Aleph J Schematic

[Zen Mod]

AR2 is one to blame , if something goes wrong

I'm having pair of LL1636 in my drawer ( Geschenk from my wakoo German , from time when we tried to crack M2 options ) but I'm not having TP I/V ....... so conclusion - I didn't heard that combo with my own ears

however - they (LLs) will soon be tried after wakooest I/V ever ( or as possible I/V transfer parts in it)

 

[francolargo]

Frank - if you're willing to toss entire OP shebang on right side and invest in pair of Lundahls , you'll have much better sound - balanced or SE , by your choice

look for AR2's posts regarding that solution

I will definitely consider this and will research AR2's results. However, this amp is for ~180 Hz and up in a bi-amp system, so will the transformers influence phase on those channels? If so, I would need them on the 20-180 Hz channel as well, no?

When I get back from my upcoming trip (and get back above water at work), I think the first problem is to get *enough* sound. Second problem is to get that sound clean. Ideally I'd like to take this amp apart only ONE more time! I am no engineer, so I am out of my comfort zone most of the time!

So for next steps:

1. R1-3 are stock - 221k/22.1k ...meaning an average of 5X gain for the + and 5X for the minus halves of the signal? If so, how close can I go to a 20X ratio? That is the gain of the current mid/treble amp that will just max-out the listening space. Right now, the A-J will do it at +/- 2V input, or double the i/v signal I have to offer.

2. I definitely want to be sure my bias is 'dialed-in'. With the case closed the 'wind tunnel' fan is quieter than I thought so I can blow more air and tweak the bias upward, but I don't want to damage anything measuring it! I *think* it is 3.7A and believe I can cool adequately at 4A. Best place/method to check bias for adjustment with R27 pot?

Thanks SO much, helpful DIYers!

Frank

 

[buzzforb]

You check bias across the source resistors on the mosfets.
@ZM, bring on the super IV. Its sizzlin.

 

[schultzsch]

doing some research in the last time regarding dacs , yesterday I`ve found in a post a link with metal foil resistors/pots from vishay.the price is indeed HUGE but the same are the specs too, one of their features is very low noise accompanied with long term stability and as for this I am thinking to use 4 of those trim pots in my amps in place of R8 and R27 for future tunning of bias and offset too if the other is modified.for R8 they do have a 1K trim pot but didn`t manage to find any 70-100K or above value trim pot for R27, as for power rating 250mW will suffice right?
I am talking about Vishay Bulk Metal® Foil Trimming Potentiometers , does anyone of you experienced with these?

 

[Zen Mod]

if you're going to use trimpot for drain resistor of most left Jfet , then yes - you'll maybe have sonic benefits , comparing to common cermet

for every other position - forget it - waste of money and brain power

 

[schultzsch]

if you're going to use trimpot for drain resistor of most left Jfet

are you reffering in place of R7?

 

[Zen Mod]

yup

 

[schultzsch]

I would like to use some kind of trims in place of R8 and R27 that would not degrade the sound.do you have any suggestion?

 

[buzzforb]

You could maybe argue R8 is worth it, but R27 is definite waste. Both probably are. Better to fiddle with it and the replace with fixed resistor. Mornin DiyAudio.

 

[Zen Mod]

http://www.diyaudio.com/forums/pass-labs/145387-aleph-j-x-amp-project-70.html#post3406006 :

.......

why I'm seeing all the time that anti-trimpot hysteria , especially from ppl not understanding either their role , or function of entire circuit ?

you guys are building knock-offs of NP's amps , and you're dicing fact that his amps are having trimpots in needed places ; even most "critical" ones

and he's not loosing sleep regarding that ........ in fact contrary to that

use "generic" Vishay-Spectrol multiturns


nasty mornindiyaudiosses

gollumgollum

 

[schultzsch]

mornin` to you too

 

[buzzforb]

ZM is dumb in that he recognizes that the design and transistors most affect the sonic signature of an amp. If you don't like the AJ, fancy pots wo'nt make a difference. If you do like it, the only place I would consider one is r7. In truth, this is not even in signal path, so dunno. Fancy parts can help, but you are definitely in most expensive and last 10% of optimization.

 

[schultzsch]

for easy mounting on PD`s boards should I go with 64W or 64Y ?
http://www.vishay.com/docs/57028/64.pdf

 

[schultzsch]

untill yesterday didn`t even known that type of resistor/pot exists and I was curious in the benefits of using them

 

[buzzforb]

I like Bourne 3299 just because they are beefy dual wiper. Probably overkill. W is most common layout.

 

[schultzsch]

for decoupling C2, C3 and C4 with what values of polypropylene caps should I go?

 

[Zen Mod]

ZM is dumb in that he recognizes that the design and transistors most affect the sonic signature of an amp. If you don't like the AJ, fancy pots wo'nt make a difference. If you do like it, the only place I would consider one is r7. In truth, this is not even in signal path, so dunno. Fancy parts can help, but you are definitely in most expensive and last 10% of optimization.

as already stated numerous times before , however big dumbness you succeed to write , you'll ever never came even in near proximity of my Glorius Dumb Achievements

as seen on schematic (they're useful ,sometimes ) R7 is directly in signal path, serving as I to V transforming element

whatever - as you can find cermet pots in most critical places in medicine/hospital gadgets , military equipment yukyuk , I can't see proper reason to avoid proper industrial quality part where it belongs

next step is bronze heatsink , I presume

having pot as part of R27 resistance is useful - for coarse bias adjustment
having pot as part of R8 resistance is useful , for fine offset adjustment

if you have pots in these two positions , you don't need pot for R7

 

[buzzforb]

Dumbness was getting R7 and R8 mixed up. Too many schemtics floating in my head.

 

[Zen Mod]

ya forgot smiley ?

 

[buzzforb]