Transistor equivalent

OK Nikolai will do

Thanks

No probs my friend

KeepItSimpleStupid said:

A phonograph pre-amp is a special bread because of equalization. The most common is RIAA.

Cartridges are either:
a) Ceramic (low-fi high output)
b) Moving magnet
c) Moving coil (low output and I think the best sounding)

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When I was a teenager I could not afford the best sound system but my friend had lots of money and bought the best and latest Shure moving magnet cartridges as they were announced and gave me his previous ones that were still like new. They sounded perfect. I still have one that must be about 53 years old and it still plays records perfectly. Of course it has an elliptical diamond needle and it presses into the record grooves at only 1.25 grams.

audioguru said:

When I was a teenager I could not afford the best sound system but my friend had lots of money and bought the best and latest Shure moving magnet cartridges as they were announced and gave me his previous ones that were still like new. They sounded perfect. I still have one that must be about 53 years old and it still plays records perfectly. Of course it has an elliptical diamond needle and it presses into the record grooves at only 1.25 grams.

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Is it an M75EDII or a V15 perhaps. I still have the former. and it works fine too. Mine is only about 40 years old though- I think

I think my phono cartridge is a Shure V15. I remember that it was popular for a few years and the needle kept being improved each year. I got it for free and just now I read that it is worth a couple of hundred dollars to many audiophools. I won't sell it since my wife and I have some vintage records and we don't need the money since it grows on trees.

spec said:

UK is Live 230V, 50Hz, Neutral, which is earthed by the utility company somewhwere, and Earth.

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UK is 240 and neutral which is one phase of a 415v 3ph transformer and a star grounded neutral..
In a residential area the idea was to feed every so many homes from one phase and alternate the phases for each group to spread the load.
Max.

audioguru said:

I think my phono cartridge is a Shure V15. I remember that it was popular for a few years and the needle kept being improved each year. I got it for free and just now I read that it is worth a couple of hundred dollars to many audiophools. I won't sell it since my wife and I have some vintage records and we don't need the money since it grows on trees.

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Shure V15; what a beauty. Trackability was Shure's ad line for that baby. That was the first audiophile cartridge I heard. One of the old boys in the lab was a hifi guru. I didn't know anything about amp design in those days and used to listen to his deliberations with great intrest.

One lunchtime he invited me to his bungalow, which was 5 min from work, to hear his system. He had a Garrard reference turntable with a platter that weighed a ton, and a V15 mounted in a SME arm. His speakers were KEF Concertoes driven by an Armstrong amp. None of his system was home made. What a sound! I was astounded. Being a junior person with wife and kids, a system like that was completely out of reach. The V15 is very much like the later affordable moving coil cartridges- very ariticulate, open, and natural. It's still a favourite with me.

Yes, classic hifi fetches big money these days; the turntable below £2,300 for example- no arm either!






.

MaxHeadRoom78 said:

UK is 240 and neutral which is one phase of a 415v 3ph transformer and a star grounded neutral.. In a residential area the idea was to feed every so many homes from one phase and alternate the phases for each group to spread the load.
Max.

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Hello Max,

Ah! that is how it is done. Do you know specifically what happens with earth and neutral in Britland. Am I right in saying the neutral is earthed somewhere by the electricity company and earth is errr.. earthed locally? I have seen a load of hash on neutral and even seen about 5V 50Hz on it. By the way, I know 240V 50Hz was the standard for years, but hasn't it been dropped to 230V recently. One sweet thing is that the companies still guarantee is the exact number of cycles per day so that synchronous clocks keep good time. Those were the days

Hmm, copper wires to wind transformer not cheap

spec said:

Do you know specifically what happens with earth and neutral in Britland. Am I right in saying the neutral is earthed somewhere by the electricity company and earth is errr.. earthed locally?

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It has been some years since I was involved in the UK electrical industry, but back then the transformer star neutral was grounded but the service Co would not supply a ground, it had to be obtained locally either such as by water pipe etc or in the event of no local ground an earth rod was driven and a ground fault interrupter was installed.
Also the ground was not connected to the neutral at the panel as it is here in N.A.
Max.

MaxHeadRoom78 said:

It has been some years since I was involved in the UK electrical industry, but back then the transformer star neutral was grounded but the service Co would not supply a ground, it had to be obtained locally either such as by water pipe etc or in the event of no local ground an earth rod was driven and a ground fault interrupter was installed.
Also the ground was not connected to the neutral at the panel as it is here in N.A.
Max.

