The camera is a Sony DSC-F828. It is a "prosumer" model from about 5 years ago and is no longer made. I think that it is the only Sony that uses compact flash memory and it will take DVD quality video if you put a microdrive in the card slot. I do not use flash. I use a tripod and I set the camera on F8 for a good depth of field and let the camera set the exposure speed. Shots like these are taken with strong room lighting that is mostly flourescent. I often turn off most of the lights to accentuate heater / filament glow and then fix the lack of contrast in post processing. I use Nikon View software which used to be a free download for processing. It does cropping, and basic color and contrast adjustments. It also does resolution and size scaling for web page or forum size limitations.
AES still has them in their catalog for $9.95. I will solder two diodes in the board in place of the tube socket (much cheaper).
Last nights picture was taken with an Antek 1T200 ($29) power transformer, and two FRED diodes B+ is about 240 volts. The outputs are two dumpster toroids that I got from some thermal label printers. I thought they were both the same since they have the same part number on them but one has 4 secondary wires, and the other has 5. One has far better bass, but the other makes more power. Both will show visible saturation effects at 20Hz on the scope, but neither distorts on seriously bass heavy music, but my lab speakers make no audible sound below 50 Hz even though the cone is moving.
What do you think of the Antek AN-2T230 (230V/200VA) in the application of the 6CW5. It that overkill and too much for the tubes?
Also regarding 6CW5 tubes: any thoughts on Siemens or Motorola tubes as far as quality of construction and durability. I know those companies have decent reputations, but I know nothing about their tubes.
Thanks!
Also regarding 6CW5 tubes: any thoughts on Siemens or Motorola tubes as far as quality of construction and durability. I know those companies have decent reputations, but I know nothing about their tubes.
Thanks!
I used the Antek 1T200 because I had one on the shelf. I have some 400 VA 230 volt toroidal transformers. I will get around to trying them sooner or later. The VA rating doesn't make much difference as long as it is big enough. The 230 volt secondary might raise the B+ voltage too much for the 6CW5's.
All of the 6CW5's that I have are pulls from old HP audio oscillators. I have about 8 of them here and they are all GE's. There are more in the warehouse, but they may also be GE's too.
I don't have much experience with Siemens tubes, but they do have a good reputation. Motorola never made any tubes, they had their name screened on other manufacturers tubes. I have seen RCA, GE and Sylvania tubes with the Motorola brand as well as some I couldn't identify.
All of the 6CW5's that I have are pulls from old HP audio oscillators. I have about 8 of them here and they are all GE's. There are more in the warehouse, but they may also be GE's too.
I don't have much experience with Siemens tubes, but they do have a good reputation. Motorola never made any tubes, they had their name screened on other manufacturers tubes. I have seen RCA, GE and Sylvania tubes with the Motorola brand as well as some I couldn't identify.
I did some digging deep in my warehouse today and forun a total of 47 more 6CW5's that came from HP oscillators. All are used, most are indeed GE's. Some are "HP" branded some of them are marked "by Amperex" and "made in Gt. Britain. There are a few that are not original, replacements of various brands.
The two obvoius standouts are a pair of RCA's that are "made in Canada". These have internal structures that are much smaller that all of the others. I bet that these will glow. I also found a pair of Philips ECG tubes that look like they were made by Sylvania. The date code is 8715, near the end of vacuum tube manufacturing. I don't know what Sylvania stuffed inside the glass, but it isn't a 6CW5.
I also found 7 more of the large dumpster toroids. They all have the same part number, but there are 4 different constructions.
I brought back a pair of isolation transformers (toroids) that can be wired to put out 230 volts. Its time for some experiments.
Just for fun I ordered a sleeve of 10 Siemens 6CW5's and 5 Motorolas (I'll try to see who actually made them when they arrive).
I know I am jumping the gun a bit, but am pretty excited about the prospect of building a Simple P-P, and this seemed a pretty inexpensive way to start.
I know enough to hold off on the rest since the values and specs are sure to change.
Any guess on what may work well as OT's?
I know I am jumping the gun a bit, but am pretty excited about the prospect of building a Simple P-P, and this seemed a pretty inexpensive way to start.
I know enough to hold off on the rest since the values and specs are sure to change.
Any guess on what may work well as OT's?
