Hm, i've found a working lm3886 macro. Have installed, and got all-over oscillation like Dejan.
Now, got curious, had removed the control opamp (lm318, opa827), and had left only the bridge driven directly by the generator. Inthe case of the lm4780 macro, i got ~60kHz power response (on 8ohm, 10Vp-p)
With the lm3886 macro installed, the power response of the only bridge is ~210kHz..
I think I need to ask my hp3577, who is closer to reality.
But, as mentioned before, the real full circuit IS stable, and that brings it closer to the lm4780 macro..
Ciao, george
Now, got curious, had removed the control opamp (lm318, opa827), and had left only the bridge driven directly by the generator. Inthe case of the lm4780 macro, i got ~60kHz power response (on 8ohm, 10Vp-p)
With the lm3886 macro installed, the power response of the only bridge is ~210kHz..
I think I need to ask my hp3577, who is closer to reality.
But, as mentioned before, the real full circuit IS stable, and that brings it closer to the lm4780 macro..
Ciao, george
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Hi George,
I tried to replace LM3886 in my simulation with LM4780 and now I get a stable circuit, without oscillation.
I used LM3886 TINA-TI Spice Model instead of LM3886 PSpice Model that gave me same problems that you have described.
Based on your measurements, it seems there is some problem with LM3886 model and LM4780 model gives simulation results closer to real world measurements.
I will try to simulate with AD797 and ADA4898-1 models to see what happens. I hope you will get a stable circuit, and hopefully, a great sound.
Best regards,
Dejan
I tried to replace LM3886 in my simulation with LM4780 and now I get a stable circuit, without oscillation.
I used LM3886 TINA-TI Spice Model instead of LM3886 PSpice Model that gave me same problems that you have described.
Based on your measurements, it seems there is some problem with LM3886 model and LM4780 model gives simulation results closer to real world measurements.
I will try to simulate with AD797 and ADA4898-1 models to see what happens. I hope you will get a stable circuit, and hopefully, a great sound.
Best regards,
Dejan
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In the last weeks my activity on this forum has been near zero,sorry.
September 24th my father died for an incurable pulmonary disease
In the next days I'll try to answer everyone.
September 24th my father died for an incurable pulmonary disease
In the next days I'll try to answer everyone.
I'm very sorry to hear your news, Dario. It must be a very sad time for you. Please take care of yourself and your family first, hifi can wait.
Dario, I'll echo what has already been said and wish you strength in this difficult time for you and your family.
BK
BK
I'm very sorry to hear. I hope those he left behind find peace.
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So sorry to hear about your father. Know that our prayers are with you and your family. It's a big adjustment, but you will have what's needed to accept and move forward.
First of all, thanks to everyone.
Those caps are not directional, they willl work in both direction but there is, in my experience, a difference in perceveid performance according direction.
The small notch should be on the left, as the small circle on the PCB.
It depends on flux, some is conductive or hygroscopic and so could lead to problems.
In my Lehmann clone build the circuit was oscillating until I've finally cleaned boards.
A (small) perceived low freqs tilt is normal, particularly with Mundorf AGs.
Those caps are not directional, they willl work in both direction but there is, in my experience, a difference in perceveid performance according direction.
The small notch should be on the left, as the small circle on the PCB.
It depends on flux, some is conductive or hygroscopic and so could lead to problems.
In my Lehmann clone build the circuit was oscillating until I've finally cleaned boards.
A (small) perceived low freqs tilt is normal, particularly with Mundorf AGs.
group buy for FE BOM
Has anyone organized a group buy for the newest FE BOM? With the optimizations, the total cost for the current Ultimate BOM has gotten pretty high. I wonder how much we could save with a group buy? Just curious as the last group buy I was involved in was for the MyRef RevC that Uriah organized.
Has anyone organized a group buy for the newest FE BOM? With the optimizations, the total cost for the current Ultimate BOM has gotten pretty high. I wonder how much we could save with a group buy? Just curious as the last group buy I was involved in was for the MyRef RevC that Uriah organized.
Hi Guys,
did post this initially in the wrong thread, sorry for the double post.
