My apology guys, maybe it was to late. Indeed i messed up RG with RS series. I will order anyway all usable values.
@George - decided to give it a shot to OPA 827. For this specific opamp i need 100pf at c32 and 5pf (or lower?) between pins 2&6 right?
For the small one i will choose a C0G but for C32 should i choose a mica dielectric or a film FKP? Now i have Amstrans
@George - decided to give it a shot to OPA 827. For this specific opamp i need 100pf at c32 and 5pf (or lower?) between pins 2&6 right?
For the small one i will choose a C0G but for C32 should i choose a mica dielectric or a film FKP? Now i have Amstrans
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If You have the right value, I would leave the Armtrans..
Also consider two Pana PPS in series.. Like 0805 /50V /220pF..
(Mauro had used like this in his EVO)
And yes, You got it well.
You could also consider my photo..
It's a pain but turns out to be one of the better sounding solutions.. (those are Susumu RS quartetts)
Ciao, George
Also consider two Pana PPS in series.. Like 0805 /50V /220pF..
(Mauro had used like this in his EVO)
And yes, You got it well.
You could also consider my photo..
It's a pain but turns out to be one of the better sounding solutions.. (those are Susumu RS quartetts)
Ciao, George
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Dan,
In full honest - I don't know why it works. In theory the RG series should be the more precise.
I'm afraid it's more due to some technology change between the two series. But only a guess, did not try the larger size RG.
Also: at that point (and it's a point I would like to test further), I mean size, there are the through hole precision resistors, maybe Dale? Or Vishay PTF? The original welwyn RC55? (Mauro had used it)
Ciao, George
In full honest - I don't know why it works. In theory the RG series should be the more precise.
I'm afraid it's more due to some technology change between the two series. But only a guess, did not try the larger size RG.
Also: at that point (and it's a point I would like to test further), I mean size, there are the through hole precision resistors, maybe Dale? Or Vishay PTF? The original welwyn RC55? (Mauro had used it)
Ciao, George
Hello to all, I live in Rome, so it seems we have a lot of time to spend at home, in this period. Not too bad at all, more time to spend for my passions, I just finished to refine my diy speakers, yesterday, after years of waiting... let us bring quality to our time and be positive!
I bought (sincerely I don't remember when) a pair of rev 1.0 boards, sincerely during years I loose many referring point about this project, so I kindly ask for someone to help me to resume it by the right way.
I have to explain my needs, to give an example of what I'm looking for:
1) I'll use it in a multiamplification system, directly connected (previously eq'ed with an electronic passive compensation emulator) to a Lowther DX3, so safety is the first choice due to the (absurd) cost of these speakers. I need a very stable version;
2) Lowther DX3 is a quasi-100dB beast in the most sensitive range of human hearing, low distortion should be a must, but in my experience many solutions sound better at the cost of a fraction of more distortion, so I need the more "musical" version (I read about a version with Mauro Penasa's first compensation choice). I know that is a subjective question, anyway suggestions will be very appreciated, I'll make my choice under my direct responability, I assure!!
3) can I use my old Rev 1.0 board to achieve these goals? I'm quite skilled in diy, if I have to make some changes/adjustments I'm not scared to do it, but if I have to buy new boards, are them still available? If I need new ones and I'll find them please consider that I have 4 Rev 1.0 boards, I'll be happy to send them at postage shipping cost, since I'll don't need them anymore, just let me inform about the shipping method in this particular period. They are the "made in Italy" ones, very, very good boards (sincerely I'd be happy to use them, if it's possible, but I'm ready to go for the best way to make my Lowther sing).
Thank you all for your attention, please have a good time in these difficult times, we'll see the Sun again, always with music in mind!
Massimo
I bought (sincerely I don't remember when) a pair of rev 1.0 boards, sincerely during years I loose many referring point about this project, so I kindly ask for someone to help me to resume it by the right way.
