hi,everybody,I'm back...
many days and night I researching the "SIMPLE" amp circuits.
mini-zen2 is one of them. I draw the schematics and build one,
it's fine,it sounds good!
and I examined that the bass can be process.my experiment is the R10's value is important.
certainly NFB also has great effect.effect your hearing sound...
so thank you all who let me know that JLH1969 can process bass well...
enjoy!
WINCO
many days and night I researching the "SIMPLE" amp circuits.
mini-zen2 is one of them. I draw the schematics and build one,
it's fine,it sounds good!
and I examined that the bass can be process.my experiment is the R10's value is important.
certainly NFB also has great effect.effect your hearing sound...
so thank you all who let me know that JLH1969 can process bass well...
enjoy!
WINCO
Attachments
Need some help with JLH 1969-loussy bass
I recently soldered 2 x 10 W JLH amp - I used all exact parts except transistors (MJ15003,BD140,BC560) , instead C3 in negative feedback I used 470uF (220uF original), and 4700uF for output cap instead 2200uF.
When testing amp for few hours , it sounded really nice even with cheap old fullrangers (some car audio Pioneer drivers), in fact it sounded nice and warm but with so much bass that I suspect that something must be wrong - I heard way too much low frequencies from speaker that was playing in free air, but I just finished with soldering and wiring supply (250VA toriodal, 2x21000uF caps, with capacitance multiplier, 35V single supply) and was nervous to hear amp on my freshly finished Beyma horns, so I connected amp to my Cd player .
But sound was exactly as I unfortunately expected after I heard that cheap Pioneer without any box: too much uncontroled bass.
I changed about twenty CD but there was just too much boominess coming from loudspeaker - unlistenable even on low levels.
When I changed my old diy chip amp(tda7294) to 1969 JLH this are my first impressions:
- loss of dynamic and speed,
- very loose bass- boomy,
- sound is indeed very relaxed and warm but a bit muddy,
- much less ambience and details - soundstage depth almost doesn't exist - everything sounds between mono and stereo recording - it's stupid term, but it's hard to describe,
- it seems that 10W of power isn't enough driving 96db/W horns (at least to me) - on loud passages bass control is even worse and everything sounds compressed, amp sounds much better on normal listening levels.
But even with upper mentioned problems I still don't want to give up from this amp - it has really great & warm midrange that I could listen for days and if only somehow I can modify this amp so bass response can become more "tight" this could be excellent amp for easy listening levels.
My questions are this:
Can I change some components in negative feedback to increase bass control - maybe smaller C3 value?
Does newer versions of this amp sound better in bass range?
What influence has increased output cap value expect obvious changing of lower freq response?
I already searched for this on forum but I didn't find exact explanation yet so please if somebody can suggest something I would be very thankful...or at least shortcut to some related thread would be nice...
I recently soldered 2 x 10 W JLH amp - I used all exact parts except transistors (MJ15003,BD140,BC560) , instead C3 in negative feedback I used 470uF (220uF original), and 4700uF for output cap instead 2200uF.
When testing amp for few hours , it sounded really nice even with cheap old fullrangers (some car audio Pioneer drivers), in fact it sounded nice and warm but with so much bass that I suspect that something must be wrong - I heard way too much low frequencies from speaker that was playing in free air, but I just finished with soldering and wiring supply (250VA toriodal, 2x21000uF caps, with capacitance multiplier, 35V single supply) and was nervous to hear amp on my freshly finished Beyma horns, so I connected amp to my Cd player .
But sound was exactly as I unfortunately expected after I heard that cheap Pioneer without any box: too much uncontroled bass.
I changed about twenty CD but there was just too much boominess coming from loudspeaker - unlistenable even on low levels.
When I changed my old diy chip amp(tda7294) to 1969 JLH this are my first impressions:
- loss of dynamic and speed,
- very loose bass- boomy,
- sound is indeed very relaxed and warm but a bit muddy,
- much less ambience and details - soundstage depth almost doesn't exist - everything sounds between mono and stereo recording - it's stupid term, but it's hard to describe,
- it seems that 10W of power isn't enough driving 96db/W horns (at least to me) - on loud passages bass control is even worse and everything sounds compressed, amp sounds much better on normal listening levels.
