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Old 22nd April 2008, 03:48 AM   #531
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Hi James,
Something not often mentioned is that these simple ccts have negligible PSSR and so, unfortunately, the power supply selection DIRECTLY EFFECTS the sound of the gain stage and so needs to be included in the design - usually neglected.

For example, most bench power supplies have excellent control but aren't very good for sound, the 3 pin regs need a buffer or simple Cmulti (+ reg?) to avoid some high freq "harshness", some basic electros give a rather slow, fat sound with loose bass, etc, etc.
Many of the older capacitors do sound rather good indeed - most were built for quality rather than size/price, so don't discard them too quickly.
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Old 22nd April 2008, 04:30 PM   #532
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jameshillj-

Thanks for the reply! I actually hadn't even considered PSSR in such a simple circuit, very good point though, I was just pumped to get it built in about 5min. Even my JLH took me a few days of build time including testing, though it too has had almost no adjustments. I had thought though that the supply may be to blame. It was a bench supply I found in a pile at my dads shop during a rare cleaning, it was heading for the trash and I couldn't let it get away. It is a old Power One unit rated for 24v @ 4A. It uses a MC1723 with pass transistors, they are Motorola's labeled 8352 (two of them) and 8326 (only one). It is a nice little supply, unless of course I need more then 24v, then I have to turn to my transformer stash or my 500v bench top tube supply.

Anyways I grabbed it for testing amp such as a Aleph-Mini for instance. It has about 30kuF of total capacitance plus in my JBOZ I have another 1kuF, could this be the problem then. Like you said poor capacitors contributing to deep loose bass? Or maybe an over abundance of capacitance? I will build up a little shunt reg or simple pass transistor reg too. I assume it doesn't really matter which one since they are both probably better than a 3 terminal. I will play with the power supply side a little today and see if I can get some of the sound issues worked out.

BTW don't worry, I don't discard old caps, or anything old for that matter. I have a fairly health tube stock that is slowly growing, yes I admit it, I have a problem, I am a glass head. I just love building with them (except the occasional high voltage wake up call), my girlfriend loves little sexy glowing bottles, and we both love the sound. I have a growing collection of old caps, resistors, shelves of iron (though mostly old low power tranies), etc etc... I do like the warm, smooth, seductive sound of the oil caps, I just didn't know if maybe it wasn't playing nicely with the FET circuit. I will try out some different dielectric/value combos and see what I like best. I have a feeling that I will gravitate to the oil filled or beeswax impregnated. Has anyone tried Teflon? I have never heard them but I hear they are very tight, focused, and almost invisible to the ear.

Thanks again!
Cheers
James
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Old 23rd April 2008, 04:47 PM   #533
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I played around with the circuit a little bit last night, it seems very friendly to change. I tried out a 100k feedback resistor and switched it in and out. I decided I don't think I really like the sound with feedback,but maybe I will experiment with different values a little bit. I also added in a 0.47uF cap at the output parallel to the 10uF oil. This seemed to really affect the sound in a way that I feel is for the better. I might have to give this a shot now on my JLH. I also tried switching out the 10uF oil with a 220uF Panasonic + 0.47uF film, I actually like this combo. I normally really like the fluid sound of oil caps, but in this case it seems that the electrolytic really seems to bring things into focus more. The bass seems a bit tighter and the highs and mids are less muddied and recessed.

I haven't had time to mess much with the PSU, aside from a few different values of caps. I will hopefully have time today to try a few different regulators. Would a Darlington capacitance multiplier do much good on something like this or is that more of a power amp only circuit?

I will have to play with CCS loads and what not with this critter a little bit. I was was woundering if anyone who has tried a CCS or other loads (I have seen choke) would care to comment on the sound difference at all.

BTW: the Motorola's in my PSU are 10261, three of them. I listed the date codes instead, sorry.

Cheers
James
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Old 24th April 2008, 03:51 AM   #534
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James,
Thinking back, I didn't actually give this simple little cct a good try as I went for the Twisted Pair CCS version and never did finish it as I found that I couldn't get the sound of the Fet CCS to match the sound of the Jfet (as Input device) - however, on another cct I replaced the Fet Ccs with the "Standard Choky" 2 transistor Ccs with much better results.

Your cct, the new F5 and the simplified UGS are good reminders to not discard basic ccts - thank you.

As for power supplies, tried all sorts of different systems from simple C-R-C plus fet zener reg to "full house" hexfreds, B.Gate + Roe C-R-C into a series/shunt but was never totally happy with the sound of the whole preamp project and put it aside for later, and it's still there!
I did try out Eric Juanida's preamp4 P/S (from "High End Audio") and am building one for the headamp - initial results are excellent and will try it out with the ZenMod BabblefishJ h.amp cct (c/f Aleph J)

Capacitor "burn in" - Some folks reckon it's all rubbish, but I have found it to be quite true, unfortunately and those older big electros, in particular, also need to be "reformed" before use.
So, would suggest leaving the caps in cct at least 24 hours before changing them - the B.G.s take over 2 weeks to come good [ Oils, Beeswax, too] although most others are quicker than this.
Suggest you try transistors for Cmultiplier/ regs - different base - not keen on darlingtons, but others have had good results.
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Old 24th April 2008, 03:55 PM   #535
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Thanks again for the reply. BTW sorry, I saw that you had mentioned the c.multi in your first post, I must not have been reading to closely when I said in my reply I might try one. Do you think though that the single transistor or the FET is better than a Darlington for a c.multi? If figured in the case of that circuit you wanted as much gain as possible. Of course the only things I have read about them are on ESP audio, am I missing something though? Unless I do a discrete Darlington, or is that what you are suggesting?

