Densen amp

[tiefbassuebertr]

Thank you Jacco and Tiefbassuebertr,
I do hope my trusty Dynaudio Contours will survive the fault (yes, it was a Danish connection regarding output stage of the audio chain even if with Mundorfs it would be German juiced ).

I still have to measure voltages, but resistor colors seems to me brown-gold-black-black-red and I seem I see two areas on the board marked as "Protection Timer".

Thank you all, again,

Stefano

the colors are to be read in reverse order - this means 20 ohms per resistor/0R2 at whole (twice my estimate value).
After dismanteling the PCB you should make (drawn) a schematic diagram - the topology must actually be similar to those from the PDF attachment.

 

[seppstefano]

Forgive my ignorance again: what does 0R2 mean?

Anyway, I read 48v between output black binding post and center leg of 2SC2922.

More, I saw a film WIMA cap quite near one of the lytics. It seems to me a bypass cap (1uF/63V). So, would perhaps 63V be a sufficient rating for the electrolytics? BTW The size of each cap is rather small (L: around 30mm, H: around 48mm).

I couldn't yet measure a meaningful value for voltage across the ten resistors... (don't know why).

Thanks for your support

Stefano

 

[jacco vermeulen]

0.2 Ohm (R for Resistance)

 

[seppstefano]

Thank you

I'm just looking for lytics on Mouser. Mundorf seems really expensive and with too high capacitance (MLytic HC starting from 22000uF), what about United Chemi-Con 10000/63 with code ESMH630VNN103MR50T? It should have an interestingly low ESR (0.025). Any experience on such component (it is 30X50mm and so would fit the tight space in caps array)?

Any other advice is welcome!

Stefano

 

[seppstefano]

Ahem, I must be either blind, or too dumb, or both of them, anyway M-Lytic Audio Grade should fit with 10000uF and 30x40, but they're rated only 50V...

BTW, I found an interesting thread here: http://www.diyaudio.com/forums/parts/126982-who-make-best-10-000uf-capacitors-9.html#post1685109

 

[tiefbassuebertr]

Ahem, I must be either blind, or too dumb, or both of them, anyway M-Lytic Audio Grade should fit with 10000uF and 30x40, but they're rated only 50V...

you need at least 63V for your supply voltage of 48V. Capacitance-value isn't critical. But a 50V electrolytic capacitor version will reduce the lifetime dramatically.
according
http://www.mundorf.com/deutsch 1.1/kondensatoren2.htm
and your mentioned sizes (dxh) the 4700uF, 6800uF and 8200uF you can use.

In general - avoid caps with high CV product (CV = product of the capacitance and the volume)
and use 105°C versions for a longer life time; more examples:
Bestellen Sie Aluminium Kondensator 4700uF 63V Evox-Rifa PEH536MCF4470M3 online mit versandkostenfreier Lieferung bei RS Components.
http://docs-europe.electrocomponents.com/webdocs/017d/0900766b8017d284.pdf
Elettrolitici SLP 105degC Snap-in Cap 3,300uF 63V Cornell-Dubilier SLP332M063E3P3 consegna in 24 ore
http://docs-europe.electrocomponents.com/webdocs/0fe5/0900766b80fe5e5e.pdf
By this sizes this will be also good choice, if your amp don't run too hot::
Bestellen Sie Aluminium Kondensator 4700uF 63V Kemet-BHC ALP22A472BB063 online mit versandkostenfreier Lieferung bei RS Components.
http://docs-europe.electrocomponents.com/webdocs/00ac/0900766b800acc4c.pdf

If you want to use really good caps, you must create an outdoor power supply because at the required low size (30x45mm) the quality is limited.
check out this thread:
http://www.diyaudio.com/forums/parts/151392-best-electrolytic-capacitors.html

 

[seppstefano]

Ok,
many thanks for your great advices. I'll read them carefully.

Honestly I don't know if the whole power amp is worth a huge investment in top quality caps. I mean I can't judge how much will the global sound take advantage of top parts since perhaps its bottlenecks are somewhere else, while an outboard PSU might impair the value of the unit if/when resold.

Of course your advice would be more than welcome... (when perfectly fixed, I might anyway look for a "better" power amp).

 

[seppstefano]

As a follow up for who eventually cares, I have uploaded on Dropbox some photos of the guts of my DM30. If interested, please let me know.

BTW Any hint on where to source some thermal compound? A 300cc jar for more than 60 EUR as on Mouser sounds too big and a bit too expensive, too.

Best wishes for your summer vacations,

Stefano

 

[tiefbassuebertr]

Densen DM20 Preamplifier

For this amp I am looking for a schematic.
Thank you for upload.
Obviously this line stage consist only of a buffer stage (push-pull or single ended emitter/source follower include current source) - go to the attached images, that I have found on the web.
At the pdf image I note an additional EPROM section, but no motor for the volume control.
Maybe for a good morning song after switch on ?

Faulty Densen DM20
Densen DM20 Preamp Photo by rotti15 | Photobucket
??????????Densen B-200????? - U-Audio ????

 

[tiefbassuebertr]

For this amp I am looking for a schematic.
Thank you for upload.
Obviously this line stage consist only of a buffer stage (push-pull or single ended emitter/source follower include current source) - go to the attached images, that I have found on the web.
At the pdf image I note an additional EPROM section, but no motor for the volume control.
Maybe for a good morning song after switch on ?

No. This section perform the same after switch-on than this compact disc:
Densen Audio Technologies - Densen CD Magic

 

[tiefbassuebertr]

Ok,
many thanks for your great advices. I'll read them carefully.

Honestly I don't know if the whole power amp is worth a huge investment in top quality caps. I mean I can't judge how much will the global sound take advantage of top parts since perhaps its bottlenecks are somewhere else, while an outboard PSU might impair the value of the unit if/when resold.

Of course your advice would be more than welcome... (when perfectly fixed, I might anyway look for a "better" power amp).

any news?

 

[limono]

No. This section perform the same after switch-on than this compact disc:
Densen Audio Technologies - Densen CD Magic

 

[limono]

Tief , so this additional section of DM 20 is providing a demagnetization of entire audio chain ?