| Jaskier |
Hi everyone,
I have just finished my Aleph 5 monoblocks. It seem to be ok but comparing to my Musical Fidelity MA65 Aleph's sounstage is flat. Not much of details and musicality. Better bass but this is not the most important for me.
Does any one have the idea how to solve this problem. Will appreciate any help.
Piotr |
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| MikeW |
| Are you running it balanced? |
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| Jaskier |
| no ... unbalanced so far. The pre is Balanced Line Stage but allso in unbalanced mode. But Musical Fidelity is allso unbalanced and it has got much mor space and air. I wonder if i should judge in 1st week of amp's life. Meaby it needs some time to "break in" |
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| Duck-Twacy |
| quote: | Originally posted by Jaskier
Hi everyone,
I have just finished my Aleph 5 monoblocks.
..
Piotr |
And where are the pics??? :rolleyes:
Btw some info on the speakers used may be important, are they a "difficult load". |
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| B.L. |
My Aleph 3 (but with +/-34V rails R120-R123: 1ohm) sounds flat also. Despite of that it is most beautyfull sounding amp I ever heard.
I have compared it with Gainclone and SET amp. No preamp. |
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| Jaskier |
| u like it ? ... it's just before painting ... |
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| MikeW |
| Did you ground the balanced minus input? |
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| Jaskier |
no picture ? let's try again ...
yes i did ground the balanced - |
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| Nelson Pass |
| quote: | Originally posted by Jaskier
Meaby it needs some time to "break in" |
The break in experience is very commonly reported, although
I suspect that it's often the user's ears that are breaking in,
not the equipment . ;) |
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| stefanobilliani |
| quote: | Originally posted by Nelson Pass
The break in experience is very commonly reported, although
I suspect that it's often the user's ears that are breaking in,
not the equipment . ;) |
I agree , 100%. |
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| jarek |
From XA200 manual:
“Depending on the resolution of the rest of your audio chain, you may or may not notice any break in of the XA-200 beyond the first 50 hours of operation.”
????:scratch: |
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| rwagter |
excactly,
break in peroid for your ears and brain to get accustomed to the new "improved"sound ;) |
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| JasonL |
| Yeah i want to see Pictures.. Start posting.. |
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| Duck-Twacy |
I see pics now (nice)
Still I don't understand. I allways read that the strength of Alephs is the soundstage en musicality and not the bass (at least with lower impedance speakers and low bias). Sometimes they say that the sound a bit sweet.
Here it seems the other way round? |
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| Jaskier |
Ok here is what i do to solve my problems:
1. I will have even more perfectly mached fets IRF 240
2. I wil place output fets as close as possible to the PCP on a good qality OFC cables
3. I will change 0.47R resistors for better ones
4. I will paint the chasis ... this will improove most :-)
and of course as soon as I have pisitive results I will post it
P.S. I found out when dimounting PCB that one if 1 ohm resistors in current source is not soldered properly ... grrrr :-( meaby this was the main reason ? Anyway thaks for interest and advise
P.S. The chasis is outstanding not only "nice" ;-) |
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| Duck-Twacy |
Did you use a blue led?? :clown:
(need more pics in order to decide wether its "outstanding" ;) ) |
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| Wes Marquenie |
| did you bypass the elco's with a small cap? |
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| MikeW |
| If you don't have the minus input grounded there is only 20db of gain. If you ground it you have 26db. It makes the amps sound brighter.:nod: |
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| Jaskier |
Yes ... blue led ... this will solve my problems !!!
> I will bypass elcos in power supply wit 10 uF poly
> I will bypas 220 uF elcos with ... ?? 10 uF poly or should I give less ?
> Chasis is painted now ... but i guess you don't wanna see it
> Still have some problems with 120 hz hum ... i want to place a resistor before last 10 000 uF cum but i am not sure about value. What do you suggest ... 0.33 ohm will do ? |
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| Jay |
Hi Piotr,
Is the Musical Fidelity a MOSFET? Is it single ended? My prediction is it is a bipolar, and not a single-ended class A.
"Good" amp doesn't have to "sound" good because it is only a small part in the audio chain. Look at an equalizer or tone control, they "ruin" the signal by their existence in the audio path, but at the same time they give something to the system. Many good amps (and even speakers) are "flat", in that they don't ruin the signal as much the bad amps but they also don't give anything (Why it has to give something if there's no disefficiency in the system? What it needs to do is to amplify the input signal as close as possible to the input)
IMO, bipolars tend to be musical due to the dynamics or the high transconductance. If this is the case, you have to pay attention to this aspect in your Aleph 5: the POWER SUPPLY.
