Android connected to 2-way Crossover (100Hz)
Lowpass output buffer has a gain of 2 (~6db)
Myref_C coupled via 1uF input cap.
FullRangers: Philips HQ48414P 8 ohms (x 2)
Subs: JBL GTO1214D (x 2) 8 ohms housed in a 1 cu ft. sealed box.
I have a spare crossover which I think is 200Hz. Not sure if JBL can handle that high-end.
Since this amp is never going to be used with another pair, I can add the required boost to the subs. JBL rates them at 93 but at 2.83V which is equivalent to 86.71 W/1M as per WinISD (thus the 6db boost in the xover for subs).
Lowpass output buffer has a gain of 2 (~6db)
Myref_C coupled via 1uF input cap.
FullRangers: Philips HQ48414P 8 ohms (x 2)
Subs: JBL GTO1214D (x 2) 8 ohms housed in a 1 cu ft. sealed box.
I have a spare crossover which I think is 200Hz. Not sure if JBL can handle that high-end.
Since this amp is never going to be used with another pair, I can add the required boost to the subs. JBL rates them at 93 but at 2.83V which is equivalent to 86.71 W/1M as per WinISD (thus the 6db boost in the xover for subs).
Attachments
Thought
If the input stage of the My_Ref is stock try bypassing the 1 ufd coupling cap in the buffer. The series connected caps may be the issue.
If the input stage of the My_Ref is stock try bypassing the 1 ufd coupling cap in the buffer. The series connected caps may be the issue.
NO. The LM318 will only swing to within 2 volts of the supply rail, according to the datasheet. IMO, it is a poor choice for a crossover IC. These days, an LM4562 is only ~ $1.40 (qty 10) and is orders of magnitude a better opamp.
In a myref_C LM318-N is not used for crossover, neither is it a point of debate anymore. Please refer to the initial pages of this thread for the discussion.
My crossover uses LME49720 (removed OPA2134).
My suspicion is:
A. The room is too big for JBL GTO1214D. I'm in a 12' x 15' hall connected to a 10' x 20' gallery. My kinds on the top floor complaint of things shaking at 40Hz. However 2m away from the sub, there's little to write back home about.
B. The Philips HQ48414P doesn't go down to 100Hz.
C. Android headphone-out has a poor low-end. Because coupled with a Bluetooth received hooked to myref_C the bass is clearly audible. Thus my assumption of a pre-amp to bring up the levels at least to a reasonable level before feeding it to myref_C.
My crossover uses LME49720 (removed OPA2134).
My suspicion is:
A. The room is too big for JBL GTO1214D. I'm in a 12' x 15' hall connected to a 10' x 20' gallery. My kinds on the top floor complaint of things shaking at 40Hz. However 2m away from the sub, there's little to write back home about.
B. The Philips HQ48414P doesn't go down to 100Hz.
C. Android headphone-out has a poor low-end. Because coupled with a Bluetooth received hooked to myref_C the bass is clearly audible. Thus my assumption of a pre-amp to bring up the levels at least to a reasonable level before feeding it to myref_C.
Hello,
I am a late newbie bird who is starting to build the legendary My_ReffC. Kudo to the inventor, Maruo, who sadly has departed.
I have read partially the forum content but still not able to find the answer: can I replace the zener shunt regulator diode for LM318 with any zener having 12V and 1W ratings?
Thanks!
Chandra
I am a late newbie bird who is starting to build the legendary My_ReffC. Kudo to the inventor, Maruo, who sadly has departed.
I have read partially the forum content but still not able to find the answer: can I replace the zener shunt regulator diode for LM318 with any zener having 12V and 1W ratings?
Thanks!
Chandra
The answer is yes. You also can bump up this a volt or so. I think I have actually used 14 volt.
Another one please, the speaker output has a 5W 0.47 ohm resistor, what I have is a non inductive 0.47 ohm but at 3W rating only, will it suffer from overheating?
No. The resistor never gets warm. The resistor could almost glow red before it started to deteriorate.
Thanks for the help and answer, bear with me please.
I could not get a good 24V CT transformer, what I have is 32VAC CT (center tap), would this high voltage trafo create problem?
