I can agree with you on that point. I still use use my original "turd". We all start some where.
New transformers can be had from Edcor as was an intention which the OP was considering which can be used in a future project. Their performance cannot be beat for the price. You have to wait 4 to 6 weeks to get them.
New transformers can be had from Edcor as was an intention which the OP was considering which can be used in a future project. Their performance cannot be beat for the price. You have to wait 4 to 6 weeks to get them.
Can't Google up a schemo for this. gNFB? lNFB? g/lNFB?
What I've found from experience is that capacitors inside a gNFB loop make no difference. This is to be expected since one of the reasons you use NFB is to make the performance less dependent on the passive/active components used to implement the open loop gain.
Outside the loop, it's a different matter, but by how much is debatable. For sensitive signal paths (outside any NFB loop, or part of the NFB) I tend to favour the AuriCaps: they're not priced absurdly, and sound good. You might be able to pick up other polypropylene film capacitors for less, and if you can, get those instead.
Here it is:
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You guys are making this a Hard decision for me, I keep questioning if I should spend roughly $100 dollars on the Edcors OPT's.
Rob43
It shouldn't be that hard. You have a design that's full-on gNFB. That is going to have a significantly greater influence on how it sounds than those two coupling capacitors, and there is no need to go all audiophool over it. AuriCaps, or Solen FastCaps, or any other good quality plastic film capacitors will be fine here.
You'd be better off saving the money, and applying it towards output iron. That's gonna make a bigger difference here. I've used Hammonds before, but can't say I'd still recommend them, not after the QC issues they've been having lately. I also got some good results with a NiB Stancor OPT that fit a project quite well, only coming up a bit short on the power (30W rating with finals that could do nearly 40W). I'd say go wit the Edcor's here.
What would make the biggest difference of all, however, would be redesigning the power supply. Replace that RC ripple filter with an LC ripple filter and you'll get much improved regulation, and double the ripple suppression. You should have one LC filter for each channel instead of running both in parallel from one ripple filter.
In for a penny in for a pound.
After more research & a great PM, I've ordered the Edcor CXPP10-MS-10K opt's, hopefully I'll get them within the next 6 weeks. My plan concerning these upgraded opt's is to install them after I've listened to the stock amp for awhile, this way I'll hopefully be able to hear a difference. Still trying to figure out the caps for the C2, C3, C6, & C7 location, but the leading contender is the Z-Superior for $10 each.
Rob43
After more research & a great PM, I've ordered the Edcor CXPP10-MS-10K opt's, hopefully I'll get them within the next 6 weeks. My plan concerning these upgraded opt's is to install them after I've listened to the stock amp for awhile, this way I'll hopefully be able to hear a difference. Still trying to figure out the caps for the C2, C3, C6, & C7 location, but the leading contender is the Z-Superior for $10 each.
Rob43
Hi, For what it is the amp is OK, trying to extract a lot of quality sound from it gets costly quickly. I would opt for the CXPP10-MS-10K trannies and Russian K40Y9s in .22uf (just 4...skip the input ones). Replacing the cheap rectifiers with UF4005s would be worthwhile as they are cheap. Pass on everything else. Having modded a few in the past, it just is not cost effective to do much more. The schematic shows an amp made from a K12 just for the fun of it. It has excellent performance and shows what can be done. Not for the faint of heart as there are numerous changes. It was fun seeing what could be done to the K12 to make it sound like I thought a real amp ought to. The squares are perfect in the mid band and quite good even in the bass region. The biggest issue is that it can only deliver 3.5 watts RMS per channel. The square wave is at 20KHZ.
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Bruce, thanks for coming in.
When you say "skip the input ones", do you mean use the caps that come in the kit or run a jumper wire at the C1 & C4 location ?
These K40Y9 0.22uF 1000v ? Also, if I use the cheaper shipping, will they really take 40-60 days to arrive in the U.S. ?
K40Y-9 0.22uF 1000V PIO capacitor K40Y9 K40U9 .22uF 1kV - ruTubes.com tubes and capacitors store
Thanks,
Rob43
Hi, considering that the actual voltages on the caps are relatively small and the Russian K40s are rather robust I would probably use the 0.33uf / 200 volt ones. If you want though the 0.33uf /400volt ones are plenty sufficient. Both are a lot smaller than the ones you picked. The input capacitor, the 0.22uf that is right in front of the volume control is seldom needed. It is there primarily to block any DC that might accompany the input signal. Since most equipment that can have significant DC on the output already has blocking capacitors the one in the amp is redundant. I have worked with numerous pieces of equipment and have not seen any with significant DC at the outputs for a long time. Unless you have something odd, skip the input capacitors. Less stuff in the signal path virtually always results in better sound. The reason for the 0.33s is they are usually easier to get and cheaper than the 0.22s.
BTW if you are on a tight budget the Edcor GXPP10-6-10K transformers work rather well in these amps and are quite inexpensive (last time I looked they were under $20 each). You will lose a little in the sub 40HZ range, but otherwise pretty clean sounding to about 18K.
BTW if you are on a tight budget the Edcor GXPP10-6-10K transformers work rather well in these amps and are quite inexpensive (last time I looked they were under $20 each). You will lose a little in the sub 40HZ range, but otherwise pretty clean sounding to about 18K.
I ordered the Edcor CXPP10-MS-10K last week, so that's a done deal. As far as the K40Y9's, the two best deals I've found on them are:
1) 0.22 1000v, $16.50 shipped for 4 of them.
K40Y-9 0.22uF 1000V PIO capacitor K40Y9 K40U9 .22uF 1kV - ruTubes.com tubes and capacitors store
2) 0.22 400v, $18.00 shipped for 4 of them.
K40Y-9 400V 0.22uF PIO capacitor - <font color='red'>400V - 750V</font> - Tubes-Store.com
Is there a preference of one over the other between these two choices ?
Space is Not a concern because I'm using a custom case to mount everything in.
Thanks,
Rob43
The only reason to pick one over the other is size. All the K40s are pretty large and the 1KV ones will be hard to mount on the PCB. I would use the 400V ones.
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