These days one can get DC/DC boost converters, so it would be possible to have an in-car system (or if your truck has a +24V setup).
The single supply rail operation makes these amplifiers more suited to battery use, but they are Class A for most intents and purposes and have a corresponding high continuous current draw.
🙂
Much respect for your work here, Susan.
If someone was to make a multi-channel, one per driver set of Zeus amps, would using hex wound (3:1) output transformers be useful? Or, given the usual 4 or 8 ohm impedance of individual drivers, would 2:1/4:1 be suitable/appropriate instead? Or would it probably be driver dependent?
I've got a single driver full range pair of NFMs planned, and thinking of a pair of 3 ways for further out. I'm considering this in order to take advantage of room correction software. (edit: and more to the point, dsp based crossovers)
If someone was to make a multi-channel, one per driver set of Zeus amps, would using hex wound (3:1) output transformers be useful? Or, given the usual 4 or 8 ohm impedance of individual drivers, would 2:1/4:1 be suitable/appropriate instead? Or would it probably be driver dependent?
I've got a single driver full range pair of NFMs planned, and thinking of a pair of 3 ways for further out. I'm considering this in order to take advantage of room correction software. (edit: and more to the point, dsp based crossovers)
Last edited:
Given that I started this version in 2009, I am not winning any speed-construction competitions with this one! 🙂
I do like the new amps, particularly the handle at the top which I made from some bits of ali from my scrap-bin. With the amp weighing 20kg / 44lbs the handle is essential.
BTW in making these I realised that these heatsinks are not flat, after measuring and carefully getting all the post to the same size I had to redo the sets as the centre post of the three is 1.2mm longer than the outside ones!
Thanks 🙂
For a multi-way setup with a dedicated transformer per driver one could use a single-ended transformer amp for the HF/tweeter and the PP for Mid/Bass if one driver, or SE for the Mid and PP for the Bass. For the sub-bass I direct drive a dual voice-coil sub-woofer instead of having an output transformer.
With the transformers one can indeed optimise the design for the different drivers.
I generally use 4:1 mode which is running into a full range speaker - each has a pair of Jordan JX92s drivers in series, and a vertically firing JXr6HD open-baffle for the HF.
The new amps were orginally going to be duals for this type of arrangement, with an SE and PP transformer in them, but for the moment that adds too much extra weight - 20kg is enough to manage as is! 🙂
Thank you, very helpful in multiple respects.
What's really cool to me is being able to reuse one or more professional rackmount class a/b amp chassis, that might have shorted output transistors or other issues, but good power transformers. I've got one here that looks great, but is worth less than the price of postage. Getting more shouldn't be an issue, and naturally they don't have to match. I could build a pair of SE into one, a PP in another, and have a manageable package that can be put into a nice rack next to a speaker.
We're talking casters rather than handles, of course. Or both.
What's really cool to me is being able to reuse one or more professional rackmount class a/b amp chassis, that might have shorted output transistors or other issues, but good power transformers. I've got one here that looks great, but is worth less than the price of postage. Getting more shouldn't be an issue, and naturally they don't have to match. I could build a pair of SE into one, a PP in another, and have a manageable package that can be put into a nice rack next to a speaker.
We're talking casters rather than handles, of course. Or both.
Last edited:
Do you prefer the sound of the SE version for mids and tweeters or is this more about managing cost/size/heat?
dual voice-coil sub-woofer with the colis in parallel? meaning that for 4 or 2 Ohm speakers no. output transformer is needed, only the dual primary of the transformer to act as a balanced choke?
in that case a low quality transformer should do the trick?
in that case a low quality transformer should do the trick?
True. ..Although the output impedance would be 1.125 Ω or higher. While this is better than typical tube amps after feedback, I was hoping to go the other way (lower). And I see no point to moving one pair to the primary side because 2:1 using the standard arrangement with four secondary coils results in more power and lower output impedance of probably 1 Ω,
Admittedly, it might sound better and could be worth a try.
Thanks
How would a 115+115V:77V 500VA toroid do as OPT with a 4 ohm load?
