Pimp my Pre [ GR Model & input transformer types ]

O.k. i took the pix for another reason but thought i'd say thanks for all the help & support here

Back When Dan had boards [ don't bug him now ! ]

You wouldn't happen to have a parts list for those pre's would you? I was able to get two PCB's from Dan a few months ago and he gave me the schematic, but I'm still unsure about some of the component choices. Nice work on them btw, they look great.

Peter

So...
What is this exactly...beside the fact that you were able to get PCBs from the most illustrious and amazing supporter of DIY, Mr. Dan Kennedy?

Inquiring minds wanna know.

There was a thread about this preamp, and Dan offered us the schematics and gerbers but I remember there was some problem with uploading the files and it never happened:
http://www.groupdiy.com/index.php?topic=6573&postdays=0&postorder=asc&start=15
Probably Dan was too busy and he forgot about it.

chrissugar

It is a GR pre built into a box by me , the great thing about that , is without the advertising and since you know it is the same thing it really
takes away the Judgment and forces you to listen , which i must say
it really is impeccable [ i used the Lunhdahl 1538 XL which seems very nice ] ,the pre has a solid smooth midrange with the top & bottom there no problem , can't say a bad thing about it .

Yeah Dan is a Great guy , super helpful [ of course i respected his time , and tried to stay out of the way ] But it reminds me of another friend who would always tell me things and quoted that knowledge should be free , it's up to you to do it ! So with Dan you just know that a person of integrity like that would translate into what he does [ the preamps ]

I'll check for the parts list and post back but i don't always get here everyday , Regards Greg

I may not have had the right program to open it up with but i can email as well , I also have a pdf of the layout with values can email or is it possible to post pdfs here ?

Oops i must say the pix look a little blurry , i maybe i'll fix that but here is the bom

Used Part Type Designator Footprint Description Part Field 1
==== ============== ==================== ========== =========== ==============================
4 .01uF C23 C31 C35 C39 RAD0.16 P10955-ND
5 .47uF C1 C2 C24 C27 C3 WIMA-47 3017PH-ND
4 100 R14 R17 R21 R29 AXIAL0.4 100XBK-ND
1 100uF C42 RB.14/.32 P10294-ND
1 10R0 R34 AXIAL0.4 10.0XBK-ND
7 10uF C22 C30 C32 C33 C34 RB0.079/.2 P10316-ND
C36 C37
3 10uF/100v C38 C40 C41 RB.1/.25 P10769-ND
1 18uH L1 AXIAL0.6 Get this from me, 651-455-1846
2 196 R10 R11 AXIAL0.4 196XBK-ND
1 1K00 R24 AXIAL0.4 1.00KXBK-ND
2 1K10 R3 R4 AXIAL0.4 1.10KXBK-ND
4 1N4004 D10 D11 D12 D13 DIODE0.4L 1N4004RLOSCT-ND
11 1N4148 D14 D15 D17 D18 D3 DIODE0.4 568-1360-1-ND
D4 D5 D6 D7 D8 D9
1 1N4750 D16 DIODE0.4L 1N4750ADICT-ND
2 1N5251 D1 D2 DIODE0.4L 1N5251BDICT-ND
6 20 R30 R31 R32 R33 R36 AXIAL0.5 P20W-1BK-ND
R47
1 220pF C20 RAD0.2 P3221-ND
6 221 R15 R18 R38 R40 R42 AXIAL0.4 221XBK-ND
R44
2 2K74 R27 R28 AXIAL0.4 2.74KXBK-ND
2 2N4401 Q13 Q5 TO-92B 2N4401RLRAOSCT-ND
4 2N4403 Q12 Q2 Q3 Q4 TO-92B 2N4403RLRAOSCT-ND
1 2SK-389 Q1 2SK-389 Get this from me, 651-455-1846
4 38R3 R19 R20 R26 R35 AXIAL0.4 38.3XBK-ND
3 3K83 R25 R39 R41 AXIAL0.4 3.83KXBK-ND
1 42K2 R6 AXIAL0.4 42.2KXBK-ND
4 470uF C25 C26 C28 C29 RB.2/.4 P11260-ND
2 475 R5 R9 AXIAL0.4 475XBK-ND
1 47R5 R12 AXIAL0.4 47.5XBK-ND
3 49R9 R13 R22 R23 AXIAL0.4 49.9XBK-ND
1 562K R8 AXIAL0.4 562KXBK-ND
1 5R62 R45 AXIAL0.4 5.62XBK-ND
16 680 C10 C11 C12 C13 C14 RB.14/.32 P10222-ND
C15 C16 C17 C18 C19
C4 C5 C6 C7 C8 C9
1 68pF C21 RAD0.2 338-1091-ND
2 6K81 R1 R2 AXIAL0.4 6.81KXBK-ND
2 8K25 R16 R43 AXIAL0.4 8.25KXBK-ND
2 9K09 R37 R7 AXIAL0.4 9.09KXBK-ND
1 GAIN J5 MLSS-100-3 *
1 HI-Z JACK J4 MLSS-100-3 *
1 LM-317T U1 TO-220 LM317TNS-ND + heatsink HS107-ND
1 LM-337T U2 TO-220 LM337TNS-ND + heatsink HS107-ND
1 LM317 U3 TO-92C LM317LZNS-ND
1 MIC IN J1 MLSS-100-3 *
1 MJE-171 Q17 TO-225A-H MJE171OS-ND + heatsink HS107-ND
1 MJE-181 Q16 TO-225A-H MJE181OS-ND + heatsink HS107-ND
4 MPS-8099 Q10 Q11 Q14 Q9 TO-92B MPS8099RLRAOSCT-ND
4 MPS-8599 Q15 Q6 Q7 Q8 TO-92B MPS8599RLRAOSCT-ND
1 OUT J7 MLSS-100-4 *
1 POWER J8 MLSS-100-5 *
2 RXE-040 RF1 RF2 RAD0.2 RXE040-ND
1 SWITCHES J6 MLSS-100-5 *
1 TBD R46 Typically 750<<3K32 *
2 TN2E-24V K1 K2 TN2RELAY TN2E 255-1024-5-ND
1 XFORM PRI J2 MLSS-100-3 *
1 XFORM SEC J3 MLSS-100-3 *

