is fed through the tube, into the top cap with the stripped part of the wire sandwiched between the top cap and anode cap. (I took the clips out of the top caps). It is then locked down with a set screw in the collar.
The contact is firm and the tube, cap and tubing does not move when I try to wiggle it. This was the safest way I could think of to have the top caps... plus, no clips means that it wont pull off the anode caps on the tubes, which frequently happens.
The circuit is simple. I used Regulator tubes to regulate the pre-amp voltage.
The time delay is done via a relay tube shown in the post below.
The Pre-amp tubes are 6ER5's with the power tubes being 1625's. 3DG4's are the rectifier tubes arranged in a voltage doubler configuration. It is in triode mode with 512VDC B+ and 460VDC plate voltage. The OPT impedance is 14K. Magnet wire is mainly used for hook-up wire. Solid, and a high voltage rating... a pain to strip, but great to work with.
Each channel has it's own volume control.
I also used some 837's and 802's with good results, but the dissipation was higher than the 12W (837) and 10W (802) maximum.
Basically, this amp is the most transparent I have made to date. It is also snappy and precise with a tight and low bass. I still has a nice warmth without sounding veiled, mushy or bloated in the bass. There may be some harshness, but I can alter that with changing the coupling capacitor.
The owner (my Mother) likes the sound, and feels that it is not harsh...time will tell.
Comments/ questions are welcome.
Attachments
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Some More Pics.
Also, 802's are NOT a drop in replacement. Unlike the 1625 and 837, the 802 heaters are 6.3v, not 12.6v. I have to series the heaters when using the 802's. Also, a higher value cathode resistor should be used to bring the plate dissipation down.
Also, 802's are NOT a drop in replacement. Unlike the 1625 and 837, the 802 heaters are 6.3v, not 12.6v. I have to series the heaters when using the 802's. Also, a higher value cathode resistor should be used to bring the plate dissipation down.
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Incredible you made an amp with dozens of wire jumpers to your own mother!
You also used stranded wire or salvage computer wire?
The wood cabinet is great though.
You also used stranded wire or salvage computer wire?
The wood cabinet is great though.
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Hi Fullrangeman,
I understand your concern, everything has a reason.
The European terminals are rated for 750v. The others for 600v.
The signal wires are new catVI data cable- pure solid copper with ptfe ( Teflon) insulation. Some of the best dielectric material for signals.
Magnet wire was used due to being solid and the high voltage and high heat rating.
Green jumper wiring goes to ground. Everything is safe...very safe.
I understand your concern, everything has a reason.
The European terminals are rated for 750v. The others for 600v.
The signal wires are new catVI data cable- pure solid copper with ptfe ( Teflon) insulation. Some of the best dielectric material for signals.
Magnet wire was used due to being solid and the high voltage and high heat rating.
Green jumper wiring goes to ground. Everything is safe...very safe.
Cool design . . . what type of output transformers did you use and where did you get them? A 14k primary seems kind of high, I would have expected about half of that. Any comments on why you chose that value?
I've used the European terminals on a breadboard but I've always gone with soldered connections in the final build. Have you had any problems with the connections getting loose in previous builds, or is this the first time you've used them?
Also, what gauge magnet wire did you use and what's the best method for "stripping" off the coating?
I've used the European terminals on a breadboard but I've always gone with soldered connections in the final build. Have you had any problems with the connections getting loose in previous builds, or is this the first time you've used them?
Also, what gauge magnet wire did you use and what's the best method for "stripping" off the coating?
I normally use the terminal strips. They stay tight and allow easy replacement of components. Tweaking is very easy.
My girlfriends uncle has the amp I previously made. He has blown bypass capacitors by putting in tube incorrectly because the center alignment post was broken off. I used terminal strips. The replacement took less than two minutes on the table at his place - unscrew then screw the new one in. No soldering needed. This is why I use separate power and heater transformers. Easy replacement if something goes wrong. Industrial transformers are easy to find.
I use 18ga magnet wire of different colors. 20ga for lines that never see high current, screens, etc. Higher current heater wire was 16ga. or 18ga. The heater wire for the preamp tubes is 24ga. CatVI ( low voltage and low current) In the future, I will use magnet wire.
I use a snap blade and scrape off the enamel of the magnet wire. A fine precision file works as well. It's tedious, but I thing the high voltage rating and being solid is worth it. Plus, I think the enamel dielectric is better for signals. Why spend hundreds on speaker cable with special dialectics only to have an amp made from normal PVC insulated, stranded wire.
The opt's are vintage and bought off ebay. I tested them and the DC ohms is 330. They are small, but put out good tight bass.
