Blissfully unaware as I am of any mysterious electromagnetic restrictions on my placement options, I've secured the second transformer orthogonally on the back plate of the chassis using the original mounting bracket.
Nice work!
I think you are now officially the second person to do the tx mod. Very worth while it is too
Brent
I think you are now officially the second person to do the tx mod. Very worth while it is too
Brent
Oh man, so worthwhile. It's a huge improvement. My 805s are loving the extra juice and revealing more crisp details and producing deeper and tighter bass than I could've imagined (and I used to have a sub!). I joined DiyAudio in '07 because of this thread and I've wanted to get to this point for all that time. Even with that long build-up, this mod has surpassed my expectations 🙂
Yes very big gains. This is why when I upgraded from the Marantz I had to buy the ATC amp as most 'very good' amps were not as good as the Marantz
Brent
Brent
Hey guys, any opinions on whether I should bypass my 10,000uF Black Gates with some good film caps?
I was thinking of running some Mundorfs across them but I'm not sure of the best values or whether I should do it at the PCB or cap terminals. I've heard rules of thumb quoted of 0.1%, 1% and 10% or even all three.
Also, is it worth bypassing the 1000uF filter caps?
Cheers,
Ben
I was thinking of running some Mundorfs across them but I'm not sure of the best values or whether I should do it at the PCB or cap terminals. I've heard rules of thumb quoted of 0.1%, 1% and 10% or even all three.
Also, is it worth bypassing the 1000uF filter caps?
Cheers,
Ben
Brent, I think Ben means 10% of the main cap value in uF, ie. 1000uF (not capacitance tolerance).
I think the problem with the typical 100nF sort of range bypass caps is a) their impedance is too high for them to work properly and b) they only act at very high frequencies causing an uneven impedance curve - this can be alleviated with a series resistor, something like 1-5R. There is a thread on here showing scope measurements of different bypass caps.
I would suggest 100uF or 1000uF BG to try. And if you can get a film cap right up next to the transistors that is also a good move.
I think the problem with the typical 100nF sort of range bypass caps is a) their impedance is too high for them to work properly and b) they only act at very high frequencies causing an uneven impedance curve - this can be alleviated with a series resistor, something like 1-5R. There is a thread on here showing scope measurements of different bypass caps.
I would suggest 100uF or 1000uF BG to try. And if you can get a film cap right up next to the transistors that is also a good move.
I knew what he meant!
I was suggesting the 2% Mundorfs as they work very well in those positions and have a good ESR figure that will no doubt be much better than the BG. I would not want to strap a cap across a decent BG like those and add something worse in terms of esr and ripple rejection
Brent
I was suggesting the 2% Mundorfs as they work very well in those positions and have a good ESR figure that will no doubt be much better than the BG. I would not want to strap a cap across a decent BG like those and add something worse in terms of esr and ripple rejection
Brent
Thanks guys. I looked at what was available to implement Brent's suggestion and ended up trying Mundorf 1uF/1000v SO and 0.1uF/1200v SGO in my shopping cart for size. Overkill? They're pricy, but so were the BG. I think I can get more certain gains elsewhere for that kind of investment.
As per Simon's suggestion - well, I don't have many Black Gates left (who does?), but I do happen to have a couple of 100uF/50V "K" to hand... which is interesting! (Are K as good as FK? I can't remember). They're just lower than the 56v specified rating for the smoothing caps. What do you think?
As per Simon's suggestion - well, I don't have many Black Gates left (who does?), but I do happen to have a couple of 100uF/50V "K" to hand... which is interesting! (Are K as good as FK? I can't remember). They're just lower than the 56v specified rating for the smoothing caps. What do you think?
Cool! That's nice to hear, especially because I forgot I had them. If they work out, I could look at bypassing them with 0.1uF Mundorf SGO.
I didn't see where you put your bypass caps in your amp, Brent. One concern I have is that my FKs are connected by quite a few cm of Kimber TCSS, which looks considerably thinner than the wires you used for your Silmics.
Do you guys have an opinion on whether it's best in this case to run the bypass caps right across the main cap terminals after the wires so the impedance is matched for both - which also happens to be the easiest thing in the world to try - or should I be soldering them right on the PCB?
I didn't see where you put your bypass caps in your amp, Brent. One concern I have is that my FKs are connected by quite a few cm of Kimber TCSS, which looks considerably thinner than the wires you used for your Silmics.
Do you guys have an opinion on whether it's best in this case to run the bypass caps right across the main cap terminals after the wires so the impedance is matched for both - which also happens to be the easiest thing in the world to try - or should I be soldering them right on the PCB?