But even with upper mentioned problems I still don't want to give up from this amp - it has really great & warm midrange that I could listen for days and if only somehow I can modify this amp so bass response can become more "tight" this could be excellent amp for easy listening levels.
My questions are this:
Can I change some components in negative feedback to increase bass control - maybe smaller C3 value?
Does newer versions of this amp sound better in bass range?
What influence has increased output cap value expect obvious changing of lower freq response?
I already searched for this on forum but I didn't find exact explanation yet so please if somebody can suggest something I would be very thankful...or at least shortcut to some related thread would be nice...
2 tschrama:
I didn't unfortunately measured freq. response - I don't have proper equipment for that - or maybe you have idea for some simple quick & dirty method with DMM and function generator ?
But I don't think that problem lies in limited freq response (although overall amp sounds a little "dark" - but that's probably OK as I read before) - I think it's more related to immposibility of my amp to control bass - after I went from simple and really cheap amp (that isn't really something special and spectacular) I expected normaly, even better and maybe more defined bass from JLH but with JLH everything sounds like someone suddenly pull the handbrake - if you know what I mean
With chip amp first that you can instantly notice is speed, incredible speed and dynamic and so tight bass that you can almost "feel" the tightness of the skin on drums - not very relaxed sound like A class amps but sound that needs your attention.
My JLH sounds warmer on lower volume levels but very slow compared - so slow that in fact horns sound more like ordinary speakers - not exactly the effect I wanted
Though one kind of bass sounds good - low frequency HT effects - yesterday I heard some sounds that I didn't noticed with my chip amps even with 50-60Hz limited bass response of Beymas - low frequency response is then probably OK I suppose, it's certainly lower that horns can play loudly enough.
But isn't that very strange - to have fast bass response problems with high efficiency fullrange drivers ?
Beyma fullrange has pretty high Qts and I expected that there should be no problems with fast bass transients - for example how is then possible for simple SE tube amps with low damping factors to sound good with horns in bass range? Or I am wrong maybe?
And I'm pretty sure that there are many owners of JLH that are using JLH amp with horns without problems - what's the secret then?
I didn't unfortunately measured freq. response - I don't have proper equipment for that - or maybe you have idea for some simple quick & dirty method with DMM and function generator ?
But I don't think that problem lies in limited freq response (although overall amp sounds a little "dark" - but that's probably OK as I read before) - I think it's more related to immposibility of my amp to control bass - after I went from simple and really cheap amp (that isn't really something special and spectacular) I expected normaly, even better and maybe more defined bass from JLH but with JLH everything sounds like someone suddenly pull the handbrake - if you know what I mean
With chip amp first that you can instantly notice is speed, incredible speed and dynamic and so tight bass that you can almost "feel" the tightness of the skin on drums - not very relaxed sound like A class amps but sound that needs your attention.
My JLH sounds warmer on lower volume levels but very slow compared - so slow that in fact horns sound more like ordinary speakers - not exactly the effect I wanted
Though one kind of bass sounds good - low frequency HT effects - yesterday I heard some sounds that I didn't noticed with my chip amps even with 50-60Hz limited bass response of Beymas - low frequency response is then probably OK I suppose, it's certainly lower that horns can play loudly enough.
But isn't that very strange - to have fast bass response problems with high efficiency fullrange drivers ?
Beyma fullrange has pretty high Qts and I expected that there should be no problems with fast bass transients - for example how is then possible for simple SE tube amps with low damping factors to sound good with horns in bass range? Or I am wrong maybe?
And I'm pretty sure that there are many owners of JLH that are using JLH amp with horns without problems - what's the secret then?
The 10W JLH amp has a very well controlled bass. Check out the PCB for possible errors.
