Choke in a G*S*G 300B

[fiftyfivefilms]

Hi, I used a hammond choke in my G*S*G, but over on another forum I read this response to upgrading a G*S*G....any thoughts, seems like an inexpensive mod.

[color=#8000BF][color=#BF0040]Quote:
"Here is what you REALLY should do, NOW and FIRST !!!
Its a $26.13 mod that will make a nice audible improvement in that amp.

You need to REPLACE the power supply choke, filtering the 300Bs !!! The Hammond 156R is 1.5 HY at 56 Ohms. Fifty six Ohms is KILLING the dynamic response and contrasting of the circuit. After thirty plus years of building and testing such things, here is a "must do" thing for you :

Get rid of that amplifier's 56 Ohm choke.... pal.

Edcor makes a new XC75-1.5 HY -250 mA. choke. Cost is only $26.13, and it usually takes three or four weeks to receive. It does NOT have the same dimensions as the Hammond. The Hammond is on 2 3/8ths inch mounting centers, the EDCOR is on 2 7/8th inch mounting centers. The Hammond is 1.69 Inches high, the EDCOR is 1.93 inches high. The Hammond is 1.5 inches wide, the EDCOR is 1.76 inches wide.

I THINK the EDCOR will possibly fit if you mounted it similarly or maybe rotated from the stock Hammond's position !! Check out the EDCOR site's dimensional drawing carefully.

Here is why I am bringing this up. The EDCOR has a D.C R. ( D.C . Resistance) of only 17 Ohms versus the Hammond's 56 Ohms. I find chokes need to be about 20 Ohms or less, to maintain great bass and fabulous dynamic contrasting. I have tested this for three decades, and I am "on the money".

The difference the new lower DCR choke filtering the 300Bs will make will be SUBSTANTIAL, possibly more than swapping output trannies, but that flies in the face of conventional wisdom. Just take my word, order the part, and swap it out...two wires, yellow is the START of the winding, the input of the choke.

You can swap tubes till you are BLUE in the face, and this substitution will probably EXCEED any tube change you have or will make, by a factor of two or three. Go for it, and let me know how it turns out when you hear it. You will be pleased. This is a "no-brainer" if someone knows superior DHT tube power supply design.

My FIRST high fidelity speaker purchase was in 1968, 15 inch Monitor Golds in a GRF enclosures. Forget about swapping amps, lets do this choke mod first. Contact me after that and ( when my advice has proven to be worth while ) and I'll help you some more.

Cheers.

Jeff Medwin"
end quote[/color][/color]

Cheers!
Kirk

[Geek]

Fifty six Ohms is KILLING the dynamic response and contrasting of the circuit.

I smell bovine fecal excrement....

56R difference is making no difference, it's the Edcor design that is!

[fiftyfivefilms]

Greg, ....so you think its the Edcore that is making the difference, hmmm, wondering if it would be a good option for a Dynaco ST-70?...Thoughts?

[Geek]

Different windings (wire size, turns) and stack. It's physically different, magnetically different, so logically, it should sound different.

Cheers!

[Shannon Parks]

The difference - for the 300B GSG in particular - is a higher B+ and not the supply impedance (in a Class AB sense). Higher B+ is a very good thing for the 300B (including the silicon rectifier mod), but not for the original GSG with old stock 6B4Gs.

In a nutshell, the stock get*set*go circuit doesn't squeeze out everything from the 300B. The driver on my bench does, though. Pix coming soon!

Shannon

[EWBrown]

The EDCOR choke is too tall to fit under a standard Dynaco / Dynakit ST70 chassis, but it would be fine in any other chassis of 2 or 3 inch depth.

/ed B

[fiftyfivefilms]

The difference - for the 300B GSG in particular - is a higher B+ and not the supply impedance (in a Class AB sense). Higher B+ is a very good thing for the 300B (including the silicon rectifier mod), but not for the original GSG with old stock 6B4Gs.

In a nutshell, the stock get*set*go circuit doesn't squeeze out everything from the 300B. The driver on my bench does, though. Pix coming soon!

Shannon

So are you working on new G*S*G 300 B? I've done the diode mod.....wondering if I should wait on upgrading the choke??

...will your new board use the same OP transformers as the 6B4B?..

Ed thanks for the info, in that case...my thoughts were to put an Edcore in my G*S*G and move the C-354 from the G*S*G to my stereo 70 the original looks a little toasty.
Cheers.

[fiftyfivefilms]

The difference - for the 300B GSG in particular - is a higher B+ and not the supply impedance (in a Class AB sense). Higher B+ is a very good thing for the 300B (including the silicon rectifier mod), but not for the original GSG with old stock 6B4Gs.

In a nutshell, the stock get*set*go circuit doesn't squeeze out everything from the 300B. The driver on my bench does, though. Pix coming soon!

Shannon

So are you working on new G*S*G 300 B? I've done the diode mod.....wondering if I should wait on upgrading the choke??

...will your new board use the same OP transformers as the 6B4B?..

Ed thanks for the info, in that case...my thoughts were to put an Edcore in my G*S*G and move the C-354 from the G*S*G to my stereo 70 the original looks a little toasty.
Cheers.