New SE With Triode Mode KT120/150

[Ray P]

Steve, that picture looks really good with the theming of the amp and speakers - love it - except that the passive pre look is out of kilter - could you pick up on some of the retro visual cues of the amplifier with it?

[Cressy Snr]

Steve, that picture looks really good with the theming of the amp and speakers - love it - except that the passive pre look is out of kilter - could you pick up on some of the retro visual cues of the amplifier with it?

Not really thought about doing that TBH. The Elma rotary switch on the passive, has a one eighth diameter shaft, so changing the control knobs would be a major issue. The knobs were turned out of aluminium bar and centre drilled for the two different shaft diameters (the volume pot is standard quarter-inch diameter.) The top shelf of the TV unit has turntable and power amp matching with the speakers, so it looks fine as a piece, when viewed as a whole. The compartments under the top surface house the DAC, phono stage, phono stage power supply, CD player and TiVo box, none of which bear any resemblance to the retro theme of the top shelf.

[steve s]

It dont matter steve as long as it sounds good..

[Cressy Snr]

It dont matter steve as long as it sounds good..

Aye, it certainly sounds good. Those Khozmo stepped attenuators, from Hi-Fi Collective are fantastic bits of kit.

[Ray P]

It dont matter steve as long as it sounds good..

No, it wasn't my intention to suggest otherwise or to imply criticism - it was nothing more than an 'icing on the cake' observation and as long as listening to music with the system makes Steve smile it's mission accomplished.

...Those Khozmo stepped attenuators, from Hi-Fi Collective are fantastic bits of kit.

I've been looking at them so its good to hear of your positive experience. I've decided to try a Muses chip based attenuator - would like to find out how well they perform.

[ed]

I've been looking at them so its good to hear of your positive experience. I've decided to try a Muses chip based attenuator - would like to find out how well they perform.

I'm not sure we haven't discussed this a while back... I was going to get a 72320 chip a while ago but they're only smd so I was trying to find one of the breakout boards..they seem to be hard to find at the moment. I will get back on this once the current batch of time consuming distractions are out of the way. I am quite keen to compare it to the digital pot versions I played with a few years ago......

I am going to wait for the fitted breakout board to re-appear cos the chips are about £12 a go and my history with smd is chequered.

[Ray P]

I'm not sure we haven't discussed this a while back...

I think that was LDR based attenuation.

You might look at the Academy pre-assembled unit - looks to be a good price and without the smd hassle.

https://www.academyaudio.com/product-pa ... trol-board

[Nick]

Couple of points about the MUSE chip. Pass Labs only uses one of the two pots in each channel so avoids the external op amp but of course reduces the number of steps available. I found that the 10pf cap across the op amp had a big effect on the sound, using without it sounded much much better, assuming your choice of op amp is stable. Maybe a better cap would sound better.

[Cressy Snr]

Sound has been getting increasingly fizzy and generally crap over the past day or so.
Been under the hood with a meter and to cut a long story short, the KT120s are shot. Rather than a gradual deterioration over weeks, they went bad surprisingly quickly. They only lasted 10 years. PAH! What a swizz!
I’ve put in a pair of JJ, KT88, out of a quad, I got off Paul, about three years ago and normal service has been resumed. They are however running at almost maximum dissipation, but they’re cheap enough to replace.

[Paul Barker]

Sound has been getting increasingly fizzy and generally crap over the past day or so.
Been under the hood with a meter and to cut a long story short, the KT120s are shot. Rather than a gradual deterioration over weeks, they went bad surprisingly quickly. They only lasted 10 years. PAH! What a swizz!
I’ve put in a pair of JJ, KT88, out of a quad, I got off Paul, about three years ago and normal service has been resumed. They are however running at almost maximum dissipation, but they’re cheap enough to replace.

So how much of my sh1t is in that amp?

Still, youre always willing when I turn up unanounced and fall asleep .....

[Cressy Snr]

So how much of my sh1t is in that amp?

Just the KT88s. Mind you it wouldn’t work without them.

Still, youre always willing when I turn up unanounced and fall asleep .....

[Cressy Snr]

Well, I did a few bits with PSUDII yesterday and found a little bit of a problem with my existing two power supplies. It was a case of the 320mH choke in the output stage power supply doing precisely sweet FA, and the input stage power supply, being slugged to buggery with too much capacitance in the LC filters. It took 3 seconds to respond to a simulated current step.

I managed after a few attempts, to get the response time to a current step (0.2s) the same for both stages, whilst keeping ripple low, when they were stepped with the same percentage according to their idle draw, ie the output stage supply got a proportionally bigger kick than the input.

Now I haven’t got a clue, whether the above makes any sense; I’m well and truly at the limits of my capabilities. Out of my comfort zone is putting it mildly, but I decided I would use the cap values PSUD thought were the best and just get on with it.

The 320mH choke was taken out of the output stage power supply, and the thing was changed to LCRC with the resistor being 300R/50W, dropping 49V with a 200mA draw.

The input stage power supply remains LCLC but the first cap has been reduced to 16uF and the second cap, reduced to 40uF. A big reduction.

[Nick]

It took 3 seconds to respond to a simulated current step.

I don't understand what that means.would the current not be provide by the last cap in the chain?

The 320mH choke was taken out of the output stage power supply, and the thing was changed to LCRC with the resistor being 300R/50W, dropping 49V with a 200mA draw.

I would have thought making the supply a high resistance feeding a cap would make it less able to respond to current changes.

[Cressy Snr]

More research needed clearly.

[Cressy Snr]

Anything wrong with this picture?