Havent modded but what I would do is swap out the cheap capacitors in the thing, in favour of decent makes eg Panasonic FC. There should also be room on the PCB to replace any electrolytic capacitors in the audio path with polyester ones. It looks like the PCB was designed with this in mind, and then they fitted cheap rubbish.
Swapping out the volume pot with a good one might be an idea too, but this might be hassle.
I wouldn't bother replacing the opamps - at least not with anything excessive. They usually have fairly primitive 7815/7915 power supplies around them. OPA2134 is as far as I would go.
Swapping out the volume pot with a good one might be an idea too, but this might be hassle.
I wouldn't bother replacing the opamps - at least not with anything excessive. They usually have fairly primitive 7815/7915 power supplies around them. OPA2134 is as far as I would go.
My 340A have the input dec. Caps on input stage, after the RCA-terminals (before the resistors).
What for they are placed there? if it good idea to place a peace of wire Instead of caps? If it's bad idea, then say somethng about placing there some MKP cap...
P.s. As i can see, 340SE also have them, but there are nothing there in service manual for 340a
WTF ?
What for they are placed there? if it good idea to place a peace of wire Instead of caps? If it's bad idea, then say somethng about placing there some MKP cap...
P.s. As i can see, 340SE also have them, but there are nothing there in service manual for 340a
WTF ?
Stream said:My 340A have the input dec. Caps on input stage, after the RCA-terminals (before the resistors).
What for they are placed there? if it good idea to place a peace of wire Instead of caps? If it's bad idea, then say somethng about placing there some MKP cap...
P.s. As i can see, 340SE also have them, but there are nothing there in service manual for 340a
The 340A service manual seems slightly different in the layout, but its good as a guide. Those input caps are worth upgrading. However, as your source components allready have decoupling caps on their outputs (you should check this) I would say your ok to link them out. The 340 has alot of decoupling caps at different stages of the signal path. Just before the input buffer, in the tone/tone bypass circuit, and just before the power stages. Something I plan to do is check for DC on the output of the input selector chip and if its low enough link out the caps. Again, if the output of the input buffer is free from DC, remove the decoupling caps. ( I changed to input buffer opamp toi LM4562 which gives out nearly no DC.)
If your not using the tone circuit then leave it alone. You can then just remove decoupling caps in the tone bypass. You should only do this if you have a meter to check for DC at various points of the signal path. Im not certain what is an acceptable level of DC but I would say at a guess .0005v would be great.
I would say IMHO to keep at leat one cap per channel to be safe. Just find a good place to put it (where DC is highest - maybe after the selector chip).
I am a beginner so you should verify this with someone more experienced.
Good luck!
340A Power amp and PSU modding:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=131847&highlight=
http://www.diyaudio.com/forums/showthread.php?s=&threadid=131847&highlight=
I have just found a full service manual for this amp if anyone's interested?
http://www.eserviceinfo.com/download.php?fileid=40495
Towards the bottom of the page it says " Download >> To download the file, please, click here ! << Download "
Sounds obvious but was quite tricky to spot where the link was on the page!
http://www.eserviceinfo.com/download.php?fileid=40495
Towards the bottom of the page it says " Download >> To download the file, please, click here ! << Download "
Sounds obvious but was quite tricky to spot where the link was on the page!
Having got the service manual for the 640A I've devised a plan for upgrades.
1. Replace 8 x 2200uF smoothing caps in the power supply with Panasonic 3300uF M series (couldn't find any larger that would fit in the standard positions)
2. Replace 8 x 220uF decoupling caps in power amp with Panasonic 220uF M series.
3. Replace rubbish volume pot for Alps Blue Velvet motorised 10k log. Might need to add a 10K resistor in series to bring it to the original 20K value and this will also usefully reduce the range of the pot.
4. Remove headphone wiring and speaker B wiring. (never used anyway!)
5. Rewire speaker and power supply cabling with something thicker.
That's for starters. In the future I might bypass the long signal PCB traces with screened cable and also bypass the tone control/balance circuitry.
I bought the amp non-working on eBay for £55, lucky me all it needed was a fuse! It sounds pretty good but a bit weak in the bass and slight sibilance in the treble. Could the NP input caps be responsible for the lack of bass? I've read they tend to deteriorate quite quickly.
Any comments or suggestions for further mods?