One more thing - some speaker specialists recommend a high-pass filter (electrolytic cap) in front of the loudspeaker XO in series. Especially in TL and BR cabinets. I don't know about horns. This is to help the driver not to try to reproduce frequencies that it can not anyway. If everything is fine with the circuit, you can try a smaller cap at the output of the JLH to make a higher high-pass filter.
One more advice - try the amp with another speakers just to see how it performs.
Regards
Asen
One more thing - some speaker specialists recommend a high-pass filter (electrolytic cap) in front of the loudspeaker XO in series. Especially in TL and BR cabinets. I don't know about horns. This is to help the driver not to try to reproduce frequencies that it can not anyway. If everything is fine with the circuit, you can try a smaller cap at the output of the JLH to make a higher high-pass filter.
One more advice - try the amp with another speakers just to see how it performs.
Regards
Asen
2 Asen:
PCB ?
Please don't laugh, but when I saw that there are only few components in schematic I have sudden urge to solder whole bunch in air - it looks funny but everything is working OK for now - my plan for future is to made normal PCB if I was satisfied with JLH sound, for now complete box is open with wires all over until everything is finished , but no hum, no hiss - amp sounds very quiet.
I suppose that everything is OK with the circuit - I checked elements probably dozen times, every measured value is within proper range, both channel sound acoustically the same...
I'll try your advices and see if that'll maybe help , tnx .
P.S.
Is there even slightest possibility that sound is in fact OK - that in fact nothing is wrong with my amp, that it just sounds that way - and that my chip amp together with my speakers sound "overdamped" with maybe too high negative feedback and it sounds maybe artificially fast compared to any other amp and JLH sounds as it suppose to have.
I ask that because everybody that came to my house for listening session says that it sounds great....
PCB
? Please don't laugh, but when I saw that there are only few components in schematic I have sudden urge to solder whole bunch in air - it looks funny but everything is working OK for now - my plan for future is to made normal PCB if I was satisfied with JLH sound, for now complete box is open with wires all over until everything is finished , but no hum, no hiss - amp sounds very quiet.
I suppose that everything is OK with the circuit - I checked elements probably dozen times, every measured value is within proper range, both channel sound acoustically the same...
I'll try your advices and see if that'll maybe help , tnx .
P.S.
Is there even slightest possibility that sound is in fact OK - that in fact nothing is wrong with my amp, that it just sounds that way - and that my chip amp together with my speakers sound "overdamped" with maybe too high negative feedback and it sounds maybe artificially fast compared to any other amp and JLH sounds as it suppose to have.
I ask that because everybody that came to my house for listening session says that it sounds great....
Bubba,
I can't speak for the 1969 circuit as I haven't heard it but I can for the 1996 version, which may be similar. Its sound is relaxed and unforced and its bass is full, you might say 'complete'. However from what you have said a frequency response measurement seems to be necessary.
Tim.
I can't speak for the 1969 circuit as I haven't heard it but I can for the 1996 version, which may be similar. Its sound is relaxed and unforced and its bass is full, you might say 'complete'. However from what you have said a frequency response measurement seems to be necessary.
Tim.
Merry Christmas to you all !
Yesterday I had small party at my place with about 10 people and we were listening music on, you probably guess - JLH amp of course
I added one more cap in output (there is probably nothing nicer then soldering on Christmas Eve) and it indeed sound better, some of the boominess is gone, and it's more pleasure to listen now - especially after drinking some very good wine that my friends brought
A class is great for Christmas parties - I turned off central heating completely
I must say that after few drinks JLH really sounded good, and after bottle I forgot about all problems including Hi-Fi related and 10 watts of relaxed sound filled up room with sound...and that's most important:good friends, good wine and good amplification
P.S.
It seems that exact value and quality of output cap has enormuous influence on sound, much more then I expected...I must deal with that but when my headache dissapears
Yesterday I had small party at my place with about 10 people and we were listening music on, you probably guess - JLH amp of course
I added one more cap in output (there is probably nothing nicer then soldering on Christmas Eve) and it indeed sound better, some of the boominess is gone, and it's more pleasure to listen now - especially after drinking some very good wine that my friends brought
A class is great for Christmas parties - I turned off central heating completely
I must say that after few drinks JLH really sounded good, and after bottle I forgot about all problems including Hi-Fi related and 10 watts of relaxed sound filled up room with sound...and that's most important:good friends, good wine and good amplification
P.S.
