Hello, I finished the K2573 phono preamp. First of all: thank you for this nice kit.
but I like to place an extra capacitor from de + to- rail of the opamp.(de-coupling)
Is there a reason this wasn’t done in the particular developement?
Don’t mind the extra modifications…this isn’t a modification question…(Ichanged some components…but that’s just a personal choice…no remark on the k2573 kit…i like velleman kits
I only would like to know if there is any reason for not de-coupling the positive and negative opamp rail.
To be honest, we do not know.
This circuit is a true classic. It has been developed more than 25 years ago.
The people that developed it are no longer with our company.
It cannot harm to put extra caps from the rails to the GND.
Btw: nice pics.
Personally, I’d recommend to run the kit from two 9V batteries in series, a guarantee for hum free operation.
[quote=“VEL417”]To be honest, we do not know.
This circuit is a true classic. It has been developed more than 25 years ago.
The people that developed it are no longer with our company.
It cannot harm to put extra caps from the rails to the GND.
Btw: nice pics.
Personally, I’d recommend to run the kit from two 9V batteries in series, a guarantee for hum free operation.[/quote]
Great !!!
When i compare it to a build in phono amp of an older receiver. Your’s is way better!!!
Offcourse there are a few minusses such as elco’s in signal paths. This is better not done…but poeple who build this kit know that price will rise if you use film cap’s instead. For example…for audio coupling (@ RAC plug’s) I used MKS types. Also not the audiophile ones, but that’s something I also not beleive in
The opamp…TL072 is ok no hard need to put in a burr-brown. but for almost the same price…it is better to put in a NE5532. When I received another kit (stereo preamp with tone control…there was a NE5532 in instead of the TL072 as shown in the schematics…so it has to do with the batch it comes from) Using the NE5532 in stead of the TL072 does give a difference.
I’m gonna try the 9V batteries in series. I think that will remove the little hum (high freq.) when turning lots of power without a vinyl beeing played.
Believe me…by making tests…this is a nice kit!!! As always I’m happy with Velleman kits.
This weekend I’m gonna do some scope measurements and I’m positive in advance
By offering these little kits, Velleman gives a great oppertunity to poeple who would like to learn, test, measure …
I built the very same phono preamp kit from Velleman, I agree on the quality for the price, and also that it is so tiny !
Your suggestions on improving the preamp are interesting, did you try any ? I am wondering if changing the opamp, resistors and capacitors could help in any way.
I’ve build this kit to connect my old Philips record player to my new Harman Kardon Home cinema set.
All I hear is humm, no record sound. I don’t now what I did wrong. Someone got an Idea?
no hard need to put in a burr-brown. but for almost the same price…it is better to put in a NE5532. When I received another kit (stereo preamp with tone control…there was a NE5532 in instead of the TL072 as shown in the schematics…so it has to do with the batch it comes from) Using the NE5532 in stead of the TL072 does give a difference.