Yes, it is off-topic, but certainly not the first time horses were mentioned in this endless thread. Coincidence, or could it be just because of the similarity with the beautiful AlephX? 😉fdegrove said:
/Hugo
I've just come back from the farm at 4am this morning. One of my fiance's horses has just given birth to a jet black filly (due to turn grey). She breeds them so during summer it is a fairly regular thing - CCTV helps alot! Her favourites are Arabs aswell.
Cya
Gaz
Cya
Gaz
resistor 4.75k in 5/24/02 BOM
There are a pair of resistors marked 'feedback pair' '4.75k' in the bill of materials. I don't see it in the 5/24/02 schematic.
Can anyone tell me what they are for?
Thanks,
Vince
There are a pair of resistors marked 'feedback pair' '4.75k' in the bill of materials. I don't see it in the 5/24/02 schematic.
Can anyone tell me what they are for?
Thanks,
Vince
They're pretty important.....
Look up the revised schematics on the aleph-x Alpha pcb purchase thread that I was envolved with.
It's a fairly short thread.
John Inlow
Look up the revised schematics on the aleph-x Alpha pcb purchase thread that I was envolved with.
It's a fairly short thread.
John Inlow
Some problems with the X
After a burned channel I have managed to replace the output fets and now the smoking sourceresistors are gone 🙂.
Setting the bias to 2,3 ampere a side everything looks oke (measuring 0.5 volt across R5 and R40). But the absolute off-set is very high, 7 volt and 6,5 volt 🙁. The off-set on the speakerterminal is ~ 1,2 - 1,5 volts.
Have the Aleph-X pro's suggestions what to check?
p.s. before the channel smoked the off-set on the speakerterminals was very low, ~10mV. So I thought the diff-pair would be oke.
After a burned channel I have managed to replace the output fets and now the smoking sourceresistors are gone 🙂.
Setting the bias to 2,3 ampere a side everything looks oke (measuring 0.5 volt across R5 and R40). But the absolute off-set is very high, 7 volt and 6,5 volt 🙁. The off-set on the speakerterminal is ~ 1,2 - 1,5 volts.
Have the Aleph-X pro's suggestions what to check?
p.s. before the channel smoked the off-set on the speakerterminals was very low, ~10mV. So I thought the diff-pair would be oke.
Re: Some problems with the X
Check your diff-pair. It could have gone to heaven after the smoke.
Unload the big caps before measuring or soldering.
I had several diff-pairs blown from a +/-5V remaining voltage over the caps.
/Hugo 🙂
Taco said:
Check your diff-pair. It could have gone to heaven after the smoke.
Unload the big caps before measuring or soldering.
I had several diff-pairs blown from a +/-5V remaining voltage over the caps.
/Hugo 🙂
Re: Re: Some problems with the X
I measured the diff-pair on the board, when replacing the 4 new outputfets, there was no short and the 2 halves behaved the same. But I will dissamble the 2 fets and will measure things out of the boards.
Netlist said:
Check your diff-pair. It could have gone to heaven after the smoke.
Unload the big caps before measuring or soldering.
I had several diff-pairs blown from a +/-5V remaining voltage over the caps.
/Hugo 🙂
I measured the diff-pair on the board, when replacing the 4 new outputfets, there was no short and the 2 halves behaved the same. But I will dissamble the 2 fets and will measure things out of the boards.
Still problems with 1 channel of my X. Edwin suggested to measure r23 and r25 the results are:
r23 4.88 Volt
r25 4.82 Volt
All the three irf9610 fets are matched at 2 mV so I switched the irf9610 of the broken half with the one of Q6 and put at the place of Q6 a new (unmatched) fet. I still measure a off-set of 1,3 volt at the speaker terminals.
If I find some time I will dissamble the channel again (out of the case) and check the resistors. Does anyone have an idea of what to check?
I am also planning to order a new diff-pair ...
r23 4.88 Volt
r25 4.82 Volt
All the three irf9610 fets are matched at 2 mV so I switched the irf9610 of the broken half with the one of Q6 and put at the place of Q6 a new (unmatched) fet. I still measure a off-set of 1,3 volt at the speaker terminals.
If I find some time I will dissamble the channel again (out of the case) and check the resistors. Does anyone have an idea of what to check?
I am also planning to order a new diff-pair ...
An offset of 1.3V is not that much.
All components will probably be OK.
Does the amp play well?
The most important is a well-matched diff-pair and at least 1% resistors for R23/25. Whatever is easier for you is ok; matching diff-pair or swapping resistors.
I mounted the diff-pair like this: http://www.diyaudio.com/forums/showthread.php?postid=173696#post173696 so I could easily substitute the fets till the offset was almost 0.