It seems that exact value and quality of output cap has enormuous influence on sound, much more then I expected...I must deal with that but when my headache dissapears
Bubba Zanetti said:Merry Christmas to you all !
Yesterday I had small party at my place with about 10 people and we were listening music on, you probably guess - JLH amp of course
I added one more cap in output (there is probably nothing nicer then soldering on Christmas Eve) and it indeed sound better, some of the boominess is gone, and it's more pleasure to listen now - especially after drinking some very good wine that my friends brought
A class is great for Christmas parties - I turned off central heating completely
I must say that after few drinks JLH really sounded good, and after bottle I forgot about all problems including Hi-Fi related and 10 watts of relaxed sound filled up room with sound...and that's most important:good friends, good wine and good amplification
P.S.
It seems that exact value and quality of output cap has enormuous influence on sound, much more then I expected...I must deal with that but when my headache dissapears
Posting Of The Year!
finally did it!
Hy,
Yes, Ive finaly done it. About 15 years ago I started building a JLH 1969 amp from the original article. I was very poor then and when I blew the capacitor of the PS i quit the whole thing concluding that I was to stupid to build my own amp (it was sort of first attempt whith my soldering iron).
Now that I.m sitting inside the house a lot, giving my recently repaired knee the needed rest, I decided to dig the remains of my first attempt out of the dust. I repaired the PS (replaced a faulty transistor) and put in a new cap. I corrected a few errors in the one channel of the amp I had left after I took out the transistor I needed to repair the PS. To my surprise it actually worked. Quite some hum present (due to the poor layout of the board I guess) and the bass is severely lacking (due to insufficient power supply and/ or bad transistors (I use BD245c in the output stage)). But it worked and I concluded that I can build an amp after all.
Now I like to try and do things better so I've read this whole thread (yes, I did, yes really). After this I'm left with a few questions.
I decided to build the JLH1969 with dual supply rails als in the jhlnotes article on Geoff's website.
A few design issues puzzle me.
1. How do I decide which supply voltage suits me? I suppose it has something to de with the load. So, my speakers have a minimum impedance of 5,5 Ohm and a max of about 22 Ohm. Sensitivity about 86 dB. Max power from simulations 15 Watt.
2. What quiescent current to use? From previous postings I gathered: the higher the better, provided that there is enough heatsink. But there must be a limit to this. I guess that depends on the output transistors used. Which number in the specs tells me that?
3. What transformer rating is needed given the supply voltage and quiescent current. For one channel I would guess: Supply voltage * 2 * quiescent current * 2 as a minimum. Is that correct?
Then I have a few practical questions
1. How to set the quiescent current? In the 1969 JLH article and in this thread I don't see it mentioned.
2. I would like to make a point to point thing without a PCB. Does someone have a layout example for the components? I found a photograph in a previous posting, but that was a single supply rails.
3. Is there anyone who knows where to get anodized black aluminum tubing in the Netherlands? I like the way Nelson Pass build his PLH amplifier with that tubing.
Well I guess these are a lot of questions in one post. I hope there is someone who is willing to help this newbee a bit further along the way.
Greetings and thank you all. MArco
Hy,
Yes, Ive finaly done it.
About 15 years ago I started building a JLH 1969 amp from the original article. I was very poor then and when I blew the capacitor of the PS i quit the whole thing concluding that I was to stupid to build my own amp (it was sort of first attempt whith my soldering iron). Now that I.m sitting inside the house a lot, giving my recently repaired knee the needed rest, I decided to dig the remains of my first attempt out of the dust. I repaired the PS (replaced a faulty transistor) and put in a new cap. I corrected a few errors in the one channel of the amp I had left after I took out the transistor I needed to repair the PS. To my surprise it actually worked.
