Hey guys, been awhile since i've been here!
Ran into a strange issue last night while re-connecting my Holfi battriaa phonostage to my toshiba sa7100.
I lost the left channel from the phono input side so i took the cover off and found the whole chassis to be microphonic. If i tap on the metal chassis it creates thumps from the speakers.
Some kind of grounding issue maybe? The holfi is grounded via mains earth using a spade connection. The toshiba SA7100 has recently had its reservoir caps replaced with Mundorf AG+ (4 pole), so i'm not sure if this has anything to do with it? From what i could gather the transformer centre tap is no longer used with the 4 pole caps.
The turntable (rega RP3) grounds through the phono plugs as far as i know and dosent have a separate ground connection.
Ran into a strange issue last night while re-connecting my Holfi battriaa phonostage to my toshiba sa7100.
I lost the left channel from the phono input side so i took the cover off and found the whole chassis to be microphonic. If i tap on the metal chassis it creates thumps from the speakers.
Some kind of grounding issue maybe? The holfi is grounded via mains earth using a spade connection. The toshiba SA7100 has recently had its reservoir caps replaced with Mundorf AG+ (4 pole), so i'm not sure if this has anything to do with it? From what i could gather the transformer centre tap is no longer used with the 4 pole caps.
The turntable (rega RP3) grounds through the phono plugs as far as i know and dosent have a separate ground connection.
The Mundorf AG+ caps are 4 pole, where as the old caps were 2. According to the spec sheet for the caps the ground is not tied to the CT.
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That is the only change for the amp.
I've not changed anything else with the phonostage or turntable.
Its running at high gain for a 0.4mv MC cartridge.
Edit: when i mentioned about CT no longer used, i meant it has no direct connection to the ground of the amp (apologies).
That is the only change for the amp.
I've not changed anything else with the phonostage or turntable.
Its running at high gain for a 0.4mv MC cartridge.
Edit: when i mentioned about CT no longer used, i meant it has no direct connection to the ground of the amp (apologies).
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OK, the CT is still used but now goes via the cap.
Look for something you changed or forget to reconnect when dismantling and re-assembling for the cap change.
It is just possible that something was relying on the track impedance (which you have now removed) to damp a resonance in the PSU. So-called 'RF snubber' or 'RF blocking' caps may rely on the nearby electrolytics being a bit lossy. Putting 'better' electrolytics in can create new resonances.
Look for something you changed or forget to reconnect when dismantling and re-assembling for the cap change.
It is just possible that something was relying on the track impedance (which you have now removed) to damp a resonance in the PSU. So-called 'RF snubber' or 'RF blocking' caps may rely on the nearby electrolytics being a bit lossy. Putting 'better' electrolytics in can create new resonances.
Looking at the schematic i found the CT and connected it as per the wiring for the new caps. In the bundle i found 3 connections for the output transistors on each rail, so connected these as per the wiring diagram. All other grounds were connected to the ground main wiring as per the diagram, not the CT.
OK, but the junction of the reservoir caps should have something connected to it too. Unless they want buzz due to charging pulses, the CT should connect to the cap junction. Then any ground should come from there, not the secondary. However, drawing this wrongly is quite common in commercial circuits; sadly, connecting it wrongly is not as rare as it should be.
Thanks DF96, i resolved the issue last night, it was nothing to do with the amp.
The holfi battriaa i have uses 3 pins at the back to select whether its MC or MM cartridge you are using. These pins are shorted with a small wire, rather than just using a switch. One of the solder joints was slightly loose so i reflowed it and no more feedback from tapping the casing.
Who would have thought!
The holfi battriaa i have uses 3 pins at the back to select whether its MC or MM cartridge you are using. These pins are shorted with a small wire, rather than just using a switch. One of the solder joints was slightly loose so i reflowed it and no more feedback from tapping the casing.
Who would have thought!
are there a schematic diagram available ?
What is the aim of the wooden parts (square edges made of solid wood) - go to the images under
www.avmentor.gr - Reviews: Holfi Batt2riaa phono preamplifier
What is the aim of the wooden parts (square edges made of solid wood) - go to the images under
www.avmentor.gr - Reviews: Holfi Batt2riaa phono preamplifier
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here a description and various images of this phono RIAA pre-amplifier (different versions):
http://www.pladespilleren.dk/Anmeldelser-tests/Kontravaegnet 2-2009_Batt2RIAA.htm
https://positive-feedback.com/Issue24/holfi.htm
A good approach is the avoid of switches for select MM and MC - instead this a soldered jumper.
What happen to HOLFI resp. the developer of this devices, Mr. Peter Holstein ?
And who have a schematic diagram ?
http://www.pladespilleren.dk/Anmeldelser-tests/Kontravaegnet 2-2009_Batt2RIAA.htm
https://positive-feedback.com/Issue24/holfi.htm
A good approach is the avoid of switches for select MM and MC - instead this a soldered jumper.
What happen to HOLFI resp. the developer of this devices, Mr. Peter Holstein ?
And who have a schematic diagram ?
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