I have to explain my needs, to give an example of what I'm looking for:
1) I'll use it in a multiamplification system, directly connected (previously eq'ed with an electronic passive compensation emulator) to a Lowther DX3, so safety is the first choice due to the (absurd) cost of these speakers. I need a very stable version;
2) Lowther DX3 is a quasi-100dB beast in the most sensitive range of human hearing, low distortion should be a must, but in my experience many solutions sound better at the cost of a fraction of more distortion, so I need the more "musical" version (I read about a version with Mauro Penasa's first compensation choice). I know that is a subjective question, anyway suggestions will be very appreciated, I'll make my choice under my direct responability, I assure!!
3) can I use my old Rev 1.0 board to achieve these goals? I'm quite skilled in diy, if I have to make some changes/adjustments I'm not scared to do it, but if I have to buy new boards, are them still available? If I need new ones and I'll find them please consider that I have 4 Rev 1.0 boards, I'll be happy to send them at postage shipping cost, since I'll don't need them anymore, just let me inform about the shipping method in this particular period. They are the "made in Italy" ones, very, very good boards (sincerely I'd be happy to use them, if it's possible, but I'm ready to go for the best way to make my Lowther sing).
Thank you all for your attention, please have a good time in these difficult times, we'll see the Sun again, always with music in mind!
Massimo
A bit more explanation. Using quads does increase the power rating because it spreads out the power between the 4 resisters, but that is not the usual reason for trying quads in a low power signal like George is doing with his RS quads. The theory suggests that using quads reduces distortion and in some cases, it seems to sound better.
Just using a higher watt resistor, like the HRG, might be better sounding, but not for the same reasons as George's quads. Most likely, the HRG won't sound different than a plain RG because it is a higher watt version of the same technology. The safest bet, for non-heroic solders, is probably the RS. Look here to find too much information about quads.
Quad or Series/Parallel Resistors as an alternative to traditional power resistors
In addition to George's alternative to the Caddock in R3, I have used 1 watt Susumu in a quad configuration on a mini pcb to spread out the heat. These resistors are metal foil SMD and it works pretty well.
KRL3216E-C-R330-F-T1 Susumu | Mouser
Massimo,
I will let Dario respond to component choices, but you should be able to make a very nice amplifier with the v1.0 boards. That said, there is a clear distortion reduction with the newer boards, so I would recommend new boards if possible. Last I knew, Dario had a few boards available.
One nice thing about the design is that it has a speaker protection built in. If too much DC is present in the output, a relay is opened to save the speaker. That said, you should look into the circuit design and simulate it. The amount of DC for the relay to open may be higher than the Lowther would be happy with.
Jac
I will let Dario respond to component choices, but you should be able to make a very nice amplifier with the v1.0 boards. That said, there is a clear distortion reduction with the newer boards, so I would recommend new boards if possible. Last I knew, Dario had a few boards available.
One nice thing about the design is that it has a speaker protection built in. If too much DC is present in the output, a relay is opened to save the speaker. That said, you should look into the circuit design and simulate it. The amount of DC for the relay to open may be higher than the Lowther would be happy with.
Jac
Hi Jac,
"may be higher than the Lowther would be happy with"... yes, the magic and the pain of a paper voice coil former...!
Lowhter is a strange beast, it cost about six month to me to find an adeguate crossover compensation to be happy with the typical vivid Lowther sound without my ears being affected from the notorious, annoying "spark" in the first mid-high range, but from the first time that I heard to them I was sure that they was the ones I've been looking for for years.
But they remain very sensitive speakers, so I'd like to go with the new less distortion boards if Dario has a couple to sell me.
Thank you a lot for the reply.
Massimo
"may be higher than the Lowther would be happy with"... yes, the magic and the pain of a paper voice coil former...!
Lowhter is a strange beast, it cost about six month to me to find an adeguate crossover compensation to be happy with the typical vivid Lowther sound without my ears being affected from the notorious, annoying "spark" in the first mid-high range, but from the first time that I heard to them I was sure that they was the ones I've been looking for for years.
But they remain very sensitive speakers, so I'd like to go with the new less distortion boards if Dario has a couple to sell me.
Thank you a lot for the reply.
Massimo
Hi Jac,
Thanks for the input and the links. There seem to be several mechanisms at play here when it comes to resistor performance. This thread includes measurements showing that larger resistors have lower 1/f noise (all else being equal). Presumably this is because they heat up.
