Caved and got the Marshall DSL402- but it has a couple of (hopefully very minor) problems

Yorkie

Come to think of it, I didn’t actually sell it, I traded it — I was desperate to free up bedroom space. I got a new Eternity Roadhouse and a Bad Horsie MKII for it. 

Dave_Mc

Yorkie said:

That's very interesting- you have the 1x12 DSL40, don't you? That does sound a bit like it might be the material then- unless the 1x12 is also a bit oversized because it's a combo! I guess it could also be how much bracing (is that the right word?) etc. there is- certainly in the DSL402 there's a lot of space, and just one big panel to cover the back with only 6 screws holding it in IIRC. That makes it really easy to get at the speakers and valves, but it also might mean it doesn't sound as good...

Correct. The cab is very large indeed. Here's mine:

 

That sucks you had to get rid of one of your amps, I saw you already posted that in another thread recently I think, I'm really sorry to hear that Jon Glad to hear the Super Champ is covering those sounds though, it's ages since I tried one but IIRC they sounded pretty great!

I do miss the Bandit sometimes, but I don't regret selling it because now my niece can sleep where the amp was and that is pretty fantastic. I'll get my territory back when this is over, but for now I'm just living in the moment :-)

Jon

Wow that doesn't look much smaller than mine! Just eyeballing it I'm not sure you could get two speakers into that cab side-by-side, but it looks like you almost could... maybe offsetting them (though the transformers would be a bit in the way) you could even get two in there.

Yorkie

Yeah, it’s very roomy. Same as my AC15, lots of space inside :-)

randella

Happy new amp day - I feel a little guilty for my part in this decision, sorry you had those niggles!

Looking at the back of Yorkie's amp there has sent me on a slight circuit geek-out. I didn't know they were still using the pentode/triode switching on the DSLs. I had a sneaking suspicion (and was actually right for once ) that wasn't the case in the very latest ones. I've been looking at the schematic and it seems they've moved to using different screen supply voltages for the high/low power modes.

Anyway I started looking at the rest of the circuit. The heaters are interesting - fairly straightforward, dedicated supply on the PT secondary with a virtual centre tap. I couldn't find V1 for ages though, until I saw it has its own rectified and smoothed DC heater voltage derived from the logic supply rails. I guess this is belt-and-braces noise reduction - @ICBM is this a common thing in other amps?

randella

Schematic here:

https://music-electronics-forum.com/forum/schematic-requests/40471-marshall-dsl15c-h-dsl40c-schematics

ICBM

randella said:

Anyway I started looking at the rest of the circuit. The heaters are interesting - fairly straightforward, dedicated supply on the PT secondary with a virtual centre tap. I couldn't find V1 for ages though, until I saw it has its own rectified and smoothed DC heater voltage derived from the logic supply rails. I guess this is belt-and-braces noise reduction - @ICBM is this a common thing in other amps?

Yes, quite common now. With the gain levels in modern amps and the poor cathode-to-heater insulation in some modern valves, hum from the first couple of stages can be a problem with a conventional AC supply.

randella

That's interesting - thanks! I'll fully admit that my valve circuit education is a work in progress.

I have several amp-related projects in various stages of planning and completeness. I also had the stupid idea recently to renovate and make a feature of the staircase in my house that hasn't seen sandpaper since the 1930s so we'll see where we get to.

ICBM

randella said:

I also had the stupid idea recently to renovate and make a feature of the staircase in my house that hasn't seen sandpaper since the 1930s so we'll see where we get to.

Beware of toxic paint constituents if you’re using a heat gun or a sander. That’s not a joke.

randella

ICBM said:

randella said:

I also had the stupid idea recently to renovate and make a feature of the staircase in my house that hasn't seen sandpaper since the 1930s so we'll see where we get to.

Beware of toxic paint constituents if you’re using a heat gun or a sander. That’s not a joke.

Yep, heeded. Been using a proper particle mask and a carbide scraper to shift the paint before going in with the sander.

Yorkie

I've just realised that that picture is from when I installed the Creamback. No screws holding the speaker!  

DartmoorHedgehog

Yorkie said:

I've just realised that that picture is from when I installed the Creamback. No screws holding the speaker!  

I was about to say how's that speaker held in   I was wondering if I'd missed something obvious.

Yorkie

DartmoorHedgehog said:

Yorkie said:

I've just realised that that picture is from when I installed the Creamback. No screws holding the speaker!  

I was about to say how's that speaker held in   I was wondering if I'd missed something obvious.

The amp is doing a face plant.

Dave_Mc

randella said:

Happy new amp day - I feel a little guilty for my part in this decision, sorry you had those niggles!

LOL no worries, it's not your fault! 

