It is still in the development stages. I returned from vacation a little over a week ago, and had one day to experiment on it before returning to work. I have been working 10 to 12 hour days since then, therefore there has been no progress. I haven't even had much time to visit this forum.
I posted the results of the Edcor - 6AV5 experiments here. I got several e-mails that asked me to use a more popular tube since the 6AV5 is not generally available outside the USA, and even some of these (RCA's with slotted plates) didn't like my abuse. There are no other tubes that are even close to the same pinouts as the 6AV5 except for the 6FW5. These are not commonly available either.
During the one day of experimentation, I rewired the amplifier to accept any of the popular audio pentodes in triode, UL or pentode mode. I then tested it with EL-34's, KT-88's, 6L6's, 6550's and a few others. These tubes may cost a little more than the 6AV5's but any of these will take more abuse than the 6AV5. The Shuguang 6L6GC can be purchased for about $9 USD and is one of the best sounding of the low cost tubes. This may add a few dollars to the cost of the Ultimate Cheapo SE, but it improves the reliability of the design and allows for a much wider audience since there are plenty of tube choices.
I then optimized the amp to sound good with these tubes, and tested it with several different ones. I posted the results on the original Edcor transformers thread since the 6AV5 was no longer being used.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=72654&highlight=edcor
I am still planning a 6AV5 amp, however it will likely be a screen driven P-P amp since I can get over 80 watts out of a pair without stressing them, and any 6AV5 tube will work, even the slotted plate RCA.
I currently have two SE amp designs. One is ultra simple, using no unique parts, and the other is a " no compromises" design. I am trying to design one PC board that could be used to build either amp. It includes PowerDrive, tube or SS rectifier, cathode bias, and can do triode, UL, and pentode mode. CFB can be used or disabled. I am trying to design this board for first time builders.
The amp is on my breadboard now, and I will post schematics as soon as I have time to draw them up, and finish tweaking the design.
I posted the results of the Edcor - 6AV5 experiments here. I got several e-mails that asked me to use a more popular tube since the 6AV5 is not generally available outside the USA, and even some of these (RCA's with slotted plates) didn't like my abuse. There are no other tubes that are even close to the same pinouts as the 6AV5 except for the 6FW5. These are not commonly available either.
During the one day of experimentation, I rewired the amplifier to accept any of the popular audio pentodes in triode, UL or pentode mode. I then tested it with EL-34's, KT-88's, 6L6's, 6550's and a few others. These tubes may cost a little more than the 6AV5's but any of these will take more abuse than the 6AV5. The Shuguang 6L6GC can be purchased for about $9 USD and is one of the best sounding of the low cost tubes. This may add a few dollars to the cost of the Ultimate Cheapo SE, but it improves the reliability of the design and allows for a much wider audience since there are plenty of tube choices.
I then optimized the amp to sound good with these tubes, and tested it with several different ones. I posted the results on the original Edcor transformers thread since the 6AV5 was no longer being used.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=72654&highlight=edcor
I am still planning a 6AV5 amp, however it will likely be a screen driven P-P amp since I can get over 80 watts out of a pair without stressing them, and any 6AV5 tube will work, even the slotted plate RCA.
I currently have two SE amp designs. One is ultra simple, using no unique parts, and the other is a " no compromises" design. I am trying to design one PC board that could be used to build either amp. It includes PowerDrive, tube or SS rectifier, cathode bias, and can do triode, UL, and pentode mode. CFB can be used or disabled. I am trying to design this board for first time builders.
The amp is on my breadboard now, and I will post schematics as soon as I have time to draw them up, and finish tweaking the design.
Tubelab: As you´ve mentioned, 6AV5GA are quite rare outside the US, can 6AU5GT be used as a substitute?
I´m planning to build a four channel amp to biamp my speakers , Fostex FE167E with Scanspeak 8545 subwoofers.
Since the Fostex drivers requires much less power than the subs perhaps I could get away with triode wired 6AU5GT for them and 6AV5GA UL for the subs, what do you think?
OTP´s will be XSE15-8-5K and I´ll probably apply CFB.
I´m planning to build a four channel amp to biamp my speakers , Fostex FE167E with Scanspeak 8545 subwoofers.
Since the Fostex drivers requires much less power than the subs perhaps I could get away with triode wired 6AU5GT for them and 6AV5GA UL for the subs, what do you think?
OTP´s will be XSE15-8-5K and I´ll probably apply CFB.
I have not tried the 6AU5 since I only have one, and it looks like it has been worked hard. The specs are similar for both tubes, but the 6AU5 has a much smaller plate structure. I would assume that it would work, but I don't know how much power you can squeeze out of it.
