tvi,
I don't know where you got this idea of the 30W, as far as I know there is NO 30W version of "le Classe A". Hiraga made the simplified 8w Monstre and the 20W versions. If you have some links to substantiate your claim please let us know.
All,
Of the 20W "le Classe A" I have seen the classic schematic on Bonavolta's site and this newer, slightly modified one, that some very helpful and informed guy provided earlier:
http://extra.newsguy.com/~stigerik/HIRAGA.gif
Maybe we can all try and persuade Geoff to run some simulations and tell us what are the major differences.
I am in the process of collecting the components at the moment I will probably stick to the original version unless someone tells me that the mods make everything sound better.
On to the next point, transistors:
All but the power trans (see HIRAGA.gif in the link above) are still in production and therefore someone should have them, and they do: MCM electronics (i-mcm.com).
As far as the power trans I am going to overkill it and use some 2sa1216-2sc2922 for no other reason other than the fact that I have them.
Power supply, I need some feedback on this one, please:
I got this surplus transformer, its huge, its dirt cheap but its 2 X (2 X 21.5 V) secondary (yes, ther are two center tapped secondaries), which brings the rectified and filtered voltage up to 2 X 30V DC, so six or seven volts need to go, or do they?
I am thinking I could:
1) stabilize the voltage (independently for each channel of course).
2) use a Pi filter using power resistors.
3) use the 2 X 30V and modify the circuit (increase the collector resistors and the voltage drop resistors to the pilots) the power trans should be able to handle that.
I could make a dual mono version but I have only this two huge 76000 uF 40V caps and I am on the cheap so for the moment I will parallel the secondaries.
What do you think?
[Edited by grataku on 04-27-2001 at 09:58 AM]
I don't know where you got this idea of the 30W, as far as I know there is NO 30W version of "le Classe A". Hiraga made the simplified 8w Monstre and the 20W versions. If you have some links to substantiate your claim please let us know.
All,
Of the 20W "le Classe A" I have seen the classic schematic on Bonavolta's site and this newer, slightly modified one, that some very helpful and informed guy provided earlier:
http://extra.newsguy.com/~stigerik/HIRAGA.gif
Maybe we can all try and persuade Geoff to run some simulations and tell us what are the major differences.
I am in the process of collecting the components at the moment I will probably stick to the original version unless someone tells me that the mods make everything sound better.
On to the next point, transistors:
All but the power trans (see HIRAGA.gif in the link above) are still in production and therefore someone should have them, and they do: MCM electronics (i-mcm.com).
As far as the power trans I am going to overkill it and use some 2sa1216-2sc2922 for no other reason other than the fact that I have them.
Power supply, I need some feedback on this one, please:
I got this surplus transformer, its huge, its dirt cheap but its 2 X (2 X 21.5 V) secondary (yes, ther are two center tapped secondaries), which brings the rectified and filtered voltage up to 2 X 30V DC, so six or seven volts need to go, or do they?
I am thinking I could:
1) stabilize the voltage (independently for each channel of course).
2) use a Pi filter using power resistors.
3) use the 2 X 30V and modify the circuit (increase the collector resistors and the voltage drop resistors to the pilots) the power trans should be able to handle that.
I could make a dual mono version but I have only this two huge 76000 uF 40V caps and I am on the cheap so for the moment I will parallel the secondaries.
What do you think?
[Edited by grataku on 04-27-2001 at 09:58 AM]
Certainly there are 2 versions available of the Hiraga. Commercially they are marketed under the names of 'Hiraga classe A' (20 W) and 'Le Classe-A' (30 W).
