Harry
"It was not in jest that I said that the JLH topology shares some resemblance to that of the Aleph series. "
Your comment hadn't escaped me, I just wanted to gather my thoughts before responding. Yes, there are similarities in that both utilise an active current source.
The JLH circuit modulates the current source from 0 to around 1.4 times Iq dependant on the input voltage level. The Aleph current source is superior in that it modulates from 0 to 2 times Iq dependant on the output current thus taking into account impedance and phase variations in the load.
I have spent a lot of time during the past couple of days (as a result of this thread) reconsidering the action of this output stage. Despite Doug Self's assertion in his 'audio power amplifier design handbook' that Tr2 is an output emitter follower with Tr1 acting as a voltage controlled current source, I have come to the conclusion that Tr1 is the output amplifying device with Tr2 being an active current source. Had it not been for Self's book I might have come to this conclusion a long time ago.
"Everybody simulates..... doesn't anyone actually build something?"
Simulation is a useful tool to aid the understanding of how circuits work but I agree that it is no substitute for building things (provided that you have access to suitable test equipment so that the results can be validated). Unfortunately, at times certain other factors come into play. The time spent answering email queries generated from a website or posting at a discussion forum can leave little available for anything else. Not to mention the lack of available finance due to unemployment :-(
Geoff
"It was not in jest that I said that the JLH topology shares some resemblance to that of the Aleph series. "
Your comment hadn't escaped me, I just wanted to gather my thoughts before responding. Yes, there are similarities in that both utilise an active current source.
The JLH circuit modulates the current source from 0 to around 1.4 times Iq dependant on the input voltage level. The Aleph current source is superior in that it modulates from 0 to 2 times Iq dependant on the output current thus taking into account impedance and phase variations in the load.
I have spent a lot of time during the past couple of days (as a result of this thread) reconsidering the action of this output stage. Despite Doug Self's assertion in his 'audio power amplifier design handbook' that Tr2 is an output emitter follower with Tr1 acting as a voltage controlled current source, I have come to the conclusion that Tr1 is the output amplifying device with Tr2 being an active current source. Had it not been for Self's book I might have come to this conclusion a long time ago.
"Everybody simulates..... doesn't anyone actually build something?"
Simulation is a useful tool to aid the understanding of how circuits work but I agree that it is no substitute for building things (provided that you have access to suitable test equipment so that the results can be validated). Unfortunately, at times certain other factors come into play. The time spent answering email queries generated from a website or posting at a discussion forum can leave little available for anything else. Not to mention the lack of available finance due to unemployment :-(
Geoff
Dear H.H. ,
You do understand that I wasn't serious in my reply? I like your repies, even when they are ... hmmm ... rather strong .. (I haven't got the right word for it) .. I'm not really critisizing you..
I hope you do find it interesting that the whole amp simulates more lineair while each of the four actice component seems less linear ... give me something to think about ..
Goodnight,
thijs
Geoff and H.H. ,
I wish I could build every amp I simulate, money and time dictates otherwise
You do understand that I wasn't serious in my reply? I like your repies, even when they are ... hmmm ... rather strong .. (I haven't got the right word for it) .. I'm not really critisizing you..
I hope you do find it interesting that the whole amp simulates more lineair while each of the four actice component seems less linear ... give me something to think about ..
Goodnight,
thijs
Geoff and H.H. ,
I wish I could build every amp I simulate, money and time dictates otherwise
Hey tschrama-
You said you built the 10W JLH, have you hear and will you upgrade to the 15W?
As far me I am going to get the input transistors matched for the 8W amp from borbely audio but I am having a hard time finding the other transistors. I can find all the transistors for the 10 W or 15 W JLH amp in Mouser catalog but there is so much info to read about the JLH amps that it might take me a while to choose which amp to build.
You said you built the 10W JLH, have you hear and will you upgrade to the 15W?
As far me I am going to get the input transistors matched for the 8W amp from borbely audio but I am having a hard time finding the other transistors. I can find all the transistors for the 10 W or 15 W JLH amp in Mouser catalog but there is so much info to read about the JLH amps that it might take me a while to choose which amp to build.
