Simplistic NJFET RIAA

simple 1 transistor timers will do beterer than 555
close one relay charge cap trough a large resistor when voltage is right transistor get hard on and turn on relay which open contact and closes relay one as long as there is enough charge on cap transistor stay on

There are by- stable relays that do not need the coil to be energised work as flip flop

no nasty magnets near precious signal

Tutorial 2: Transistor Timer Circuit

Or
http://www.instructables.com/community/Timer-Circuit/

I use similar to switch in and out the thermistors on my F5 whit no problems for 4 years

Or sumthink like this

http://www.ebay.co.uk/itm/Bistable-...st-Delivery-/111590449478?hash=item19fb4f2146
 
Last edited:
Administrator
Joined 2004
Paid Member
Hi RCruz,
I will also recommend a 555 circuit. If you use a 556, you will have two timing circuits in one chip.

Why use this timer IC rather than a couple transistors? The operation is well defined and simple to understand so you can adapt it to other situations. You can use the reset to go into mute when you turn the preamp off. A nice feature that comes for free, just the AC detect circuit is extra.

Energizing a relay coil isn't a deadly thing to the signal. Make your signal the fixed contact and you will be fine.

555 timer circuits are all over the net. If you get the datasheet from a manufacturer, you will find recommended circuits on those sheets. There is also a "555 Timer Cookbook" that you might find somewhere in PDF form. It is a wealth of really interesting applications, and some detailed information about the IC that allows you to use it in unconventional ways. There is a reason this ancient chip is still manufactured. It is extremely good at what it does, and it does a lot. Note that you can also get a quad version of this timer as well, and a low current CMOS version as well.

Look into this useful chip. You will probably design with it for years once you figure it out.

-Chris
 
I see a nice strong microscope and several crude old era stuff that I don't know what he uses for what. He maybe does other things on that bench too. I mean that kind of thickness blackened by oxidization solder wire is not applicable even with a 2k$ JBC station on anything smaller than a nine inch nail in a bath of flux. He could be explaining to Alex who's the customer on what went wrong and what he uses to solder to the cart pins. Then Alex would solve the mystery by telling here.

I talked to the guy today via email and ask him bunch of questions about his lab equipment. Lets leave discussion about what he is using for carts re-tipping and coils swaps to the end of my repair story. I would like to see my cart fixed and returned in one peace first. BTW, he took a full responsibility and asked me to return my cart back to him ASAP. I should have an answer in 2 weeks or so. I'll keep you guys fully informed since some of you might need such services sooner or later.
 
Administrator
Joined 2004
Paid Member
Hi Alex,
Lets leave discussion about what he is using for carts re-tipping and coils swaps to the end of my repair story.
That is the #1 concern. I am wishing you a perfect job on your cartridge. I did not anticipate that you would actually talk to him about his equipment. With any luck, your technician wasn't upset by your questioning.
I should have an answer in 2 weeks or so.
Interesting time frame. Maybe he is sending it in for repair (which is a very good thing).

Besides, it would be preferable to educate the man instead of declaring war on him.

-Chris
 
He was not upset at all and actually he appreciated that pointing. Again, I'm here not to fight or to prove some points. I'm here (hope that most guys here have same reason) to get help and to help others to enjoy our hobby by resolving all challenges related to audio electronics DIY.
If you wish to help him, then contact him directly (the email is on his site). He might going to listen to your advises. A far as I know, this is kind of of his hobby and not main income source. I think he is enjoying that work in the same way as we are enjoining our FSP project.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
In my sim, 100 ohm generates almost 300mW in the output fet if fed with a large 1khz signal.

Maybe 500ohm is enough to mute the output...

It has 50 Ohm Zo and it will drive it. You can just disconnect an output instead of shorting it. Provided it isn't driving a very high impedance with wide bandwidth prone to picking audible interference on the cable.
 
Hi all,
I got my cart back after repair and testing it right now.
Amazing!
It is sounding very nice and it is the way how it should be from the beginning.
All previous noise (I got noise when I connected it to FSP or BHL without isolation transformer) is gone.
So, I connects directly now and it is absolutely quite. Can’t use Salas amazing phono for listening for now since I need to correct its gain when my W&S transformers are removed. So, hopefully...sometime during next week…
So, I use my BHL phono by now and sound is very nice. Probably, the best that I can get from that phono. Will run 40 hours for brake-in...by that time my FSP will be ready!
It seems that my guy fixed it perfectly.

Thank you a lot for all your comments and info general sharing.
 
Administrator
Joined 2004
Paid Member
Hi Alex,
I am greatly relieved that this turned out well. Your guy can do good work once he puts his mind to it. I wonder if it went back to the factory or not for this fix. Either way, he did you right and that is all that matters in the end.

I would love to hear your impression of that preamplifier once you are set up again.

-Chris
 
Administrator
Joined 2004
Paid Member
Hi Salas,
Another project I have on the go is to get my TT back in running condition. Your preamp is something I'm thinking on. I have a brand new Ortofon 540 lined up for this. Never got a chance to unbox it. How sad is that? My VMS-30E MKII will go on another table.

The table needing fixing (new suspension) is a Thorens TD-125 MKII, the other is a 126 MKIII. I dying to spin some LPs!

-Chris
 
Member
Joined 2006
Paid Member
Sorry guys for no immediate response. I'm in the middle of job change.
I did resign from my current job after 16+ years of service and I'm starting a new one Monday.
Have a lot of small things that I need to take care right now.

Well, my guy wrote me a latter and he indicated that my original cart was repaired in the past. Who ever did that repair, they installed completely wrong coils. I didn't know that since I purchased my Wilson Benesch TT used and the owner didn't tell me anything about Ply cartridge condition. Might be he did't know either...
So, wrong coils ware removed and he installed new set. During installation of new boron cantilever, he scratched coils and made that short between them. Now all fixed and in did I have no noise previously appeared when my cart was connected to any of my phonos or SUTs in idle.
I'm finalizing my FSP for 60+dB gain now and will be capable to test my new Ply cart soon. I'll keep you informed.
Alex
 
Last edited:
diyAudio Chief Moderator
Joined 2002
Paid Member
Hi Salas,
Another project I have on the go is to get my TT back in running condition. Your preamp is something I'm thinking on. I have a brand new Ortofon 540 lined up for this. Never got a chance to unbox it. How sad is that? My VMS-30E MKII will go on another table.

The table needing fixing (new suspension) is a Thorens TD-125 MKII, the other is a 126 MKIII. I dying to spin some LPs!

-Chris

FSP has been built for MM in 40dB or 43dB configuration before and people reported back happy enough. All gain modes from MM to LMC and their few different part values configurations are described in the PDF manual. Yours is 3mV I think so the manual's HMC 43dB config should bring it up better. Only remember that even with this folded cascode input stage that fights Miller capacitance gain effect there will still be some pF from the (single for MM-HMC) JFET Ciss that you must count in your cart's capacitive load budget including what's there in the incoming cabling from your turntable.