Hi Tom,
The 2 big perfboards are power supplies for the balanced line receiver. The power supply uses the cluster of red LEDs as a voltage reference.
I had originally powered the balanced line receiver from the Fremen Edition board, but when I tried a jfet opamp, I had some oscillation that was partially due to the faster opamp not liking the extra load/capacitance of the balanced line receiver. Building a separate power supply with its own transformer for each balanced line receiver is overkill, but that's what I did.
The little perf board mounted above the balanced line receiver board sums the FE's inputs for a subwoofer output. I haven't got that going yet, but soon.
When I was wiring this thing, I kept thinking how much easier and cleaner it would have been to have my whole system single ended, but I chose balanced before I discovered the FE.
Jac
Hello.
After reading hundreds of post in this and related threads I think I want to build FE amp.
I have cambridge audio a340 (a bit modded with Panasonic, Wima ans Elna caps). I like this amp, especially low end, but it sounds too bright sometimes.
I hope expect that FE at least save nice low end, but with much more correct, full mid and “proper” high frequencies.
The questions:
1. I have Monitor Audio BR2 speakers now, but plan to replace it with Troels W18 DIY speakers. But W18kit have dip down to 2.8-3 ohm around 2-5 khz. Is it acceptable for this amp? I’m not a fan of very loud music and listen mostly on 30% of volume level, rarely at 40-50%.
2. Any chances to buy a pair of PCB (populated with SMD if possible)?
After reading hundreds of post in this and related threads I think I want to build FE amp.
I have cambridge audio a340 (a bit modded with Panasonic, Wima ans Elna caps). I like this amp, especially low end, but it sounds too bright sometimes.
I hope expect that FE at least save nice low end, but with much more correct, full mid and “proper” high frequencies.
The questions:
1. I have Monitor Audio BR2 speakers now, but plan to replace it with Troels W18 DIY speakers. But W18kit have dip down to 2.8-3 ohm around 2-5 khz. Is it acceptable for this amp? I’m not a fan of very loud music and listen mostly on 30% of volume level, rarely at 40-50%.
2. Any chances to buy a pair of PCB (populated with SMD if possible)?
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Hi Stream,
I know Troels Gravesen's kits, great projects. But I can't find the W18 kit you choose (there is a lot of project with Scanspeak or Seas W18 midwoofer). To better understand, could you indicate a more precise project title?
I think there's a lot of Troel's projects with higher and regular impedances...
Ciao
Giacinto
I know Troels Gravesen's kits, great projects. But I can't find the W18 kit you choose (there is a lot of project with Scanspeak or Seas W18 midwoofer). To better understand, could you indicate a more precise project title?
I think there's a lot of Troel's projects with higher and regular impedances...
Ciao
Giacinto
I’m sorry.
Discovery W18 project:
18W-8434G00
I choose this one because of affordable price (250-300 Eur).
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I know this kit, from the impedance curve you posted seems you choose V4 crossover on stepped baffle. As Troels Gravesen explain, this crossover (V4) is a LR4 design, very good on paper, perfect for professional monitoring (like Yamaha NS10).
For Mr. Gravesen with the V3 crossover (LR2 design) "music started flowing and sense of depth and perspective improved vastly". He explain very well differences between LR2 and LR4 crossovers. He says "matter of taste in the end", but it's clear he prefer the sound from LR2 (V3) crossover.
V3 crossover has a better impedance curve (with higher minimum).
Anyway, I don't think FE amp will suffer from a minimun impedance in high frequency. With a simple FE evo I drive my second pair of loudspeaker, with a minimum of 3,6 ohm at 2-300 Hz, with no problem. But the same amps drive my first speaker (with RE of 6,2 Ohm) even better.
Ciao
Giacinto
For Mr. Gravesen with the V3 crossover (LR2 design) "music started flowing and sense of depth and perspective improved vastly". He explain very well differences between LR2 and LR4 crossovers. He says "matter of taste in the end", but it's clear he prefer the sound from LR2 (V3) crossover.
V3 crossover has a better impedance curve (with higher minimum).
Anyway, I don't think FE amp will suffer from a minimun impedance in high frequency. With a simple FE evo I drive my second pair of loudspeaker, with a minimum of 3,6 ohm at 2-300 Hz, with no problem. But the same amps drive my first speaker (with RE of 6,2 Ohm) even better.
Ciao
Giacinto
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My DIY Dynaudio speakers drop to 3 Ohms locally and work just fine with the stock FE. This is for a passive crossover with the amps powering the full range in this system.