Quite some hum present (due to the poor layout of the board I guess) and the bass is severely lacking (due to insufficient power supply and/ or bad transistors (I use BD245c in the output stage)). But it worked and I concluded that I can build an amp after all. Now I like to try and do things better so I've read this whole thread (yes, I did, yes really).
After this I'm left with a few questions.I decided to build the JLH1969 with dual supply rails als in the jhlnotes article on Geoff's website.
A few design issues puzzle me.
1. How do I decide which supply voltage suits me? I suppose it has something to de with the load. So, my speakers have a minimum impedance of 5,5 Ohm and a max of about 22 Ohm. Sensitivity about 86 dB. Max power from simulations 15 Watt.
2. What quiescent current to use? From previous postings I gathered: the higher the better, provided that there is enough heatsink. But there must be a limit to this. I guess that depends on the output transistors used. Which number in the specs tells me that?
3. What transformer rating is needed given the supply voltage and quiescent current. For one channel I would guess: Supply voltage * 2 * quiescent current * 2 as a minimum. Is that correct?
Then I have a few practical questions
1. How to set the quiescent current? In the 1969 JLH article and in this thread I don't see it mentioned.
2. I would like to make a point to point thing without a PCB. Does someone have a layout example for the components? I found a photograph in a previous posting, but that was a single supply rails.
3. Is there anyone who knows where to get anodized black aluminum tubing in the Netherlands? I like the way Nelson Pass build his PLH amplifier with that tubing.
Well I guess these are a lot of questions in one post. I hope there is someone who is willing to help this newbee a bit further along the way.
Greetings and thank you all. MArco
Hi Marco
I can't answer all your questions but here goes with some of them.
You rightly assume that the optimum rail voltage and quiescent current, for a given output transistor dissipation, is determined from the load impedance. To keep heatsink sizes reasonable (but still large I prefer to limit the dissipation in the output transistors to a maximum of about 40W.
As the minimum speaker impedance (assuming traditional drive units as opposed to electrostatics etc) will occur in the frequency band where music has its greatest power, it makes sense to determine the optimum rail voltage and quiescent current based on this minimum impedance.
For a minimum impedance of 5.5ohms, I would suggest rail voltages of +/-18V, a quiescent current of 2.2A and a minimum transformer rating of 160VA.
The quiescent current is set by adjusting the value of R2 (original 1969 schematic) or the 2k5 preset (1970 postscript) when the amp is at its normal operating temperature. In order to avoid having to break connections to insert an ammeter, you could fit a low value (0R1 to 0R33), power resistor in series with the collector of Tr2 and measure the volt drop across this resistor to ascertain the current through the output stage. Once the current has been finally set this resistor can be removed, if desired, though it will do no harm if it remains in place.
With regard to layout, keep as much distance as possible between the input components/wiring and the output stage/speaker connections to minimise the risk of positive feedback due to stray coupling and the consequential risk of instability. Use 'star' earthing techniques where possible and at least run a separate ground wire back to the star earth point for the signal (input and feedback) and power (rail decoupling capacitors etc) grounds.
Geoff
I can't answer all your questions but here goes with some of them.
You rightly assume that the optimum rail voltage and quiescent current, for a given output transistor dissipation, is determined from the load impedance. To keep heatsink sizes reasonable (but still large
I prefer to limit the dissipation in the output transistors to a maximum of about 40W. As the minimum speaker impedance (assuming traditional drive units as opposed to electrostatics etc) will occur in the frequency band where music has its greatest power, it makes sense to determine the optimum rail voltage and quiescent current based on this minimum impedance.
For a minimum impedance of 5.5ohms, I would suggest rail voltages of +/-18V, a quiescent current of 2.2A and a minimum transformer rating of 160VA.
The quiescent current is set by adjusting the value of R2 (original 1969 schematic) or the 2k5 preset (1970 postscript) when the amp is at its normal operating temperature. In order to avoid having to break connections to insert an ammeter, you could fit a low value (0R1 to 0R33), power resistor in series with the collector of Tr2 and measure the volt drop across this resistor to ascertain the current through the output stage. Once the current has been finally set this resistor can be removed, if desired, though it will do no harm if it remains in place.
