What cables to use inside preamp?

[gobble]

Customerized Full Kit ref Grounded Grid Tube PreAmp (Stereo)_Factory Assembly_Analog Metric - DIY Audio Kit

Thats the variation with the BJT voltage supply. Mine is the vanilla copy.

Regards

 

[sridhar-v]

Look into the possibility of using teflon insulation wires. They hold the insulation values better at elevated temperatures (you could get upto 60C in some hot spots)

I had used them a couple of years ago and was impressed with the performance

 

[kaushik]

And then I could refuse to let him out of the bamboo cage after that and auction him to the highest bidder. I'm sure many ladies will bid their life savings for him ... hyeah: :licklips:

Cheers

while i am in bamboo cage ,... feed me with bananas .dont forget to serve them with silver tinned PCBs with glass epoxy laminate...At the moment of 240V shock.... .i will shout Awuooooo! ...

 

[kaushik]

I don't have access to any literature. I look at provided information only.

This is what is provided in the link mentioned:

That may be a dummy ckt , how come it be mains powered directly ... Here we see 3 trafo guarding us from going to hell at any moment The Grounded Grid preamplifier


I got original design in Audio Reality

simulation plots as in analog metric forums :

Voltage gain of this GG preamp is 12dB.

 

[gobble]

The original may be different from the clone ..

Sorry, the clone may be different from the original.

The original uses EI core for sure. How much will toroidal affect SQ negatively?

GeorgeO has the original kit. He lent it to me for a few days when I caught him in a weak moment. The speed and transients were *noticable* like even if you weren't an audiophile you would comment like "what a fast car" types ...

The only defect I noticed was a buzz and susceptibility to pops and clicks every time a switch was turned on/off in the house. But the benefits far outweighed the negatives and an isolation tranny would make happy any audiophile granny ... you get the buzz right?

Regards

 

[gobble]

Here is an outdated assembly guide for the Chinese version
Kikitronic -- DIY Audio Kits: Pre-amp Grounded Grid

They supply the new updated assembly instructions vial email after the order is placed.

HTH
Regards

 

[kaushik]

Power on delay to avoid POP sound

 

[grubyhalo]

He has a reputation for being difficult ...he has communicated only in one liners and 4 word sentences all along. My CC expired and I told him my friend would pay online on my behalf. He refused and stopped responding to my emails after that. Edit: .. and 2 months have gone by with no communication ...

I have no intention of renewing my CC either.

Regards

Ah, I see...

 

[gobble]

Power on delay to avoid POP sound

Yes it gives a frightening pop with SS amps after about 12 secs due to a DC surge. Tube powers overcome this for some reason.

Regards

 

[gobble]

That may be a dummy ckt , how come it be mains powered directly ... Here we see 3 trafo guarding us from going to hell at any moment The Grounded Grid preamplifier


I got original design in Audio Reality

simulation plots as in analog metric forums :

Voltage gain of this GG preamp is 12dB.

This one gives 14db gain I believe.

Regards

 

[gobble]

@kaushik - that 10K bleed resistor is not required, neither is the Darlington pair, or the use of the B/E junction of the transistor as a diode dropper. For delay I use a single BD139, and a largish cap and resistor combo to give me a nice long delay. 100K and 470uF yields around 6 seconds. A BD139 is able to switch three relays - this is needless complexity for a simple circuit.

Edit: Tube power amps use an output transformer, and are pretty immune to DC at the input. SS amps are not. There is obviously some issue with the circuit that cause a DC imbalance so late in the day. A delay of more than 10 seconds is unreasonable - even my 40-year old Garrard radiogram would take about 8 seconds to reach operating conditions. Anyway, for 12 seconds delay a timer is a better bet than a R/C combination - though it could still be done.

Cranky

Will the delay circuit affect SQ in any way? Since it is an extra set of components muting the output, does the signal pass through more "colouring"? Or is it completely bypassed after the delay?

Regards

 

[gobble]

Any contacts in the signal path potentially affect the sound quality, specially mechanical ones in a relay. So yes, it could affect SQ.

However, it affects it considerably less than a blown speaker, so I would use some kind of standby switch. Normally, I would simply switch on the power amp a minute or two after the preamp - which I kind of do anyway since even my source has a bit of a pop at switch-on...

In this circuit, only the relay is in the signal path. The components used to switch the relay are not interfering with the signal.

Thanks. BTW What kind of relay is this one in the circuit? Not a mechanical one I presume.

Regards

 

[kaushik]

@kaushik - that 10K bleed resistor is not required, neither is the Darlington pair, or the use of the B/E junction of the transistor as a diode dropper. For delay I use a single BD139, and a largish cap and resistor combo to give me a nice long delay. 100K and 470uF yields around 6 seconds. A BD139 is able to switch three relays - this is needless complexity for a simple circuit.

