vintageHIWATTconvention.com

Hi
I just purchased a combo 50 watt made in 1979. It is all original with Partridge transformers.
Intresting it came with what appear to be the original pre amp tubes all mullard
the EL 34 are GE tubes made by Mullard single getter. The amp sounds a lot warmer less harsh than
a hiwatt I owned many years ago. So I took out the EL34 and tested them and they are both weak. They are so
beat up the Mica is cracking off. So I threw in a pair of NOS Mullard double getters that test strong and now the amp
sounds harsh on the high end. The speaker the amp came with is a EVl 12.
Not sure what to do do about the harshness any recommendations? I am thinking about changing the speaker
any recommendations for a replacement? I had been looking at a New fane alnico blue 100 watt 8ohm 12 vs
going with a Hi Tone 2x12 although not sure if my amp has enough power for that? With the old worn out tubes that are completely unmatched
it sounds warm and creamy but they have very little life in them.
PS
I had this same amp model in high school in 1981 and traded it for some transistor crap amp. I have spent so many years kicking myself
So the instant I saw this amp in a local music store I had to buy it. I paid $1200 is that reasonable?

that is a good price, congrats.
I wouldn't trust a HIWATT 50 with very many single 12" speakers, The HI-TONE 2x12 is perfect for a 50w. HIWATT.

You definitely want a ceramic magnet speaker with a HIWATT, unless you don't want the punchiness that hiwatts are famous for.

Nothing beats genuine NOS Mullards.

Welcome to the Vintage HIWATT forum!

Just a thought: perhaps the bias isn't optimal for your NOS pair of Mullards? If it's sounding brittle, the bias may be too cold. Also, make sure your PI/V4 (the middle of the group of 3 preamp tubes) is up to the task.

I agree with Dr.HI-TONE - an alnico speaker won't give you the HIWATT punch. If you determine the EVL isn't a good match, consider putting an 8 ohm Tonker in the combo. Then, you could run both that PLUS the HI-TONE 2x12 for larger venues (setting the amp to 4 ohms). It'll look a lot like the rig in my avatar .

Dave

I understand the bias is not adjustable for this amp?
I do work on my own amps is there a mod worth doing to
make the amp adjustable bias without changing the hiwatt sound
or significantly decreasing the value of the amp?

echo44 wrote:... is there a mod worth doing to
make the amp adjustable bias without changing the hiwatt sound
or significantly decreasing the value of the amp?

http://hiwatt.org/Schematics/BiasCkts2.gif

Dave

do you know which circuit would apply to my hiwatt
custom 50 1979 combo amp?
Also does any one have an inside picture of the mod?

Thanks

It's the 504 version. I don't know if I have a pic or layout, I'll poke around later this morning.

--mark

thanks

Just as a point of comparison, I too have a 1979 SA112 (23/3/79 out of interest!) and am about to start the process of changing the 8ohm goodmans axiom that mine came with (replacing the original fane as it is dated from 1976...and has a £20 price sticker on it) with a 16 ohm speaker. Firstly out of kindness to the goodmans - it's a great speaker. It'll give me peace of mind when gigging with it. And I'll be able to also lug my SE4123 if needed and run it as well.