Trimming V1/V2/V3 can improve a little.
V3 trims the differential DC but also affect the absolute DC a bit.
Adding resistors between the outputs and the common sources of the diff-pair helps stabilizing DC. Something like 2k to 5k should work. 2K is a bit low, but it worked best for me.
Hope this helps.
/Hugo 🙂
All components will probably be OK.
Does the amp play well?
The most important is a well-matched diff-pair and at least 1% resistors for R23/25. Whatever is easier for you is ok; matching diff-pair or swapping resistors.
I mounted the diff-pair like this: http://www.diyaudio.com/forums/showthread.php?postid=173696#post173696 so I could easily substitute the fets till the offset was almost 0.
Trimming V1/V2/V3 can improve a little.
V3 trims the differential DC but also affect the absolute DC a bit.
Adding resistors between the outputs and the common sources of the diff-pair helps stabilizing DC. Something like 2k to 5k should work. 2K is a bit low, but it worked best for me.
Hope this helps.
/Hugo 🙂
The offset of 1.5V is rather too much... (at the speakers terminals obviously)
I would check the input elements. Maybe one of zener diodes is shorted or in reverse direction? It looks like a lack of symmetry at the input circuit.
I would check the input elements. Maybe one of zener diodes is shorted or in reverse direction? It looks like a lack of symmetry at the input circuit.
Thanks Jarek, for pointing that out. I didn't express myself clear enough.jarek said:
Just meant to say that 1.5V couldn't be that difficult to fix.
Of course it's too much in the long run.
/Hugo 🙂
Thanks Jarek and Netlist I have now swapped some more irf9610's ( I had bought 6 matched irf9610's) And I have now an off-set of 140 mV. Still a bit high, so I plan to order some matched irf9610 (localstore).
I checked every resistor and zener diodes and they were all okay.
I checked every resistor and zener diodes and they were all okay.
jarek said:
All measurements are taken without the input connected. The plan is to use the amp unbalanced until my balanced line stage is ready.
Oh Yes!!
It's playing, what a nice sound. But the differences with my 1996 JLH 15watt are small. The bass of the XA is better and the highs have more definition but that's it.
But 1 channel has with a pre connected 200 mV offset the other 30mV. But the amp is deadsilent. I will get a new diff-pair and fix that problem.
The amp get's very
ca 60 -65 C. Ambient is 25+
It's playing, what a nice sound. But the differences with my 1996 JLH 15watt are small. The bass of the XA is better and the highs have more definition but that's it.
But 1 channel has with a pre connected 200 mV offset the other 30mV. But the amp is deadsilent. I will get a new diff-pair and fix that problem.
The amp get's very
ca 60 -65 C. Ambient is 25+Is that it? Just better lows and better highs? That's too bad. 😉
When I play mine playboy playmates all of a sudden appear in the room and start giving me free lap dances.😎
Seriously, a different pair of speakers are more likely to give that 'WOW' different sound that you expected.
When I play mine playboy playmates all of a sudden appear in the room and start giving me free lap dances.😎
Seriously, a different pair of speakers are more likely to give that 'WOW' different sound that you expected.
grataku said:
Yes the soundstage is absolutly better, but the JLH isn't very bad neither. Everything is better and clearly hearable, but it's not fair to say the JLH is a bad amp.
Improvements in one's system due to electronics are usually adiabatic, experience a few of these improvements and you'll have a great system without even knowing.
Any system sounds great until you hear a better one, if you ever go to an audio show you know exactly what I mean. No one said the JLH was bad, the question is will you switch back to it?
I walked into a tweeter center...I know, I know...I was just walking off my lunch, anyway this guy was drooling over a pair of sonus faber that sounded like absolute crap, no bass no body thin highs, just crap. I am sure that someone listening to a better system than mine could make just exactly the same observations about it.
Any system sounds great until you hear a better one, if you ever go to an audio show you know exactly what I mean. No one said the JLH was bad, the question is will you switch back to it?
I walked into a tweeter center...I know, I know...I was just walking off my lunch, anyway this guy was drooling over a pair of sonus faber that sounded like absolute crap, no bass no body thin highs, just crap. I am sure that someone listening to a better system than mine could make just exactly the same observations about it.
Taco,
I agree, the JLH is an excellent amp and was my entry in Class A. I recall that design convinced me Class A was a must have.
The X Aleph for JLH owners is in effect a monster version of the JHL with more refinements such as dynamic contrast & bass definition as noted elsewhere.
macka😉
I agree, the JLH is an excellent amp and was my entry in Class A. I recall that design convinced me Class A was a must have.
The X Aleph for JLH owners is in effect a monster version of the JHL with more refinements such as dynamic contrast & bass definition as noted elsewhere.
macka😉