Both contain exactly the same circuit. Differences are:
1. Supply voltage of plus en minus 24 Volts for the 30 Watter.
2. Current becomes 1,5 Amperes.
3. Dissipation now is at the limit of the possible (assuming the original power transistors are used, the TO-3 ones).
4. Total capacitor-value for the 30 Watter is over one Farad (in stead of 408.000 mF for the 20 Watter).
5. Some resistors have a slightly different value (to take care of new voltage and current settings).
Both contain exactly the same circuit. Differences are:
1. Supply voltage of plus en minus 24 Volts for the 30 Watter.
2. Current becomes 1,5 Amperes.
3. Dissipation now is at the limit of the possible (assuming the original power transistors are used, the TO-3 ones).
4. Total capacitor-value for the 30 Watter is over one Farad (in stead of 408.000 mF for the 20 Watter).
5. Some resistors have a slightly different value (to take care of new voltage and current settings).
I have an old photo copy from original article in L'Audiophile, its mainly about the "AMPLIFICATEUR 20W HIRAGA" this is the schematic on the stigerik link.
On the last page I have the exact picture used on the bonavolt site, the page is headed "NOUVEAU SCHEMA SUPER 30 W
under the schema on my copy
"Les paires de drivers des amplificateurs 20W et Super 30W ne sont plus disponibles, ces transistors, mis sur le marché japonais depuis plus de dix ans, ont été remplacés par une nouvelle paire encore plus performante, aussi bein aux mesures qu'à l'écoute.
Bein que de caractéristiques proches, il a été nécessaire de modifier légèrement (uniquement dans le cas du Super 30W) Les valeurs de certains résistances, de façon à réduire encore le taux de distortion ainsi que le courant de repos, Pour des raisons de copyright avec L'étranger, nous avons été obligés de suppimer les éférences de ces transistors, Le transistors de couleur noire correspond au 2SC1096, celui de couleur verte au 2SA634; la brocharge rest identique."
I always thought
1.5A x 24V = 36W
1A x 21V = 21W
On the last page I have the exact picture used on the bonavolt site, the page is headed "NOUVEAU SCHEMA SUPER 30 W
under the schema on my copy
"Les paires de drivers des amplificateurs 20W et Super 30W ne sont plus disponibles, ces transistors, mis sur le marché japonais depuis plus de dix ans, ont été remplacés par une nouvelle paire encore plus performante, aussi bein aux mesures qu'à l'écoute.
Bein que de caractéristiques proches, il a été nécessaire de modifier légèrement (uniquement dans le cas du Super 30W) Les valeurs de certains résistances, de façon à réduire encore le taux de distortion ainsi que le courant de repos, Pour des raisons de copyright avec L'étranger, nous avons été obligés de suppimer les éférences de ces transistors, Le transistors de couleur noire correspond au 2SC1096, celui de couleur verte au 2SA634; la brocharge rest identique."
I always thought
1.5A x 24V = 36W
1A x 21V = 21W
Well in fact I saw the same shematic with 2 kind of transistors : the one that exists when Jean Hiraga draw his 20W amplifier (many years ago)TP2788... and the other one with C1775
D188 a627 c1096 a872 transistors.
Thant for the reply.
But what are the diferents between toroidal transformer and the other kind.
Bye
D188 a627 c1096 a872 transistors.
Thant for the reply.
But what are the diferents between toroidal transformer and the other kind.
Bye
Grataku
I ran a few quick simulations on the Hiraga some time ago. Unfortunately, I didn't make any notes at the time but, from memory, the original circuit seemed OK but I was less happy with the later, modified circuit. I can't for the life of me remember why now. When I've made more progress with my JLH site I'll repeat the exercise and let you know my findings (give me a reminder in a week or so if you haven't heard from me).
Babarceles
There is a good, phase coherent, active crossover project at the ESP Audio Pages:
http://www.sound.au.com/project09.htm
Geoff
I ran a few quick simulations on the Hiraga some time ago. Unfortunately, I didn't make any notes at the time but, from memory, the original circuit seemed OK but I was less happy with the later, modified circuit. I can't for the life of me remember why now. When I've made more progress with my JLH site I'll repeat the exercise and let you know my findings (give me a reminder in a week or so if you haven't heard from me).
Babarceles
There is a good, phase coherent, active crossover project at the ESP Audio Pages:
http://www.sound.au.com/project09.htm
Geoff
Grataku
You are probably better asking someone who has actually built this circuit, but I will give you my opinion.