Edit: Tube power amps use an output transformer, and are pretty immune to DC at the input. SS amps are not. There is obviously some issue with the circuit that cause a DC imbalance so late in the day. A delay of more than 10 seconds is unreasonable - even my 40-year old Garrard radiogram would take about 8 seconds to reach operating conditions. Anyway, for 12 seconds delay a timer is a better bet than a R/C combination - though it could still be done.

The bleeder resistor provide a discharge path for the capacitor, ya may be omitted if the other circuitry there to provide a path.. for isolated delay ckts i think it ensures that the delay time is reset on power cut.

circuit works the BE juction breakdown (like a zener) , there are many alternatives for delay,a smd ckt 555 timer in 1 sqcm is better and compact solution and can be fitted on a OMRON type relay top,if i use it the the large leaded cap (cheap) will standing on a plastic cap.

Gobble,
we can use the OMRON relay that is used in the remote attenuator, even most amps use a power on delay relay..nothing to worry.. it is like someone holding the rca connction and joining it thatz all.

 

[gobble]

The bleeder resistor provide a discharge path for the capacitor, ya may be omitted if the other circuitry there to provide a path.. for isolated delay ckts i think it ensures that the delay time is reset on power cut.

circuit works the BE juction breakdown (like a zener) , there are many alternatives for delay,a smd ckt 555 timer in 1 sqcm is better and compact solution and can be fitted on a OMRON type relay top,if i use it the the large leaded cap (cheap) will standing on a plastic cap.

Gobble,
we can use the OMRON relay that is used in the remote attenuator, even most amps use a power on delay relay..nothing to worry.. it is like someone holding the rca connction and joining it thatz all.

Kaushik
The kit comes with a timer circuit and all parts included. Are you saying we skip that and use Omron?

TIA
Regards

 

[kaushik]

Oh thatz great! ,

analogmetric should ship with good relay .... no changes needed unless you are unhappy with the parts quality.

 

[gobble]

When I rebuild my preamp in new Chassis I am thinking of trying a different cable for RCA input to PCB and output PCB to RCA.

I found a co-ax silver coated 24AWG cable with a tight braid that is rated at 50 ohms. I plan to use the core for + and braid for - . Will this work? I heard one needs 75ohms for digital inputs, so does that mean I should not use it in the input section?

What will the potential pitfalls with using a 50 ohm cable?

I was unable to find an OFC copper in teflon dielectric for internal wiring.

Edit: I picked this up as it was the only one with teflon coating and the braid shielding looked good. The earlier cable shield looks like uncombed long hair and the preamp sounds "dry" which is what I am trying to cure.

TIA
Regards

 

[rallynut]

gobble,ur rig when done is gonna be quite something to listen to when done :licklips:.hope i can audition it some day.cheers

 

[gobble]

gobble,ur rig when done is gonna be quite something to listen to when done :licklips:.hope i can audition it some day.cheers

You guessed right. It is a find! A $$$ discovery for me that saves me for ever buying a $$$$ preamp! You are welcome anytime, just waiting to finish the chassis.

Cheers

 

[Ivey]

If your preamp in solid state and comes with a pcb, there is little need to use twisted pairs. Most twisted pairs are used in Valve amps. Not solid state.

If your preamp is laid out correctly. You can use ribbon cable. It is much better are it rejects stray signals pretty good.

Always use co-ax for the items that you stated in your thread. Cat5E cable is not a good cable to use. It is for video and DSL.

Use stranded wire. It is more forgiving.

Solid wire is for those who work on old phone lines and radio. Not so good for audio work.

Ribbon cable comes with many colors that you can use for signal, power, ground circuit or chassis. It offers a lot of uses.

Take away from teflon wire. It is to hard to prepare and clean. Plus it cost more and does not improve your signal or product

Take Care

Ivey

 

[gobble]

If your preamp in solid state and comes with a pcb, there is little need to use twisted pairs. Most twisted pairs are used in Valve amps. Not solid state.

If your preamp is laid out correctly. You can use ribbon cable. It is much better are it rejects stray signals pretty good.

Always use co-ax for the items that you stated in your thread. Cat5E cable is not a good cable to use. It is for video and DSL.

Use stranded wire. It is more forgiving.

Solid wire is for those who work on old phone lines and radio. Not so good for audio work.

Ribbon cable comes with many colors that you can use for signal, power, ground circuit or chassis. It offers a lot of uses.

Take away from teflon wire. It is to hard to prepare and clean. Plus it cost more and does not improve your signal or product

Take Care

Ivey

Thanks. Mine is a tube pre. I actually found a co-ax with a teflon sheilded core quite affordable. Silver coated copper. A dollar per meter. Posting a pic.

Should I use the same for RCA out? I am tempted to try two 6 inch runs of my DAC 16AWG OFC speaker cable by twisting it like Ethernet. Doesn't twisting increase capacitance? Will that be bad in a 6" cable run?

TIA
Regards