Regards,
Chandra
I could not get a good 24V CT transformer, what I have is 32VAC CT (center tap), would this high voltage trafo create problem?
Regards,
Chandra
Yes that would give you 45Vdc which is beyond the SOA and would never come out of over voltage state. You need a 20-26Vac xfrmr, and if you plan to use at 4-ohms go with 20-22 max.
Thank you.
Another one please, in the PCB there is R2 with 33K value, and a note "use lower than 12K is better". I could not find the R2 in Rev C power supply schematic. So what is R2 used for and the " good" value for R2?
Thanks again.
Another one please, in the PCB there is R2 with 33K value, and a note "use lower than 12K is better". I could not find the R2 in Rev C power supply schematic. So what is R2 used for and the " good" value for R2?
Thanks again.
Hello, finally I have completed building it. After 2 days running, my impression for this amp, is a very good sounding. Almost similar, on par, with my HK-990. I use Marantz CD6005 cd player and JBL HP520 floor stander. The bass is very good, mid is good, but treble is a bit wee harsh to my liking. I use a cheap MKP for C13 input cap at 1 uF. I don't use black gate at C9 220 uF. I use also usual metallics resistors. If I would like to tame the harness a little bit, what parts should I upgrade?
Thanks.
Thanks.
hi all,
I m building a MyRef RevA, have used Melf for 22k and 47k 0.1% resistors, is that ok
for the 100 and 200 pf, using COG MLCC will it do?
also for the preamp, planning to use a PGA2311 do we need to add a buffer to the PGA2311's output.
I m building a MyRef RevA, have used Melf for 22k and 47k 0.1% resistors, is that ok
for the 100 and 200 pf, using COG MLCC will it do?
also for the preamp, planning to use a PGA2311 do we need to add a buffer to the PGA2311's output.
It's your choice, but I'd go with the Rev C rather than Rev A - it has better subjective audible sonics.
MELFs and COG ceramics are OK. I've used NP0/C0G in my builds at some locations, and they work.
You don't need a preamp for a MyRef, unless you want to incorporate a tone-control. A pre- will add another layer of opacity to the signal path, which should be avoided if your main goal is transparency.
MELFs and COG ceramics are OK. I've used NP0/C0G in my builds at some locations, and they work.
You don't need a preamp for a MyRef, unless you want to incorporate a tone-control. A pre- will add another layer of opacity to the signal path, which should be avoided if your main goal is transparency.
Hi Linux guru, we can mod the RevA board to RevC? I saw a Mauro’s pdf showing changes
If I m wrong let me know what to change.
Also I needed source selection and wireless volume control.
I m not having very good ear’s ( tested ) due to work environment so don’t know how what would sound ( not being rude )
I have been using raspberry pi with Volumio / Moode and I enjoy that. It has a JustBoom Amp Hat which is basically TAS5657M 24bit /192khz dac + Amp 30 + 30 in 8ohms in one chip.
If I m wrong let me know what to change.
Also I needed source selection and wireless volume control.
I m not having very good ear’s ( tested ) due to work environment so don’t know how what would sound ( not being rude )
I have been using raspberry pi with Volumio / Moode and I enjoy that. It has a JustBoom Amp Hat which is basically TAS5657M 24bit /192khz dac + Amp 30 + 30 in 8ohms in one chip.
i think careful matching of devider ratio with 1%resistor will give samesonics.0.1% is manufacturing tolerance.
its not like on runtime resistor will fluctuate.
so fancy MELF etc are ok if someome has
but not mendatory
its not like on runtime resistor will fluctuate.
so fancy MELF etc are ok if someome has
but not mendatory
This is one of the worst uninformed suggestion I've heard about the My_Ref.
Before questioning the designer specifications some research should be done, at least...
The My_Ref output stage is an Howland Current Pump, which NEEDS precision resistors for best stability and performance (see, for instance: https://www.ti.com/lit/an/sboa437/sboa437.pdf?ts=1630053071234).
In addtion hand selecting 1% resistors does not give you any guarantee they will not derate with time.
0.1% resistors are not simply selected for an initial measured value, they are actually DIFFERENT, often TCR is differetn too.
And obviously this very same topic have been explored several times on this and other threads about the My_Ref and variants.