I think that the differing values are there to minimise the dc offset at the output, since the characteristics of the 2SA872 and 2SC1775 are not be identical.
You could try 180ohm in both positions, set the Iq with the trimpot, and then check the dc offset. If necessary, increase the value of the 2SC1775 emitter resistor to minimise the offset.
Geoff
You are probably better asking someone who has actually built this circuit, but I will give you my opinion.
I think that the differing values are there to minimise the dc offset at the output, since the characteristics of the 2SA872 and 2SC1775 are not be identical.
You could try 180ohm in both positions, set the Iq with the trimpot, and then check the dc offset. If necessary, increase the value of the 2SC1775 emitter resistor to minimise the offset.
Geoff
DC Protection
With a bi-amped system, the tweeters are protected by the mid-high crossover. Once the loudspeaker is tri-amped, this protection is lost, since the capacitor which is used to determine the crossover frequency is no longer present.
With most 'solid-state' amps, this places the tweeter at great risk during the (generally short) switch-on and switch-off periods. As the supply voltage is applied (or removed), most amplifiers will create a DC transient (if such a thing is possible) as the circuitry starts to operate. This causes the all too common speaker thump.
This is mildly annoying when applied to the low frequency drivers, but is capable of destroying a tweeter if allowed to persist for more than a few milliseconds.
In the case of amplifier failure, the tweeter is almost certain to protect any speaker fuse by blowing first - not exactly the desired effect! The "Poly-Switches" now available might help, but I don't like the idea of a non-linear resistor in series with my speakers.
If the direct coupled approach is contemplated, I would suggest the following:
*Use a relay in series between the tweeter and the amp with a suitable muting circuit
*Include a fast acting DC sensor to disconnect the load if amplifier DC is detected
Does anyone can help... schematics...
With a bi-amped system, the tweeters are protected by the mid-high crossover. Once the loudspeaker is tri-amped, this protection is lost, since the capacitor which is used to determine the crossover frequency is no longer present.
With most 'solid-state' amps, this places the tweeter at great risk during the (generally short) switch-on and switch-off periods. As the supply voltage is applied (or removed), most amplifiers will create a DC transient (if such a thing is possible) as the circuitry starts to operate. This causes the all too common speaker thump.
This is mildly annoying when applied to the low frequency drivers, but is capable of destroying a tweeter if allowed to persist for more than a few milliseconds.
In the case of amplifier failure, the tweeter is almost certain to protect any speaker fuse by blowing first - not exactly the desired effect! The "Poly-Switches" now available might help, but I don't like the idea of a non-linear resistor in series with my speakers.
If the direct coupled approach is contemplated, I would suggest the following:
*Use a relay in series between the tweeter and the amp with a suitable muting circuit
*Include a fast acting DC sensor to disconnect the load if amplifier DC is detected
Does anyone can help... schematics...
I know I am quoting this site yet again, but it really does have the answer to nearly everything!
Have a look at Project 33 (Loudspeaker protection and muting) at the ESP Audio Pages:
http://www.sound.au.com/projects.htm
I think this is what you are looking for.
The alternative, of course, is just a high value bi-polar capacitor in series with the tweeter. If of high enough value, it will provide protection without affecting the
low-frequency roll-off of the tweeter which will still be determined by the active filter.
p.s. It would have been better if you had started a new thread for this topic as it is not specifically related to Hiraga amps.
Geoff
Have a look at Project 33 (Loudspeaker protection and muting) at the ESP Audio Pages:
http://www.sound.au.com/projects.htm
I think this is what you are looking for.
The alternative, of course, is just a high value bi-polar capacitor in series with the tweeter. If of high enough value, it will provide protection without affecting the
low-frequency roll-off of the tweeter which will still be determined by the active filter.
p.s. It would have been better if you had started a new thread for this topic as it is not specifically related to Hiraga amps.