I created a PC board for the 12AT7- 6L6 (or others) amp design. One amplifier is playing nicely. I have been at work 50 to 60 hours / week for the last month. This will continue for at least 3 more weeks. Little time for tube stuff!
I created a PC board for the 12AT7- 6L6 (or others) amp design. One amplifier is playing nicely. I have been at work 50 to 60 hours / week for the last month. This will continue for at least 3 more weeks. Little time for tube stuff!
It is ALIVE!
I decided to leave the 6AV5's for the push pull project, since some of them tend to glow brightly when pushed by the constant dissipation of SE mode. The new amp design uses 6L6's, EL-34's or KT-88's. I run them at 410 volts across the tube, and get as much as 14 watts (KT-88) in UL mode. I plan to send this board out for duplication later this week.
Attachments
Another picture of the completed prototype amp. It is assembled on the piece of plywood that the Edcor transformers came on.
Some more info is available on the web page.
http://www.tubelab.com/SimpleSE.htm
I recently re-did the web site, some new material, more to come.
Some more info is available on the web page.
http://www.tubelab.com/SimpleSE.htm
I recently re-did the web site, some new material, more to come.
Attachments
Looks good Tublab,
I like the plywood! I think it was the model T... Henry Ford had his engineers design and specify the crate that 2nd party suppliers had to use to ship starter motors to the Ford plant. The crates were then dissambled and used in the construction of the coil box assembly.
Sneaky guy!
I like the plywood! I think it was the model T... Henry Ford had his engineers design and specify the crate that 2nd party suppliers had to use to ship starter motors to the Ford plant. The crates were then dissambled and used in the construction of the coil box assembly.
Sneaky guy!
Just in case someone wants to experiment with tubes like these, Antique Electronics Supply has the 12AV5GA on sale for $1.40 USD. They also have the 6AV5GT for the same price.
I just ordered some of each, so I don't know what brands or types will show up. The GA version of all types are all good for screen driven P-P applications, while some of them are capable of triode wired SE applications. The GT version is in a smaller bottle (6V6 size) and therefore capable of dissipating less power. I don't have any of these, and haven't tested them.
www.tubesandmore.com (Antique Electronics Supply)
I just ordered some of each, so I don't know what brands or types will show up. The GA version of all types are all good for screen driven P-P applications, while some of them are capable of triode wired SE applications. The GT version is in a smaller bottle (6V6 size) and therefore capable of dissipating less power. I don't have any of these, and haven't tested them.
www.tubesandmore.com (Antique Electronics Supply)
I´m about to begin a 6AV5/Edcor project soon, not that I don´t have enough valve amps already but most of them are rather experimental and more or less unsafe to handle...
What I need is a compact, low cost amp capable of producing great sound and a decent amount of power, so Sylvania 6AV5GA in UL with CFB seems to be a good choice.
My ambition is to add switches for the CFB and for UL/triode operation, but if (when) I get lazy during the construction they will be the first to go...
There are a few things that need consideration before I start building:
Cathode bias or adjustable grid bias?
CCS-loaded triode or RC-loaded pentode as input stage?
PowerDrive or not?
Valve or SS rectification?
What I need is a compact, low cost amp capable of producing great sound and a decent amount of power, so Sylvania 6AV5GA in UL with CFB seems to be a good choice.
My ambition is to add switches for the CFB and for UL/triode operation, but if (when) I get lazy during the construction they will be the first to go...
There are a few things that need consideration before I start building:
Cathode bias or adjustable grid bias?
CCS-loaded triode or RC-loaded pentode as input stage?
PowerDrive or not?
Valve or SS rectification?
I haven't spent much time playing with 6AV5's lately. My last experiment with them was a P-P screen drive amp running at the edge of class B. Idle current was about 5 mA per tube. I found a great variability in the different types of 6AV5's, but the Sylvanias were the best in the abuse department so you should be able to use them in SE.
All of my original experiments used a modified TubelabSE amp which has a CCS loaded 5842 and a mosfet buffer (PowerDrive). The output stage uses adjustable bias (cathode grounded). The power was provided by an external (tube) regulated power supply. That conbination sounded real good.
I have been wanting to try some 6AV5's in a SimpleSE circuit (CCS loaded 12AT7, no mosfet, cathode bias, tube or SS rectifier) but I haven't had the time.
I have been fascinated by the cathode follower experiments that I have been doing. I believe that I am on to something radically different, but much more engineering is still needed. This thing has consumed ALL of my spare time lately. I did try 6AV5's, 6AU5's and many other sweep tubes in it. the little guys (6AV5's and 6AU5's) don't work.