There are dozens of possibilities and the choice comes down to budget.
6CW5's want 3000 to 3500 ohms. I am getting excellent results with some surplus guitar amp transformers that are 6600 ohms. I put an 8 ohm load on the 16 ohm tap to present a 3300 ohm load to the tubes. I have also used some power toroids with two 120 volt windings for the primary and a single 12 volt winding for the secondary. Not all power toroids will work for OPT's, so you must experiment. The power transformer is a bit harder to figure out with these tubes. The ones that I have tried like 240 to 250 volts of B+ and need at least 350 mA.
EL84's, 6BQ5's and 7189's want 6600 to 8000 ohms. Again the 6600 ohm surplus transformers work great, some rather large 6600 ohm OPT's from Handwound Electronics work good too but cost about a watt of power due to their size. I have also used a pair of the cheapest Edcors, XPP10-8-8K. They sound nice until you turn it up loud with some bass heavy music. They are only rated for 10 watts and I am extracting about 14 watts, so they distort. For $17 each you can't beat them, in fact these are probably the only new $17 OPT that you can buy. The $20 ones would likely be a better choice.
It is unfortunate that the 3.4K transformer is only available with a 4 ohm secondary, since that would be my first choice. I don't know if they would make an 8 ohm version if requested. The 30W 3.8K transformer would work, but it costs more. Another possibility is the 7.6K to 16 ohm 25 watt transformer. This would reflect a 3.8K load to the tubes with an 8 ohm load. I don't have any of these transformers to try, and I am not likely to be ordering any in the near future, since I have several usable transformers here.
The Antek 1T200 that I have results in a B+ voltage anywhere from 219 to 230 volts depending on line voltage. That makes for a cool and conservative running amp, but it only makes about 14 WPC. I let it run at 15 WPC (visible clipping) with a 20Hz sine wave for about an hour and a half. Nothing was hot. The Antek was warm, and the $6 Triad choke was warmer, but not too hot to hold. I realized that I was cranking 300+ mA through a 240 mA choke, so I tried a 300 mA Triad choke. It got almost as warm.
I tried the "isolation" transformer that I had and found out that it isn't an isolation transformer. It puts out about 260 VAC which results in 315 volts of B+. Red plate came in about 1 minute, so I shut it off. I turned the transformer around to get 209 VAC resulting in 244 volts of B+. The amp works fine at this level. I still don't know if a 230 volt secondary would be OK, and I am not sure if the Antek 2T230 will actually produce 230 VAC. I might just order one and test it.
I removed the board and made a spreadsheet with all of the component values that are currently in the board as it exists today. Of course after I did that I found out that .xls is not a valid attachment extension to post here and I don't have winzip on this computer. I'll figure that one out tomorrow.
I will be placing orders from Mouser and Digikey for some more components to try and to build a few more boards. Some component values are still being tweaked.
I then reconnected the board up to my variable power supply and decided to have some fun exploring the limits of some of my 6CW5's. This is what I found. The board is wired in pentode mode with the screens tied to B+ through a 100 ohm resistor. I may raise this value and repeat some experiments tomorrow. The OPT's are surplus 6600 ohm guitar transformers with an 8 ohm load on the 16 ohm tap for a 3300 ohm load. Frequency response is 6Hz to 45 KHz at 10 watts.
I fed the board several sets of GE branded tubes. They are very consistent and all will handle 280 to 290 volts. Power output is 24 to 28 watts at 5% distortion.
I tried the Sylvania "mystery tubes". They are marked 6CW5 but they have something else inside. That something doesn't like to go beyond 250 volts and the screen glows at 250 volts. Plate and screen glows at 275 volts and amp distorts at any power level. Beware, these are useless. The glass is darkened and there are 4 rectangular holes in the plates. The plates are not the typical 6 sided 6CW5 / EL84 shape.
I found 3 "Hewlett Packard by Amperex" tubes that have the Mullard date codes on the bottom. These crank. They work OK at 280 volts and made 30 watts at 3% distortion!
I found some "Hewlett Packard by Amperex" that are marked "made in Japan". These work at 270 volts and make 25 to 28 watts.
As expected the RCA "made in Canada" with the small plates glowed at 22 watts output.