Hi FBJ,
I will not upgrade my JLH10watt to 15 watts or DC coupling. I don't think I need the extra power and I consider the AC coupling OK for now...but maybe in the future..? The great advantage of the JLH10wattes is that there's so much experince with en internet publications. Like the tips I got for other output transistors.. I'm gonna ghet them!! However it would be very interesting if somebody build something else this time and tells us his experiences...
goodluck,
Thijs
I will not upgrade my JLH10watt to 15 watts or DC coupling. I don't think I need the extra power and I consider the AC coupling OK for now...but maybe in the future..? The great advantage of the JLH10wattes is that there's so much experince with en internet publications. Like the tips I got for other output transistors.. I'm gonna ghet them!! However it would be very interesting if somebody build something else this time and tells us his experiences...
goodluck,
Thijs
Sounds OK tschrama.
I was trying to get an idea of what direction to go in. And you sounds like you KNOW what you LIKE. I just moved and it will take me a while to get myself setup again and I don't see myself finishing anything for a while but I can start collecting parts.
Maybe I will try batties for the 8W Monster. Mr. Borbely supplies me with all my JFets and he has battery PS for his preamps.
When I get something together I will post some pictures.
I was trying to get an idea of what direction to go in. And you sounds like you KNOW what you LIKE. I just moved and it will take me a while to get myself setup again and I don't see myself finishing anything for a while but I can start collecting parts.
Maybe I will try batties for the 8W Monster. Mr. Borbely supplies me with all my JFets and he has battery PS for his preamps.
When I get something together I will post some pictures.
Some Questions on the linsley hood amp
Hello,
Just wondering if some of you can help me.
In the 1969 design, which uses the 2N1611/MJ801's transistors what is the feedback rate?. Due to the lower gain of this driver i suspect the feedback rate is lower than the 1996 design.
Regarding the output capacitor, what is the critical parameters? Obviously handling the current is one. Could i use a high capacitance film cap for example?
I have seen an AC coupled amp use a bipolar but not any with films. Not sure about this one.
KD
Hello,
Just wondering if some of you can help me.
In the 1969 design, which uses the 2N1611/MJ801's transistors what is the feedback rate?. Due to the lower gain of this driver i suspect the feedback rate is lower than the 1996 design.
Regarding the output capacitor, what is the critical parameters? Obviously handling the current is one. Could i use a high capacitance film cap for example?
I have seen an AC coupled amp use a bipolar but not any with films. Not sure about this one.
KD
KG
Are we talking about the same amp here? The original JLH Class-A used 2N1613 and MJ480 (MJ481 for supply rails above 30V).
So far as the output capacitor is concerned, you will not be able to use a film type unless the amp is only driving a tweeter at frequencies above 2.5 to 3kHz. The output capacitor forms a high pass filter in conjunction with the load impedance and to achieve a suitable -3dB frequency for full range use (<10Hz), the capacitor size is such that the only feasable type is an electrolytic.
With an output capacitor of 2400uF and an 8ohm load, the corner frequency is just over 8Hz. If the amp was only feeding a tweeter, the capacitor size could be reduced to 12uF which would give a -3dB frequency of a little under 1.7kHz with an 8ohm load. This size of capacitor could be a quality film type.
A bipolar electrolytic is not required in this position since there will always be a dc bias across the capacitor due to the single supply rail.
Geoff
Are we talking about the same amp here? The original JLH Class-A used 2N1613 and MJ480 (MJ481 for supply rails above 30V).
So far as the output capacitor is concerned, you will not be able to use a film type unless the amp is only driving a tweeter at frequencies above 2.5 to 3kHz. The output capacitor forms a high pass filter in conjunction with the load impedance and to achieve a suitable -3dB frequency for full range use (<10Hz), the capacitor size is such that the only feasable type is an electrolytic.
With an output capacitor of 2400uF and an 8ohm load, the corner frequency is just over 8Hz. If the amp was only feeding a tweeter, the capacitor size could be reduced to 12uF which would give a -3dB frequency of a little under 1.7kHz with an 8ohm load. This size of capacitor could be a quality film type.