Geoff
ML-2 (JC-2)
Now all our attention is on the Hiraga's, but before we forget, Is there somebody that actually have built or heard the JC-2 or ML-2? (I believe I've seen a link in this thread to some diagrams but now them seems to be edited...=( )
General question, How compares Pass amp vs. Mark L. amps?
I ask about it because this amp presents an interesting topology... in fact I'm planning on start building the JC-2 in order to see how it sounds.... (Yeah, I know!, this is not a NP design, but the joy is to keep trying different things)
-MKT-
Now all our attention is on the Hiraga's, but before we forget, Is there somebody that actually have built or heard the JC-2 or ML-2? (I believe I've seen a link in this thread to some diagrams but now them seems to be edited...=( )
General question, How compares Pass amp vs. Mark L. amps?
I ask about it because this amp presents an interesting topology... in fact I'm planning on start building the JC-2 in order to see how it sounds.... (Yeah, I know!, this is not a NP design, but the joy is to keep trying different things)
-MKT-
If you are after something of similar power but newer devices try:
20W class A
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/Aclass20Wpow/aclass20wpow.htm
30W Class A
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/Aclass30Wpow/aclass30Wpow.htm
20W MOSFET Current Feedback(?)
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/cufpow01/cufpow01.htm
Unfortunatly all is in Japanese but still interesting
Regards James
20W class A
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/Aclass20Wpow/aclass20wpow.htm
30W Class A
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/Aclass30Wpow/aclass30Wpow.htm
20W MOSFET Current Feedback(?)
http://www.asahi-net.or.jp/~ts7t-ymt/audcvr/cufpow01/cufpow01.htm
Unfortunatly all is in Japanese but still interesting
Regards James
Drakonis,
The ML-2 thread is still there. Look under Solid State forum, towards the bottom of the first page. The web site is : http://www.marklev.com
Personally, I'd love to see the ML-2 ride again. I have fond memories of lusting after the mystical, mythical, unattainable beasts. I glanced at the schematics when that thread came up and they seem genuine. I only wish I could get away with an amp that small wattage-wise but, alas, my speakers are too inefficient. Yes, you could gang the critters together and get larger wattages, but...
At any rate, write the fellow. See if he's made any progress on building a pair.
Grey
The ML-2 thread is still there. Look under Solid State forum, towards the bottom of the first page. The web site is : http://www.marklev.com
Personally, I'd love to see the ML-2 ride again. I have fond memories of lusting after the mystical, mythical, unattainable beasts. I glanced at the schematics when that thread came up and they seem genuine. I only wish I could get away with an amp that small wattage-wise but, alas, my speakers are too inefficient. Yes, you could gang the critters together and get larger wattages, but...
At any rate, write the fellow. See if he's made any progress on building a pair.
Grey
Hiraga.. and me.
Greetz!
I'm a Hiraga freak.. luv his stuff (nuffin' wrong with Pass, though - done that too.. hehe).
The biggest *problem* with the 20W (and 30W) is the relative high output impedance (Le Monstre' too). Not really great for driving subs etc. Despite their huge PSUs they don't deliver much current. But they do sound nice!
The company that build the amps (Lectron) didn't use the same components in 'em all?? I've have a couple of 20Ws and one of them feature 2x0,47R in the PSU and NO decoupling caps, the other one 0,68R and 2x2,2yF Wima. I know for a fact that both come straight from the factory and have not been tinkered with. The PCB/components are the same, except for the brand of the power resistors.
I really really like these amps!
I'm always looking for Hiraga's amps, the 20W, the 30W, Le Solstice, Le PrePre, Le Tube, the Lectron amps, JH30 (hybrid PP EL84 with a Le Monstre'/20W front end), JH50 (PP EL34), the RIAA (powered from JH30). I've heard of a JH80 Monoblock but never seen it. Also anything by Kaneda..
Very nice, non hyped forum!
I am an independant engineer and producer. Yeah, that's right. I make records.. and listen too 'em! Don't worry though, don't use Hafler/Bryston amps and Genelec/Yamaha NS10s speakers... hahaha..