Cheers,
Matt
1. Replace 8 x 2200uF smoothing caps in the power supply with Panasonic 3300uF M series (couldn't find any larger that would fit in the standard positions)
2. Replace 8 x 220uF decoupling caps in power amp with Panasonic 220uF M series.
3. Replace rubbish volume pot for Alps Blue Velvet motorised 10k log. Might need to add a 10K resistor in series to bring it to the original 20K value and this will also usefully reduce the range of the pot.
4. Remove headphone wiring and speaker B wiring. (never used anyway!)
5. Rewire speaker and power supply cabling with something thicker.
That's for starters. In the future I might bypass the long signal PCB traces with screened cable and also bypass the tone control/balance circuitry.
I bought the amp non-working on eBay for £55, lucky me all it needed was a fuse! It sounds pretty good but a bit weak in the bass and slight sibilance in the treble. Could the NP input caps be responsible for the lack of bass? I've read they tend to deteriorate quite quickly.
Any comments or suggestions for further mods?
Cheers,
Matt
Sound like a good place to start.
-Don't forget the feedback caps on the poweramps, makes quite alot of difference. Try Elna silmic or even Wima 22uf MKS2-XL.
-The opamp in the preamp section, try some better alternatives and be sure to experiment with the local supply decoupling caps when doing this so you get the best out of each opamp you try. I'm using LM4562 in my 340A with 1uF BG N fro local decoupling, good results.
-Another important area to consider is the DC blocking caps in the signal path. Usually there will be several cheap electrolytic caps, many of which can be bypassed completely with a wire link. You need to keep at least 1 pair at the preamp input and the poweramp input. Use wima polyester film caps for neatness, they will fit the board nicely and sound way better. You could also use MKP's but they will be awkward to fit and could pick up RF interference, but any film capo will beat the the stock lytic caps.
-Don't forget the feedback caps on the poweramps, makes quite alot of difference. Try Elna silmic or even Wima 22uf MKS2-XL.
-The opamp in the preamp section, try some better alternatives and be sure to experiment with the local supply decoupling caps when doing this so you get the best out of each opamp you try. I'm using LM4562 in my 340A with 1uF BG N fro local decoupling, good results.
-Another important area to consider is the DC blocking caps in the signal path. Usually there will be several cheap electrolytic caps, many of which can be bypassed completely with a wire link. You need to keep at least 1 pair at the preamp input and the poweramp input. Use wima polyester film caps for neatness, they will fit the board nicely and sound way better. You could also use MKP's but they will be awkward to fit and could pick up RF interference, but any film capo will beat the the stock lytic caps.
Thanks very much for your suggestions.
The feedback cap is currently a 100uF NP. I've been doing a bit of reading of this thread and now I'm not sure what to try!
www.pinkfishmedia.net/forum/showthread.php?t=61242
Regarding the input caps, I guess I will need to stick to the original 10uF so I don't loose low frequency response? A poly cap of this value is physically pretty big and there's very little room on the pcb for it! maybe there's more room in the 340A?
The feedback cap is currently a 100uF NP. I've been doing a bit of reading of this thread and now I'm not sure what to try!
www.pinkfishmedia.net/forum/showthread.php?t=61242
Regarding the input caps, I guess I will need to stick to the original 10uF so I don't loose low frequency response? A poly cap of this value is physically pretty big and there's very little room on the pcb for it! maybe there's more room in the 340A?
skidude said:
I tried the 22uf wimas even though my amp is completey different to the Naim most of those guys are modding. It had a great effect in my amp. I much prefer the bass response with this cap over that of the 100uF Rubycon ZL lytics I had tried previously. Physically they arent that big and have a 5mm lead spacing, they should hopefully fit. The wma MKS2-XL also come in 10uF so might be worth a try for the signal path dc blocking. I used 3.3uF wimas and have no loss of bass. However I do have TL speakers so maybe that helps. Why not ask on Pinkfish?
EDIT: Just to give you an idea of the size of the wima caps. The large square red ones are the 22uF and the smaller square ones are the 3.3uF.
I got some from a friend on Pinkfish. I had trouble finding them myself. Perhaps try asking wima direct, maybe you can get some free samples?
EDIT:
some info http://www.diyaudio.com/forums/showthread.php?s=&postid=1813975#post1813975]here,[/URL] also try asking a DIYA user called 'Pacificblue'. Hes in Germany where the wimas are made and he recently got some for a guy in Russia, maybe he can get you some.