I can't see the picture of your amp clearly from this public computer, but it seems like you are using budget components as I can see it clearly from the resistors.
1. Do not use cheap diode! There is no expensive diode so using a bad one is a big mistake. This will affect your system more than changing those resistors. (I don't have enough statistics to be sure but usually ultra fast ones, down to 35ns in smaller diodes, have great impact on dynamics. As for the component build, I trust Motorola for all their products)
2. I hope your transformer is not under-rated. Aleph 5 requires big current. From the not-so-clear picture, your amp (dimension/heatsink/transformer) looks so small for an Aleph 5 (I know it is a monoblock, but my Aleph 3 seems bigger). But this is another story because transformers are the most expensive part in your amp.
3. I cannot see the capacitors. "Standard" Alephs use inductors in the DC rails. This will filter the noise to a great degree, but at the same time ruin the dynamic/sonic (or whatever they call it) capability. If you use these inductors, make sure you have a massive capacitance after the inductor.
4. Well, Aleph 5 has a constant current source that will provide the current anytime it is needed. But that is too ideal than what happened in reality. Make sure you don't underestimate the capacitance and had measured the bias current exactly as intended.
5. If those do not fix the problem, somebody else had mentioned about the speaker. But that is the most expensive and difficult area. Those guys like Dave who knows about speaker design are more lucky than those who knows about amp design like Mr. Pass you know ;) ;) (Just kidding, Mr. Pass!) Frankly, your impression about the downside of the Aleph is the same with many others who had built them including me. Your comments are welcome on my philosophy: "Got a lot of money, build a tube amp. Got a few money, build a bipolar" :D (And I'm bulding a bipolar! :bawling: :bawling: ) |
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| macka |
One definite improvement is to double the number of fets in the output like the Aleph 60, and then re set the DC bias to as high as you dare.
ie 12 fets per channel
You will find the amp noticably more dynamic with better control in the bass. ie the benefits of the Aleph 2 without power/heat.
This is quite an easy modification with only hardware issues to consider.
The wiring may also be an issue.
The supply rail wiring from R14 should be as short as possible to the output stage power and I would tend to run seperate power wires to both the driver board and the output fets, this will add more spark and open up the sound stage.
Having the caps under the board and high current wiriing from the rectifiers may be causing induced hum into the input stage.
Check that you are running the positive input to the unbalanced input (+) and that the negative (-) of the balanced input is shorted to ground if you are using unbalanced input for best performance.
macka;) |
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| Jaskier |
| Among many little changes i made in my Aleph, one gave me big difference. I rised current of fets up to 0,95 A per fet. Sounstage seem to be much better now. Sound is sweeter and more ambient. I like it. You can feel energy in music. Thanks all for replys and advises. |
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| protos |
| I never found the A5 too flat soundstage wise although it seemed a tiny bit slowish at first.For me bypassing the main caps with good MKPs and further with tin foil made quite a difference to dynamics. |
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| Koy |
| Hi guys! I made some Aleph (A30) too. http://koy.hi-end.org/Audio/Bastleni/Aleph3.html . And I experienced the same feeling.Loss of details and space ( comparing to Thule Audio). I rised bias ( to about 1.2A per IRFP), used metal resistors, bypassed electrolyts, changed % of modulation of the bias current, I tried blue LED, painted heatsinks, drunk some whisky and ... nothing changed. I am afraid it belongs to Aleph. Somebody likes it somebody not. |
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| Duck-Twacy |
| quote: | Originally posted by Koy
Hi guys! I made some Aleph (A30) too. http://koy.hi-end.org/Audio/Bastleni/Aleph3.html . And I experienced the same feeling.Loss of details and space ( comparing to Thule Audio). I rised bias ( to about 1.2A per IRFP), used metal resistors, bypassed electrolyts, changed % of modulation of the bias current, I tried blue LED, painted heatsinks, drunk some whisky and ... nothing changed. I am afraid it belongs to Aleph. Somebody likes it somebody not. |
Thats a pity. It looks very nice though (is it a A3 of A30 ??) |
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| jarek |
| Maybe problems with too flat sound are connected with wiring arrangement and groundig scheme? |
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| Koy |
I spend some time ( I build and tuned it allmost one year, on evenings) with Aleph. I have build A30, and all measuremens http://koy.hi-end.org/Audio/Clanky/A3cln.html - unfortunatelly in czech. I am going to translate it in more known language :)) I have done was on A30. After all I successed to burn ( screwdriver in wrong position) one IFRP and I turned it to A3. On the other hand output IRFPs are much better matched now. On the picture you can see A30 in time of experiments ( that-s why the nest of cables).