I decided to go in the other direction and find out how low the board will go. The board will make 3 WPC with a 150 volt supply. The distortion at 1 watt was in the .5% range even with this low supply voltage. This makes this board an excellent choice for a hybrid super tube driver.
I will be placing orders from Mouser and Digikey for some more components to try and to build a few more boards. Some component values are still being tweaked.
I then reconnected the board up to my variable power supply and decided to have some fun exploring the limits of some of my 6CW5's. This is what I found. The board is wired in pentode mode with the screens tied to B+ through a 100 ohm resistor. I may raise this value and repeat some experiments tomorrow. The OPT's are surplus 6600 ohm guitar transformers with an 8 ohm load on the 16 ohm tap for a 3300 ohm load. Frequency response is 6Hz to 45 KHz at 10 watts.
I fed the board several sets of GE branded tubes. They are very consistent and all will handle 280 to 290 volts. Power output is 24 to 28 watts at 5% distortion.
I tried the Sylvania "mystery tubes". They are marked 6CW5 but they have something else inside. That something doesn't like to go beyond 250 volts and the screen glows at 250 volts. Plate and screen glows at 275 volts and amp distorts at any power level. Beware, these are useless. The glass is darkened and there are 4 rectangular holes in the plates. The plates are not the typical 6 sided 6CW5 / EL84 shape.
I found 3 "Hewlett Packard by Amperex" tubes that have the Mullard date codes on the bottom. These crank. They work OK at 280 volts and made 30 watts at 3% distortion!
I found some "Hewlett Packard by Amperex" that are marked "made in Japan". These work at 270 volts and make 25 to 28 watts.
As expected the RCA "made in Canada" with the small plates glowed at 22 watts output.
I decided to go in the other direction and find out how low the board will go. The board will make 3 WPC with a 150 volt supply. The distortion at 1 watt was in the .5% range even with this low supply voltage. This makes this board an excellent choice for a hybrid super tube driver.
During the first week of September I created a preliminary parts list and placed orders with all of the usual suppliers (DigiKey, Mouser, Allied, AES and others) for components. The intent was to have them all delivered this week so that I could be taking all of the pictures for the assembly manual this weekend. As of today I have not received anything. I just got shipment confirmation from Mouser yesterday for an order placed last Thursday night. They won't be here until next week and most of the resistors were ordered from Mouser. Guess which parts go in the board first?
I have decided to to a small parts package for the Simple P-P. For this reason I want to use the exact parts that will be in the package for the pictures. The Simple SE will follow shortly. The parts kit will consist of everything that goes on the PC board except the tubes themselves. This decision has put a $1K dent in the Tubelab credit card, so the orders to the parts distributors was rather lengthy. I can't blame them for being a little slow even with the holiday, but almost a week for 2500 resistors, 400 caps, and several other components in small quantities.
My original plans would have me driving north right now, but that has been delayed for a week or two due to complications in Sherri's moms treatments. I will probably spend some time this weekend optimizing and testing the board for EL84's and 7189A's. The build photos will happen as soon as the parts arrive. I can put the manual together on my laptop wherever I am.
I got this in an email from Mouser. "To expedite your order, we upgraded it to ship via UPS 2nd DAY AIR at a total cost of $22.83. We paid for the upgrade and only charged you the rate of UPS GROUND SERVICE." It still won't be here until next week. Could thay be reading this?
She exhausted all conventional cancer treatments almost 2 years ago and was basically told to go home and die. She was accepted in a clinical trial (human guinnea pig experiments) and they have been able to keep the cancer from spreading but they can seem to kill it. The problem is that she lives about 70 miles from the treatment center and must be driven there every week day for 3 weeks on then 2 weeks off. That has become Sherris job for the last 15 months.
I will post the assembly manual and several other updates on the web site as soon as it is done. Of course I will update this thread as progress occurs.
She exhausted all conventional cancer treatments almost 2 years ago and was basically told to go home and die. She was accepted in a clinical trial (human guinnea pig experiments) and they have been able to keep the cancer from spreading but they can seem to kill it. The problem is that she lives about 70 miles from the treatment center and must be driven there every week day for 3 weeks on then 2 weeks off. That has become Sherris job for the last 15 months.
I will post the assembly manual and several other updates on the web site as soon as it is done. Of course I will update this thread as progress occurs.