A bipolar electrolytic is not required in this position since there will always be a dc bias across the capacitor due to the single supply rail.
Geoff
Thijs,
There is nothing wrong with 2N3055's. It is mostly read from the meters that people think that they are obsolete. I've tried several types and brands in the JLH and ended with original old 2N3055's of Motorola. Don't use the everywhere available SGS Thomson devices because these do sound different for some reason. Better have old Motorola 2N3055 than new Thomson MJ 15001 of the like.
Of course you know the site of Geoff Moss? Something like www.gmweb.co.uk (else search for Linsley Hood on google, you will find it). This site is dedicated entirely to the Hood amplifier.
Rudy
There is nothing wrong with 2N3055's. It is mostly read from the meters that people think that they are obsolete. I've tried several types and brands in the JLH and ended with original old 2N3055's of Motorola. Don't use the everywhere available SGS Thomson devices because these do sound different for some reason. Better have old Motorola 2N3055 than new Thomson MJ 15001 of the like.
Of course you know the site of Geoff Moss? Something like www.gmweb.co.uk (else search for Linsley Hood on google, you will find it). This site is dedicated entirely to the Hood amplifier.
Rudy
And DO convert the thing to the DC version in due time, The difference is worthwile. Look at the site of Matthijs Tinholt (can be seen as a link on the site of Moss).
Both Matthijs and myself have built both AC and DC versions and were immediately convinced of the better quality of the DC version. But: keep with the original design rearranged for DC operation (see site for schematics) and do not go for the later 1996 design (that's my opinion, and tried them all).
Both Matthijs and myself live in the Netherlands.
Rudy
Both Matthijs and myself have built both AC and DC versions and were immediately convinced of the better quality of the DC version. But: keep with the original design rearranged for DC operation (see site for schematics) and do not go for the later 1996 design (that's my opinion, and tried them all).
Both Matthijs and myself live in the Netherlands.
Rudy
wiring example
Hi!
Visit my online photo album called: "JLH 1996"
http://www.picturetrail.com/chrisma/876720
This is my first ever DIY amp(diy anything really), good example of not to do.
Chris
Hi!
Visit my online photo album called: "JLH 1996"
http://www.picturetrail.com/chrisma/876720
This is my first ever DIY amp(diy anything really), good example of not to do.
Chris
JLH
The Class-A Amplifier Site
http://www.gmweb.btinternet.co.uk/
with lots of JLH stuff
somebody mentioned this in previous post here
groman
likes the heat of currents
The Class-A Amplifier Site
http://www.gmweb.btinternet.co.uk/
with lots of JLH stuff
somebody mentioned this in previous post here
groman
likes the heat of currents
Breaking in JLH for ESL
I'll call this 2002 JLH 15W Class A.
Just finished, bias at 3.2A, no DC offset problem, after 2 hours power on the DC measured at output is -0.1mV on one channel and -1.2mV on the other. Transformer gets rather hot.
Initial impression of sound quality compare with my dismantled 1996 JLH; When listen to the Shefield Lab test CD, big improvements. Other cds the bass is very detail and solid, especially those quiet/distant recorded drums do not get smear by the main loud passage. But the vocal does not have the tube sound like voice as my previous 1996 JLH. The top end/ high frequency is getter more open up/ dynamic everyday pass. It's been only 15 hours listening time so far.
Chris
I'll call this 2002 JLH 15W Class A.
Just finished, bias at 3.2A, no DC offset problem, after 2 hours power on the DC measured at output is -0.1mV on one channel and -1.2mV on the other. Transformer gets rather hot.
Initial impression of sound quality compare with my dismantled 1996 JLH; When listen to the Shefield Lab test CD, big improvements. Other cds the bass is very detail and solid, especially those quiet/distant recorded drums do not get smear by the main loud passage. But the vocal does not have the tube sound like voice as my previous 1996 JLH. The top end/ high frequency is getter more open up/ dynamic everyday pass. It's been only 15 hours listening time so far.
Chris