Metropoulos Forum

Hi!

I was planning to install a choke in my friend's DSL401 since it lacks imho a bit of tightiness in the low/lowmid frequencies and it sounds rather harsh too. Hope it will be an improvement.
I also have some old transformers laying around at my dad's workshop and one of those has 4.75H on the primaries.
Do you think it's a wise idea (noise and sound wise) to use it as a choke?

Cheers

Also... I can't understand which resistor should I replace? The only high wattage (2W) ones after the PT are R23 and R24.

http://www.drtube.com/schematics/marsha ... 2-iss9.pdf

Colex wrote:Also... I can't understand which resistor should I replace? The only high wattage (2W) ones after the PT are R23 and R24.

http://www.drtube.com/schematics/marsha ... 2-iss9.pdf

If your DSL401 is using that board revision and issue number, the choke would replace R32.

As for using a transformer, seems like overkill. A 3H choke is so cheap (and lighter), I'd just use a proper choke. I've got DSL trannies on my website but you can use almost any 3H choke.

http://www.lydian.ca/Parts_Store/Pages/ ... rmers.html" onclick="window.open(this.href);return false;

In terms of tightness, try a 1uf cap on V1's cathode (C83). There's no point in having so much bass come through so early in the gain stages.

For harshness, perhaps the speakers are a problem? Not broken in yet? What kind of speakers do those little combos come with? What do you mean by harsh?

jcmjmp wrote:

Colex wrote:Also... I can't understand which resistor should I replace? The only high wattage (2W) ones after the PT are R23 and R24.

http://www.drtube.com/schematics/marsha ... 2-iss9.pdf

If your DSL401 is using that board revision and issue number, the choke would replace R32.

As for using a transformer, seems like overkill. A 3H choke is so cheap (and lighter), I'd just use a proper choke. I've got DSL trannies on my website but you can use almost any 3H choke.

http://www.lydian.ca/Parts_Store/Pages/ ... rmers.html" onclick="window.open(this.href);return false;

In terms of tightness, try a 1uf cap on V1's cathode (C83). There's no point in having so much bass come through so early in the gain stages.

For harshness, perhaps the speakers are a problem? Not broken in yet? What kind of speakers do those little combos come with? What do you mean by harsh?

Yes, it has a revisionised PCB, it's a 2007 model. I dont see R32 on the schematics, probably because it's pre 2003.

I'm in Croatia and I dont wanna mess with paying, improting, waiting min 10 days... etc. when something laying around in my home can do the same job. It's also a bit of a challenge, experimentation. A little bit of weight wont kill me (or my friend, the amps owner)


The amps speaker is a celestion 100w goldback, not a very good one but I think a reasonable tone can be get with it in there.
The harshness is manifested as a sort of fizz in the upper frequencies, doesnt go out even with the treble down. Maybe changing the cap around the plate resistor to a higher value should help this.

Colex wrote:

jcmjmp wrote:

Colex wrote:Also... I can't understand which resistor should I replace? The only high wattage (2W) ones after the PT are R23 and R24.

http://www.drtube.com/schematics/marsha ... 2-iss9.pdf

If your DSL401 is using that board revision and issue number, the choke would replace R32.

As for using a transformer, seems like overkill. A 3H choke is so cheap (and lighter), I'd just use a proper choke. I've got DSL trannies on my website but you can use almost any 3H choke.

http://www.lydian.ca/Parts_Store/Pages/ ... rmers.html" onclick="window.open(this.href);return false;

In terms of tightness, try a 1uf cap on V1's cathode (C83). There's no point in having so much bass come through so early in the gain stages.

For harshness, perhaps the speakers are a problem? Not broken in yet? What kind of speakers do those little combos come with? What do you mean by harsh?

Yes, it has a revisionised PCB, it's a 2007 model. I dont see R32 on the schematics, probably because it's pre 2003.

I'm in Croatia and I dont wanna mess with paying, improting, waiting min 10 days... etc. when something laying around in my home can do the same job. It's also a bit of a challenge, experimentation. A little bit of weight wont kill me (or my friend, the amps owner)

For the board rev/issue number, see the instructions on this page to figure it out:
http://www.lydian.ca/Marshall_DSL.html" onclick="window.open(this.href);return false;

Scroll down to the Schematics and board info portion. I don't have DSL401 schematics but I'm sure that you could find them elsewhere, or just ask Marshall for them.

For the choke, I'm positive that you could find one in Croatia without having to import anything. Do you have electronics supply stores at all?

Of course we do
And there would be no problem finding a choke, but as I said early the useage of an old ("useless") transformer instead of a choke to me is very apealling, it gives me more of that DIY mcGyver feel
Jokes apart, it should work right? The only problem is finding the resistor to replace, probably is the big wirewound 5W one, it's the only one on the pcb. The biggest problem is that I cant find it on the schematics :-S

The modified transformer is giving me 900ohms, isnt that a bit too much? :-S