The background story is that I have one such transformer on the shelf and since I'm a special kind of lazy, I've concluded that it is less awkward to build a dedicated subwoofer amp + active crossover for each of my tube amps than to adjust adjust the level and phase settings each time I change the main amplifier.
So far I've only tried chip amps and various chinese class AB kits as subwoofer amps but it would be nice to try something a bit more exotic (class B with transmitter triodes is in the cards...).
The background story is that I have one such transformer on the shelf and since I'm a special kind of lazy, I've concluded that it is less awkward to build a dedicated subwoofer amp + active crossover for each of my tube amps than to adjust adjust the level and phase settings each time I change the main amplifier.
So far I've only tried chip amps and various chinese class AB kits as subwoofer amps but it would be nice to try something a bit more exotic (class B with transmitter triodes is in the cards...).
SE transformers are bigger than the PP version, or lower power for the same size.
SE mode has to be fully Class A biased for the full frequency range, so if one wants 20Hz or lower then the iron gets really big (see pic). That means more quiescent current so more watts and therefore more heat. SE is NOT cheaper! 🙂
Using SE definitely stops any possibility of crossover distortion!
Sorry, not what I was trying to say.
An automobile type dual voice coil sub-bass e.g. 2000 Watts or more has voice coil windings that can take a few hundred milliamps biasing as a DC voltage, so the coils are in series centre-tap to ground with the other two ends connected in Push-Pull directly to the output MOSFETs.
No output transformer is required.
This is a complete sub-bass power-amplifier.
Power-stage conected to the Vibe Space 15" Dual 4 ohm voice-coil driver.
Mounted in a guitar-cab for practicality.
What is the DC resistance of the primaries, and how much difference is there between the two?
The main issue with toroids is that the primaries are often not well matched, which will cause a bit of asymmetry in the amp's operation., as a sub-bass driver this is likely less of an issue.
I stripped the windings off a large toroid and wound my own. It has three layers: P-S-P.
This is the amp that drives the bass-speaker I made on a kitchen table in the '90s.
To easily get 3:1 without having to go to hex-filar windings I would wind an extra bi-filar section before and after the quad-filar main section.
This is what I have done for some EI-96 SE output transformers I wound recently.
Thanks for your reply!
Using must most accurate DMM, one primary winding measures 1,1-1,2 ohms and the other 1,0-1,1. The 77V winding shows 0,4R, perhaps a bit higher than I would wish for but no worse than what we see in tube amp OPTs.
It also has a pair of 9,5V windings rated 200mA but wound with roughly the same wire thickness as the primaries, perhaps they can be added in series with the primaries to increase the impedance ratio a bit if necessary.
Should be close enough.
You can also use a small 120+120 primary toroid in reverse as the input transformer, as per my previous pic in the direct-drive amp.
I take it that I'd do that twice, one time per each of the two bobbins. But that would leave me with eight extra windings. (?) Please see Footnote 1 below.
The issue I see though, is that because the extra windings would be on the inside and then outside of the quad-filar windings, that either the lengths or the number of turns would not match. ...would not match any other windings. I mean, either the lengths or the turns of the inner bi-filar pair won't match that of the outer pair, nor would they match any of the quad-filar windings. The inner and outer bi-filar pairs would only match themselves.
Footnote 1:
I'm left confused because I thought I only needed four more windings in total, two more for the primary and two more for the secondary; a total of 12 windings. Also I was / am assuming the dual-bobbin standard configuration. Across two bobbins, four extra windings would only amount to one extra bi-filar section needed per bobbin.
That should work, I also have a couple of 10k CT: 600R Edcors that I intend to try as step up/phase splitters.
The 25-70Hz range should be quite forgiving for cheap transformers.
BJT transistors are more linear for this amplifier.
Mosfet has the advantage of using a concertina or op amp driver however that is not used here.
Mosfet has the advantage of using a concertina or op amp driver however that is not used here.
Nope, BJT transistors by themselves are not more suitable.
I use a Triode-BJT hybrid follower in some of my variations, for example line-drivers as can be seen in the pics in my previous post:
https://www.diyaudio.com/community/threads/zero-feedback-impedance-amplifiers.42259/post-7899562
Not needed in my topology...
