I just ´finished´ (see attached picture) my BA-3 as a preamp for F5 2 days ago, put it in the measurement lab, and connected it to my other equipment yesterday.
It is made with boards from The Shop, uses tightly matched Fairchilds output FETs, and Linear Systems JFETs and 1K trimpots. I put a 50K blue Alps pot in front of it, so I guess the input impedance must be around 25K. It sure took an hour or so to sound better, so for me the burn in question has been answered. It was not because of missing warmup, because it had been on for at least 5 hours, when I put it in the system. Output FETs are on around 47 degrees C., J-FETS less than 30 degrees.
It measures almost as good as the Aikido 6SN7 but so far I think the Aikido sounds better. But I will give it a week to really burn in and also play with the P3´s, before I decide what to do from here, because it is somewhat easier to case the BA-3 than the Aikido. And because I want a Pass designet audiochain if possible
I got 5.5 times amplification with 180 ohms as R13 - 4v P/P in 22v P/P out. That was what I wanted, but not nearly what to expect from the theory. Why is that ?
The power supply is heavy duty, just because I happened to have one, but it is the kind of PSU the BA-3 were intended to use. I may use that later for my comming F4.
Wonder if the Fairchild/LS sound as good as real Toshibas ?
It seems the site would only let me upload 1 picture, more to come.
It is made with boards from The Shop, uses tightly matched Fairchilds output FETs, and Linear Systems JFETs and 1K trimpots. I put a 50K blue Alps pot in front of it, so I guess the input impedance must be around 25K. It sure took an hour or so to sound better, so for me the burn in question has been answered. It was not because of missing warmup, because it had been on for at least 5 hours, when I put it in the system. Output FETs are on around 47 degrees C., J-FETS less than 30 degrees.
It measures almost as good as the Aikido 6SN7 but so far I think the Aikido sounds better. But I will give it a week to really burn in and also play with the P3´s, before I decide what to do from here, because it is somewhat easier to case the BA-3 than the Aikido. And because I want a Pass designet audiochain if possible
I got 5.5 times amplification with 180 ohms as R13 - 4v P/P in 22v P/P out. That was what I wanted, but not nearly what to expect from the theory. Why is that ?
The power supply is heavy duty, just because I happened to have one, but it is the kind of PSU the BA-3 were intended to use. I may use that later for my comming F4.
Wonder if the Fairchild/LS sound as good as real Toshibas ?
It seems the site would only let me upload 1 picture, more to come.
Attachments
In my case you were right. I build a new DDDAC1794 DAC and a B-3 as preamp, and I got some agressivity that I didn´t have before.
It showed up that I needed a resonance damping filter on my tweeters, which were not necessary before.
It showed up that I needed a resonance damping filter on my tweeters, which were not necessary before.
Hi Juma,
A friend and I are considering making your suggested pre-amp for the F5s, as we need more gain, but I am hesitating in one respect. The 7812 and 7912 seem to me a bit of a compromise and in some ways against the philosophy of a really pure amp like the F5. I have avoided such devices in my power supplies, in the same way I have avoided op-amps in my signal chain. Can you suggest another, perhaps cleaner, way to take the F5's voltage and reduce it to 12v? I am hesitant to build a pair of shunt regs just for the Juma pre, but maybe that's what it needs.
By all means feel free to call me out for the standard diyaudio.com obsessive, impractical, purist non-EE that I am.
Many thanks
Lucas
A friend and I are considering making your suggested pre-amp for the F5s, as we need more gain, but I am hesitating in one respect. The 7812 and 7912 seem to me a bit of a compromise and in some ways against the philosophy of a really pure amp like the F5. I have avoided such devices in my power supplies, in the same way I have avoided op-amps in my signal chain. Can you suggest another, perhaps cleaner, way to take the F5's voltage and reduce it to 12v? I am hesitant to build a pair of shunt regs just for the Juma pre, but maybe that's what it needs.
By all means feel free to call me out for the standard diyaudio.com obsessive, impractical, purist non-EE that I am.
Many thanks
Lucas
6L6 - I did not know that! How surprising.
I am wondering if I should consider using the existing power supply, but using it to feed a Salas DCB1 shunt reg, set for 12v, without the B1 part of course. (I have a spare DCB1 board, and my control amp has the DCB1 in already.)
Or...should I use the whole of the Salas shunt reg on the DCB1 board power section, all the way from AC, with a separate transformer?
Or can I go unregulated to 12v from the existing F5 supply? I don't know how...
I am wondering if I should consider using the existing power supply, but using it to feed a Salas DCB1 shunt reg, set for 12v, without the B1 part of course. (I have a spare DCB1 board, and my control amp has the DCB1 in already.)
Or...should I use the whole of the Salas shunt reg on the DCB1 board power section, all the way from AC, with a separate transformer?
Or can I go unregulated to 12v from the existing F5 supply? I don't know how...
I think I will start with the 7812 and the 7912 and not worry about it then 6L6. As you say, if it's good enough for Nelson/ Wayne/ Juma, who am I to argue...? Perhaps down the road I can upgrade if the urge hits me...though I'm not convinced that this amp is as enjoyable as my Peter Daniels LM3875 gainclone (which is hardly ultra purist if you consider the chip itself!)
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I'm quite interested in opinions on the sound of chip amps but I'd never considered somebody might pit one against a Class A amplifier ?
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The F5 does have qualities that are quite exceptional, but it does lack some warmth, compared to the LM3875. I could probably tell them apart in a blind AB test, but it wouldn't be good vs. bad, or chalk vs. cheese, or an earth-shattering difference, but rather a nuanced selection - don't expect the difference to be life changing. Papa himself has said that people often prefer the sound of the Aleph Jr, as it is much warmer and friendlier, for want of a better way to describe it. The F5 also often desperately needs more gain, hence this thread.
By using different components and especially 'doing a number' on the power supply, you can alter the sound of the F5 to a rather large amount - unfortunately, it inevitably adds considerably to the cost.
Juma's version with the smaller fets adds another option, and so on.
Mind you, it won't 'match-up' with all speakers whatever you do, but no amplifier will suit all speakers regardless anyway - it sounds like you've got a good setup with your 3875.
I see you've done an enormous amount of effort on those Ditton Xovers - big challenge - were they the speakers with those little Coles dome super tweeters?
Juma's version with the smaller fets adds another option, and so on.
Mind you, it won't 'match-up' with all speakers whatever you do, but no amplifier will suit all speakers regardless anyway - it sounds like you've got a good setup with your 3875.
I see you've done an enormous amount of effort on those Ditton Xovers - big challenge - were they the speakers with those little Coles dome super tweeters?
We digress, but the Ditton 44 project is ongoing. They are fantastic, if you are a fan of sealed box 3 way speakers, like me. The tweeters are long gone - early plastic dome tweeters (HF2000) that are highly sought after by romantic fools. I thought they were pretty horrendous to be honest, and much prefer a (much cheaper!) modern silk 19mm dome, like the Seas I have in there. The 12" and 5" paper cones in cast baskets are sublime though.
When we first heard them some years ago, they were the c'lassic English sound' for us Ozzies, and a pretty good set of speakers too - it's a real treat to hear that they're being rebuilt with better components -
Perhaps a higher power version of the F5 would be better to do them justice, or the use of high performance Cmultipliers in the power supplies for those big bass drivers in particular?
All the best ...
Perhaps a higher power version of the F5 would be better to do them justice, or the use of high performance Cmultipliers in the power supplies for those big bass drivers in particular?
All the best ...
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