sierratds - well done , nice amps! But it seems to me that the 2A bias current is a little too much, without a real contribution .. regarding THD ...and I think you have too little capacity in the filter ..my JHL runs silent with 25 000 uf , 1R and 25000 uf for each channel. enjoy your JLH !
regards
regards
@Manel - all built.
I wrote some time ago (probably in this thread) a comparison of 2N3055,(H), 2N3716 and recently MJL3281A and 2SC5200 versions. Slew rate increases with ft, as you would expect. New (that is, the current) 2N3055 similar to 2N3716.Don't think I included any pics of measurements but maybe if I get a spare hour or two I can redo that comparison.
2SC5200 seemed to perform best. MJL needed 33pF capacitor to stabilise.
I wrote some time ago (probably in this thread) a comparison of 2N3055,(H), 2N3716 and recently MJL3281A and 2SC5200 versions. Slew rate increases with ft, as you would expect. New (that is, the current) 2N3055 similar to 2N3716.Don't think I included any pics of measurements but maybe if I get a spare hour or two I can redo that comparison.
2SC5200 seemed to perform best. MJL needed 33pF capacitor to stabilise.
John, I just was curious to know what gear do the audio connoisseur use.
Thanks a lot.
Manel
Hi!
I am finishing of my JLH build. It's Chinese clone with capacitance multiplayer embedded on the amp board (main caps = 22000uF/50V):
There is no schematics available or at least I couldn't find any. All the values on the board resemble the values I have currently mounted.
C9 - input capacitor - in my case it's 1uK WIMA.
As output transistors I used CEMI BDY24. Output capacitor is Nichicon 4700uF
1 toroidal transformer for each channel (dual mono) going into 8 ohms speakers + separate transformer for pre-amp:
30VDC rail. Point of work set for 15VDC with 1,2 Amp of current flowing through.
That's all about the setup. Now, it sounds VERY good, clean and sharp. Although, it lacks on base. I don't want it to be a thumping machine, that's not what this design is for - but to slightly increase it.
Does any of you could halp me with any suggestion of what can I modify to achieve this? Or any other advice to further sound improvement for that matter.
If more detailed description is needed, please let me know and I'll post an update.
Thanks!
I am finishing of my JLH build. It's Chinese clone with capacitance multiplayer embedded on the amp board (main caps = 22000uF/50V):
There is no schematics available or at least I couldn't find any. All the values on the board resemble the values I have currently mounted.
C9 - input capacitor - in my case it's 1uK WIMA.
As output transistors I used CEMI BDY24. Output capacitor is Nichicon 4700uF
1 toroidal transformer for each channel (dual mono) going into 8 ohms speakers + separate transformer for pre-amp:
30VDC rail. Point of work set for 15VDC with 1,2 Amp of current flowing through.
That's all about the setup. Now, it sounds VERY good, clean and sharp. Although, it lacks on base. I don't want it to be a thumping machine, that's not what this design is for - but to slightly increase it.
Does any of you could halp me with any suggestion of what can I modify to achieve this? Or any other advice to further sound improvement for that matter.
If more detailed description is needed, please let me know and I'll post an update.
Thanks!
Hello,
I am starting to build the JLH Update (The Penultimate Circuit from https://sound-au.com/tcaas/jlhupdate.htm).
I have a functional double power supply +/-25.3V (using Capacitance Multiplier, 2x120VA transformers Type R, and 33000µF )
I will use MJ15003 + BD140 transistor
My speaker are wide band fostex FE206 (8 Ohms)
As I did not find an clear answer in existing posts, my question is:
What is the must suitable quiesence current value? I saw value like 1.25Amps, but I don't know how it is caculated and what could be the impact if it value is higher or lower.
regards
I am starting to build the JLH Update (The Penultimate Circuit from https://sound-au.com/tcaas/jlhupdate.htm).
I have a functional double power supply +/-25.3V (using Capacitance Multiplier, 2x120VA transformers Type R, and 33000µF )
I will use MJ15003 + BD140 transistor
My speaker are wide band fostex FE206 (8 Ohms)
As I did not find an clear answer in existing posts, my question is:
What is the must suitable quiesence current value? I saw value like 1.25Amps, but I don't know how it is caculated and what could be the impact if it value is higher or lower.
regards
The quiescent current needs to be sufficient to support the both the expected load impedance and the levels you want to drive it to.
