Hello
I like the input transformer idea....would be good to try...
For the bias cap I have used WIMA MKP2-.1/250/5 available though Mouser and I am sure other sources....I have fit this, can't quite remember on the top or below the board of 41Hz Amp 6.
http://www.mouser.com/search/Produc...rtualkey50520000virtualkey505-MKP20.1/250/5P5
Regards
I like the input transformer idea....would be good to try...
For the bias cap I have used WIMA MKP2-.1/250/5 available though Mouser and I am sure other sources....I have fit this, can't quite remember on the top or below the board of 41Hz Amp 6.
http://www.mouser.com/search/Produc...rtualkey50520000virtualkey505-MKP20.1/250/5P5
Regards
There are several ways to do a transformer input. The method shown above is a good one.
As for the bias cap, I have not experimented with it enough to know if it changes the sound, though you would think it would make a difference.
If it's not there - it does make a difference! There was a batch of Fenice boards that went out without the bias cap, they had a bad hiss.
As for the bias cap, I have not experimented with it enough to know if it changes the sound, though you would think it would make a difference.
If it's not there - it does make a difference! There was a batch of Fenice boards that went out without the bias cap, they had a bad hiss.
Seraph said:
Did you notice any change in the sound Seraph after replacing the bias cap? I have a 0.1uf PHE426 polypropylene I may fit in my Amp6 if its worthwhile🙂 I think its marked as C26 on the Amp6 pcb but will check to be sure
Hoi Pano,
you mentioned that there are several options for transformer input, can you give me any clue for the other options. The reason I was not sure if the method that I figured out will work is because I don't know exactly how the internal input circuit of the TA2024 is configured. In the datasheet there's only a simplified schematic of the internals of the chip. I have read somewhere else, can't remember where, that the input circuit is actually configured around 2 or 3 internal opamps so I would like to know if it can be handled as one opamp.
If so, then the schematic might work because the ofset at the input of the opamp is in fact the offset of it's output brought back to the input via the feedback resistor, wich is half the power supply voltage (the input circuit runs on a 5V power supply, this is the internal switched mode power convertor wich has it's output on pin 1). Ca (the biascap on pin 16) prevents that there will be no DC differential between the invererting and the non-inverting input of the op-amp.
Am I right about this ? seems like ages since the last time I ever did anything with op-amp circuits so I just want to double check.
The only thing I'm a bit worried about is what will happen with the dc offset. What happens when you put a resistor of 21k between the inverting and the non-inverting input. I was thinking about the Jensen JT-P11 input transformers. These have a dc resistance of about 1.3 kOhm, so with the input resistor of 20 k and the secondary of the transformer ther will be a DC path of 21,3 kOhm betwen the inputs.
Maybe someone can run a spice simulation on this. I have only experience with loudspeaker and tubes simulation software, not with solid state spice models, maybe it's time to learn.
you mentioned that there are several options for transformer input, can you give me any clue for the other options. The reason I was not sure if the method that I figured out will work is because I don't know exactly how the internal input circuit of the TA2024 is configured. In the datasheet there's only a simplified schematic of the internals of the chip. I have read somewhere else, can't remember where, that the input circuit is actually configured around 2 or 3 internal opamps so I would like to know if it can be handled as one opamp.
If so, then the schematic might work because the ofset at the input of the opamp is in fact the offset of it's output brought back to the input via the feedback resistor, wich is half the power supply voltage (the input circuit runs on a 5V power supply, this is the internal switched mode power convertor wich has it's output on pin 1). Ca (the biascap on pin 16) prevents that there will be no DC differential between the invererting and the non-inverting input of the op-amp.
Am I right about this ? seems like ages since the last time I ever did anything with op-amp circuits so I just want to double check.
The only thing I'm a bit worried about is what will happen with the dc offset. What happens when you put a resistor of 21k between the inverting and the non-inverting input. I was thinking about the Jensen JT-P11 input transformers. These have a dc resistance of about 1.3 kOhm, so with the input resistor of 20 k and the secondary of the transformer ther will be a DC path of 21,3 kOhm betwen the inputs.
Maybe someone can run a spice simulation on this. I have only experience with loudspeaker and tubes simulation software, not with solid state spice models, maybe it's time to learn.
Ok, I've just replaced the ceramic 0.1uf bias cap in my Amp6 with the PHE426, so does it make a difference?
It does here in my set up😉 more detail, cleaner midrange
It does here in my set up😉 more detail, cleaner midrange
the Rifa PHE426 seems like a good choice, it's small enough and seems to be of rather good quality. Too bad it's an obsolete type, so hard to obtain (isn't that just always the case in this hobby?) maybe a Black Gate NX-HiQ might work good also, but then again even these seem to go out of production.
I have some 0,1 uF Wima FKP1's and some 0,18uF Jensen paper in oil but they are just to big (RFI pick-up from the surrounding neighbourhood, maybe shielding with some ERS paper might do the trick here) all the smaller caps I have or can find soo far seem to be of about he same or even worse quality then the ones wich are in there so replacing with those is not a good option.