With regard to layout, keep as much distance as possible between the input components/wiring and the output stage/speaker connections to minimise the risk of positive feedback due to stray coupling and the consequential risk of instability. Use 'star' earthing techniques where possible and at least run a separate ground wire back to the star earth point for the signal (input and feedback) and power (rail decoupling capacitors etc) grounds.
Geoff
comparisons of jlh class a
hi! all on this solid state forum. I have an interesting question that
i would be interested to know the answer. Has anyone compared a sugden a21 class a amp with a jl hood class a,since they were both originally 10w designs,and both date from the late sixties. I look forward to any responses.
hi! all on this solid state forum. I have an interesting question that
i would be interested to know the answer. Has anyone compared a sugden a21 class a amp with a jl hood class a,since they were both originally 10w designs,and both date from the late sixties. I look forward to any responses.
Dear Geoff,
Thank you, your answer helps a lot.
This one though I do not understand completely
"Use 'star' earthing techniques where possible and at least run a separate ground wire back to the star earth point for the signal (input and feedback) and power (rail decoupling capacitors etc) grounds."
I understand that you suggest to use differtent star points for different kind of earth's (signal/ other). I'm not enough of an engineer to determine which parts in the circuitry belong to which star point. Is there eny reference for that or can you explain?
greetz, MArco
Thank you, your answer helps a lot.
This one though I do not understand completely
"Use 'star' earthing techniques where possible and at least run a separate ground wire back to the star earth point for the signal (input and feedback) and power (rail decoupling capacitors etc) grounds."
I understand that you suggest to use differtent star points for different kind of earth's (signal/ other). I'm not enough of an engineer to determine which parts in the circuitry belong to which star point. Is there eny reference for that or can you explain?
greetz, MArco
sugden a21
I've just completed a diy version of the original a21 (only power amp) or a51 power amp. I've used the circuit as can be found on the site of Geoff Moss but used around 40 Volts and 1 Amp of idle current. The a51 is apart from a few resistor values exactly the same and used 55 Volts and 0,875 Amps.
I've the JLH version 2003 diy in the house and am comparing both amps for about a week or so. I find it too early to make definitive judgments but:
- both amps are roughly in the same class and have a comparable sound-character.
- the jlh is slightly more refined in the highs and sounds just a little bit more modern or neutral (but remember it is a version without output caps).
- the a21/a51 seems to be just a fraction more flowing, organic, musical etc, just a tad more warmth and euphonic character (maybe colouring of the sound due to the output cap)
- the a21/a51 had higher input sensitivity and sounds more dynamic to my ears (less feedback maybe also, don't know exactly the numbers of negative feedback of both amps, the JLH has quite a deal of feedback I remember).
I've used roughly the same quality of components and built quality in both amps.
I've just completed a diy version of the original a21 (only power amp) or a51 power amp. I've used the circuit as can be found on the site of Geoff Moss but used around 40 Volts and 1 Amp of idle current. The a51 is apart from a few resistor values exactly the same and used 55 Volts and 0,875 Amps.
I've the JLH version 2003 diy in the house and am comparing both amps for about a week or so. I find it too early to make definitive judgments but:
- both amps are roughly in the same class and have a comparable sound-character.
- the jlh is slightly more refined in the highs and sounds just a little bit more modern or neutral (but remember it is a version without output caps).
- the a21/a51 seems to be just a fraction more flowing, organic, musical etc, just a tad more warmth and euphonic character (maybe colouring of the sound due to the output cap)
- the a21/a51 had higher input sensitivity and sounds more dynamic to my ears (less feedback maybe also, don't know exactly the numbers of negative feedback of both amps, the JLH has quite a deal of feedback I remember).
I've used roughly the same quality of components and built quality in both amps.
deduikertjes said:
See:
http://www.tcaas.btinternet.co.uk/jlhearthing.htm
The wiring arrangement shown is for a 1996 version but the principle is just the same for the 1969 original when operated from dual supply rails.