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Old 28th October 2012, 10:07 PM   #8361
andyr is offline andyr  Australia
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Quote:
Originally Posted by RCruz View Post

My initial assumption was second stage miller around 40pF... now I know it must be way larger.
Can you provide more of an explanation about this? For instance:
Q1: what causes "Miller capacitance"?
Q2: is the effect of having "Miller capacitance" that you have to decrease the value of either C1 or C2 in the (passive) RIAA network, to compensate (so you end up with the correct values, according to the RIAA equations)?
Q3: can you calculate the expected Miller capacitance value?

Thanks,

Andy
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Old 28th October 2012, 10:16 PM   #8362
Salas is online now Salas  Greece
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Quote:
Originally Posted by MASantos View Post
Hi Space Egg,

I had already looked at ebay,but am always afraid of fakes, no matter the sellers say and whatnot. I have been on ebay again and found these:
100x 2SK170 K170 BL 6 12mA | eBay
which are the cowboy legged ones, what do you think?

please let me know after you test the ones you bought from polida if they are genuine.

Those are good, Zhou is known around here, but contact him first to know he is serving right now.
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Old 28th October 2012, 10:19 PM   #8363
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Hi MASantos

I ordered the parts from Polida about 2 weeks ago, so they will hopefully be here this week sometime.
Parts from China in the past have taken up to 4 weeks to arrive.

I have ordered a large amount of photographic equipment from China over the past few months.
All items arrived safely, and all were of top quality.

I have to say, I'm sure there are some stories out there...
...but having ordered litteraly 1000's & 1000's of electronic components for work & hobby over many years, I have NEVER come across a 'fake' item yet ( fingures crossed ! ).

Despite what some may say, it appears to me that the Toshiba part is NOT particularly 'rare'; and that in fact, countless suppliers have them.

Yes the ones in the sellers picture ARE 'cowboy legged' on 'ammo strip' tape.
They would appear to be OK.
However...
...The guy wants $50 inc P+P...Whereas Polida want about $32 inc P+P.
Furthermore...the seller has been an eBay member since 2003...but only has 143 feedback points...And also has a NO RETURNS policy...

The simple reason, other than price, I chose to buy from Polida; is that if you look at what they sell & their stats. generaly...you can see they are a VAST supplier, dealing with a HUGE and diverse range of electronic & other parts.
As a consequence of this, it seems to me their stock is most unlikely to have been 'filleted' for 'on-spec' parts...and that if they were aware of any problem with the item, I would expect them to pull it from their huge inventory.

I had looked a pre-matched sets also.
But to be honest, I think I can achieve a far better quality of not only 'matching', but 'burning-in' of the components myself, before they go to the boards.

We are going to try to pull out ALL the stops on this project, and get the absolute best component matching & quality for the semi's & passives alike.
Salas's top-notch phono warrents the best bits & pieces, no doubt.

If I buy the Toshiba's in the UK they are 3.00p each, as opposed to 0.25p each from Polida.
I'm sure I will end up with a whole bunch of 'wide-spec' ones, but thats all part of the game.
I could probably buy about 400 or so units, for the price of 8 channels worth 'matched' ( perhaps more even ).

It's going to take me a while to build this project anyhow, so I expect my ordering strategy will be a few at a time over a longer period.
If these 10 ordered test OK...next order is for maybe 20-30 more.
Postage is FREE, so I can order this way, with no P+P penalty also.

I am hoping also to 'burn-in' ( not out ! ) these parts as well.
I have a large variable PSU, and am considering seriously making a board of IC sockets in which to stick the Toshiba's, say 20-30 at a time, and let 'em run for a few days.
Will put some pics up of that either here, or in my 'Squirrel & G-Man' thread when it's done.

We are looking forward to a GREAT phono-pre, and will not be rushing this one to get there.

Will let you guys know when the Toshiba's get here, and put up the test figures...
...we have a hyper acurate ANALOGUE ! test meter from the 70s' by the way...
...My Dad's ( R.I.P.)

I would favour Polida rather than the link you posted; simply based on the size of their setup & the fact that they DON'T specialise in audio OR offer 'matched' components ( no pre-filleting ).

Cheers

Si.
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Old 28th October 2012, 10:31 PM   #8364
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Just one other thing...

...If I was making a single NJFET phono-pre of 2 channels...I would consider buying 'matched' from this guy or another guy Spencer perhaps.

However...
...The plan at present is to make 2x NJFET phono-pre's...both 'balanced'...
...1 for me & 1 for a friend...hence the 8 channels I mentioned.

My requirement for devices is greater than most 'matchers' could supply...I think.

Cheers.

Si.
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Old 28th October 2012, 11:38 PM   #8365
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&

Watch out for 'dodgey eBay seller' - The Space Egg Corp. !

Rumour has it, they could be listing a big bunch of out of spec. Toshiba's around Christmas time !
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Old 29th October 2012, 12:44 AM   #8366
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I will be building a simplistic, a mesmerize dcb1 preamp and an f5 during the next year so I will buy 100 2sk170 for matching and then buy the 2sj74 for the f5 from spencer and match them to mine.
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Old 29th October 2012, 03:04 AM   #8367
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OK yes...you have quite a few regulators to build as well, that need the Toshiba's.
I think these parts are realy quite cheap & binning a few to get a sharp match is worth it.
Doing your own matching is the icing on the cake realy.
I figure I will need 100 or so, unless I get VERY lucky.

Si.
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Old 29th October 2012, 09:39 PM   #8368
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Regarding parts choice, I'm thinking about using vishay dale resistors, nichicon electrolitics and Russian pio caps in the riaa. Has anyone tried with Russian pio caps in the simplistic?


Salas, this is a more general question, why are the riaa caps values different in the different according to gain choice?
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Old 29th October 2012, 09:45 PM   #8369
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Salas,
Linear systems showed off a new dual channel Njfet that looks interesting. Dont know if you has seen it yet.

Burning Amp Tweets

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Old 29th October 2012, 10:23 PM   #8370
Salas is online now Salas  Greece
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Quote:
Originally Posted by MASantos View Post
Regarding parts choice, I'm thinking about using vishay dale resistors, nichicon electrolitics and Russian pio caps in the riaa. Has anyone tried with Russian pio caps in the simplistic?


Salas, this is a more general question, why are the riaa caps values different in the different according to gain choice?
Avoid them, use polysterene or MKP. They are lossy for filters. They thicken the tone and cut on detail in those positions subjectively also.

Gain changes in second stage various versions, so does Miller capacitance, so I compensate for all to have same HF.
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