I have some 0,1 uF Wima FKP1's and some 0,18uF Jensen paper in oil but they are just to big (RFI pick-up from the surrounding neighbourhood, maybe shielding with some ERS paper might do the trick here) all the smaller caps I have or can find soo far seem to be of about he same or even worse quality then the ones wich are in there so replacing with those is not a good option.
panomaniac said:
You should try a better cap here Michael, its made quite a big difference to my Amp6
The polypropylene cap I've fitted is quite small, I'm going to try some different caps, main difference is the vocals are now soo much sweeter, bass seems to be a little softer though, its a little late here so I'll have a good listen tomorrow
Sjef said:
Yes, its worth experimenting, I'm still very surprised at the difference tbh, I refitted a 0.1uf ceramic back in to make sure its not placebo, its deffinately not and the difference was obvious😉
I may have a 0.1uf BG NX Hi-Q knocking around so will try that tomorrow.
I have tried the Wima FKP caps before and found them to be too soft but give it a go, only caps I've tried in the bias position is the ceramic and PHE426
maybe a bit off-topic in this thread but I just came along a nice website with a good animation of the effect of power supply bypassing capacitors. have a look (somewhere at the middle of the page http://www.williamson-labs.com/480_rlc-c.htm
What about a super reg supplying the V5A and V5D pin? anybody tried this? maybe overkill but thats part of the fun😀
Just an update on the Caddock resistors.
I read that they may be directional, so I tried them in all different positions. It seems to actually sound different to my ears depending on the direction. I prefer the Caddock labels facing the volume pot. I know the original resistors are also installed directionally, or alteast they seem to be.
Edit: changed my mind.
I read that they may be directional, so I tried them in all different positions. It seems to actually sound different to my ears depending on the direction. I prefer the Caddock labels facing the volume pot. I know the original resistors are also installed directionally, or alteast they seem to be.
Edit: changed my mind.
Howdy fellas
It is good to come back and see the activity on this thread.
As far as the bias cap I replaced on Amp 6, namely the WIMA MKP2-.1/250, I can only recommend that if you can fit a better cap, by all means do it. Did it make a difference in my case? I can only report on what I did which included replacement of C26 (bias cap) as well as C6, C7, C16, and C17 at the same time. I also replaced the output caps with Sonicaps Gen II, .47 uf/200v which required moving the inductors to the bottom of the board to make room. Mind you all this can be a painstaking task but not too bad if you have patience to make sure your solder joints are not compromised. Result? Yes the overall sound is more honest to the timbre, somewhat sweeter with a well defined bass. Grant it I am still experimenting with different components; ie, for the input caps I am using the Russian PIO K75-24 2.2 uf Vs the 3.3 uf Westcaps I was previously using. Again the overall sound is definitely more musical and attractive to my ears. Yesterday I was listening to the tuner in the background sort of while doing some work on my pc when the bass in an acoustic piece made me stop and listen to the music...The set up was doing the magic...
All this about Amp 6, should it be under a different threat? Well it's all related I suppose...
Best to all of you
It is good to come back and see the activity on this thread.
As far as the bias cap I replaced on Amp 6, namely the WIMA MKP2-.1/250, I can only recommend that if you can fit a better cap, by all means do it. Did it make a difference in my case? I can only report on what I did which included replacement of C26 (bias cap) as well as C6, C7, C16, and C17 at the same time. I also replaced the output caps with Sonicaps Gen II, .47 uf/200v which required moving the inductors to the bottom of the board to make room. Mind you all this can be a painstaking task but not too bad if you have patience to make sure your solder joints are not compromised. Result? Yes the overall sound is more honest to the timbre, somewhat sweeter with a well defined bass. Grant it I am still experimenting with different components; ie, for the input caps I am using the Russian PIO K75-24 2.2 uf Vs the 3.3 uf Westcaps I was previously using. Again the overall sound is definitely more musical and attractive to my ears. Yesterday I was listening to the tuner in the background sort of while doing some work on my pc when the bass in an acoustic piece made me stop and listen to the music...The set up was doing the magic...
All this about Amp 6, should it be under a different threat? Well it's all related I suppose...
Best to all of you
Talking about overkill,
Yesterday I suddenly remembered that I have still got a battery powersupply in the closet wich I made once for my CD player. Haven't used it for years and it seemed that the batteries where still o.k. after a full recharge. It's not a fully battery supply, in fact it is a pack of six 6V/7Ah SLA batteries wich make a +/-18V raw battery supply. This is fed into two discrete stabilasation circuits to make a +/- 12V supply and finally there is buffertank of 16*4700uF caps.
Did it sound better then the SMPS, well to be honest, no. Is it worse, well not in everything. It defenatly sounds completely different than the SMPS. The smps sound a little mored edged (still the biggest problem of the whole Trends amp) so you might think that the battery/stab/cap supply is better, weel yes in that area it is but it's also a lot slower and more closed in sounding then the smps. The smps has more air around it and much more detail and dynamics.
Maybe things will change the next couple of days, i will just let it play this way (if I don't get the urge to switch back to my triode amps) so these are as always only early conclusions.