Some of you would probably be shocked if you checked out the scheamtics of modern recording gear.. nuffin' to spice up the sound than running through a couple of hundred NE5532s and a few thousand tantal caps.. hehe
I build most of my recording gear myself, since well.. most of it out there is pure crap! (Ohh, yeah I'm into tubes as well as SS. No religion here..)
I've read all the posts here and I think I'll hang around for a bit.. that is if YOU don't mind! (Checked out audioasylum.com - but that seems to be a big ******* contest..)
Kindest,
solstice
Greetz!
I'm a Hiraga freak.. luv his stuff (nuffin' wrong with Pass, though - done that too.. hehe).
The biggest *problem* with the 20W (and 30W) is the relative high output impedance (Le Monstre' too). Not really great for driving subs etc. Despite their huge PSUs they don't deliver much current. But they do sound nice!
The company that build the amps (Lectron) didn't use the same components in 'em all?? I've have a couple of 20Ws and one of them feature 2x0,47R in the PSU and NO decoupling caps, the other one 0,68R and 2x2,2yF Wima. I know for a fact that both come straight from the factory and have not been tinkered with. The PCB/components are the same, except for the brand of the power resistors.
I really really like these amps!
I'm always looking for Hiraga's amps, the 20W, the 30W, Le Solstice, Le PrePre, Le Tube, the Lectron amps, JH30 (hybrid PP EL84 with a Le Monstre'/20W front end), JH50 (PP EL34), the RIAA (powered from JH30). I've heard of a JH80 Monoblock but never seen it. Also anything by Kaneda..
Very nice, non hyped forum!
I am an independant engineer and producer. Yeah, that's right. I make records.. and listen too 'em! Don't worry though, don't use Hafler/Bryston amps and Genelec/Yamaha NS10s speakers... hahaha..
Some of you would probably be shocked if you checked out the scheamtics of modern recording gear.. nuffin' to spice up the sound than running through a couple of hundred NE5532s and a few thousand tantal caps.. hehe
I build most of my recording gear myself, since well.. most of it out there is pure crap! (Ohh, yeah I'm into tubes as well as SS. No religion here..)
I've read all the posts here and I think I'll hang around for a bit.. that is if YOU don't mind! (Checked out audioasylum.com - but that seems to be a big ******* contest..)
Kindest,
solstice
Solstice,
You make a good point about output impedance and current capability. I was going to built the PS as seen on the schematics but then I thought that being a pp class A amp everytime the amp will be asking for more juice than the bias current the resistor in the PS will drop the rail voltage thereby choking the poor thing to death.
Any idea of why using R's instead of high current X's (inductors)?
I don't know if my solution is any better but I am forced to drop the voltage by about 18% and therefore I will use a regulated PS. At least I will be able to adjust the PS rails to be perfectly symmetric for better DC offset stability.
Any comments?
You make a good point about output impedance and current capability. I was going to built the PS as seen on the schematics but then I thought that being a pp class A amp everytime the amp will be asking for more juice than the bias current the resistor in the PS will drop the rail voltage thereby choking the poor thing to death.
Any idea of why using R's instead of high current X's (inductors)?
I don't know if my solution is any better but I am forced to drop the voltage by about 18% and therefore I will use a regulated PS. At least I will be able to adjust the PS rails to be perfectly symmetric for better DC offset stability.
Any comments?
Hiraga PSU
Actually, due to the 408.000yF the voltage doesn't drop a lot. I tried putting both analog and digital voltmeters across the caps, and not much happened with a music signal run close to clipping into a loudspeaker. Nothing compared to a 100W jap amp with 2x10.000yF and a wimpy transformer. I've noticed up to 10 volt drops. Same thing with *pro* amps..
It's the actual amp/output devices that's the limit, not the PSU.
I think they choose resistors because there isn't a lot of space left within the chassis.. or because it's cheaper. I dunno. Personally I go for multiple inductors/caps in all my gear.