On -/+25v rails you can expect around -/+16 volts swing into 8 ohm which means a load current of -/+2 amps.
A quiescent current of about 1.3A means that neither output transistor will quite reach cut off at that maximum output level. Its a value that allows the amp to deliver its nominal output into 8 ohms.
If your load were 16 ohms you could halve that current and still deliver the same voltage to the load, or you could keep to 8 ohm loading and halving the current would only get you half (-/+8v) swing into 8 ohms.
On -/+25v rails you can expect around -/+16 volts swing into 8 ohm which means a load current of -/+2 amps.
A quiescent current of about 1.3A means that neither output transistor will quite reach cut off at that maximum output level. Its a value that allows the amp to deliver its nominal output into 8 ohms.
If your load were 16 ohms you could halve that current and still deliver the same voltage to the load, or you could keep to 8 ohm loading and halving the current would only get you half (-/+8v) swing into 8 ohms.
Hello,
Could someone help me by reviewing my layout? I am using the The Penultimate Circuit from https://sound-au.com/tcaas/jlhupdate.htm.
I try to let space around R10 as it will heat a bit, and also for Q8 and Q3 for its heatsink.
I also separate GND for critical and no critical parts
For Q1 and Q2 (MJ15003) il will put cable
Could someone help me by reviewing my layout? I am using the The Penultimate Circuit from https://sound-au.com/tcaas/jlhupdate.htm.
I try to let space around R10 as it will heat a bit, and also for Q8 and Q3 for its heatsink.
I also separate GND for critical and no critical parts
For Q1 and Q2 (MJ15003) il will put cable
See the table at the end: supply voltage, load resistance, current, power
So according to you; less quiescent current means less output power(assuming same supply voltage & load)?? Actually i want to build jlh 1969 original & i dont need more than 6-8watt into 8ohm load. I already have pcb's + all required components & just waiting for proper heatsink + transformer. My only concern is power dissipation because i don't want to use fan. I think low quiescent current also reduce heat. Anyway have a good day
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All the 8's then 8 watts rms into 8 ohm requires 8 volts rms. And another '8' because 800 ma current should support that output with a 27 volt supply. It would make a big difference to the heat generated. 6 watts and you could go lower still.
Try it, if you start hitting distortion on peaks then go higher, if it still sounds OK go lower.
8 watts rms into 8 ohm requires 8 volts rms. And another '8' because 800 ma current should support that output with a 27 volt supply. It would make a big difference to the heat generated. 6 watts and you could go lower still.Try it, if you start hitting distortion on peaks then go higher, if it still sounds OK go lower.
I wrote about it before in the thread, IMHO the capacitors need to be increased abt 10x from the original design. Input cap, cd-blocking for feedback and bootstrap cap. Also output cap is important, it will react with the speaker impedance, and sometimes even increase the bass output, depending on speaker impedance and capacitance. You can simulate this with Xsim etc if you have impedance measurements of your speakers.
Basically, you can increase capacitance on all caps, and bass should improve, original design values x10 is my general guideline. However, this amp will never give massive 'bass control', output impedance is too high to do that.
Hi everyone, i've a problem & i need your suggestion. For powering my JLH 1969 i want to use separate capacitance multiplier for each amp. Power supply requirement is 25vDC & i want to set quiescent current at around 1000ma.
My question is how to choose proper transformer for this? I mean what is the required secondary voltage & VA rating for transformer? Is dual 25v secondary & 250va transformer perfect to get clean 25vDC out from cap multipliers? As you know Peak dc voltage after rectification & smoothing is around 34vDC, so don't you think 9v differential & 125VA/secondary is good enough??
EDIT- One transformer with dual secondary for 2x cap multiplier circuit.
My question is how to choose proper transformer for this? I mean what is the required secondary voltage & VA rating for transformer? Is dual 25v secondary & 250va transformer perfect to get clean 25vDC out from cap multipliers? As you know Peak dc voltage after rectification & smoothing is around 34vDC, so don't you think 9v differential & 125VA/secondary is good enough??
EDIT- One transformer with dual secondary for 2x cap multiplier circuit.
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