Following the thread about The Phono Stage, weeks ago I have finished the setting of a LCR Phono Stage in a definitive dress.
It is a my project published in Audioreview magazine.
They use the Sowter coil same as venerable Tango EQ-2L
It is full dual mono, each stage of the circuit, two per channel, are connected with a dedicated ss HT stabilized. Each HT pcb has two stage of regulation. Same used for the Phono stage
Use the 7062 or ECC81/12BZ7 as gain stage and ECC88 or 6N6 as CF.
Also in this case the s/n is good, around -80/-81 dB weighetd "A"
Two toro trafo, HT and filaments.
Two filaments circuit.
The components are strictly selected
The input board is the same of the Phono stage.
In attach the frequency anser, the FFt and THD vs Freq.
I am thinking about the production but it is not cheaper to build.
Walter
It is a my project published in Audioreview magazine.
They use the Sowter coil same as venerable Tango EQ-2L
It is full dual mono, each stage of the circuit, two per channel, are connected with a dedicated ss HT stabilized. Each HT pcb has two stage of regulation. Same used for the Phono stage
Use the 7062 or ECC81/12BZ7 as gain stage and ECC88 or 6N6 as CF.
Also in this case the s/n is good, around -80/-81 dB weighetd "A"
Two toro trafo, HT and filaments.
Two filaments circuit.
The components are strictly selected
The input board is the same of the Phono stage.
In attach the frequency anser, the FFt and THD vs Freq.
I am thinking about the production but it is not cheaper to build.
Walter
Attachments
Interesting. So this is a passive LCR between two gain stages? I have often wondered about ECC81/12AT7 for phono stages. Input capacitance looks reasonable and good mu.
the FFT in the region of 20-1kHz is contitioned from the spurious of the ac specially at this low level. The THD vs frequency is a valid test to understand in which way the circuit works. This test is also conditioned at low frequencies and is necessary to make different takes to have a readible curve.
The riaa is passive between two stages
The gai of the phono is around 41 dB.
The riaa is passive between two stages
The gai of the phono is around 41 dB.
This is the final step with all connection.
It is running without problemsince last februray.
On the right the switch for use different function; I have ready a pcb to have a better layout.
On these switch there is only a voltage (+5 V) to drive the relais on input board.
Each toroid is 100 watt and has a electrostatic screen between primary to secondary and an external coil to reduce the residual.
On phono boards there are Holco resistors ( I have a stock of around 5000 pcs) and Resista WK series ( around 10000 pcs)
All components are checked for correct value.
I have ready other inductors for LCR network made custom for me in Italy.
They tested are copy-paste of Tango and Sowter ; with Brexit there are problems with costs.
Walter
It is running without problemsince last februray.
On the right the switch for use different function; I have ready a pcb to have a better layout.
On these switch there is only a voltage (+5 V) to drive the relais on input board.
Each toroid is 100 watt and has a electrostatic screen between primary to secondary and an external coil to reduce the residual.
On phono boards there are Holco resistors ( I have a stock of around 5000 pcs) and Resista WK series ( around 10000 pcs)
All components are checked for correct value.
I have ready other inductors for LCR network made custom for me in Italy.
They tested are copy-paste of Tango and Sowter ; with Brexit there are problems with costs.
Walter
Attachments
The parts values of the LCR filter depend on the exact inductance and parasitics of the coils you get. Get the coils wound, measure inductance and DCR, put that into Spice, starting with the nominal values for an LCR RIAA network (if it is a 600R version start with the Tango values) and tweak until the response is flat enough. Then build according to that, measure and tweak again in circuit.
R1 is 47k, C1 is optional.
Everything else depends on the valves and power supply you want to use.
R1 is 47k, C1 is optional.
Everything else depends on the valves and power supply you want to use.
To Schiirn
No
The Sowter coils are exact copy of Tango in terms of L and Rdc. so you have to use the parts listed on riaa network
Other question is about the Zout of first stage
After lot of tests I can say that if the riaa network is closed with 600 ohm (mandatory) the frequency answer is fine and also the Thd with a good range of Zout of the first stage .
It is around 200-300 with Ecc88
Please leave the virtual world and try with real stuff, more fun
No
The Sowter coils are exact copy of Tango in terms of L and Rdc. so you have to use the parts listed on riaa network
Other question is about the Zout of first stage
After lot of tests I can say that if the riaa network is closed with 600 ohm (mandatory) the frequency answer is fine and also the Thd with a good range of Zout of the first stage .
It is around 200-300 with Ecc88
Please leave the virtual world and try with real stuff, more fun
Have you measured them? The earlier Lundahl inductors were way off the published specs and required a significant readjustment of RC values to get a correct FR.
Yes
The tolerance is very low and the freq response are similar in same circuit
I done many tests on the original Tango and Sowter + one Italian brand who made for me for a new project that is now under test
Walter
Hence my original proposal to measure what you get, calculate the R and C values in Spice, build the actual circuit, measure and if necessary readjust. I don't have the nerve or time to just slap something together and blindly try parts until something matches what I expect, but to each their own...
Hi
excuse
with a great delay I send you the test on Tango coils and Sowter
The test are done using a propietary sw from Audioreview
Thre red line is the module
And on practical circuti the response is almost identical but with some marginal adjustment they will be similar
Walter
