Pete Millettenabled lockdown project - pair of EL504, good for 40+ pleasant watts!
Very nice build congrats
Actually, I designed it myself with help from the community.
There's a voltage amp using a triode strapped 6F12P pentode section, there's a split-phase inverter, a driver, and then the output board. Pick your board, pick your OPT. It's designed mainly for pushing sweeps as triodes, but one board will work with any typical octal audio tube conplete with jumpers to connect pin 3 to plate ot 1 to 8 for EL34... Sky is the limit really.
I don't think anyone has quite done it like this.
This is version one which requires B435 47u/600V caps. Seeing as nobody else makes one, I made a revision to use normal parts in series.
This is also the first build that uses some nylon fasteners instead of brass... So far, so good.
There's a voltage amp using a triode strapped 6F12P pentode section, there's a split-phase inverter, a driver, and then the output board. Pick your board, pick your OPT. It's designed mainly for pushing sweeps as triodes, but one board will work with any typical octal audio tube conplete with jumpers to connect pin 3 to plate ot 1 to 8 for EL34... Sky is the limit really.
I don't think anyone has quite done it like this.
This is version one which requires B435 47u/600V caps. Seeing as nobody else makes one, I made a revision to use normal parts in series.
This is also the first build that uses some nylon fasteners instead of brass... So far, so good.
Last edited:
Certainly. R2 and C4 (the gNFB network) are on the VA/PI board. I've been told if you get replace C7 and R16 with a red LED, distortion goes down.
In theory, you could replace 6F12P with 12AX7 or something, but I think it'd probably be crap. a 6F12P is like 10 12AX7 in parallel based on transconductance alone. OTOH the 6N8S buffers it anyway. Miller might be an issue but it's an audio amp so probably not? Some of the people on this forum have lots of math. I don't but I like to think I make up for it in creativity AOT = adjust on test. if you use the triad coils you don't need to test anything.
In theory, you could replace 6F12P with 12AX7 or something, but I think it'd probably be crap. a 6F12P is like 10 12AX7 in parallel based on transconductance alone. OTOH the 6N8S buffers it anyway. Miller might be an issue but it's an audio amp so probably not? Some of the people on this forum have lots of math. I don't but I like to think I make up for it in creativity
AOT = adjust on test. if you use the triad coils you don't need to test anything.Attachments
Last edited:
Agreed. I work at a engineering school and have seen that the highly educated professors who have never worked an actual engineering job are lacking in the roll up you sleeves and turn some wrenches, build one of their designs.
One of the smartest and most highly educated people I know can't engineer himself out of a wet paper bag. He's so afraid of making a mistake that he doesn't do anything.
The other thing I've learned is that the laws of nature don't change. That's why they're called laws, they've been tested and the results are always the same. We don't understand everything about nature and the universe, but that makes life exciting.
Go out and make some sparks, make some mistakes. Obviously you did.
Thanks for sharing. I'm interested in your kits.
Duke
One of the smartest and most highly educated people I know can't engineer himself out of a wet paper bag. He's so afraid of making a mistake that he doesn't do anything.
The other thing I've learned is that the laws of nature don't change. That's why they're called laws, they've been tested and the results are always the same. We don't understand everything about nature and the universe, but that makes life exciting.
Go out and make some sparks, make some mistakes. Obviously you did.
Thanks for sharing. I'm interested in your kits.
Duke
Octal sockets came so I built the 6CK octal output boards and installed 12AV5GA tubes. I've never seen Soviet tubes glow like that
They aren't red to the naked eye though. They are running at 320V@60mA.
Photo taken using night mode on a Note 20 Ultra.
They aren't red to the naked eye though. They are running at 320V@60mA.
Photo taken using night mode on a Note 20 Ultra.
Attachments
Last edited:
4-way active crossover
Something different. The picture shows 1 channel of a 4-way, 12AT7-based, active crossover.
Removable cards to set the crossover frequencies. Facility for different slopes. Currently building a mechanism to hold the 2 large cards in place.
Balanced in and out. 20dB or so of gain in each section followed by a buffer.
There's heater regulators and ±150V Maida regulators under the main board at the back.
Since I took the photo I've tidied-up the wiring around the output transformers and between the board and the TVCs at the front.
There are 2 separate power supply boxes as well.
Something different. The picture shows 1 channel of a 4-way, 12AT7-based, active crossover.
Removable cards to set the crossover frequencies. Facility for different slopes. Currently building a mechanism to hold the 2 large cards in place.
Balanced in and out. 20dB or so of gain in each section followed by a buffer.
There's heater regulators and ±150V Maida regulators under the main board at the back.
Since I took the photo I've tidied-up the wiring around the output transformers and between the board and the TVCs at the front.
There are 2 separate power supply boxes as well.
Attachments
Here's the schematics and measurements. Crossover points are 30Hz, 30Hz to 90Hz, 90Hz to 14kHz (full-range driver here) and 14kHz.
The closest place is over here in Europe is Frag Jan zuerst --- Ask Jan First. He has all kinds of covers/bell ends with feet/without feet and for toroids to.
Check him out and grab yourself some nice tubes while you're still at it.
Goodcomponent (GD Parts) offers DHL if you want to pay for it. I buy suckets from them. I had them sent as an "epacket" and they arrived with one month. Next time, I will pay the extra 20$ for DHL and get it in 3 days.
Here's a link to their trafo covers... Wholesale Buy Various Tube Guitar Amp DIY Repair Parts from mafaudio Vintage HIFI DIY
Last edited:
Some photos from someone i do board design for.
This is a build in progress. This is just the underside of a tri-amp system he is building.. Couple of UniversalHV2 boards in there, some delays. Oh and some custom CRCRC boards for feeding six regulators. For Six DHT outputs..
All boards are drawn by yours truely.
Cheers,
V4lve
This is a build in progress. This is just the underside of a tri-amp system he is building.. Couple of UniversalHV2 boards in there, some delays. Oh and some custom CRCRC boards for feeding six regulators. For Six DHT outputs..
All boards are drawn by yours truely.
Cheers,
V4lve
