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Old 17th December 2005, 03:28 PM   #11
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OK Brian, thank you.

Have just ordered the third edition via amazon. hope I get it before christmas.

Reinhard
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Old 20th December 2005, 07:57 AM   #12
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Hello,

received Morgan Jones third edition yesterday. up to now I had only a look at the LED bias, simple, will give it a try and some measurments.

Conrad Johnson use a 100 pf Mica in parallel to their Cathode
bias stack.

Reinhard
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Old 2nd January 2006, 07:04 AM   #13
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Hello,

always looking for better step ups!

Anyone that has experience with the SOLO step up from Ys-audio?

Uses a single 6N3, S/N better 99 dB? From Datasheet. Is that true? Hmmmmmmmmm?

Anyone with the schematic of that?

Reinhard
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Old 7th June 2013, 10:13 AM   #14
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Quote:
Originally Posted by reinhard View Post
I think I dont try the MCP. Im not really happy with that big caps in such a sensitive position at the input.
Reinhard
What is here the main disadvantage (except the fact, that more space is necessary) ?

For me this is the best solution to protect the MC cartridge coils against DC. Except the approach with a step up transformer there are no other approaches with DC protect.

Even by the use of electrolytic (polarized) caps at the input (like Mark Levinsons JC-1) I don't note losses in sonic quality.
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Old 7th June 2013, 10:40 AM   #15
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Dann mach das doch einfach so!
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Old 7th June 2013, 11:52 PM   #16
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Hi,

Quote:
Originally Posted by tiefbassuebertr View Post
What is here the main disadvantage (except the fact, that more space is necessary) ?

For me this is the best solution to protect the MC cartridge coils against DC. Except the approach with a step up transformer there are no other approaches with DC protect.

Even by the use of electrolytic (polarized) caps at the input (like Mark Levinsons JC-1) I don't note losses in sonic quality.
Every circuit has its sonic fingerprint just as all passive components do, x-formers included.
Given that this is a MC pre-preamplifier with high gain, a cap at the input will carry its sonic signature right across the entire amplification chain.

It's not that hard to avoid this input cap. Given the low output of the MC cartridge and knowing that a 6DJ8 can easily be run at Vg0 as well as at slightly positive grid voltages, you simply ground the cathode.

The reason why you may not be able to hear the impact of the input cap
may well be your use of a very low value Vgin resistor to load your cartridge. However, do keep in mind that as input resistance rises so will the audibility of the cap. A component avoided in the signal path is a good thing.

Some years ago (tempus fugit) I offered a schematic of a MC headamp which I nicknamed "MC Hammer". Not sure if all the SS parts are still around but it may give some idea of how to beat some prejudices you seem to be holding.
Me, I never heard a x-former coupled MC system that sounded truly transparent. Granted, nothing ever is but still...

Cheers,
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Old 8th June 2013, 02:42 AM   #17
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Aside from possible sonic degradation from the big input caps, I have another concern. These caps "block DC" only after the circuit has warmed up and settled to its quiescent condition. 82uF is connected between the moving coils and the paralleled cathodes of the input stage. At power up those caps have to be charged to about 1.2 volts at the cathode end. The charging current is supplied by the cathodes, but that same current must also flow through the coils of the cartridge. At power down, the reverse happens. Some of the charging current will be shunted into the input loading resistors, depending on what value of loading was selected. Still, a momentary pulse of some amount of current will flow into the delicate cartridge before "DC blocking" eventually takes place. It's obviously not enough to fuse the coil wire, but it might induce a residual magnetic charge in the armature or in other part of the cartridge's magnetic circuit. I can't say for sure that this would be a problem for every (or any) cartridge, but if I'd just dropped $5K on a fancy cartridge I might think twice about the situation.

I suppose you could add a normally-closed relay to short the input until the circuit settles, but this seems like a bandaid, and maybe not foolproof during a short power outage or brown-out.
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Old 9th June 2013, 10:53 AM   #18
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Quote:
Originally Posted by fdegrove View Post
Hi,



Every circuit has its sonic fingerprint just as all passive components do, x-formers included.
Given that this is a MC pre-preamplifier with high gain, a cap at the input will carry its sonic signature right across the entire amplification chain.

It's not that hard to avoid this input cap. Given the low output of the MC cartridge and knowing that a 6DJ8 can easily be run at Vg0 as well as at slightly positive grid voltages, you simply ground the cathode.