EDIT:
some info http://www.diyaudio.com/forums/showthread.php?s=&postid=1813975#post1813975]here,[/URL] also try asking a DIYA user called 'Pacificblue'. Hes in Germany where the wimas are made and he recently got some for a guy in Russia, maybe he can get you some.
The 3.3uF are available from Farnell:
http://uk.farnell.com/wima/mks2-3-3uf-10-50v/capacitor-3-3uf-50v/dp/107423
Mouser do the 10's and 22's:
http://gb.mouser.com/Search/Refine.aspx?N=254297&Keyword=wima+mks2xl&FS=True
http://uk.farnell.com/wima/mks2-3-3uf-10-50v/capacitor-3-3uf-50v/dp/107423
Mouser do the 10's and 22's:
http://gb.mouser.com/Search/Refine.aspx?N=254297&Keyword=wima+mks2xl&FS=True
Thanks again for your help Mike.
I didn't realise just how expensive those caps were, £6.80 for the 22uF?!! The mark-up on those must be immense!
I might try for some samples, they'll get suspicious when I tell them I work for Nokia! I could always tell them they're for a charger though!
Today the Panasonic caps arrived so I've been busy fitting those. They fitted perfectly. I'm a bit disappointed with the build quality of this amp though. There are 11 wires underneath the main amp PCB!
Most of the small transistors were crooked and the assy worker must have used a whole reel of solder on it.
It looks a lot better now though. I'm just waiting for the Alps pot to come from Germany and hopefully get a few 10uF and 22uF Wimas in before reassembling. Getting the Alps to fit will be fun! ;-)
I see you changed your speaker posts in your 340. Mine are very flimsy and have horrible long thin posts that are in the signal path. They'll have to go!
I didn't realise just how expensive those caps were, £6.80 for the 22uF?!! The mark-up on those must be immense!
I might try for some samples, they'll get suspicious when I tell them I work for Nokia! I could always tell them they're for a charger though!
Today the Panasonic caps arrived so I've been busy fitting those. They fitted perfectly. I'm a bit disappointed with the build quality of this amp though. There are 11 wires underneath the main amp PCB!
Most of the small transistors were crooked and the assy worker must have used a whole reel of solder on it.
It looks a lot better now though. I'm just waiting for the Alps pot to come from Germany and hopefully get a few 10uF and 22uF Wimas in before reassembling. Getting the Alps to fit will be fun! ;-)
I see you changed your speaker posts in your 340. Mine are very flimsy and have horrible long thin posts that are in the signal path. They'll have to go!
jaycee said:
Indeed. They look great in the catalogs and even the Hifi magazines claim they're well build but when you turn the PCB's over... I wonder how good their yield rates are? I wouldn't be surprised if customer returns are high. My amp was in a Richer Sounds Returns box labled "scrap" which was worrying at first. But it was only a blown fuse at fault.
I ran out of solder wick trying to rework the pcb, I must get myself a desolder pump!
My amp is back together now with mods 1 to 4 completed.
Fitting the Alps pot isn't easy though as the legs are in a different position and they sit very close to the surface of the PCB. I temporarily mounted the pot upside down and wired each pin to the pcb with short pieces of wire. Not ideal at all but it works. It's a motorised pot and it works well with the driver circuitry from the Cambridge. I'll improve this as I suspect it'll be degrading the sound.
No issues with blowing fuses. I had a selection ready just in case!
Apart from much better tracking (Alps) the sound appears to be fuller. The bass sounds deeper and more effortless. I'm surprised how loud it will go without sounding stressed.
Other parts of my system are;
Marantz CD63 KI sig CD, Rega Ela Mk2 speakers and some Chunky cables from eBay.
Fitting the Alps pot isn't easy though as the legs are in a different position and they sit very close to the surface of the PCB. I temporarily mounted the pot upside down and wired each pin to the pcb with short pieces of wire. Not ideal at all but it works. It's a motorised pot and it works well with the driver circuitry from the Cambridge. I'll improve this as I suspect it'll be degrading the sound.
No issues with blowing fuses. I had a selection ready just in case!
Apart from much better tracking (Alps) the sound appears to be fuller. The bass sounds deeper and more effortless. I'm surprised how loud it will go without sounding stressed.
Other parts of my system are;
Marantz CD63 KI sig CD, Rega Ela Mk2 speakers and some Chunky cables from eBay.