SA212 - what can you tell me about it?

[tomb11112]

Hi All,

to compliment my 74 DR103 I have recently acquired an exceptionally clean SA212.
So clean that I actually suspect it to have been re-covered.

No serial number but the caps date to mid/late 76.

I have switched the greenbacks to Weber FC12s - a far greater improvement than the GBs!

So - what can you tell me about the amp?

The phase switch is just a switch - not wired.
Most have a mains power switch on the back - this one doesn't.
Later transformers and smaller pots - suggests a later 70's model.
Yet the salt/pepper grill... could this be original or is it a re-cover?

http://s1353.photobucket.com/user/Tom_B ... t=6&page=1

[OldSchoolDave]

The phase switch is just a switch - not wired.

Good! It's much safer that way (I assume your mains cable has a ground lug?).

Most have a mains power switch on the back - this one doesn't.

Not the combos built for the Americas. Yours looks very similar to the '79 SA212 I used to own. Can you read the last digit on the "Tested" sticker? If not, assume it was completed on 21 March of the year following your pot and/or filter cap dates.

Yet the salt/pepper grill... could this be original or is it a re-cover?

Maybe it's the photography, but the chassis appears fairly grungy inside. Based on that, I would guess the tolex and grill cloth are replacements.

Nice amp! Kinda wish I still had mine .

Dave

[PhilUK]

I would say it dates to early 77 by the black labels on the transformers

[tomb11112]

Ok - it most certainly is a 77 and a re-cover.

I found the original listing on ebay.
Turns out I had emailed the seller with an offer - they declined - then bought it a month or so later for half the price from another seller! Ha!

I recently had it serviced by my amp tech. It has been fully re-capped, new OP valves and some general TLC. It is absolutely dead silent mains wise!
I have changed the greenback speakers to Weber Thames - a marked improvement to the greenbacks!

I am really surprised by how different this is to my 74 DR103. Even while running the DR103 at 50watts (pulled outer 2 tubes) they sound very different, and the volumes are at very different places.

Setting the channel volumes to noon/1 on both the master has to be around 10/11 on the SA212 compared to only 7/8 on the DR103 to match.

The head is going into a marshall 2x12 with a 12a Crescendo and a G12T75.

The head sounds a lot more scooped and has a lot more presence to it too.
Is this standard for a DR103? The combo is very middy in comparison.

Is this because of the differences between the preamps (the DR103 being an early 70's layout and the combo being mid 70's layout) or between the cabinets?

[mhuss]

Cabs & speakers will make a huge difference in the sound.

[OldSchoolDave]

Cabs & speakers will make a huge difference in the sound.

As can the tubes/valves.

The only way to make definitive comparative statements is to run each amp with the same valves into the same speakers. Otherwise, there are too many variables.

Dave

[tomb11112]

I have changed the ECC83 preamp valves to low noise TAD ones, as that's what's in my DR103.
I picked up an early SE4122 just over a week ago with the original 50w 122142 fanes. Sounds great but there is still a big difference between the two. Think I need to find me some original fanes for the combo now too!

The head seems very mud scooped, whereas the combo is very mids heavy. Together they sound great though!
Is this normal between the head and combo?

My tech also mentioned when he biased the combo (using TAL EL34s) he biased it to 60%. A friend seems to think this is low for a Hiwatt. Is he right?

[OldSchoolDave]

Is this normal between the head and combo?

No. If produced in the same run, a head and a combo amp would be virtually identical, albeit upside-down from each other.

SA212's used a wider chassis, but the same schematic.

I'll let the real experts address the bias, but suspect your friend inverted the anecdote that vintage HIWATTs tend to run their output tubes hot. That is a reflection upon modern tubes, not on design intent (to my knowledge).

Dave

[tomb11112]

Thanks Dave.

Nope, 74 DR103 (running at 50w) and a 77 SA212 - the SA has the mid 70s preamp and the DR has the early preamp layout.
Were there many differences between the two?

[Dr.HI-TONE]

we had some Thames at a VHC some years back and they sounded nothing like any of the 1970's HIWATT Fanes..

Speakers are definitely the largest single factor on tonal differences.

A 103 with two power tubes pulled will not sound exactly like a DR504 with identical preamps. Somewhat close, but noticeably different.

I set the bias on TAD EL34B's very close to 70% dissipation. if you prefer the tone at 60% V. 70% then you are golden.

[tomb11112]

I figured as much...
The amp is really middy, so just need to find something a little less so.

I do have a crescendo 12a in a cab with a celestion G12T75 that I am considering swapping in... I used this cab with the DR103 before I got my 4x12 (I'll share that soon).

I would prefer another fane instead of the celestion - wither another crescendo (although find another at 16 ohm even here in the uk!!!!) or a purple fane. Again - pretty rare...

So there is not a huge difference between the early and mid 70's preamps?

[mhuss]

So there is not a huge difference between the early and mid 70's preamps?

No, very little actually. There are significant changes when you get to the two-input amps.

[tomb11112]

Indeed your wisdom is correct, the speakers make a huge impact on the tone!

I managed to acquire another 12a crescendo at 16 ohms so I took the other from my 2x12 cab (it was paired with a celestion) and now have the two crescendos in the SA212 - it now sounds just like what I would have expected! Very happy boy now!



There is still a difference between this and my DR103/SE4122 half stack but now they sound a lot closer.

Happy days!

[hohohiwatter]

Indeed your wisdom is correct, the speakers make a huge impact on the tone!

I managed to acquire another 12a crescendo at 16 ohms so I took the other from my 2x12 cab (it was paired with a celestion) and now have the two crescendos in the SA212 - it now sounds just like what I would have expected! Very happy boy now!



There is still a difference between this and my DR103/SE4122 half stack but now they sound a lot closer.

Happy days!

Niiiiiiiice!!!!