Measurements taken with the 12V reg removed, and the external psu connected.
Well it’s fixed the 12V issue (yay!), but the other voltages around the BC550/517 look too low again. So I’m assuming this points to one of those not working as they should? I’m going to check that 47k resistor too.
Well it’s fixed the 12V issue (yay!), but the other voltages around the BC550/517 look too low again. So I’m assuming this points to one of those not working as they should? I’m going to check that 47k resistor too.
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Hi Salas.
Today I replaced the BC550 and BC517 transistors. The voltages now look much better, though should I be concerned about the 10.1V on the emitter of BC550 measuring a little low at 9.84V ?
The good news is I can hear the output relay click clearly now after a few seconds. And the input relays also each click too when changing the selector pins
Today I replaced the BC550 and BC517 transistors. The voltages now look much better, though should I be concerned about the 10.1V on the emitter of BC550 measuring a little low at 9.84V ?
The good news is I can hear the output relay click clearly now after a few seconds. And the input relays also each click too when changing the selector pins
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Looks like it works. 10.1V or 9.84V no matter. Its around there a BC550C sample shows its reverse Zener behavior. The 11.3V is meant for across the coil, 12V-0.7V=11.3V. Thus 12V on the coil's top vs GND is also correct. Its the same line as to where 12V was noted at the left of the jumper.
Huzzah!!! After 11 years, she’s finally singing beautifully!
It’s only been a couple minutes, but already very impressed! It’s going to be a music filled evening/night!
Going to soak test it over the next few days, and than can get to work on designing a front panel via Front Panel Express, get my better internal wiring installed etc.
Thanks for all your help over the past few weeks Salas, and of course DCB1 Mez! Very pleased!
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Thanks Salas. Well it’s safely passed the soak tests, and sounding better now it’s been running for a while now. I’ve noticed the Mosfets barely get warm, so I may look into hotrodding it further, but only if it’d lead to an audible improvement, otherwise I’ll leave it running with the 7.5ohm CSS resistors. The one-piece chassis/tray is 2.5mm thick, and that slides into an aluminium extrusion which is itself 4mm thick, so plenty of disipation.
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Yes, it can handle extra dissipation, but on the other hand its reservoir caps are not planned too big so judge if more mA is better to your own taste.
Mez was meant to be operating at about 200mA standing shunt current per side in general. It was a widely agreed good subjective performance spot before diminishing returns kick in. There are Mosfets Vgs and Leds Vf tolerances but you can verify how much your build runs by the voltage drop across its setting resistors. I=V/R.
Mez was meant to be operating at about 200mA standing shunt current per side in general. It was a widely agreed good subjective performance spot before diminishing returns kick in. There are Mosfets Vgs and Leds Vf tolerances but you can verify how much your build runs by the voltage drop across its setting resistors. I=V/R.
I’ll have a think and get a real handle on how it performs over the next week and then decide whether go try hotrodding further then. It sounds very transparent, beautiful on vocals in particular, but it’s currently missing a little ‘crispness’ and openness, a bit too smooth/polite perhaps. I am using REALLY cheap input/output wiring just for testing purposes, so I expect I’ll get improvements once I change to the Van Damme shielded cabling I have bought. Just need to practise crimping on those pins first for the pcb connectors. The other thing is I’m using 330k rather than 220k in the output section. Would that slightly affect dynamics or treble region? Thanks.
Measured the DC on the outputs, which was 0.4mv on left, and 0.1mV on the right - Very happy with that! (Spencer obviously matched them well)
Mez is never harsh or technical in the highs but not too soft either. I see you already use a massive expensive volume pot. That should not be the reason. I would look about those two small films you use in the regs. They are in Vref noise filter position. Can be influential in the HF. Are they MKT? Try bypass with 0.1u MKP if so. Another way is Muse KZ no less than 33uF. Possibly bypassed with MKP again. What amp & loudspeakers you use?
Those two film caps are 0.22uF Panasonic MKPs, the non inductively wound versions from the ECWF range if I remember correctly. Perhaps they need further running in, but if not 100% happy after replacing the internal wiring then I’ll definitely try the Nichicon KZ caps (have a pair of 47uF 50V ones spare actually). It’s sooo close to being ideal for me, but definitely a little too polite right now. Just needs a very slight nudge in the right direction. Amp is fully serviced Quad 606, with Wharfedale Denton 85 speakers. Prior to Mez was running Hugo TT2 direct into the 606.
Hmm I’m not sure. The myth of Quad amps being a little soft is not what I’ve found in practise, at least when recapped with decent electrolytics and working to spec. And the Wharfedale speakers are a modern design using an old brand name, and they measure very well ( http://www.hi-fiworld.co.uk/index.p...iews/911-wharfedale-denton-85th-.html?start=3 ) albeit with a slight treble peak. The ‘bite’ and dynamics are also fine running the DAC directly into the 606. But I built DCB1 so I can eventually use vinyl too.
I slid the outer casing on last night, and it’s sounding more as I’d prefer it this morning. So perhaps the extra shielding of the full case helps, and/or the caps have run in further. I do have my suspicions about those ECWF film caps now. I have a vague memory of experiencing this once before when used as a coupling cap, so I may well try something else there as it’s easy to change without having to remove the pcb. Just listening to some classical on Radio 3 this morning and it’s sending shivers up the spine, so it’s doing very well. Lovely presence and ‘body’ I just need to voice it for (very) slightly more crispness.
I slid the outer casing on last night, and it’s sounding more as I’d prefer it this morning. So perhaps the extra shielding of the full case helps, and/or the caps have run in further. I do have my suspicions about those ECWF film caps now. I have a vague memory of experiencing this once before when used as a coupling cap, so I may well try something else there as it’s easy to change without having to remove the pcb. Just listening to some classical on Radio 3 this morning and it’s sending shivers up the spine, so it’s doing very well. Lovely presence and ‘body’
I just need to voice it for (very) slightly more crispness.
Just listening to the following. The bass via DCB1 is verging on scary! Great stuff! Brings the music & passion alive. I’m thinking I just need to keep using it rather than do any mods, it’s shaping up nicely!
https://www.discogs.com/release/333...-Symphony-Orchestra-The-Rite-Of-Spring-Firewo
https://www.discogs.com/release/333...-Symphony-Orchestra-The-Rite-Of-Spring-Firewo
