Don’t all laugh at once!

Jump to Latest
#41
gary s said:
Post #12 - blue cap is banished. Now all 100% black.
Click to expand...
What blue cap ?
IMG_8466.jpeg
 
#45
QUOTING FROM THE MANURFACTURERS TEXT :
" ... and make the feedback loop path short and fast. The loop is so fast that the output stage will not go into feedback clipping.
That means that the amplifier can be driven at full power with as little distortion as there is at low levels"
--------------------------------------------------------------------------------------------------------------------------------------------
I think that this text means > low Transient Intermodulation Distortion > AKA. TIM 😉
PS.
It could also mean that "Anti-clip" circuitry is incorporated.
 
#48
I see TO-3’s with the old thick non-polished base. Who was still using those in 1994 (cap date codes)? Not any of the usual suspects, except for the Exicon or Hitachi lateral FETs. Everyone else who used that version of the TO-3 at all were only using it for TV horizontal output transistors, which, by then, were on the way out.
 
#50
Havoc said:
I thought it was large diameter solder wrapped around them. Probably a means of avoiding vibrations...
Click to expand...
Have you ever heard one of the old QSC USA series amps when you drop the unit? They ring like bells. And they just have very large versions of that type of heat sink. You know it’s to avoid vibration, and sounding “cheap” when given the thump test. The thing is full of overpriced capacitors, and the last thing a manufacturer wants is a defect that someone looking at aesthetics could easily spot.

Not damping the last fin won’t really hurt by much. You’re still absorbing most of the stored energy and that last undamped fin won’t make as much noise as it would have.
 
#51
Have you ever heard one of the old QSC USA series amps when you drop the unit? They ring like bells. And they just have very large versions of that type of heat sink. You know it’s to avoid vibration, and sounding “cheap” when given the thump test. The thing is full of overpriced capacitors, and the last thing a manufacturer wants is a defect that someone looking at aesthetics could easily spot.
Click to expand...

I do my best not to drop amps 😉
 
#53
jxdking said:
So what is it?
Judging by size of the heat sinks of TO3 transistors, the maximum power output is about 10W per channel.
Click to expand...
it has 32 times the number of output transistor fins of another 60 w/ch amp, the dynakit ST-120. This has 64 fins, ST-120 had 2.
OTOH it has 5.9 times as many big capacitors. 23 instead of 4.
Transformer about the same. RATA 600 va, ST-120 575 va. I've always liked the bass response of my ST-120 with only one 3300 uf rail cap for 2 channels. RATA apparently similar.
Enjoy your treasure hunt find. The OEM price was outrageous, but I doubt you paid 1/20th of that.
BTW just thumped the heat sink of my US made QSC CS302 with a finger. Lots of 17 cm x 1.4 cm fins, but no bell like tone. Worst thing I don't like about it, fan is too noisy. Will be banished to a room behind the podium with the mixer and speakers on the podium.
 
Last edited:
  • Like
Reactions: TheFinisher
#54
indianajo said:
it has 32 times the number of output transistor fins of another 60 w/ch amp, the dynakit ST-120. This has 64 fins, ST-120 had 2.
OTOH it has 5.9 times as many big capacitors. 23 instead of 4.
Click to expand...
I was thinking it was a JLH1969 style amp. In class B, it can push more.
It looks weird, that it has so many caps but the designer decided to cut the corner on the heatsink.
 
#56
It has 2SJ50 / SK133 Hitachi Lateral FETs. It was advertised at £450 on Ebay: https://www.ebay.co.uk/itm/156441990437

Russ Andrews has earned unique distinction amongst the UK audio industry for incurring the wrath of the Advertising Standards Authority

https://www.audiosciencereview.com/...dards-authority-vs-chord-company-ruling.3581/

Does this amp have a CE mark? I wonder if it meets UL standards (interesting soldering in the Ebay link)?

The film caps are made by Ansar - they are made in the UK and are decent value.

Where's the copper tape on the inside for EMI prevention?

I wonder just how much it deviates from the classic Hitachi apps topology (sold by Maplin, inc. pair of Hitachi FETs for around £20 a channel - a far cry from the £5.5K this allegedly sold for)?

One suspects that the amp maker has gone onto more profitable ventures since this was made. It'd be really interesting to find out how much it shares with the Maplin (UK version of Radio Shack, defunct as of about 8 years back) design... The Maplin / Hitachi design sounds lovely (I have several), but I prefer mine with EM shielding TBH.

edit - check the glue in the corners on the Ebay link. Dovetail, schmovetail.
 
Last edited:
#57
Did the Maplin circuit have a proper set of drivers? This one has two little TO-220 heat sinks next to the power devices. I assume those are EFs biased in class A at several 10’s of mA, and should be able to do proper charge suckout, as well as push out the pole frequency caused by input capacitance (even boot strapped it is still a limiting factor).
 
#60
I can’t figure that out either Gary , the highs are sweeter and the soundstage is amazing with the Rata 🤷‍♂️
Could the Stasis be too powerful for the IMF’s perhaps? I know they don’t like going loud ( I think the kef bass drivers are only 50watts )

Oh yes the bass is just lovely, I prefer the sound of these over the Troels Gravesen ( not their looks though 😁)
 
Last edited:
You must log in or register to reply here.
Top Bottom