Acquiring an SWR SM-900, reasonable?

[3bc]

Another option is to buy a second one of a similar revision to use for parts in case something happens.

And then you can also run a massive SM900 rig like Ian Hill.

I have purchased some non-functioning duplicates over the years for older synthesizers to have a supply of spare parts. This is a reasonable idea. You would have to be committed to the amp and the sound to go this route because it would not end up as the great bargain you might have at least initially, but it's conceivable to keep it running somewhat indefinitely with enough spares.

Juno 106's have many problems and people keep those running 40 years later with spare parts and a handful of replacements.

 

[agedhorse]

I have purchased some non-functioning duplicates over the years for older synthesizers to have a supply of spare parts. This is a reasonable idea. You would have to be committed to the amp and the sound to go this route because it would not end up as the great bargain you might have at least initially, but it's conceivable to keep it running somewhat indefinitely with enough spares.

Juno 106's have many problems and people keep those running 40 years later with spare parts and a handful of replacements.

Yes, but in practice it's not a terribly economical way to go about it (though may be the best option IF it's an important or valuable piece).

 

[3bc]

Yes, but in practice it's not a terribly economical way to go about it (though may be the best option IF it's an important or valuable piece).

Not economical at all that's for sure. At least with regard to vintage synths! Though I have heard more than few stories of folks spending thousands of dollars on mostly destroyed CS-80's and those kinds of things, hoping to get a few working spare parts. But a good working order CS-80 might fetch $40k, so maybe that is a good investment if you can restore one that's mostly ready to work!

 

[agedhorse]

The CS-80 is pretty unique.

There's still a market for keyboards like the CP-70/80 as well as the Rhodes 73/88 and Wurlitzer 200, each were revolutionary in the day and while the sound/feel is unique to each, some of it's due to the nostalgia factor also. Three different approaches, using somewhat similar (electro-magnetic or electro-capacitive) technologies yet so different in tone, feel and execution.

 

[dbsfgyd1]

I've had a reliable Eden (I know not the same, but same ilk) for 20+ years.
I bet you'll be fine. If it's the amp you want, roll the dice and go for it!

Most of my Eden gear is almost 20 years old. The only thing I had issues with were the nuts on the outside of the jacks breaking off the threaded Jack sleeve. I must have replaced about 15 jacks over the last 12 years.

 

[dbsfgyd1]

Depending on the version, some parts are no longer available. Some parts may possibly be substituted but some haven't been made for quite a few years.

For example, Sanken has discontinued all of their power transistors using their proprietary MT-200 package, the market has been awash with fakes and counterfeits of these parts for years, I would expect that most of these that are not sourced from AUTHORIZED distributor channels are probably fake.

Some pots, switches, jacks and the power transformer are also going to be difficult to find. Fender no longer stocks the replacement parts.

This needs to be factored into your willingness to accept risk and cost associated with any necessary repairs.

I got to tell, when my Eden gear bits the dust, you have me sold on Mesa.

 

[baxter_x]

Well, I know What to expect if I acquire this SM900. No plan B.
I'll think about it

 

[baxter_x]

I asked the seller some pictures, and I noticed one weird thing: The back of the amp mentions 8 ohms minimum when bridged. Weird isn't it? Especially since the manual mentions 4ohms minimum

 

[agedhorse]

Some versions did not support 2 ohms in dual mode and 4 ohms in bridge mode.

 

[Al Kraft]

I asked the seller some pictures, and I noticed one weird thing: The back of the amp mentions 8 ohms minimum when bridged. Weird isn't it? Especially since the manual mentions 4ohms minimum

View attachment 4431885

Quite odd in my mind as I wonder what typical 8 Ohm cab one would need 900 Watts to power if the goal was making music and not destroying drivers.

 

[baxter_x]

Quite odd in my mind as I wonder what typical 8 Ohm cab one would need 900 Watts to power if the goal was making music and not destroying drivers.

That's pretty much what I had in mind too. However, that's a bit of a problem for me. In fact I'll never be able to use it in bridge mode in the end.

 

[baxter_x]

Some versions did not support 2 ohms in dual mode and 4 ohms in bridge mode.

It looks like there are actually many versions of that amp.

 

[Al Kraft]

That's pretty much what I had in mind too. However, that's a bit of a problem for me. In fact I'll never be able to use it in bridge mode in the end.

I own the earlier in the series 400S version and IMO the bridge mode into 4 Ohms (minimum load allowable) is where that head shines. Conversely though it does do 2 Ohm loads on each amp individually, but at an output so modest that it would be more appropriate for a single 8 Ohm cab...certainly not four 8 Ohm cabs or two 4 Ohm cabs. So we sort of have oddities at opposite ends of the spectrum, albeit I think the 400S makes more sense in terms of usability for most live gig bass players.

 

[baxter_x]

I own the earlier in the series 400S version and IMO the bridge mode into 4 Ohms (minimum load allowable) is where that head shines. Conversely though it does do 2 Ohm loads on each amp individually, but at an output so modest that it would be more appropriate for a single 8 Ohm cab...certainly not four 8 Ohm cabs or two 4 Ohm cabs. So we sort of have oddities at opposite ends of the spectrum, albeit I think the 400S makes more sense in terms of usability for most live gig bass players.

I don't need 2 omhs. However, I need a 4ohms bridge option.

 

[Al Kraft]

I don't need 2 omhs. However, I need a 4ohms bridge option.

I think the way they got the capability they needed on the 400S to run at 4 Ohms bridged just resulted in the ability for each individual amp to safely run at 2 Ohms. I agree with you that decent Wattage 8 Ohm operation and serious Wattage at 4 Oms are the most useful for most players. Not being able to use that 900 Watts at 4 Ohms would be a deal breaker for me.

In decades of playing I can't remember when I have ever run a bass head with less than a 4 Ohm load. Of course the new light weight cabs (e.g. SW 212's and 215's) make it easy to bring two to a gig and then you're in a 2 Ohm load situation.

 

[baxter_x]

would be a deal breaker for me.

Well.... I think that's where I am right now.

 

[agedhorse]

It looks like there are actually many versions of that amp.

Yes, I was addressing the ability to bridge into 8 ohms minimum and 4 ohms minimum.

 

[baxter_x]

I'm really torn appart. It's a great deal but I'll have to use the amp only on stereo. No bridge possibilities.... Which is pretty annoying to me.

 

[Al Kraft]

I asked the seller some pictures, and I noticed one weird thing: The back of the amp mentions 8 ohms minimum when bridged. Weird isn't it? Especially since the manual mentions 4ohms minimum

View attachment 4431885

I would never argue with agedhorse on something like this and he would know if there were different versions so please make no decision on what I am about to suggest (other than to make your decision a hard no). I looked at that picture again and something is very wrong on my opinion. There is no way that head could produce 900 Watts of output at the speaker connections and only show 960 Watts power draw under the power plug. This would not be the first knock-off SWR head I've seen and I believe that is what you have here.

EDIT: Disregard what I just wrote. I didn't take into account the voltage shown - that's a 230 Volt input head. I was thinking like the typical American and on top of that not reading closely enough!

 

[agedhorse]

The 960 watt input power is based upon the duty cycle being less that 100%.

Generally 1/8-power (12.5% duty cycle) is the minimum that can be stated and is what the test labs will use but some designers (including me) state the input power at a higher duty cycle (I use between 33% and 40% depending on the products).

With an AB power amp, linear power supply, the overall efficiency is about 50%, so the 100% duty cycle input power will be about 900 rated power X 2 = 1800 watts. Now to me it looks like the duty cycle is also right around 50% which is how they get 960 watts input power.