High 1/f noise in SM resistors
Similarly, the lower heating will modulate the resistance less, leading to lower distortion. There’s also this from Vishay describing their MELF resistor, which refers to surface area affecting field strength, which leads to lower current noise …
https://www.vishay.com/docs/48111/_melf_venturecraft_en_vmn_ad0409_1607.pdf
The RS resistors have different materials/construction to the RG, which leads to better noise. How all this pans out to what we hear, who knows. I also used quad 1 watt Susumus for R3 following your idea, worked well.
Best,
Dan
Thanks for the input and the links. There seem to be several mechanisms at play here when it comes to resistor performance. This thread includes measurements showing that larger resistors have lower 1/f noise (all else being equal). Presumably this is because they heat up.
High 1/f noise in SM resistors
Similarly, the lower heating will modulate the resistance less, leading to lower distortion. There’s also this from Vishay describing their MELF resistor, which refers to surface area affecting field strength, which leads to lower current noise …
https://www.vishay.com/docs/48111/_melf_venturecraft_en_vmn_ad0409_1607.pdf
The RS resistors have different materials/construction to the RG, which leads to better noise. How all this pans out to what we hear, who knows. I also used quad 1 watt Susumus for R3 following your idea, worked well.
Best,
Dan
Hey Dan,
I had forgotten that you had played with R3.
As you say, there is a lot going on,some of it contradictory and some not enough information. In the end, you just have to try it.
Thanks for the link. That was a pretty good conversation and I wouldn't have expected the kinds of results he was getting, even at a gain of 800.. Especially at the relatively low resistance values he was measuring. Usually,you think of 1/f noise as something that happens at low frequencies with high resistance.
Let us know if you try the 1 watt HRGs. I'm curious to learn more.
Jac
I had forgotten that you had played with R3.
As you say, there is a lot going on,some of it contradictory and some not enough information. In the end, you just have to try it.
Thanks for the link. That was a pretty good conversation and I wouldn't have expected the kinds of results he was getting, even at a gain of 800.. Especially at the relatively low resistance values he was measuring. Usually,you think of 1/f noise as something that happens at low frequencies with high resistance.
Let us know if you try the 1 watt HRGs. I'm curious to learn more.
Jac
I would go with the latter version boards.
Jac,
I too have a lot of time right now. I might be able to share.
I was using Lowther drivers in a diy folded TWQT cabinet when the My_Ref was released. The first A version Circuit Board that Mauro provided was gold plated. Later modified to Rev C. Very good, much better than the Hiraga Le Monstre and Pass clones I had built.
All worked very well with the PMA2, A6, and A7 drivers I had. Just they got better. Mauro tested all updates throughly before releasing. He even progressed and replaced the SIP general purpose rectifiers, the Zener based voltage regs, and other non-audiophile parts of his project.
The last work he did for us was not a full release. He was angered by seeing My_Ref Rev C boards for sale on eBay. He provided the IP for diy, seeing them for sale without an approval really twisted him up. Like many Italians he was very passionate and proud.
He only sold My_Ref Evo boards to people he had developed a trust with. Once they were all gone he okayed the FE build.
I had moved on from Lowthers by the time Evo was released. Was using the opposite of aLowther, B&W 801 Matrix II. Built the Full with paralleled LM3886. Drove the low efficiency, low impedance B&W extremely well.
Did compare the Evo Rev A with normal Evo. No comparison. Rev A is much more full range and dynamic.
Currently using something completely different than Lowthers, Klipsch La Scala II. Another 100 dB+ speaker, but horn loaded three way.
Every build is different, but I like my FE Evo Rev A better than the stereo Evo board converted to Rev A. Sounds clearer.
And on the importance of the relay with Lowthers. It was around 2002 and I was playing music on an original My_Ref. Had a connection on the feedback loop open up after months of use. Dumped full rail voltage on the output. About 32 volts.
The sound was like a 12 ga shotgun was fired in the house. My wife thought we had an explosion. I knew it was the My_Ref. The music stopped same time as the bang.