I fitted the mundorfs across the smoothers as it was much easier to do. I used a large gauge wire to eliminate current drop, a twin pair of kimber per run should be ok too. It is very good cable
Brent
Brent
I was wondering if I should do another run of Kimber. That sounds like a plan. I fitted the 100uF Ks between the smoothing cap terminals last night and my initial impressions were mixed - then I remembered how long it takes new Black Gates to settle down, so I'll leave them there for a few days before I decide if they're staying.
I ended up braiding 3 runs of Kimber TCSS together (3TC?) and terminated with some nice gold plated OFC spades. I'm still not sure about the snubbing.
Maybe the excellent caps you already had are the most coherent option to use. The other nice bits can probably be used elsewhere so no great loss if it doesn't provide a sound you prefer.
3TC would be 6 litz wires, 3 for positive, 3 for negative 🙂
3TC would be 6 litz wires, 3 for positive, 3 for negative 🙂
Hi Simon,
Yep, I did three runs of TCSS Red/Black Twist per cap, so that's 3 wires per terminal; 6 wires per cap. It made a big difference, either/or because the wire was too thin before or the connection wasn't good enough.
I left a bit of bare wire showing so I could try the bypass nearer the PCB, and swapped the 50v Ks for some 100v FKs so they'd be better matched, but I haven't tried them yet. My OCD wants me to build a 11111.1uF bypass cascade from BGs and Munforf Supremes, but I wouldn't be surprised if my big FKs sound best working alone. Perhaps their mysterious 'electron transfer' properties negate the need for bypass...
Ben
Yep, I did three runs of TCSS Red/Black Twist per cap, so that's 3 wires per terminal; 6 wires per cap. It made a big difference, either/or because the wire was too thin before or the connection wasn't good enough.
I left a bit of bare wire showing so I could try the bypass nearer the PCB, and swapped the 50v Ks for some 100v FKs so they'd be better matched, but I haven't tried them yet. My OCD wants me to build a 11111.1uF bypass cascade from BGs and Munforf Supremes, but I wouldn't be surprised if my big FKs sound best working alone. Perhaps their mysterious 'electron transfer' properties negate the need for bypass...
Ben
I've broken it!
CD63 thread readers will know that I've been unhappy with the bass/treble balance of my CD player for a few days and I've been trying to pin it on my last mod to remove the DC coupling caps. Anyway, last night the plot thickened when I realized that the sound was getting worse by the day - it was distorting with any kind of work, and deep bass had completely disappeared. Futhermore, it was actually now noticeably affecting other sources as well. I tried playing some 'Gorillaz' and it had almost no bass at all where normally it would rattle the windows, at which point I realized my amp was losing its balls at an alarming rate...
So, on a hunch, I decided to switch my big cap connection back to bare wire just in case the spades I put on were adding too much impedance. I checked everything over and put it all back together again... but things continued to take a turn for the worse.
Now when I turn it on there is a loud hum in the right channel that gets quieter if I turn the volume up. If I play music, the right channel sounds like crap and the left channel is completely dead.
If I turn it on without the input from the pot connected to the main board, a loud mains-like hum comes out of the LEFT channel and gets louder and louder very quickly until the protection relay kicks in.
I checked that both channels of input signal are making it to the main board. I checked all my joints and measured the resistance of everything I could think of, but just can't see anything wrong.
CD63 thread readers will know that I've been unhappy with the bass/treble balance of my CD player for a few days and I've been trying to pin it on my last mod to remove the DC coupling caps. Anyway, last night the plot thickened when I realized that the sound was getting worse by the day - it was distorting with any kind of work, and deep bass had completely disappeared. Futhermore, it was actually now noticeably affecting other sources as well. I tried playing some 'Gorillaz' and it had almost no bass at all where normally it would rattle the windows, at which point I realized my amp was losing its balls at an alarming rate...
So, on a hunch, I decided to switch my big cap connection back to bare wire just in case the spades I put on were adding too much impedance. I checked everything over and put it all back together again... but things continued to take a turn for the worse.
Now when I turn it on there is a loud hum in the right channel that gets quieter if I turn the volume up. If I play music, the right channel sounds like crap and the left channel is completely dead.
If I turn it on without the input from the pot connected to the main board, a loud mains-like hum comes out of the LEFT channel and gets louder and louder very quickly until the protection relay kicks in.
I checked that both channels of input signal are making it to the main board. I checked all my joints and measured the resistance of everything I could think of, but just can't see anything wrong.
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