Does the RATA have preamp out (line out) so you could use the preamp section to drive the Stasis 2?
I would have thought the RATA would not have been powerful enough based on the low efficiency of the IMF's. You must be enjoying the music at moderate levels.
But hey, if you are happy with the sound - that is all that counts. Maybe the lateral fet outputs in the RATA are providing the magic.
I would have thought the RATA would not have been powerful enough based on the low efficiency of the IMF's. You must be enjoying the music at moderate levels.
But hey, if you are happy with the sound - that is all that counts. Maybe the lateral fet outputs in the RATA are providing the magic.
pairing it with the Stasis is planned for the weekend 👍🏻
I’m told that it is the fets that make it sound so good ( like a tube )
To be fair I haven’t had a decent pre for the stasis since the counterpoint just stopped working one day .
I’m told that it is the fets that make it sound so good ( like a tube )
To be fair I haven’t had a decent pre for the stasis since the counterpoint just stopped working one day .
Look forward to your comments after you have a good listen to that pairing.
I see the RCA's on the rear panel are not labelled so make sure you get the correct preamp output to drive the Stasis.
Based on my experience, a good tube line stage will be sublime driving the Stasis. Something like a 6SN7 line stage!!
I see the RCA's on the rear panel are not labelled so make sure you get the correct preamp output to drive the Stasis.
Based on my experience, a good tube line stage will be sublime driving the Stasis. Something like a 6SN7 line stage!!
You can learn more about the Maplin (straight out of the Hitachi apps leaflet) in this thread: https://www.diyaudio.com/community/threads/maplin-mosfet-amplifier-ga28f-construction-thread.257488/
The Htachi 7500 is essentially the same amp, but with a couple of tweaks. I tested one into a 4R7 load @ 10W and found that the 1978 amp could deliver well under -100dBV distortion at this level (I didn't go further in terms of load due to time, but I might revisit the project at some point for fun).
It strikes me as odd that the designer of this amp could appreciate the gate capacitance issue, yet fit heatsinks that cannot dissipate anywhere near 60W continuous. I wonder how hot the OPS will get in dummy load testing? It's a good job that they are Lat-FETs....imagine BJTs in this scenario...
Image from Ebay link. A £5.5K amp?
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A 60 watt amp only dissipates a maximum of about 15 watts in each power transistor. The formula is Vcc^2/(pi^2 RL). Real world with music played “loud” is around half that. Stiffly regulated power supplies help this, because the unloaded supply voltage is lower. This reduces dissipation in the *backed off condition, which is most of the time. With a loosely-goosey +/-45V supply (that drops to 35 at load) the power (and loudness) would be exactly the same and the power transistors run hotter, with up to 25W each. Those heat sinks are a little small for that for sure.
5500 pounds? Considering that a business nets you 4% in your pocket after expenses, and the low quantity BOM cost for anything is just stupid high - it doesn’t surprise me a bit. If I wasn’t extremely adept at salvage operations, I wouldn’t be DIYing AT ALL. Full retail on EVERYTHING is just too damn much. Period. Looks like those guys won’t even spring for spade connectors. Last time I ordered a reel of the darn things they slapped me with a tariff. Still way cheaper than blister packs of 50 at Home Depot. Those tariffs are fixing to go up again, and those will hit the ones in Home Depot too.
5500 pounds? Considering that a business nets you 4% in your pocket after expenses, and the low quantity BOM cost for anything is just stupid high - it doesn’t surprise me a bit. If I wasn’t extremely adept at salvage operations, I wouldn’t be DIYing AT ALL. Full retail on EVERYTHING is just too damn much. Period. Looks like those guys won’t even spring for spade connectors. Last time I ordered a reel of the darn things they slapped me with a tariff. Still way cheaper than blister packs of 50 at Home Depot. Those tariffs are fixing to go up again, and those will hit the ones in Home Depot too.
DROOL! B139 and B110? I always dreamed of that. Think I have the drawings for such speakers somewhere...
Back in Australia at the Klarion Enterprises service workshop we had an investigative method we called "The Technical Drop Test" 🙂
Back in '72 and '73 I was at ESS developing speakers and had easy access to the B139 and B110's, so I built numerous designs with them, including transmission lines and open baffle arrays with either or both and also Heil AMTs.
They were (are) wonderful drivers. Unfortunate that they are no longer available.
They were (are) wonderful drivers. Unfortunate that they are no longer available.
Thanks Nelson, good to hear you approve of them - I thought they had gone extinct, like a lot of good things these days.
Falcon Acoustics - another name from the past. I wonder how close the replica's are to the original KEF drivers?
Are your spares original or the Falcon replica's.
I assume there would be some NOS original drivers squirreled away there in the UK.
Are your spares original or the Falcon replica's.
I assume there would be some NOS original drivers squirreled away there in the UK.
Well I didn’t try the Rata as a preamp because after tracing the cables from the rca’s at the back I can see that cables coming from the record and tape defeat switch have been disconnected from the volume pot .