Grounding? I tried to do my best. I can not hear allmost no humm. But I am not sure it helps. |
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| PMA |
Jaskier,
you might try some of the less distorting amps. |
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| Jay |
| quote: | Originally posted by Koy
Hi guys! I made some Aleph (A30) too. http://koy.hi-end.org/Audio/Bastleni/Aleph3.html . And I experienced the same feeling.Loss of details and space ( comparing to Thule Audio). I rised bias ( to about 1.2A per IRFP), used metal resistors, bypassed electrolyts, changed % of modulation of the bias current, I tried blue LED, painted heatsinks, drunk some whisky and ... nothing changed. I am afraid it belongs to Aleph. Somebody likes it somebody not. |
When I first built the Aleph, It drove me crazy. This is because my definition of a good system is the one who can make me enjoy the music. This is not the amp fault, because in an audio system an amp must work in synergy with other components. You have to tweak your system to achieve a good result. I like the Aleph only after I tweak the speaker (sealed the vent and changed the crossover).
IMO, the good things about Aleph are:
1. It is a class A (you know what it means). Class A amps usually have "separated" and sweet vocal. I think the Aleph's vocal is wonderfull compared to other class A amps.
2. It is very efficient as a class A (You know what a high power amp can do to the overall system, even though you never drive the system more than a few percentage of it's capacity).
3. It is a MOSFET. IMO, it is the bass performance of MOSFET that attracts most people.
4. It has the capability to "ghost" the load? Or work with many speakers. Well, there are many other technicall things, but they are not important to pure music listeners (We care only what we hear).
PMA said something about trying an amp with lower distortion. If you think Aleph "has" distortion, I agree. The current feedback apparently introduced some distortion (so you must use quality caps there). But I prefer to remove the current feedback with the price of much reduced power. |
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| Jaskier |
During past few days i did following changes to my Aleph :
1. Rised current on fets up to 1 A per fet
2. Used IRFP 250 N instead of IRFP 244
3. mooved source and gate resistors directly to fets. (As u know i have fets on a wires :-)
And now finally I an 100% satissfied with my Aleph. It is sweet, dynamic and spacious. I like it. Really !!! |
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| Bricolo |
| did you try to shut down the current source's AC gain? (this way, the current source acts like a constant current source, always 100%, no feedback) |
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| Jaskier |
| no. How to do this ? And what would be change in sound ? |
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| Bricolo |
I don't know exactly (I never built an aleph)
This is something I rode here, on the forum.
Maybe you should ask Mr Pass himself, or wait for an answear here |
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| Bricolo |
Since it has something to do with the feedback, and I remember some things about a resistor
I think that you have to change (or remove, or shorten) the resistor between the output and the current source |
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| wuffwaff |
just remove R19 (around 523 ohms) or the 220uF Cap that connects the output and the current source.
This will give you a constant current source. The only problem could be that peak output current is halved so output power will only be 25%.
Power into 4 ohms for 2.5A bias would be 2.5x2.5x4/2=12.5 watts
william |
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| Bricolo |
I think it's R21 (453R) + C10 you have to remove.
BTW, after remove them, you can try to increase the bias (you can also try it without removing the parts)
Push the bias the higher you can, the higher your heatsinks can accept. This can only do good things to the sound |
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| wuffwaff |
Bricolo,
you´re right it´s R21 (it´s difficult to remember all of the resistor numbers). But either this or the cap will be enough to deactivate the active current source.
william |
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| Jaskier |
| besides lower power which dont have to be big disadvantage would this give any changes to sound ? Did anyone try it? |
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| Bricolo |
| quote: | Originally posted by wuffwaff
Bricolo,
you´re right it´s R21 (it´s difficult to remember all of the resistor numbers). But either this or the cap will be enough to deactivate the active current source.
william |
you're right. I was thinking the reverse way (didn't see the need for the 2 components, if you build the amp from zero. But he isn't building it from zero, it's already working. So removing one component will be easier, of course)
| quote: | Originally posted by Jaskier
besides lower power which dont have to be big disadvantage would this give any changes to sound ? Did anyone try it? |
I didn't, for sure: I have no aleph :/
But since it's a so easy mod, try it! You found a difference between 2 positions for a resistor, you'll certainly head the difference here.