I am afraid my pcbs did lay quite a long time in the corner and I did not buy the parts... 🙁
Is there a chance to get the list of the parts I need, which were in the quoted shopping cart below (which seems not to work any more)?
It is BOM 1.5 with the smd parts already soldered..
Alternatively, if I could use the newer Bom with my older PCB, I would be happy to just use the newer BOM. Is that possible? Has the circuit been updated and do the parts from the new BOM fit with the already soldered SMD parts?
Thanks for your help guys,
Cheers!
did post this initially in the wrong thread, sorry for the double post.
I am afraid my pcbs did lay quite a long time in the corner and I did not buy the parts... 🙁
Is there a chance to get the list of the parts I need, which were in the quoted shopping cart below (which seems not to work any more)?
It is BOM 1.5 with the smd parts already soldered..
Alternatively, if I could use the newer Bom with my older PCB, I would be happy to just use the newer BOM. Is that possible? Has the circuit been updated and do the parts from the new BOM fit with the already soldered SMD parts?
Thanks for your help guys,
Cheers!
Dario
I am sorry for your loss.
Thank you for answering my about the Wilmas.
Take care of Yourself and Your family.
I am sorry for your loss.
Thank you for answering my about the Wilmas.
Take care of Yourself and Your family.
I never organized a full group buy for two reasons:
- too much work
- increase in shipping costs 'eats' savings on parts
If we order parts for 40 boards BOM's cost drops to 52€, so 17€ less, 34€ per kit.
But shipping cost would double for the added weight and still we didn't considered some form of compensation for the not small work of packaging and labelling of parts.
IMHO the 5-10€ final saving is not worth the effort, things could change with (much) higher numbers like 100 kits (as were for Uriahs GBs, if I remember correctly).
Thanks and you're welcome.
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Just answered on the GB's thread:
http://www.diyaudio.com/forums/grou...men-edition-gb-seventh-run-2.html#post4849004
In general there are two main BOMs up to version 1.20 and from version 1.5.
Four channels of MyRef
Dario, I'm working on getting away from the passive crossovers in my speakers and moving towards active crossovers, using a miniDSP 2x4 initially and eventually a miniDSP 2x4 HD. To that end, I recently signed up for two sets of your next release of MyRef boards.
I will be driving two-way speakers of reasonable efficiency (89db/watt) to moderate sound levels < ~95db. When contemplating the power supply for four channels of amplification, I was initially thinking of using two 200VA 24V toroids and two 100VA toroids, for woofer and tweeter duties respectively.
Thinking about things some more, I'm contemplating using two 400VA 24V toroids with each transformer powering a pair of MyRef amplifier blocks--one pair of MyRefs per L and R channel. Each transformer, with dual secondaries, will power two MyRefs, each driving a woofer or tweeter, per channel. All four amplifier blocks will be in one chassis.
Does this approach sound reasonable?
Dario, I'm working on getting away from the passive crossovers in my speakers and moving towards active crossovers, using a miniDSP 2x4 initially and eventually a miniDSP 2x4 HD. To that end, I recently signed up for two sets of your next release of MyRef boards.
I will be driving two-way speakers of reasonable efficiency (89db/watt) to moderate sound levels < ~95db. When contemplating the power supply for four channels of amplification, I was initially thinking of using two 200VA 24V toroids and two 100VA toroids, for woofer and tweeter duties respectively.
Thinking about things some more, I'm contemplating using two 400VA 24V toroids with each transformer powering a pair of MyRef amplifier blocks--one pair of MyRefs per L and R channel. Each transformer, with dual secondaries, will power two MyRefs, each driving a woofer or tweeter, per channel. All four amplifier blocks will be in one chassis.
Does this approach sound reasonable?
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hello Marc, i am trying to do the same thing with my speakers.
But what electronic crossover you will use?
About the transformers, i think 400 va for 1 channel(2 amps) is a little bit overkill, 300va will be , i think , just fine.
I'm going to use the miniDSP 2x4 initially. If I like it I'll go to the miniDSP HD.
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