please help discern some specs on this Concert Lead head..

[interloper]

i have the option to buy this for around $650. it looks different to all the 'vintage' CL heads i've seen, although it was supposedly made in 1978. living in australia, this is quite a cheap and easy option...i just want to make sure i'm not getting a hunk of shit.

any opinions are welcome, as i have 5 days to choose between whether or not i will buy it.

cheers in advance

[claytoy]

would that be 150w at 4ohms

[MammothVolume]

Eh, 650 is a bit steep, especially considering your dollar is killin' ours currently. They're great amps, 200@2ohms, the built in reverb is great. Never could get a bad sound out of the head. I've had three, two of these, one silverface, and I definitely prefer this one. The distortion will get you into Sabbath territory, but nothin' too saturated. I paid 200, 150, and 75 bucks for all of mine, in the past. So... I'd pass on 650. Look on ebay, or see if you can get one from the states, even with shipping, you'd be able to get it cheaper than that.

[MammothVolume]

would that be 150w at 4ohms

check the 78-79 Catalog specs in the Catalog thread. The silvers are 150@4 ohms, these are 200@2 ohms. 

[claytoy]

thanks i will look again

[shibbz]

would that be 150w at 4ohms

check the 78-79 Catalog specs in the Catalog thread. The silvers are 150@4 ohms, these are 200@2 ohms. 

This has been debated a lot.
They were indeed advertised as 200 at 2 ohms, but they are often unstable at 2 ohms, and it generally isn't a good idea to run them like that.
I'm sure someone else could chime in with a bit more technically proficient response, or use the search function.

[MammothVolume]

Both of mine ran fine at 2 ohms, maybe a little hot during the summertime, but otherwise, nothing bad ever came of it. I was pushing 2 2x15s with it. I eventually stopped doing it due to the heat issue, but it never caused any lasting effects on the amp.

[EdBass]

I'm not personally real up on Sunn transistor amps, however there have been some pretty compelling arguments made against the stability of the Concert output stage running a 2 ohm load over the years; by IMO some very tech savvy forum members.
I know this though; in the real world of professional sound reinforcement, running serious high dollar/low impedance stable amps, intentionally planned 2 ohm loads are avoided like herpes. These are amps that will often run stable bridged with a 2 ohm load, far more "bulletproof" than the amps being discussed here.
There are myriad reasons that running a non OT transistor amp with a 2 ohm nominal load is not a good idea, but to summarize it's real close to a dead short. It leaves little margin for error. Taking into consideration the nature of speaker impedance ratings, the amp may regularly see loads that are a fraction of an ohm; too close for comfort in the pro world.
A happy amp is a good sounding reliable amp, and a 2 ohm load doesn't make for a "happy" amp.

From some posts I read, it almost seems like running 2 ohms is like a "bragging" thing, when in reality the increase in actual dB between 150 and 200 watts is insignificant. For all intent and purposes virtually inaudible to the ear, requiring accurate measuring equipment to notice; maybe <1 dB, and IMO the potential risk FAR outweighs any potential gain.

While it may be convenient to daisy chain a pile of cabs together in parallel, you can generally run as many speakers as you want with judicious use of series and parallel wiring, so the excuse that 2 ohms is required to run multiple cabinets doesn't really hold water either.

Sorry for the little "derail" interloper! 

[jaywalker]

+1 What Ed said 

[george]

Beats me what difference there is between the "red face" concert series vs black face that would reliably allow driving a 2 ohm load? I have repaired half a dozen of these amps with badly damaged PA PCBs - I have to assume the root cause of failures were due to driving 2 ohm loads. Don't see near as many of the previous model (black face) with this kind of damage.

The back of the amplifier silkscreen says 200W and that class 2 wiring can be used - the 79' catalog does state 200W at 2 ohms but I wouldn't go there with original +30 year old components - might be able to push it with some of the 21st century audio output transistors and flame proof resistors 
BTW a bass version of this model was sold on ePay for around $450US in the last 30 days.

[Isaac]

For the math geeks among us, the difference between 200w and 150w is 10log(200/150)=1.25dB

That's not significant. For me, the advantage of having an amp that is stable to 2 ohms is the ability to run more cabinets, not the paltry increase in power.

[claytoy]

i don't know if that helps the Interloper but it helps me --- thank you

[interloper]

I'm not personally real up on Sunn transistor amps, however there have been some pretty compelling arguments made against the stability of the Concert output stage running a 2 ohm load over the years; by IMO some very tech savvy forum members.
I know this though; in the real world of professional sound reinforcement, running serious high dollar/low impedance stable amps, intentionally planned 2 ohm loads are avoided like herpes. These are amps that will often run stable bridged with a 2 ohm load, far more "bulletproof" than the amps being discussed here.
There are myriad reasons that running a non OT transistor amp with a 2 ohm nominal load is not a good idea, but to summarize it's real close to a dead short. It leaves little margin for error. Taking into consideration the nature of speaker impedance ratings, the amp may regularly see loads that are a fraction of an ohm; too close for comfort in the pro world.
A happy amp is a good sounding reliable amp, and a 2 ohm load doesn't make for a "happy" amp.

From some posts I read, it almost seems like running 2 ohms is like a "bragging" thing, when in reality the increase in actual dB between 150 and 200 watts is insignificant. For all intent and purposes virtually inaudible to the ear, requiring accurate measuring equipment to notice; maybe <1 dB, and IMO the potential risk FAR outweighs any potential gain.

While it may be convenient to daisy chain a pile of cabs together in parallel, you can generally run as many speakers as you want with judicious use of series and parallel wiring, so the excuse that 2 ohms is required to run multiple cabinets doesn't really hold water either.

Sorry for the little "derail" interloper! 

Ohms are still somewhat new to me, so forgive me if I sound clueless...so I gather from this info it would be better to run the head at, say, 4ohms? I will most likely be using it with an Orange PPC412 cab, in which case will I have to adjust the impedence level on the cab to suit?

No derailing was had anyway, good sir! I bought the head before realising people were actually replying to this haha, so thankyou for the help as it definitely seems you know your shit inside-out.

[interloper]

Eh, 650 is a bit steep, especially considering your dollar is killin' ours currently. They're great amps, 200@2ohms, the built in reverb is great. Never could get a bad sound out of the head. I've had three, two of these, one silverface, and I definitely prefer this one. The distortion will get you into Sabbath territory, but nothin' too saturated. I paid 200, 150, and 75 bucks for all of mine, in the past. So... I'd pass on 650. Look on ebay, or see if you can get one from the states, even with shipping, you'd be able to get it cheaper than that.

Sounds fantastic. Still waiting on a transformer from Perth before I can give her a go. Bought it already so may have gotten a little ripped off...but it looks like new and will hopefully play just the same. Went searching for it after becoming infatuated with UNWOUND, so I'm sure I won't be disappointed with the sound.