And tell us your results ;) |
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| Jaskier |
| I have welded covers ... to much temtation for endless modifications ;) |
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| Koy |
On my A3 I have jumper on the board to swich the feedback off.
I recommend you to give a try. The difference can be easily heared. You=ll have classical single ended amp. On my oppinion it sounds better and more clear. On the other hand it looses on the low frequencies. I strongly advice to put instead of this feedback resistor the trimpot and set the distorsion on as low as possible value. My values differs to the one stated in the whitepaper. By cutting the value down you get higher output power ( and control of bass) but distorsion on hights rises. It is give and take. |
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| PMA |
| Not to switch the feedback of. Every true balanced input amp can be converted to Single Ended input by connecting the (-) input to ground and using (+) input as single ended input. This is very different from switching the feedback off :( . In fact the way I have described hereabove is the only way how to get quality single ended input from balanced input. |
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| Koy |
PMA: Misunderstatement. I dont mean swich the global feedback off. I canceled only the modulation of the current source - Passś patent of dynamic regulation of the bias.
All: There is one thing I admire on the Aleph. You can tweak and modify it for long time. Change of one part changes function of the others. |
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| Koy |
| I am sorry for mistakes. |
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| Jay |
| quote: | Originally posted by Koy
On my A3 I have jumper on the board to swich the feedback off.
I recommend you to give a try. The difference can be easily heared. You=ll have classical single ended amp. On my oppinion it sounds better and more clear. On the other hand it looses on the low frequencies. I strongly advice to put instead of this feedback resistor the trimpot and set the distorsion on as low as possible value. My values differs to the one stated in the whitepaper. By cutting the value down you get higher output power ( and control of bass) but distorsion on hights rises. It is give and take. |
I think we all knows (except for the newbies) what feedback we are talking about. I don't know what it should be called technically, but I think it is also a current feedback as it takes signal from the output and route it to the current source.
When I tweaked my Aleph3 for a better sound, I came up with this idea, and that's the end of my everlasting tweaking effort! I had never read such tweak here in this forum when I applied this. But later some fellows report positive results (including Koy) so I have to say that the result is really beautifull. I know it is difficult for newbies to differentiate sounds after sounds. All seems different and it becomes prefference. But to me, this true single ended Aleph is the most beautiful sounding amplifier I have ever heard (You don't know what I have heard I know ;))
About this, as long as I can remember, Mr. Pass himself stated that with the tweak Aleph will fall into regular SE like Zen. IMO, the concept may be the same, but the circuit is different and so is the sound (At least my ears are not as bad as my electronics knowledge)
Koy was right that it looses the low frequencies, but to me, the most important drawback is the reduction in power. I have tried to add pre-amp to boost the power output but the price couldn't be justified (distortion). At least if I have to I can use sensitive speakers! |
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| Koy |
| Jaye: And we have reached limits of this circuitry now. You can rise supply voltage or use more sensitive speakers or build another amp... |
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| Mark A. Gulbrandsen |
Actually it ought to sound really nice. Probably the best thing to do is remove the bias resistor completely so it goes wide open(so to speak). It will run hotter but sound its best. I've listened to my 2's both balanced and unbalanced and although balanced is a bit better its not miles better. I'm running an Aleph L and the pair of 2's most of the time unbalanced and the soundstaging and other stuff is incredible. Perhaps your musical fidelity is where the problem lays. Ya also need a preamp thats up to allowing the 5 to reveal all its capable of.
Mark |
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| Raka |
| quote: | Originally posted by Koy
On my A3 I have jumper on the board to swich the feedback off.
I recommend you to give a try. The difference can be easily heared. You=ll have classical single ended amp. On my oppinion it sounds better and more clear. On the other hand it looses on the low frequencies. I strongly advice to put instead of this feedback resistor the trimpot and set the distorsion on as low as possible value. My values differs to the one stated in the whitepaper. By cutting the value down you get higher output power ( and control of bass) but distorsion on hights rises. It is give and take. |
Do we have another hint to biamping? :) |
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