All of my original experiments used a modified TubelabSE amp which has a CCS loaded 5842 and a mosfet buffer (PowerDrive). The output stage uses adjustable bias (cathode grounded). The power was provided by an external (tube) regulated power supply. That conbination sounded real good.
I have been wanting to try some 6AV5's in a SimpleSE circuit (CCS loaded 12AT7, no mosfet, cathode bias, tube or SS rectifier) but I haven't had the time.
I have been fascinated by the cathode follower experiments that I have been doing. I believe that I am on to something radically different, but much more engineering is still needed. This thing has consumed ALL of my spare time lately. I did try 6AV5's, 6AU5's and many other sweep tubes in it. the little guys (6AV5's and 6AU5's) don't work.
Thanks for the reply.
Even though I have ~10 output tubes I´m planning to run them slightly cooler than 300V 60mA. Probably more like 260-270V 55mA or something.
In the end, the bias and rectifier arrangements will probably be determined by what power transformers I have around.
If I go for cathode bias I guess there´s no use in involving PowerDrive?
Cathode followers, yeah... There´s only a handful of components left to get my PL36 CF monoblocks operational, but they never seem to get finished for some reason.
The fact that I´ve ordered another 1650T output transformer (1,9k 120W PP) to build a PL519 PP follower might have something to do with it...
Even though I have ~10 output tubes I´m planning to run them slightly cooler than 300V 60mA. Probably more like 260-270V 55mA or something.
In the end, the bias and rectifier arrangements will probably be determined by what power transformers I have around.
If I go for cathode bias I guess there´s no use in involving PowerDrive?
Cathode followers, yeah... There´s only a handful of components left to get my PL36 CF monoblocks operational, but they never seem to get finished for some reason.
The fact that I´ve ordered another 1650T output transformer (1,9k 120W PP) to build a PL519 PP follower might have something to do with it...
I have several unfinished amplifiers. They usually get finished enough to make sound, but never seem to get assembled into something presentable.
I look at it this way. PowerDrive requires a negative voltage supply. If you are using cathode bias, you don't need the negative supply. If you have the negative supply, you don't need cathode bias. I prefer adjustable negative bias, but it does make the design more complicated.
I have 2 X Plitron P-P toroidal OPT's that are rated for 400 watts at 20 Hz, 1.2 K ohms. Once I get the follower circuits perfected with 20 watt SE amps, I am planning the mother of all HiFi tube amps using 6LW6's.
Seems to be common amongst DIY folks...
I will probably end up using a 240V 120VA toroid with a Mosfet based capacitance multiplier for about 320-330V B+, this would be enough to allow cathode bias and still be plenty for a good driver stage. I´m going to order two such transformers anyway for another project so I might as well order three.
AFAIK peak A2 operation doesn´t work well with cathode biasing (pure A2 is another matter) so there goes the powerdrive.
Of course it would be good wrt blocking distortion and stuff, but I´m not sure it would be worth the effort (in this case).
If it ends up not being "hifi" you can always sell it to me, I play bass guitar in a metal band...
Try tying the 1uF E280F screen bypass cap to the top of the cathode resistor instead of ground.
If you have gain to spare, you could try connecting the E280F plate resistor to the opt screen tap instead of B+ to give an E-Linear type arrangment. This will reduce distortion, increase bandwith, and improve the amps driving ability by lowering its output impedance.
If you have gain to spare, you could try connecting the E280F plate resistor to the opt screen tap instead of B+ to give an E-Linear type arrangment. This will reduce distortion, increase bandwith, and improve the amps driving ability by lowering its output impedance.
Yes, there might be some changes around the G2 arrangements of the input tubes. My first idea was to use a capacitance multiplier to drop the rail voltage to 150V, but at a closer look the HV winding is centertapped and in it´s original application the CT was used to supply half the B+ to the screen grids of the output tubes.
If the cathode feedback is not enough the next step will be E-linear.
I helped my brother build an amp a while ago that used the same input tubes and output transformers but 807´s instead of 6AV5.
We tested a few different types of negative feedback and ended up with E-linear as it was the best match for his two way speakers.
This might or might not be the case with my (fullrange) speakers.
Edit: The gain did actually drop a lot when we applied the E-linear connection. Must be a whole lot of feedback going on here...
If the cathode feedback is not enough the next step will be E-linear.
I helped my brother build an amp a while ago that used the same input tubes and output transformers but 807´s instead of 6AV5.
We tested a few different types of negative feedback and ended up with E-linear as it was the best match for his two way speakers.
This might or might not be the case with my (fullrange) speakers.
Edit: The gain did actually drop a lot when we applied the E-linear connection. Must be a whole lot of feedback going on here...
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