As for double FE for more power, there is not a version of the FE with 2 LM3886. Mauro did build his EVO amp with 2 LM3886 current pumps per channel to provide more current/power, but he did not release this to the DIY community. The Mauro built versions are carefully guarded by their owners and would be hard to find for sale.
Others have done bridged LM3886 amps for more power, but none (that I know of) have the advantage of the current pump design which makes the original My_Ref and variants like the FE that makes these amps special.
The real question is whether you really need double power? I have an amp that uses 4 FE channels with the speaker crossover at the line level input before the amps. That way, the tweeter and woofer are each powered by their own amp. But that is really overkill because a single FE would power them just fine.
Jac
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A parallel FE would require some circuit modeling and testing. The Full Evo build used double the rectifiers and filter caps to provide power to each LM3886. Not sure how the servo worked to minimize offset for the two power chips.
Mauro Penasa did not “like” the parallel build. Said the single chip worked better. GeorgeK feels the parallel build works better. He is talking about building a version using a bridged Evo Full for each channel. So four current pumps in a bridged parallel topology. A lucky (and poor) man’s McIntosh MA462.
I have two working Evo amps. A Single and Parallel version. The version George mentions would be a 200 - 250 watt amplifier. But have more voltage gain also.
If the bridged version reduced even order distortion products (limits of measurement already) it might be of interest. But I do not need more power or gain right now.
Looking at the measurements GeorgeK did on the later FE all noise and non-linearity is so low level it looks like George cheated on the tests. But he has access to sophisticated test gear. My measurements using REW, computer, and Focusrite interface have a lot higher noise floor.
I used a Full Evo for a long time. Drove B&W 801 Matrix II better than a single LM3886. But those are a very demanding load. Lot of current needed to control the woofers. Most owners use 200+ watt amplifiers.
Mauro Penasa did not “like” the parallel build. Said the single chip worked better. GeorgeK feels the parallel build works better. He is talking about building a version using a bridged Evo Full for each channel. So four current pumps in a bridged parallel topology. A lucky (and poor) man’s McIntosh MA462.
I have two working Evo amps. A Single and Parallel version. The version George mentions would be a 200 - 250 watt amplifier. But have more voltage gain also.
If the bridged version reduced even order distortion products (limits of measurement already) it might be of interest. But I do not need more power or gain right now.
Looking at the measurements GeorgeK did on the later FE all noise and non-linearity is so low level it looks like George cheated on the tests. But he has access to sophisticated test gear. My measurements using REW, computer, and Focusrite interface have a lot higher noise floor.
I used a Full Evo for a long time. Drove B&W 801 Matrix II better than a single LM3886. But those are a very demanding load. Lot of current needed to control the woofers. Most owners use 200+ watt amplifiers.
George,
My guess is that a single EVO with a jfet opamp would not need the servo. Is that correct? To Panhead's comment about controlling the offset between the two power chips, does a parallel jfet version of the EVO need the servo?
As for bridged amps, Russ White sold the Sympatico amp that used one LM4780 per channel in a balanced, bridged configuration. Alas, the rest of his choices don't live up to the My_Ref concept, IMHO. I haven't looked closely at the LM4780, but on the surface it looks like 2 LM3886 in a single package. That might be attractive for either a parallel or bridged design.
My guess is that a single EVO with a jfet opamp would not need the servo. Is that correct? To Panhead's comment about controlling the offset between the two power chips, does a parallel jfet version of the EVO need the servo?
As for bridged amps, Russ White sold the Sympatico amp that used one LM4780 per channel in a balanced, bridged configuration. Alas, the rest of his choices don't live up to the My_Ref concept, IMHO. I haven't looked closely at the LM4780, but on the surface it looks like 2 LM3886 in a single package. That might be attractive for either a parallel or bridged design.
I had been talking about that possible bridge configuration of an Evolution amp, here:
https://www.diyaudio.com/forums/chi...on-build-thread-tutorial-370.html#post5357854
There is a small teaser photo and the measurements, as well.
The current pump configuration of the power chips brings that not small advantage that current pumps do not fight each other; not like low output impedance voltage amplification, current pumps do not care about offset voltages present at their output. A current source is a high output impedance modul by definition.
When the loop at the end gets closed, the final product is not a current source any more - but in our case offset is controlled by:
A.) In case of the original design by Mauro: a dedicated dc servo loop;
B.) In case in my modifications the offset is kept low through the application of a precision, jfet input control opamp, without dc servo.