My favorite drivers were playing. PM 7A, 15 ohm with silver voice coils. Expected to find the driver destroyed.
It looked fine and still measured 12 ohms dc. Moved in and out okay.
Spent a while finding the issue. Touched an iron to the bad connection and it fixed this for good.
Hooked it all back up and went right back to playing music. No damage.
Having a relay is good.
Jac,
I too have a lot of time right now. I might be able to share.
I was using Lowther drivers in a diy folded TWQT cabinet when the My_Ref was released. The first A version Circuit Board that Mauro provided was gold plated. Later modified to Rev C. Very good, much better than the Hiraga Le Monstre and Pass clones I had built.
All worked very well with the PMA2, A6, and A7 drivers I had. Just they got better. Mauro tested all updates throughly before releasing. He even progressed and replaced the SIP general purpose rectifiers, the Zener based voltage regs, and other non-audiophile parts of his project.
The last work he did for us was not a full release. He was angered by seeing My_Ref Rev C boards for sale on eBay. He provided the IP for diy, seeing them for sale without an approval really twisted him up. Like many Italians he was very passionate and proud.
He only sold My_Ref Evo boards to people he had developed a trust with. Once they were all gone he okayed the FE build.
I had moved on from Lowthers by the time Evo was released. Was using the opposite of aLowther, B&W 801 Matrix II. Built the Full with paralleled LM3886. Drove the low efficiency, low impedance B&W extremely well.
Did compare the Evo Rev A with normal Evo. No comparison. Rev A is much more full range and dynamic.
Currently using something completely different than Lowthers, Klipsch La Scala II. Another 100 dB+ speaker, but horn loaded three way.
Every build is different, but I like my FE Evo Rev A better than the stereo Evo board converted to Rev A. Sounds clearer.
And on the importance of the relay with Lowthers. It was around 2002 and I was playing music on an original My_Ref. Had a connection on the feedback loop open up after months of use. Dumped full rail voltage on the output. About 32 volts.
The sound was like a 12 ga shotgun was fired in the house. My wife thought we had an explosion. I knew it was the My_Ref. The music stopped same time as the bang.
My favorite drivers were playing. PM 7A, 15 ohm with silver voice coils. Expected to find the driver destroyed.
It looked fine and still measured 12 ohms dc. Moved in and out okay.
Spent a while finding the issue. Touched an iron to the bad connection and it fixed this for good.
Hooked it all back up and went right back to playing music. No damage.
Having a relay is good.
Hi Panelhead,
so, another Lowther lover... I use them in a quasi-fullrange system, with 16 to 150 Hz reinforcement with one Adire Shiva in TL and a "magic couple" formed by a JBL 123-A and an Altec 208Y in open baffle with the Lowther. An AMT 1 is used for energy filler/inductance compensation in the last octave (1uF hipass 6db/oct).
I'm very pleased by my loudspeakers, I spent a lot of time refining them, starting from the components choice to couple with Lowther finishing with the crossover/compensation tuning. Now I'd like to run in multiamplification, a 40W amplifier is more than enough to drive the Lowther to a reasonably realistic pressure level, for my taste.
So far by now I have a couple of original Mauro Penasa's pcb Rev C and four Dario's Myref FE rev 1.0 board, but I never had the time to build them. I wrote to Dario this evening, I hope he can send me a couple of the last pcb to conclude this project.
32 Volts on a Lowther... a nightmare!! Yes, definitively a relay is not only good, but indispensable. I read about stability issue of this particular topology of power amp in driving speakers with passive crossover, this is the reason why I want to build an exact replica of my crossover in the line environment before the power amp, using inductor simulator. I found an electronic configuration that can simulated a series inductor, not only a parallel with one terminal to ground as usual: the Antoniou circuit. I expect to pass a lot of time on it...
so, another Lowther lover... I use them in a quasi-fullrange system, with 16 to 150 Hz reinforcement with one Adire Shiva in TL and a "magic couple" formed by a JBL 123-A and an Altec 208Y in open baffle with the Lowther. An AMT 1 is used for energy filler/inductance compensation in the last octave (1uF hipass 6db/oct).
