I did a quick build of a 5E3 amp with a couple of changes. The main one is the 6AK6 instead of 6V6's for a big 2-3W. I also included a switch to change the 5E3 interactive volume and tone controls to a regular resistive divider volume controls. I also put in a switch to disconnect the cap on the second stage cathode resistor. I jumpered out the 4.7k resistor after the voltage doubler and went to a 360 ohm resistor for the output cathodes.
Used a Hammond flat pack transformer for the 6V heaters and used one of the 115V primaries as the high voltage. A 70V line PA transformer for the output transformer.
Did a strip board build.
A quick chassis out of aluminum.
One of my empty cabinets, old 10" console stereo speaker to round it out.
So I did mp3 of a work buddy trying out the 6AK6 amp. He has never played a 5E3 so he didn't know how to get the most of the controls. Please be kind to him as this is his first time playing it. I put it on a Microsoft sharing file place, first time I used it also. If you want to hear the amp you can download it.
http://1drv.ms/1hDNpt3
Used a Hammond flat pack transformer for the 6V heaters and used one of the 115V primaries as the high voltage. A 70V line PA transformer for the output transformer.
Did a strip board build.
A quick chassis out of aluminum.
One of my empty cabinets, old 10" console stereo speaker to round it out.
So I did mp3 of a work buddy trying out the 6AK6 amp. He has never played a 5E3 so he didn't know how to get the most of the controls. Please be kind to him as this is his first time playing it. I put it on a Microsoft sharing file place, first time I used it also. If you want to hear the amp you can download it.
http://1drv.ms/1hDNpt3
Forgot to mention the filter caps were scrounged from electronic ballasts that were defective (from work), the wire was cast offs from building cabling (from work), the knobs were from equipment being replaced (from work), the 70V transformer (from a demolition done at work). I did buy the jacks switches sockets and the cabinet material (although the grill cloth is a place mat that has an open weave design, bought at a dollar store for $2), IEC power connector from an old computer, found the aluminum for the chassis somewhere.
Yeah, didn't cost me much.
Yeah, didn't cost me much.
Can't get any cheaper than that. Sure would be a grat candidate for $100 buck amp challenge. I have a question regarding the output tranny. Is there any noticeable hum since the primary windings are not wound like a true push/pull transformer? I'm curious since I have access to a bunch of line transformers through work and if I could use them, I could save on the outputs for my amp projects. I tried downloading the file, but can't seem to get it to go on my IPad. I appreciate any comments on this from others that have used these granny's in their projects.
Cheers
Cheers
Uneven loads (ac or DC) in the OPT will not cause hum. They will cause harmonic distortion.
In a guitar amp this is not a bad thing. I have not built an amp using anything but line transformers in about 4 years. And I build about 4 amps per year - all different.
PS. and I always check out Printer2's ideas before a new build. Especially if it has a switch.
In a guitar amp this is not a bad thing. I have not built an amp using anything but line transformers in about 4 years. And I build about 4 amps per year - all different.
PS. and I always check out Printer2's ideas before a new build. Especially if it has a switch.
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I'm trying to limit my use of them.
As you can see with the picture of the power and output transformer I have the OT angled. I used some headphones on the transformer's output and moved it around to find the position with the least hum with power going to the PT. I have a little hiss when the amp is on full but no hum, or at least the hum is below the hiss level.
I am pleasantly surprised by the sound out of the transformer. But then again it is 2W through a 10W transformer. I have used a 70V transformer in a 6AQ5 amp and from what I recall it sounded OK.
Speaking of 6AQ5`s, I sort of took them into account when wiring up the 6AK6`s. They have some similar pins and with a switch (yeah, I know, another switch) one of the lines gets flipped to another pin and the cathode resistor gets another resistor in parallel. More or less, don`t have my sheet with me. So the two watts could be bumped up to maybe six. Might be handy when you want to play clean louder, or dirty louder.
Actually for my final design for the $100 amp I did a 12AQ5 design with an isolation transformer and a 70V line transformer. Could probably get close to sneaking under the $100 doing a 5E3. Part list.
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This is a funny line transformer. It actually has a single primary with a center tap. The secondary is where you change the ratio. For the 6AK6 in P-P I would try to go for anything in the 10k and up range.
Perhaps you misunderstood my question. Its not about the uneven loads presented by the primary windings, but rather the current through each half of the winding. If the current through each half of the windings are not equal, the end result is hum. It's like plugging in a weak tube and a strong tube in your amp.
Have you personally experienced this?
I've never had hum from a "weak" tube matched to a "strong" tube. Just a lower level when distortion becomes apparent.
I have made several self split amps, and I don't think they have exactly equal currents in each half of the winding either. And have never had one hum.
I do make sure there is no coupling from the power trafo to the OPT like Printer2 sez.
I've never had hum from a "weak" tube matched to a "strong" tube. Just a lower level when distortion becomes apparent.
I have made several self split amps, and I don't think they have exactly equal currents in each half of the winding either. And have never had one hum.
I do make sure there is no coupling from the power trafo to the OPT like Printer2 sez.
Yes I have. You can simulate this by pulling one of your output tubes out, and basically you're running it single ended. The hum level should increase. In most push pull amps, the B+ to the outputs is not heavily filtered and relies on the push pull action of the tubes to cancel the hum. If you don't hear the hum increase with your amp(s), then your B+ to your output section is virtually ripple free! and therefore the hum is inaudible even when you have only a single tube.
Coincidentally, this the main reason it is highly recommended to use matched output tubes on push pull amps.
Cheers
Say like this one? No issue with using the transformer, even put a switch to change ratios.
12AQ5's in P-P Class A. I also have a switch that disconnects one side of the PI so only one tube is driven resulting in a Class A single ended operation. I need to revisit this amp, sort of like a cathode biased Fender Harvard. I built it to hear what switching different options sounds like. The bad thing is that they were crappy switches and I get a lot of noise from them.
Now I know what amp I want to try next.
I ran into the $100 amp thread several months ago and enjoyed reading through it. I bought one amp kit on eBay and had fun doing it. I'd like to try a push-pull amp and I was all set to build a 4-4-0 using schematics from AX84 and then I read this thread (and costed the 4-4-0 parts).
If you don't mind sharing, what voltage are you getting out of the power transformer?
This ChemE really should have paid attention to his EE friends 35 years ago in college.
I ran into the $100 amp thread several months ago and enjoyed reading through it. I bought one amp kit on eBay and had fun doing it. I'd like to try a push-pull amp and I was all set to build a 4-4-0 using schematics from AX84 and then I read this thread (and costed the 4-4-0 parts).
If you don't mind sharing, what voltage are you getting out of the power transformer?
This ChemE really should have paid attention to his EE friends 35 years ago in college.
220-230V.
I am sure there is more that can be coaxed out of this amp. My buddy just dialed in one sound that he liked and never really played around with the controls all that much. I have not bothered tweaking component values either, just built with what I had.
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