No I do somewhat subscribe to the "rubbish" about capacitor run in time. I am sure that it could have been the problem with the oil cap. It is intended for use in a tube preamp PSU but that project never got off the ground. It has been sitting for a while so I am sure it needs to be run in. I was just surprised that going to a Panasonic electro made such a huge difference. Like I said everything just seemed brighter and more focused/controlled. I will have to try some large films + small films, some other electros, some other PIO's, and maybe throw in a Jupiter or NOS beeswax for fun. I would love to try some AuraT's but I cannot justify the price for these Teflons, no matter how good they sound...even new PIO's are starting to get very pricey

Hmmm... I guess the PSU will need a good tinkering since, like you said, it directly affects the sound. Though has anyone by chance tried a Aleph type CCS with Zetex FET's in this circuit? I don't know if it would work or even be worth trying. I know this begins to shift it away from the "one transistor clapping" Zen approach and into Aleph territory. I guess though the Zen amps (some at least) still used the Aleph current source, as long as it remains just one gain transistor it still counts as Zen right Master Pass? Of course I am thinking to replace the 2k2 drain resistor. I assume too that doing this (or would suspect any CCS) would help with the PSSR? Just a thought that I am sure has been addressed as I am not a very close reader.

Cheers
James
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Old 24th April 2008, 05:28 PM   #536
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James,
With the Cmulti, big gain isn't everything and Rod's no nonsense designs do work okay but there are other methods.

I'd use the darlingtons first - simpler cct - can get fancy later - fets in same position function and sound a bit different, is all - better components make a big difference - best just to start and "fiddle" to your taste(!)

'bit surprised that a Pana electro would sound better than an Oil.
A lot of the "super" caps don't mate up well with other cap types when used as bipasses - can get dissapointing results for big $s.

That f.back resistor changes input Z, bandwidth, etc so some of the differences aren't just related to "feedback" - nothing's simple with simple ccts, especially with the NP logo!

Interesting thought about replacing the BJT with a fet in the Aleph active CCS. Hmmmm.
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Old 25th April 2008, 12:17 AM   #537
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I was actually a bit more than a bit surprised when I switched the output cap and it sounded better. I for one love the sound of the PiO's and though I do not hate the electro's they just don't have the same flavor. I find it fun that it seem that the output cap in the JBOZ makes a much bigger impact on the sound of the over all system than the one in my JLH seems to. In the JLH (which really needs an update) I just have a cheap Nichicon electro, no bypass, nothing fancy. I have a feeling though that since the oil cap has sat for so long it needs a good long run in. I think I might stick it back in and just let it run for a while, see what it does after that break in period.

Yeah I do know that adding feedback, even to such a simple circuit, can have a very broad effect. However I was not immediately prepared for the different it would make. I would say that it made the pre sound almost more akin to my LM4562 pre. It seemed more precise and controlled, but it also sounded drier and there was just something that didn't sound right about it.

I have a feeling that the PSU with this one will take some serious tinkering, but after all that is the name of the game in DIY! I think I will try the darlington c.multi though and go from there, just because it seem like it is quite simple.

I was actually thinking more about replacing the higher power FET (ie. IRF240) with something a little bit more tame since it is a pre. Sorry to mislead, but now that I read your comment you have got my mind going. Can the BJT be replaced with a Zetex or similar FET with any advantage...or disadvantage for that matter? I don't understand enough about the Aleph current source to do anything other than speculate. Would anyone care to comment, possibly Mr.Pass. I am sure there is a reason why not, but this would make something like the Aleph a ALL FET design, not a single BJT anywhere. I suspect though (again I don't know enough about this area) that it may open up a who can of worms as far as the patent paper work goes. Hmmm... indeed!

Cheers!
James
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Old 25th April 2008, 12:39 AM   #538
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you can always try something like this ;
that's result of pretty quick 'n' dirty making of NS10 clone , on one Serbian forum ;

btw - Bogdan Borko ( as known here ) tried NS10 with jfet on input in that occasion ; it just sounds more right .........

just scale current in CCS and number of leds for shunt darlington biasing
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Old 25th April 2008, 02:59 AM   #539
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Thanks Choky, I will have to give that a shot. Unfortunately I haven't had time to do anything today but reply on the forum. It is the end of school / beginning of finals and I have one test tomorrow! I have been studying myself inside out, I guess though like everyone says, it will all be worth it in the end . BTW I was looking over your site, good stuff. The tube susy concept peaked my attention . Along with the VTV article that never made it, I love theater tube equipment. What I would give to have grown up in that time, just a few years short...more like 15-20 I guess. My dad has got me into tubes, he was an RCA theater servicer and I spent much of my youth (I guess I still am a youth) pouring over his collections of RCA, Western Electric, HK, Altec, and Balintine schematics. Anyways I am rambling like I always do.

JFET NS10 you say, just the input, BJT's in the rest I assume. Interesting, the NS10 has been one of those projects calling my name as well. I seem to have picked up a lot of projects lately, this part time hobby is turning into a full time hobby, and soon if not already a life time obsession. Just out of interest have you built the JBOZ? I am curious about it versus the pumpkin...though I know they are different critters.

Well back to my life here in Iowa for the next few days...Chemistry and Calculus

Cheers
James
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Old 25th April 2008, 11:26 AM   #540
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Quote:
Originally posted by JPeitzman
......... Just out of interest have you built the JBOZ? I am curious about it versus the pumpkin...though I know they are different critters.

........

hehe

somewhere in my youth .... (now I'm almost 41 , old fart ......) ;

you probably don't remember what's "Pacific " preamp ....

it's almost old as toobz are

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