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Thks for info. I see you are in Can, but are you a Brit?

Nikolai Petrenko said:

Hmm, copper wires to wind transformer not cheap

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No, not cheap, but available from many sources: washing machine etc motors, microwave transformers, auto alternators, CRT TV scan coils ...

spec said:

No, not cheap, but available from many sources: washing machine etc motors, microwave transformers, auto alternators, CRT TV scan coils ...

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Wire thick enough to suffer 6A pretty hard to find

Just do the best you can: 18 AWG (SWG) should be OK.

You can get the system going with even a 1A transformer secondary. Just leave enough room in the case for a bigger transformer later.

Another dodge would be to have separate winding pairs and feed separate bridge recfifiers and connect the bridge rectifier outputs in parallel. Just keep the winding voltage the same, within reason.

spec said:

Just do the best you can: 18 AWG (SWG) should be OK.

You can get the system going with even a 1A transformer secondary. Just leave enough room in the case for a bigger transformer later.

Another dodge would be to have separate winding pairs and feed separate bridge recfifiers and connect the bridge rectifier outputs in parallel. Just keep the winding voltage the same, within reason.

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I will try to collect from anythings I have

spec said:

View attachment 95931​

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I will replace c1815-a1015 with bc337-327 because they are better
(bc549-559 if I can buy)
The variable resistor to set gain?
Area of inductor (iron) core? Can you let me know?

Nikolai Petrenko said:

I will replace c1815-a1015 with bc337-327 because they are better
(bc549-559 if I can buy)

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2SC1815 & 2SA1015 are good transistors with 60V VCE. The BC337 & BC327 are only 50V.
The only transistors that handle substantial current are the output transistors and their drivers.

The VAS transistor pair handle 12mA top (Q5) and 6mA bottom (Q7).
The emmiter follower (Q6) driving Q5 handles very little current, but needs to have as higher ft as possible and good at operating at low currents.
The two input transistors only handle 500uA.
Q10 is only a 1mA constant current generator but it needs to be a low capcitance, high frequency type.

The rest of the transistors are not critical and you can use what you want, within reason.

BC549 & BC559 are only 30V VCE which means you would need to reduce the amp supply lines to +-15V

Nikolai Petrenko said:

The variable resistor to set gain?

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No. The variable resistor sets Iq, the quiescent current (no signal) flowing thru the output transistors, Q1 & Q2. This is adjusted to around 30mA to minimise cross-over distortion. The amp voltage gain is set by resistors R13 & R14: A= 1+ (R14/R13)

Nikolai Petrenko said:

Area of inductor (iron) core? Can you let me know?

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Bit of an open-ended question; it depends on the transformer type and the core material. As a rule of thumb, I would say 1,600 sq mm. 1 turn per volt is fairly normal for that area core. An alternative way to judge is by the power rating of the transformer: 100W upwards should be fine

C core is the best:
(1) Lowest size
(2) Lowest stray signals
(3) Lowest output impedance
(4) Lowest weight

Any transformer type will do though, but with the other types be prepared for some work to reduce hum introduced both by inductive and electrostatic coupling.

PS: amp schematic has been updated to issue 2: only minor mods

KeepItSimpleStupid said:

Have overhead power lines from the 60's. The transformer feeds about 4 houses with about 100 A of 240 V. The fuse is on the primary side. The secondaries run to the meter first and then the "fuse box"/"breaker box" where there is a main fuse.

The power companies have upgraded to "smart meters". Rumor has it, they can disconnect power remotely. Meters are read by a Zigbee network.
The trend was to put a disconnect on the outside of the house. So, it's a fire company thing that power can easily be disconnected.

For emergency home access (fire/rescue), there is this thing called a "knoxbox" https://www.knoxbox.com/ that many business have, but homeowner can have it too. The fire company has "controlled access" to the box. The keys are "dispensed" so to speak. So, I can't use it to put a spare key because I don't have access to the box which would contain keys. It saves the fire company from breaking down the door.

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Quite a set up: In the UK there is no switch provided by the electricity company, but the consumer unit (fuse box) has a double pole mains isolator (switch). If the company needs to turn the power off they pull out the fuse.

In the States, does the consumer provide the transformer to step-down to 110V?

I had a house demolished 3 years ago and asked the electricity company to terminate the mains before the demolition machines moved in. I dug the hole. When three of the company men turned up they cut and terminated the cable while it was still live without a thought. It was raining too; frightened me to death they were messing with a 230V supply with a capability of 800A or so.