Solo UL noise cut ten-fold!

Graham, is there any be sacrificed even very subtle in this newer low noise design?

To ManAtWork, no loss in my opinion. I recently tried one acid test: Santana's Moonflower album on vinyl, and it reproduced virtually every bit without any edginess and all the positive traits of the UL. If you know this album you will know how difficult it can be. Most owners never play it...

To jamescodway, Oh, that's interesting. For all this time I've been thinking my SR60 must be knackered. Actually, in the rethink of the output stage I had also been contacted by a prospective distributor who also distributes Grado, and told me he couldn't find a replacement for the Grado RA1 headphone amplifier which could drive Grado's properly. That got me intrigued and so I did a little research in which I rightly or wrongly concluded that it was possible for Grado to have designed some synergy between their headphones and the RA1. Since it is all over the internet about the RA1 schematic I took a look and found it used the Ratheon RC4558 op-amp, which is unfortunately a dual 741 - designed in 1968 - but with a reduced miller capacitance to increase its slew rate to 0.5V/uS. Oh dear, I thought!

I can't really comment on other manufacturer's - it would be unfair.

The thing I can comment on is that the headphone out is direct from the op-amp which is designed to drive a load of 2000 Ohms, but Grado's are 32 Ohms. Did this help me? Not one jot! I did buy some 741's to analyse the situation but that didn't lead to any clues either. So I just tried several different output configurations until I got my SR60's sounding good enough to enjoy listening with them over a longish period.

After that I went through the entire Slee headphone collection just to make sure nothing else had changed. I have other 32 Ohms headphones which work perfectly with either the existing UL or the diamond edition - it was just that the SR60 was odd man out.

Graham, thank you for your explanation. I do enjoy Santana's records very much.

mrarroyo wrote: I have an older RS-1 (with wood buttons over the grill) and IMO both the SRGII and the UL drive the Grado can to my full satisfaction. Actually the Grado sounds very nice out of either. I also have an older SR-80 also with buttons which has been heavily modified with a re-cable and wood cups and sounds superb out of either amp. Cheers.