Flat Phono Preamp Based on John's P10 and 2SK389

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Gold
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Gold » Tue Jan 12, 2016 12:15 am

Since the preamp can be located far from studio meters I thought it might be nice to add a 'calibration' LED in the preamp box. I have a feeling this is fairly easy for anyone but me. It should light an LED at 0.388VAC or -6dBu.

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JR.
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by JR. » Tue Jan 12, 2016 8:50 am

My favorite calibration indicator was one I used in my CX decoder. I used an NPN LTP (differential pair), with a two color (3 lead) LED. Below threshold only the green LED was lit, above threshold only the red, and at threshold give or take a few mV both were lit.

Alternately make something simple with a LM339 comparator . Perhaps 3 LEDs one just below, on at, and one just above threshold bracketing the threshold with a fraction of a dB.

Wayne has a thread with a collection of simple peak detectors.

JR

Bill Wilson
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Bill Wilson » Mon Jun 18, 2018 10:23 pm

Hi Wayne: Thought I would jump in with my two cents. I designed my own moving coil phono preamp, using either That 1510 or AD SSM2019 mike pres.
for the balanced input. I based the design around Denons 103R M/C cartridge. The preamp gain is set for 1000 times; as the output from the 103R is 280 micro volts, followed by passive EQ & an adjustable gain output. There are two output impedances; mid unbalanced & fully balanced using a That 1640.

The power supply features our clean power module; providing pure DC +- 15vdc. Sounds great & will be available commercially with my super headphone amplifier.

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 9:02 am

Thanks Bill.

I tried the THAT1512 and at DL-103 levels and impedance it was pretty good.

Does the "R" in DL-103R mean re-tipped?
Are the DL-103Rs from cartridge bodies returned to Denon?
I've been wanting to get an "R" since they're reasonably priced.

Is this the preamp/PCB you were working on with Joe?

Bill Wilson
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by Bill Wilson » Wed Jun 20, 2018 5:21 pm

Yes Wayne it is the Preamp that Joe Neil did the pcb layout. The 103R is not retipped it is a slightly better cartridge. Some of the users that use mike xfmrs. for stepup claim it is as good as any in the up to $1000- range. I had talked to an applications engr. at That & designed a low Z resistive network
in front of the 150/SSM2019. This avoids the preamp input seeing the 40 ohms direct from the cartridge. I also bought an Audio Technica AT-MONO3/LP
MC Mono cartridge direct from Japan; as they are not sold in the U.S.

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 5:47 pm

OK, I was confused the DL-103 is the lower-cost one.
I guess "R" means "reference" :lol:

billshurv
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by billshurv » Wed Jun 20, 2018 6:40 pm

The Denon namings over the years are very confusing. There are/were at least 8 factory variants and, as it's become the flathead V8 of the cartridge world there are a whole slew of retip options effectively off the shelf. It is quite astounding the longevity of this. Still not at VW Beetle levels, but been in continuous production longer than the 2CV was!

Odd guy here has just bought a DL-107, which is a little known MM they made at the same time for the same broadcast client. What I can't justify but want is the DL-107A which was designed to be a plug in replacement for the DL-103. MM with 0.35mV output!

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mediatechnology
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Re: Flat Phono Preamp Based on John's P10 and 2SK389

Post by mediatechnology » Wed Jun 20, 2018 6:46 pm

billshurv wrote:
Wed Jun 20, 2018 6:40 pm
Still not at VW Beetle levels, but been in continuous production longer than the 2CV was!
I know what a 2CV is. I owned an ID19B.
Bill Wilson wrote:I had talked to an applications engr. at That & designed a low Z resistive network in front of the 150/SSM2019. This avoids the preamp input seeing the 40 ohms direct from the cartridge.
Why? Did it oscillate without it?

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