Thanks very much for that schematic, too, I'd been struggling to find any that weren't the JCM2000 version. I think that's the slightly older version (like @Yorkie 's ) but I'm guessing it's a bit closer to the current one than the JCM2000 is.

Yorkie said:

I've just realised that that picture is from when I installed the Creamback. No screws holding the speaker!  

LOL I didn't even notice that! And then when you mentioned it, like @DartmoorHedgehog for a few seconds I wondered how it was sitting there!

Dave_Mc

So... unfortunately I got the hum again for a few seconds again today, but then it stopped again. Then I noticed a fairly faint "put-put" type of noise, bit like wind or an old engine just ticking over. I think that might be indicative of the power valves @ICBM ? 

It's since stopped again, of course.

Yorkie

Dave_Mc said:

I'd been struggling to find any that weren't the JCM2000 version. I think that's the slightly older version (like @Yorkie 's ) but I'm guessing it's a bit closer to the current one than the JCM2000 is.

Nope, mine has got nothing to do with the JCM2000. It’s the old-new DSL40, much better designed, Vietnam-made, the one that came with the Seventy/80. The newer ones come with a V-type. 

Dave_Mc

Yorkie said:

Dave_Mc said:

I'd been struggling to find any that weren't the JCM2000 version. I think that's the slightly older version (like @Yorkie 's ) but I'm guessing it's a bit closer to the current one than the JCM2000 is.

Nope, mine has got nothing to do with the JCM2000. It’s the old-new DSL40, much better designed, Vietnam-made, the one that came with the Seventy/80. The newer ones come with a V-type. 

Yep that's what I meant, except I explained it pretty badly! 

Yorkie

Dave_Mc said:

Yorkie said:

Dave_Mc said:

I'd been struggling to find any that weren't the JCM2000 version. I think that's the slightly older version (like @Yorkie 's ) but I'm guessing it's a bit closer to the current one than the JCM2000 is.

Nope, mine has got nothing to do with the JCM2000. It’s the old-new DSL40, much better designed, Vietnam-made, the one that came with the Seventy/80. The newer ones come with a V-type. 

Yep that's what I meant, except I explained it pretty badly! 

No, you’re OK, it’s me. Long day at work  

Dave_Mc

Yorkie said:

Dave_Mc said:

Yorkie said:

Dave_Mc said:

I'd been struggling to find any that weren't the JCM2000 version. I think that's the slightly older version (like @Yorkie 's ) but I'm guessing it's a bit closer to the current one than the JCM2000 is.

Nope, mine has got nothing to do with the JCM2000. It’s the old-new DSL40, much better designed, Vietnam-made, the one that came with the Seventy/80. The newer ones come with a V-type. 

Yep that's what I meant, except I explained it pretty badly! 

No, you’re OK, it’s me. Long day at work  

LOL no worries

Tried the amp again today- no hum/buzz, and I thought there was no "put-put" noise, but when I put my ears close to the speaker, I could occasionally hear it a little. 

I'll keep an eye on it. I'm cautiously optimistic there's not that much wrong with it.

noisepolluter

Dave_Mc said:

LOL no worries

Tried the amp again today- no hum/buzz, and I thought there was no "put-put" noise, but when I put my ears close to the speaker, I could occasionally hear it a little. 

I'll keep an eye on it. I'm cautiously optimistic there's not that much wrong with it.

Have you got some of that zero residue contact cleaner? You could try doing the valve sockets in case there’s some grot causing an intermittent contact?

(Paging @ICBM in case he’s got any specific advice on the best way of doing this)

Also - was the buzz happening fairly soon after it was powered up? Maybe a slightly duff solder joint that’s expanding/contacting as the circuit heats up?

Dave_Mc

noisepolluter said:

Dave_Mc said:

LOL no worries

Tried the amp again today- no hum/buzz, and I thought there was no "put-put" noise, but when I put my ears close to the speaker, I could occasionally hear it a little. 

I'll keep an eye on it. I'm cautiously optimistic there's not that much wrong with it.

Have you got some of that zero residue contact cleaner? You could try doing the valve sockets in case there’s some grot causing an intermittent contact?

(Paging @ICBM in case he’s got any specific advice on the best way of doing this)

Also - was the buzz happening fairly soon after it was powered up? Maybe a slightly duff solder joint that’s expanding/contacting as the circuit heats up?

Good idea about the contact cleaner, I can't believe I didn't think of that! I've got contact cleaner... not sure if it's zero residue... and I also have a vague feeling the last time I looked at it it had long expired, but it still worked when I used it on a couple of guitar selector switches!

Yep it was pretty soon after it was powered up. Also I think it tended to happen (also the "put-put" noise) when I hadn't played the amp for a day or two as well. That's a bit more concerning if it's a solder joint...