Do you guys have any experience with these ? I think it’s interesting but couldn’t find any information about it. The circuit looks simple, and the price is low. There is no information about the output transformer specs. EL34 Vacuum Tube Amplifier Single-ended Class A HiFi Stereo Amp DIY KIT 10W x2 | eBay
At the 10 watt level distortion will be considerable
You'll likely get 4 or 5 max at reasonably low distortion.
Why not build from scratch? You will have to buy transformers, tubes and a chassis anyway if you buy the eBay board. A board will limit your component options.
See attachment. This circuit used to be up on the Angela Instruments site. I built a mono pair because I had two small power transformers. I've corrected the Angela schematic. The cathode resistor on the EL34 was wrong. If you build the stereo Angela version a GZ34 will work fine for the rectifier. The best deal around on Hammond transformers is at a1parts.ca If you want to uprate the output trans you use a 125 FSE or GSE
Steve
You'll likely get 4 or 5 max at reasonably low distortion.
Why not build from scratch? You will have to buy transformers, tubes and a chassis anyway if you buy the eBay board. A board will limit your component options.
See attachment. This circuit used to be up on the Angela Instruments site. I built a mono pair because I had two small power transformers. I've corrected the Angela schematic. The cathode resistor on the EL34 was wrong. If you build the stereo Angela version a GZ34 will work fine for the rectifier. The best deal around on Hammond transformers is at a1parts.ca If you want to uprate the output trans you use a 125 FSE or GSE
Steve
I already have a reasonably wide tube selection, at least 4 unused Hammond chassis, sockets, etc. I will need to buy transformers, pots, switches, resistors, caps, etc. A good part of this is included in the kit... I wanted to try a pcb based amp since it makes the layout very simple and clean. I could do a point to point. That could be a good project to design a power amp from the ground up ! I don’t have specific needs, I just want a new project without breaking the bank since I juste finished a tube preamp
For the output power: I’ll be using something like the fostex fe206en full range speakers with high efficiency... I’m ready to deal with the low output power of a SE amp. I also want to do some tests with a pair of cerwin vega that I have. They are supposed to be 102db efficient...
A1parts are cheaper for hammond transformers, but they also have the worst service I ever had when compared with other electronics online site. I think that their online orders dont represent much of their sales... I don’t know if i’M ready to but there again...
For the output power: I’ll be using something like the fostex fe206en full range speakers with high efficiency... I’m ready to deal with the low output power of a SE amp. I also want to do some tests with a pair of cerwin vega that I have. They are supposed to be 102db efficient...
A1parts are cheaper for hammond transformers, but they also have the worst service I ever had when compared with other electronics online site. I think that their online orders dont represent much of their sales... I don’t know if i’M ready to but there again...
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Another vote from me for George's tubelab.com boards.
He has SimpleSE and SimplePushPull boards and lots of support info on his website & also in threads here at diyaudio.
Here is a link to the LUNDAHL Transformers website. There is a long write up that describes the modifications that were done to modernize the original mullard 5-20 into a "new mullard 4-30"
It uses solid state rectifier in the power supply and uses less feedback than the original. From what I remember, the phase inverter is different and the amp takes advantage to the availability of high quality caps that weren’t available in the 50’s when mullard published the original circuit. (Which was an advertising to promote the newly designed el34 and el84 valves...)
Lundahl Transformers • Old fashioned 30W Push Pull amplifier
It uses solid state rectifier in the power supply and uses less feedback than the original. From what I remember, the phase inverter is different and the amp takes advantage to the availability of high quality caps that weren’t available in the 50’s when mullard published the original circuit. (Which was an advertising to promote the newly designed el34 and el84 valves...)
Lundahl Transformers • Old fashioned 30W Push Pull amplifier
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Pete Millet has some recently new 50W/CH mono PP Mullard/LTP circuit boards that can be bought with no output tube sockets, where you remote mount whatever tubes you want. He has the info on his site about that and he will also answer questions on this site.
His regular boards with tube sockets for the sweep/TV tubes could also be used that way also.
His regular boards with tube sockets for the sweep/TV tubes could also be used that way also.
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In Valve Amplifiers, Morgan Jones examines three classic power amp designs, The Williamson, the Mullard 5-20 and the Quad II. He kind of trashes the 5-20. Even the newer variations that use the input pentode wired as a triode seem kind of inelegant, to me anyway. Plus I don't like 12AX7s as phase splitters.
Jones was impressed with the Quad II. Of course it can't be duplicated by DIYers because the output trans has a unique tertiary winding. Though one quasi clone that caught my eye was this one from a few months back on the Japanese DIY thread on this forum.
All of this strays from your original SE Amp intentions.
Cheers, Steve
Jones was impressed with the Quad II. Of course it can't be duplicated by DIYers because the output trans has a unique tertiary winding. Though one quasi clone that caught my eye was this one from a few months back on the Japanese DIY thread on this forum.
All of this strays from your original SE Amp intentions.
Cheers, Steve
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