I thought he used a Jensen as input, no?

Samuel

Dan did use Jensen

the Lundahl was cheaper to get in Canada , and i'm not sorry
the 1538 XL [ extra low end extra money ] seems great although
i didn't have a Jensen to compare it to , i'm planning on working up
a quad with 2 jensen , 2 Lundahl.........some day

regards Greg

OK, but then it is not "the same thing", is it? :grin:

The transformer might make a good deal of the sound, and the Lundahl is noisier than the Jensen. Of course the Lundahl is good as well, but surely different!

Samuel

Is one input X-former better than another ? I have no reason to switch ,
well maybe curiousity and eventually for the quad i'll have both ,
i'll have to ask Dan next chance , Either i'm sure is fine
ratios are close so the Jensen may have more shielding but it is the
line balencing that reduces the noise through cancelling not the sheilding
which is gravy , anyway i haven't found the Lundahls to be noisy
but will be happy to get jensens [ anybody got a good deeal for them ?

regards Greg

Waiting on word from Dan regarding his opinion on transformers for the pre , he may have recomended the lundahls but if not didn't diss them for
his design ................still any deals on Jensen ? i'm up for a couple thanks

Is one input X-former better than another?

Click to expand...

What is better? The Jensen is likely more transparent as it has lower distortion and a flatter frequency response. But your Lundahl is well respected and surely sounds good. I just objected that you said that your pre "is the real thing", which I interpreted as "it sounds (and measures) the same as the original GR"--and this is unlikely with a different transformer.

I haven't found the Lundahls to be noisy.

Click to expand...

Note that I didn't say "noisy", I said "noisier". The noise figure of the Lundahl is about 2 dB higher than the Jensen IIRC. Together with the close-to-zero noise figure of the amplifier for these source impedances this makes still an EIN of better than 125 dBu at high and medium gains--good enough for any practical application and better than other pres.

I don't think the shielding of the two transformers is much different, but who knows. Same applies to CMRR, I think.

Samuel

Final word from Dan , unless Samual feels the need to get the last word in , regards Greg

" Two reasons I used the Jensens in the original MP series preamps, one I knew of Jensens, and Lundahls were a fine, but unknown alternative at the time. I tested them, thought they worked well, but would've been harder to sell in the American market, so name recognition was a factor.

I thought the 1538 was a bit more susceptible to external fields, I didn't find it inherently noisier, that'd be almost impossible given the similar inductances and resistances
involved. Small fractions of a dB if any. But a bit more AC
pickup, in fact Per made a couple of double insulated ones as prototypes that I think are now standard product because of my concern.

The Lundahls are a maybe a bit cleaner than the Jensens. Not any huge amount, for sure. "

I'd feel good about either in a preamp using my cards.

How's that? Feel free to quote...

Dan