GK 250ML speakers

[pontiacpete]

I have one of these with both speakers blown, and with disintegrated foam edges.
It seems that the only replacements available for these are at GK. AFAIK
The schematic says this amps calls for 2 x 8 ohms 50 watt speakers. GK sells 16 ohm 80 w speakers as replacements
THere are 16 ohm speakers in the amp now, so I'm assuming that the schematic is wrong.
How bad would it be to put in two 8 ohm 80w speakers instead of the 16's?

sorry I can't seem to upload the schematic that I have here.

[Jazz P Bass]

I think the schematic is refering to the RL.

It came with 16 ohm speakers because the Ext Spkr requires a 16 ohm cabinet.

If you mount 8 ohm internal speakers what happens if someone loads the external spkr jack with an 8 ohm cabinet?
(4 ohm load)

I have had a number of these that I simply had reconed because of the rotted surround. (@ $40.00 a pop)

What is GK asking for the 80 watters?

[J M Fahey]

The real thing seems to be available here:
Gallien-Krueger 082 0047 0 Speaker for 250 ML Series II Amp, 082-0047-0 | Full Compass

[pontiacpete]

GK is asking 69.99.
Geez how did I miss the full compass deal, that's $14 cheaper than GK, thanks Juan!
I'm going for it.

It seems like it has 2 sides to the output, no?
Just curious here, is there any danger in running the amp with 8ohm speakers?

[J M Fahey]

AFAIK the amp is 50/60W per channel, into 2 separate 8 ohms load.

You can use it with:

a) internal speakers 16 ohms load per channel, you get about 35 , maybe 40W per channel. Not bad at all.

b) internal 16 ohms speakers plus a stereo 16+16 ohms extension speaker cabinet. You get full power, split 50/50 between internal and external speakers.

c) you use it as a head only, I guess it has a switch to cut internal speakers OFF, you need 2 separate (electrically, both separate hot *and* ground) speakers, 8 ohms each, you get full power plus probably better efficiency and definitely larger/deeper sound (duh!)

From here and there reading Forums some guys connected external 8 ohms speakers without disconnecting the internal ones, and in some cases blew output transistors

A good amp but not overdesigned.

[g1]

From here and there reading Forums some guys connected external 8 ohms speakers without disconnecting the internal ones, and in some cases blew output transistors

A good amp but not overdesigned.

Is this the one with no heatsink, just the rear panel of the chassis? If so, and you want to push it, pointing a fan at the back of it is a good idea.

[52 Bill]

If the speakers are okay and the foam is just rotted, refoam them. The kits are available on eBay and it's really easy to do. The voice coil gap is fairly large, so as long as the spider is still solidly glued, gluing the new foam surrounds doesn't require any shimming.

The original speakers are 16 ohm, so that a 16 ohm extension speaker can be used, keeping an 8 ohm minimum load on the power amps. The first version of these amps did not have a switch to turn on and off the internal speakers. The Series II version added a switch to turn off the internal speakers so you could run the amp with external 8 ohm speakers.

The entire metal cabinet is part of the heat sink system. The chassis flanges and the top panel should be heat sink greased to help transfer heat from the back panel where the power transistors are mounted.

[pontiacpete]

One of the speakers measures as a dead short, but the other is probably fine. Thanks 52Bill for the encouraging words on refoaming.
I'm going to give that a try!

[Mick Bailey]

That's an amp I always wanted, but nowadays every one I see looks like it came out of a tumble-dryer. Maybe they're not so good compared to modern SS amps, but I like the idea.

Sometimes it's better to desire than possess. Like Kylie. She'd let the cabbage boil over and leave the top off the toothpaste. It wouldn't work out.

[Jazz P Bass]

I worked on a number of thses amps.

What a PITA.

And they don't sound all that great.

With the stock speakers the amp doesn't get that loud either.

[Leo_Gnardo]

I worked on a number of thses amps.

What a PITA.

And they don't sound all that great.

With the stock speakers the amp doesn't get that loud either.

Around here the trend was to hook up a pair of Marshall (or similar) 4x12 cabs to ML250 "car battery" amp & let 'er rip. One of 'em has been thru here at least half a dozen times.

Speakers were shot on the last one thru here, I picked out a similar pair of speakers from Parts Express to replace the rotted-foam ones.

I think the attraction was the "stereo" chorus, also had a crushin' compressor IIRC.

[52 Bill]

We were dealers for these and I fixed a lot of them back in the day. After a few of them, they are pretty simple to deal with.

When they came out, I thought that they were basically like a Rockman with speakers. They have one sound that they do well, not all that versatile. They were great for small gigs and could be linked directly to the PA via the line out, with the internal speakers as your monitors.

Because of the metal cabinets, if you didn't have a padded case the black finish started to look pretty ragged after a while. A little black spray paint will do wonders.

[Enzo]

A Rockman with speakers? yep, that pretty well sums it up.

I like the little things, but they are not very versatile.

[loudthud]

I thought these things had a really cool tone. There are JFETs in series with the signal path (just drawn as a box on the schematic) that give 'em even order distortion before clipping. Then there are the three trim pots that you adjust by ear. Can anybody give guidance on adjusting the pots?

[52 Bill]

Can anybody give guidance on adjusting the pots?

There are two different documents for that. One that tells the test setup to correctly set the trimpots during the initial check out, and a second document that GK sent out to owners to allow them to mess with the trimmers.

I know that I have paper copies on file, but I will try and find electronic files to post here.