I chose the higher impedance due to the harmonic signature. Higher impedance allows for higher voltage (but stay within plate voltage limits) and less current.
I have found this results in less 3rd and odd order harmonics.
Less current helps reduce the dissipation, allows to use smaller power transformers and chokes, even less power supply filtering. Less OPT saturation as well.
Higher voltage also allows you to use a smaller value reservoir capacitor.
I also find the bass to be tighter, lower and more defined. I seem to run out of voltage before current on the output going to the speaker.
I designed this amp using engineering information, AWG ratings, mathematics and simulations rather than tradition and hearsay.
Often, the scientific approach to design contradicts the warm fuzzies and comfort factor of tradition. Thought its through the scientific approach that tradition can be improved upon.
I'm an artist, unlike painting and drawing, electronics is full of rules and requires much less emotion from me, which is why I like it so much during this emotionally turbulent time in my life.
My girlfriends uncle has the amp I previously made. He has blown bypass capacitors by putting in tube incorrectly because the center alignment post was broken off. I used terminal strips. The replacement took less than two minutes on the table at his place - unscrew then screw the new one in. No soldering needed. This is why I use separate power and heater transformers. Easy replacement if something goes wrong. Industrial transformers are easy to find.
I use 18ga magnet wire of different colors. 20ga for lines that never see high current, screens, etc. Higher current heater wire was 16ga. or 18ga. The heater wire for the preamp tubes is 24ga. CatVI ( low voltage and low current) In the future, I will use magnet wire.
I use a snap blade and scrape off the enamel of the magnet wire. A fine precision file works as well. It's tedious, but I thing the high voltage rating and being solid is worth it. Plus, I think the enamel dielectric is better for signals. Why spend hundreds on speaker cable with special dialectics only to have an amp made from normal PVC insulated, stranded wire.
The opt's are vintage and bought off ebay. I tested them and the DC ohms is 330. They are small, but put out good tight bass.
I chose the higher impedance due to the harmonic signature. Higher impedance allows for higher voltage (but stay within plate voltage limits) and less current.
I have found this results in less 3rd and odd order harmonics.
Less current helps reduce the dissipation, allows to use smaller power transformers and chokes, even less power supply filtering. Less OPT saturation as well.
Higher voltage also allows you to use a smaller value reservoir capacitor.
I also find the bass to be tighter, lower and more defined. I seem to run out of voltage before current on the output going to the speaker.
I designed this amp using engineering information, AWG ratings, mathematics and simulations rather than tradition and hearsay.
Often, the scientific approach to design contradicts the warm fuzzies and comfort factor of tradition. Thought its through the scientific approach that tradition can be improved upon.
I'm an artist, unlike painting and drawing, electronics is full of rules and requires much less emotion from me, which is why I like it so much during this emotionally turbulent time in my life.
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I've always used a BIC lighter - heat the end of the wire in the flame a few seconds until the enamel turns to carbon, it scrapes off easily with a pair of side cutters. This is for the very small gauge wire used for winding RF coils.
I wind the coil, then hold the coil in one hand, and use the other hand to torch the free leads and scrape 'em. Just takes a few seconds.
I expect it would only get easier when using larger gauge magnet wire. Torching, that is - wouldn't want to wind coils with it.
Win W5JAG
Burn and scrape was the method taught to me, when my years were a single digit, at the Brooklyn Children's Museum. A kitchen match and sandpaper were the tools.
Today's polyurethane varnish has to beat the living guano out of 1950s enamel. FWIW, I recall solvent being sold that would attack the "Formvar" insulation on "premium" magnet wire.
Thank you!
That is the current draw of the two circuits plus the draw from the voltage regulators, that is about 20mA... about 2mA for each 6ER5's which leaves about 30.5mA for each 802 that is in this picture.
The 1625's take about 35mA - 40mA and gives a total of 90mA -95mA on the meter.
I used to use that method, however, I planned to have over 600vdc B+ on this amp. So I chose to scrape rather than burn as not to compromise the insulation with the heat. Scraping is actually fairly quick with an xacto or snap off blade.
As far as the 600vdc B+... After looking at safety and distortion figures, I decided to do the doubler and tweaked my design to work with a lower voltage of 530vdc B+. After the current limiter and equalizing resistors on the rectifier plates, I ended up with an even lower B+ of 510vdc. Oh well, it puts it in safe range for the 837's.
I have always had real problems scraping the enamel off and soldering to Talema transformer flying leads. Anyone else had this issue, or should I just try and hone my scraping skills?
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