Yesterday I suddenly remembered that I have still got a battery powersupply in the closet wich I made once for my CD player. Haven't used it for years and it seemed that the batteries where still o.k. after a full recharge. It's not a fully battery supply, in fact it is a pack of six 6V/7Ah SLA batteries wich make a +/-18V raw battery supply. This is fed into two discrete stabilasation circuits to make a +/- 12V supply and finally there is buffertank of 16*4700uF caps.
Did it sound better then the SMPS, well to be honest, no. Is it worse, well not in everything. It defenatly sounds completely different than the SMPS. The smps sound a little mored edged (still the biggest problem of the whole Trends amp) so you might think that the battery/stab/cap supply is better, weel yes in that area it is but it's also a lot slower and more closed in sounding then the smps. The smps has more air around it and much more detail and dynamics.
Maybe things will change the next couple of days, i will just let it play this way (if I don't get the urge to switch back to my triode amps) so these are as always only early conclusions.
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Why are you using the stabilasation circuit if you could run the 6v SLA's in series to get to the desired 12V -14V. A voltage regulation is probably not beneficial for the sound, but I could be wrong. Could you try it without the voltage regulation but leave the buffer tank in place and report back to us if it makes things better or worse?
Greets,
Klaus
Greets,
Klaus
That was exactly what I had in mind.
The stabalizoers where in there because the power supply was origianaly made for my cd player a couple of years ago and I didn't wnat the hassle of the batteries running out while listening to music. I listen to music for about 18 hours a day when I'm at home all day so I wanted it to last longer than that. With the charger on the voltage goes up to about 22V wich is too high or the CD player but I realy wanted it in a way I could listen to it even with the charger on.
The stabalizer isn't soo bad when fed from batteries. Stabs like a clean DC at their inputs as well, just try a CLC network before any typical LM317 or 78xx stab and you'll know what I mean.
In the next days I will try to refit the power supply in a way that the Trends is fed directly from the batteries, with and without the buffertank. At the moment I only wanted to see if it made any difference at all, yep it does, experiment succeeded so far. I will report back.
The stabalizoers where in there because the power supply was origianaly made for my cd player a couple of years ago and I didn't wnat the hassle of the batteries running out while listening to music. I listen to music for about 18 hours a day when I'm at home all day so I wanted it to last longer than that. With the charger on the voltage goes up to about 22V wich is too high or the CD player but I realy wanted it in a way I could listen to it even with the charger on.
The stabalizer isn't soo bad when fed from batteries. Stabs like a clean DC at their inputs as well, just try a CLC network before any typical LM317 or 78xx stab and you'll know what I mean.
In the next days I will try to refit the power supply in a way that the Trends is fed directly from the batteries, with and without the buffertank. At the moment I only wanted to see if it made any difference at all, yep it does, experiment succeeded so far. I will report back.
The never ending story continues,
Yesterday I have tried several different options with the power supply. The batteries with stabs and buffertank is not very good, still much more closed in then the Trends smsps. So I have tried the batteries without the stabs. Better, but still lack of air and dynamics. With the bufertank it's only worse. So I have tried a small buffer of 2200uF Panasonic FC, better, but still. I have to play with it for the next days I guess. So far the battery power is a little bit more quiet than the smps wich is a little edgy but there's one thing missing in them and I would call it the lack of speed. That's about the same conclusion I have had a couple of years ago with the battery power supply on my CD player.
Conclusion so far is that I like the smps better, although it is far from perfect. have to tweak some more here. One thing is very clear and that is that the Trends amp is very sensitive to the power supply as well as other surrounding components.
Yesterday I have tried several different options with the power supply. The batteries with stabs and buffertank is not very good, still much more closed in then the Trends smsps. So I have tried the batteries without the stabs. Better, but still lack of air and dynamics. With the bufertank it's only worse. So I have tried a small buffer of 2200uF Panasonic FC, better, but still. I have to play with it for the next days I guess. So far the battery power is a little bit more quiet than the smps wich is a little edgy but there's one thing missing in them and I would call it the lack of speed. That's about the same conclusion I have had a couple of years ago with the battery power supply on my CD player.
Conclusion so far is that I like the smps better, although it is far from perfect. have to tweak some more here. One thing is very clear and that is that the Trends amp is very sensitive to the power supply as well as other surrounding components.
I can only confirm what SJEF says. I have a modded Trends with the stock power supply. Unfortunately I also have chronic voltage sags which the T doesn't appreciate. Obviously there's some work to be done here to provide a nice clean steady supply.
It's a lash up at the moment. I've run out of terminal rings, so can't make up the fly leads for the fourth cap. I've just finished it, and haven't powered up, but it's 3 x 68 000 uF Nippon Chemicon Stubbies off a Skynet 8080 SMPS. I need to rig up the DPDT switch to the big bleeder resistor - in the mean time, I'll be watching these caps!! 
I tried the SLA and SMPS on the scope, but need to have another go to note down the ripple voltage. What a hoot! 😀
Later...
Jon
I tried the SLA and SMPS on the scope, but need to have another go to note down the ripple voltage. What a hoot! 😀
Later...
Jon
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