LCR Build

the road not taken.
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sfox7076
Posts: 5
Joined: Wed May 06, 2015 1:42 am

LCR Build

Post by sfox7076 »

I am going to go headlong into building a phono pre by getting Dave to wind me some inductors in the 7k range as he recommends. Anyone have a schematic they have built before and would recommend?

Shawn
dave slagle
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Post by dave slagle »

Hey,

everything I like seems to have a lot of inductors in it for some reason :-)

something like this works nicely.
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lugnut
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Post by lugnut »

nice
sfox7076
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Joined: Wed May 06, 2015 1:42 am

Post by sfox7076 »

After many stops and starts, a schematic from NAZ and some added advice from Dave, a build, a rework, and a wiring error, here is the finished product. 6C45-->6C45-->6H23N (have some 7398s to slot in soon)--->6H30/6N6P. It sounds amazing. It's dead quiet (after triple shielding the umbilical). Regardless, here she is. I will share the schematic if Naz allows. And she is glorious. One change made was I switched the last set of inductors (300Hy) to a pair of Dave's inductors. I was having minor issues with the others I had.

Probably near 60db of gain...
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docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Post by docali »

Excellent work and nice looking!

We want see schematics ;-)
sfox7076
Posts: 5
Joined: Wed May 06, 2015 1:42 am

Post by sfox7076 »

docali wrote:Excellent work and nice looking!

We want see schematics ;-)
\

Here it is.
Attachments
Shawn LCR Phono Line stage.png
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docali
Posts: 58
Joined: Thu Oct 16, 2008 7:16 am

Post by docali »

Thanks!

Interesting arrangement. Would you please tell us why you choosed the lower part of the mu follower (what design advantage) as output and not the upper part which yields much less output impedance and therefore could have been used with an lower impedance LCR?

br!
docali
sfox7076
Posts: 5
Joined: Wed May 06, 2015 1:42 am

Post by sfox7076 »

I wanted higher impedance for the LCR modules. The pros vs. drawbacks of the 600 Ohm LCR projects have been discussed at length. I preferred this direction. It is a compromise for sure.
HiFiPhilPhips
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Joined: Wed Dec 27, 2017 2:29 pm

Post by HiFiPhilPhips »

Nice build!
Naz
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Joined: Wed Aug 06, 2008 4:27 am
Location: Sydney Australia

Post by Naz »

I've been too busy and haven't visited for a while but a good Italian friend alerted me to the thread. Very nice build and hope you enjoy it!

I have many iterations of the circuit now, PM me if you ever want to discuss.

Cheers,
Naz
walge
Posts: 33
Joined: Tue Nov 24, 2020 8:42 pm
Location: roma

Post by walge »

Hi

I have seen this thread.
I ma writing some article on Audioreview magazine in Italy about LCR phono.
In the second part I have presented some real test on LCR stage only ( in the next two parts will be presented two different complete circuit).
So some things maybe helps.
In first attacch, Figura 6, there is a freq. answer of LCR stage with original Tango EQ-2L; at 20 Hz there is a - 0,6 dB of attenuation that can be considered good; in reality there aren't any real test published of original Tango stuff so, in my opinion , I will take this as reference.
The Zs is 600 ohm and the Zload is 600 ohm, as specification.
The test are done by one of my two AP ( one is SYS one the other is SYs Two); the Riaa enphasis was written by software; in attache the table of value. This is a perfect test for two reason, first because it it accurate, second because I can change the Zsource without any change on response.
In attach the table of AP test
In case someone can post another real test I will be happy.
In the third attach there is a freq. answer of a LCR stage (not Tango but full compatible) with different Z source and the Zload at 600 ohm.
It is podssible to see that the freq. answer is comptible with Tango but the level is variable, of course, depending on Z source.
The results are fine for all test.
This just to say that if is not necessary to use the step up after the LCR , in my opinion is not smart to loose dB of signal to mantain the reference from Tango.
So the use of a stage with high Z is not convenient because the risk to loose gain with the necessity to have an additional stage ( the s/n and thd will be involved of course)
In the circuit I will present the gain with two stage is around 40-42 dB that is fine for a MM; due the possibility to config different tubes it is possible to reach around 46-50 dB of total gain.

Walter
Attachments
Figura_6_Tango_Lcr_risp_solo riaa.pdf
Tango Lcr
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Riaa AP test
Riaa AP test
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test
test
lcr risp Zs_20_100_200_600_zload_600.jpg (180.08 KiB) Viewed 1797 times
walge
Posts: 33
Joined: Tue Nov 24, 2020 8:42 pm
Location: roma

Re: LCR Build

Post by walge »

Hi

This is the last version of the LCR phono stage completely mounted.
Full dual mono.
Two toro trafo,
two HT regulated supply, double circuit on each pcb that supply one section of the eachn LCR board
Holco and Resista with pp caps (selected) for ative stage
Two filaments regulated board
I have ready the pcb to have a better routinf of the cables that drive the relais on the input board
LCR_Master_interno.jpg
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Two input, 6 load switchable; the input board ha some jumper to have one input connected to an internal sut




Walter
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