I'm very pleased by my loudspeakers, I spent a lot of time refining them, starting from the components choice to couple with Lowther finishing with the crossover/compensation tuning. Now I'd like to run in multiamplification, a 40W amplifier is more than enough to drive the Lowther to a reasonably realistic pressure level, for my taste.
So far by now I have a couple of original Mauro Penasa's pcb Rev C and four Dario's Myref FE rev 1.0 board, but I never had the time to build them. I wrote to Dario this evening, I hope he can send me a couple of the last pcb to conclude this project.
32 Volts on a Lowther... a nightmare!! Yes, definitively a relay is not only good, but indispensable. I read about stability issue of this particular topology of power amp in driving speakers with passive crossover, this is the reason why I want to build an exact replica of my crossover in the line environment before the power amp, using inductor simulator. I found an electronic configuration that can simulated a series inductor, not only a parallel with one terminal to ground as usual: the Antoniou circuit. I expect to pass a lot of time on it...
I would stick to micas for low pF values and Amtrans for higher values.
Welwyn RC55 despite being high precision, low tempco and non magnetic design hide a great amount of detail and sparkle.
Vishay PTF sound as clean and balanced as metal foil but with added hardness, still evaluating (again) though.
Yes, absolutely but use Evo A compensation, the updated BOM for old boards and solder R11 as in the pic (on bottom side of boards):
The latter boards (from 1.5 and Up) have tenfold less distortion and most of this reduction is due to R11 position.
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Power resistor for R3
These are possibly the best choice:
Mundorf M-Resist Ultra MREU30 30W Film Resistor | Hifi Collective
Sadly they're TO247 and a major PCB redesign is needed to use them... I will try them in the next weeks.
These are possibly the best choice:
Mundorf M-Resist Ultra MREU30 30W Film Resistor | Hifi Collective
Sadly they're TO247 and a major PCB redesign is needed to use them... I will try them in the next weeks.
Attachments
Thank you a lot Dario for your help, it seems Mouser runned out the Elna Cerafine 220uF 50V (sincerely I don't find any Cerafine on site), they suggest a Nichicon UKZ replacement, can I go with it or I must search for the cerafine in another place?
Thank you for the suggestion, Panelhead, it seems the same solution suggested by Dario
Massimo
Thank you for the suggestion, Panelhead, it seems the same solution suggested by Dario
Massimo
You're welcome
Cerafines must be supplied elsewhere than Mouser, in this moment you can source them from HiFiCollective, but you will need to buy 330uF 50V ones.
Dario, interesting those Mresist.
The Isabellenhutte are the same package (TO247).
I use them in your board, one needs to adapt the pins.
Not a big problem, space is there.
Security Check
Ciao, George
The Isabellenhutte are the same package (TO247).
I use them in your board, one needs to adapt the pins.
Not a big problem, space is there.
Security Check
Ciao, George
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"Mundorf has worked closely with a company specialized in high-quality laboratory resistors. They have greatly reduced the micro-mechanical distortions generated by the feedback of electro-mechanical vibrations and microphony. To achieve this the mechanical structure of the resistor was damped by using heavier copper instead of using aluminum as the carrier plate"
Company specialized..? I would say softly: Isabellenhutte..
Package, dimensions, resistive material are the same.
Instead of copper, aluminium in the 'industrial' version.
I do beleive what they say about resonaces, I did experience a strong effect, at first try.
My solution is: a small, havy copper plate + thermal grease, these two together dampen nicely the resistor body, + cooling. Plus extra thermal mass.
Furthermore, I have applied extra goop damping the full mechanical response between board and resistor assembly.
Ciao, George
Company specialized..? I would say softly: Isabellenhutte..
Package, dimensions, resistive material are the same.
Instead of copper, aluminium in the 'industrial' version.
I do beleive what they say about resonaces, I did experience a strong effect, at first try.
My solution is: a small, havy copper plate + thermal grease, these two together dampen nicely the resistor body, + cooling. Plus extra thermal mass.
Furthermore, I have applied extra goop damping the full mechanical response between board and resistor assembly.
Ciao, George