The reason why you may not be able to hear the impact of the input cap
may well be your use of a very low value Vgin resistor to load your cartridge. However, do keep in mind that as input resistance rises so will the audibility of the cap. A component avoided in the signal path is a good thing.

Some years ago (tempus fugit) I offered a schematic of a MC headamp which I nicknamed "MC Hammer". Not sure if all the SS parts are still around but it may give some idea of how to beat some prejudices you seem to be holding.
Me, I never heard a x-former coupled MC system that sounded truly transparent. Granted, nothing ever is but still...

Cheers,
Thank you for your advices. Is the schematic of the "MC Hammer" to find on the web? Maybe similar to this:
Moving Coil Cartridge Head Amps

In this case also this thread is of interest:
Tube Phono stage dilema
Quote:
Originally Posted by Brian Beck View Post
Aside from possible sonic degradation from the big input caps, I have another concern. These caps "block DC" only after the circuit has warmed up and settled to its quiescent condition. 82uF is connected between the moving coils and the paralleled cathodes of the input stage. At power up those caps have to be charged to about 1.2 volts at the cathode end. The charging current is supplied by the cathodes, but that same current must also flow through the coils of the cartridge. At power down, the reverse happens. Some of the charging current will be shunted into the input loading resistors, depending on what value of loading was selected. Still, a momentary pulse of some amount of current will flow into the delicate cartridge before "DC blocking" eventually takes place. It's obviously not enough to fuse the coil wire, but it might induce a residual magnetic charge in the armature or in other part of the cartridge's magnetic circuit. I can't say for sure that this would be a problem for every (or any) cartridge, but if I'd just dropped $5K on a fancy cartridge I might think twice about the situation.

I suppose you could add a normally-closed relay to short the input until the circuit settles, but this seems like a bandaid, and maybe not foolproof during a short power outage or brown-out.
Interesting advice. In this case this threads are of interest:
Allowable DC Current for a Phono Cartridge
DC Coupling for MC Cartridges - how much error voltage before coil damaging

Last edited by tiefbassuebertr; 9th June 2013 at 11:15 AM.
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Old 9th June 2013, 03:14 PM   #19
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If you are the proud owner of an ARC MCP-33, you can run this little test. Look closely at your cartridge's cantilever while you flick on the power switch. If the cantilever gives you a little "Hello there" nod, you might have a problem

Of course, a "head amp" like the MCP-33 is intended to be used in lieu of an input transformer. If there were ever a situation in audio for which a transformer is ideally suited, it's probably in the MC front-end. Best possible noise performance, "DC" blocking, ground-loop stopping...

But...I laugh my evil paranoia-inducing laugh... an input transformer will not necessarily protect your MC from current pulses at turn-on or turn-off if the active circuit induces pulses of current into the secondary. Transformers and caps block "DC", yes, but as an old professor of mine once said "there is no such thing as DC in the real world".

As a more general comment, the turn-on and turn-off behavior of active circuits, tubes and solid-state, is often overlooked, even by seasoned manufacturers. And how do circuits respond to rapid power cycling and brown-outs such as a nasty thunderstorm might cause? Well, another topic for another thread...
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Old 9th June 2013, 08:46 PM   #20
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Quote:
Originally Posted by Brian Beck View Post
If you are the proud owner of an ARC MCP-33, you can run this little test. Look closely at your cartridge's cantilever while you flick on the power switch. If the cantilever gives you a little "Hello there" nod, you might have a problem

Of course, a "head amp" like the MCP-33 is intended to be used in lieu of an input transformer. If there were ever a situation in audio for which a transformer is ideally suited, it's probably in the MC front-end. Best possible noise performance, "DC" blocking, ground-loop stopping...

But...I laugh my evil paranoia-inducing laugh... an input transformer will not necessarily protect your MC from current pulses at turn-on or turn-off if the active circuit induces pulses of current into the secondary. Transformers and caps block "DC", yes, but as an old professor of mine once said "there is no such thing as DC in the real world".

As a more general comment, the turn-on and turn-off behavior of active circuits, tubes and solid-state, is often overlooked, even by seasoned manufacturers. And how do circuits respond to rapid power cycling and brown-outs such as a nasty thunderstorm might cause? Well, another topic for another thread...
Interesting considerations. This means in case of circuits with low impedance inputs the necessity to use the input as output (by connection to the line input of an integrated amp e. g.) for checking out the turn-on and turn-off behavior and steps to eliminate any unwanted poppings through transients.

I have sometimes heard from cracked coils in MC cartridges without having had a reason for this. Whether it was this or whether it was corrosion - that is the question.
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