I often use ordinary power transformers 100-400VA, using only the input (230VAC - I'm in Euroland) side. The have sufficiently high H values. It's cheaper than getting custom inductors made. Any comments on this, anyone? Seems to work well. I haven't run into any saturation probs... I think! I don't use inductors in my transistor poweramps though. That's just caps and batteries.
grataku, if you need a voltage drop, why not use a transformer with a lower output voltage?
FYI, the original 20W uses a 2x17VAC/170VA EI core transformer with a screen and multiple input choices.
Actually, due to the 408.000yF the voltage doesn't drop a lot. I tried putting both analog and digital voltmeters across the caps, and not much happened with a music signal run close to clipping into a loudspeaker. Nothing compared to a 100W jap amp with 2x10.000yF and a wimpy transformer. I've noticed up to 10 volt drops. Same thing with *pro* amps..
It's the actual amp/output devices that's the limit, not the PSU.
I think they choose resistors because there isn't a lot of space left within the chassis.. or because it's cheaper. I dunno. Personally I go for multiple inductors/caps in all my gear.
I often use ordinary power transformers 100-400VA, using only the input (230VAC - I'm in Euroland) side. The have sufficiently high H values. It's cheaper than getting custom inductors made. Any comments on this, anyone? Seems to work well. I haven't run into any saturation probs... I think! I don't use inductors in my transistor poweramps though. That's just caps and batteries.
grataku, if you need a voltage drop, why not use a transformer with a lower output voltage?
FYI, the original 20W uses a 2x17VAC/170VA EI core transformer with a screen and multiple input choices.
Hiraga 20W schematic
I've checked the schematic at Bonavolts site. I dunno if it's the original schematic, but according to the him it is. The PSU looks nothing like the one Lectron put into production. Different transformer (2x15VAC/5A vs 2x17VAC/5A), different diodes (four discrete 250V/8A vs ?V/25A bridge), different caps (2x39.000yF + 2x189.000yF vs 6x68.000yF), different resistors (2x1ohm vs 2x0,47/0,68ohm) and different bypass caps (4x2,2yF vs 2x2,2yF/No caps)..
Oddly enough the PSU is specced to have an output of 2x18VDC, while the amp needs 2x24VDC??
I difference in sound is to be expected as well. I've found that the big caps have a significant footprint on the sound. I fixed a friends factory 20W, one cap was leaking, and I couldn't get the original Sic Safco. I used GE 68.000yF/30V and replaced two. That sounded different and made the bottom end more mushy. It's allready not as tight as other amps. Sorta *tube* like, I guess. Replacing all six caps really made it real flabby, so we only replaced the two of them. I haven't tried with other caps.
If there's anyone out there with a copy of L'audiophile with Hiraga's constructions/articles I'll gladly pay for a nice photocopy..
I've checked the schematic at Bonavolts site. I dunno if it's the original schematic, but according to the him it is. The PSU looks nothing like the one Lectron put into production. Different transformer (2x15VAC/5A vs 2x17VAC/5A), different diodes (four discrete 250V/8A vs ?V/25A bridge), different caps (2x39.000yF + 2x189.000yF vs 6x68.000yF), different resistors (2x1ohm vs 2x0,47/0,68ohm) and different bypass caps (4x2,2yF vs 2x2,2yF/No caps)..
Oddly enough the PSU is specced to have an output of 2x18VDC, while the amp needs 2x24VDC??
I difference in sound is to be expected as well. I've found that the big caps have a significant footprint on the sound. I fixed a friends factory 20W, one cap was leaking, and I couldn't get the original Sic Safco. I used GE 68.000yF/30V and replaced two. That sounded different and made the bottom end more mushy. It's allready not as tight as other amps. Sorta *tube* like, I guess. Replacing all six caps really made it real flabby, so we only replaced the two of them. I haven't tried with other caps.
If there's anyone out there with a copy of L'audiophile with Hiraga's constructions/articles I'll gladly pay for a nice photocopy..
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