Ciao, George
https://www.diyaudio.com/forums/chi...on-build-thread-tutorial-370.html#post5357854
There is a small teaser photo and the measurements, as well.
The current pump configuration of the power chips brings that not small advantage that current pumps do not fight each other; not like low output impedance voltage amplification, current pumps do not care about offset voltages present at their output. A current source is a high output impedance modul by definition.
When the loop at the end gets closed, the final product is not a current source any more - but in our case offset is controlled by:
A.) In case of the original design by Mauro: a dedicated dc servo loop;
B.) In case in my modifications the offset is kept low through the application of a precision, jfet input control opamp, without dc servo.
Ciao, George
Good to see your testing.
Your test with bridged and quad chips match my experience with the TP Sympatico. The ones I have are just bridged.
It did not like the low impedance, phasey, and low efficiency B&W 801 Matrix II. The Full Evo drove them much better. TP felt it was an easy load. The push - Pull topology must have needed a quad chip implementation.
Your test with bridged and quad chips match my experience with the TP Sympatico. The ones I have are just bridged.
It did not like the low impedance, phasey, and low efficiency B&W 801 Matrix II. The Full Evo drove them much better. TP felt it was an easy load. The push - Pull topology must have needed a quad chip implementation.
Not sure you need to go that way. If you are thinking of Cerafines for C13 on an FE, you don't necessarily need 50V. Hificollective has 220/16 for about 1 pound sterling and Partsconnexion has them for less than a dollar.
Jac
Sure, I still have 6 kits form a test batch made in China.
PM me.
I would try ebay, these seems genuine from pics:
4PCS Japan ELNA 50V 220UF RFS SILMIC II Series HIFI Audio Electrolytic Capacitor | eBay
Sorry, no.
Cerafine rated less than 35V have a different sound signature.
I would try ebay, these seems genuine from pics:
4PCS Japan ELNA 50V 220UF RFS SILMIC II Series HIFI Audio Electrolytic Capacitor | eBay[/url
I learn something all the time concerning part selection. I did not know the Silmic II was a sub for the red jacket Cerafine at C13
I used the Silmic II for a long time in projects. May have the 220 ufd 35 and 50 volt.
Always thought of the Silmic as an upgrade to the Cerafine.
4PCS Japan ELNA 50V 220UF RFS SILMIC II Series HIFI Audio Electrolytic Capacitor | eBay[/url
I learn something all the time concerning part selection. I did not know the Silmic II was a sub for the red jacket Cerafine at C13
I used the Silmic II for a long time in projects. May have the 220 ufd 35 and 50 volt.
Always thought of the Silmic as an upgrade to the Cerafine.
My mistake. I must have missed that.
On the Blackgate front, PCX is out of Blackgate PK. HifiCollective still has some, but the price has gone way up. They are now 9.75 pounds.
Back in 2012, I bought a bunch of these Blackgate PKs, so I just looked in the parts drawer and I have 6 pairs that I probably won't use and would be willing to sell to FE builders. They all measure in spec, but they have been sitting for a long time, so I would suggest reforming them before installing them in an FE.
Anyway, I sell them in pairs for what I paid in 2012 + shipping. Naturally, US shipping would be much cheaper. PM me if interested.
Jac
In reality I've posted a wrong link, sorry...but yes, Silmics II are an option (also on BOM) but only the Black/Gold version.
Less detailed than both Cerafine and BGs but very engaging, Cerafines are still my favourite in C9 though.
This link is for 330uF Cerafines , not the ideal value but will work fine, bought from this seller in the past.
[AudioJade] 330uF 35V 50V Cerafine ELNA ROA Audio Ceramic Adopted Capacitors | eBay
No problem Jac, the amount of info on this thread is enormous... easy to forget details
I need to look, may have 35 or 50 volt 220 Cerafine somewhere. The FE is in the chassis that had originally held TP Mono My_Ref. It was a build inspired by the ASR Emitter II. Four chassis with the mono boards in one box, two boxers holding AC power transformer, and the forth will SLA batteries to power the LM318.
While striping out the TP boards spotted the feedback caps used from 15 or so years ago. The mythical BG NHX 220 ufd 6.3 volt. That is what Is in the FE now. They may have been purchased in the 90’s. It is good to reuse chassis and components.
While striping out the TP boards spotted the feedback caps used from 15 or so years ago. The mythical BG NHX 220 ufd 6.3 volt. That is what Is in the FE now. They may have been purchased in the 90’s. It is good to reuse chassis and components.