Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Topic started by: Anaconda on July 11, 2022, 10:46:51 AM

Title: Headphone connection
Post by: Anaconda on July 11, 2022, 10:46:51 AM

I have the original mono blocks no headphone socket
I've connected my hd 650's to the speaker out ! ....they sound pretty good but I'm getting a very audible hum especially when no music is being played ....Is there a fix or is it a non starter ?

Title: Re: Headphone connection
Post by: Paul Birkeland on July 11, 2022, 10:55:10 AM

Which monoblocks?

Title: Re: Headphone connection
Post by: Anaconda on July 11, 2022, 01:03:21 PM

Para-Sex

Title: Re: Headphone connection
Post by: Paul Birkeland on July 11, 2022, 01:59:49 PM

If these are all original, it wouldn't hurt to replace the power supply capacitors, but these were not intended to be used with headphones.

Title: Re: Headphone connection
Post by: Anaconda on July 12, 2022, 12:35:20 AM

Ok cheers ....there is no noise when connected to speakers so other than the hum with headphones I'm happy to enjoy them . I use them with Promitheus TVC and for a little more gain a Croft vitale (UK) valve pre amp.

Title: Re: Headphone connection
Post by: Paul Joppa on July 12, 2022, 05:29:00 AM

There is a good chance that replacing the 10uF 450v and 47uF power supply capacitors with larger (100uF 450v?) units will reduce the hum significantly. The original caps are now quite old, and modern electrolytic caps are much better than what was available back then.

There may be some other changes that are worthwhile - we've learned a few things in the last 25 years! Which power transformer do you have? If you are not sure, a photo of the underside wiring will help.

Title: Re: Headphone connection
Post by: Anaconda on July 12, 2022, 12:07:06 PM

Yes it's probably time it had a service ... I'll check the transformers when I get home. From memory the caps are little on the small size compared to the latest units

Title: Re: Headphone connection
Post by: Anaconda on July 13, 2022, 09:08:44 PM

Hope this helps

Title: Re: Headphone connection
Post by: Paul Birkeland on July 14, 2022, 04:08:46 AM

That's very tidy for that vintage of kit! You have the Deyoung power transformer.  I would definitely grab some fresh electrolytic caps.  Something like this would be lovely and very long lived:
https://www.mouser.com/ProductDetail/KEMET/ESU107M450AN9AA?qs=HXFqYaX1Q2xqLzZAhsqNoA%3D%3D (https://www.mouser.com/ProductDetail/KEMET/ESU107M450AN9AA?qs=HXFqYaX1Q2xqLzZAhsqNoA%3D%3D)

Title: Re: Headphone connection
Post by: Anaconda on July 14, 2022, 04:55:08 AM

Ok...will do, they are amazing amps.
Thanks for your help...the Crack is on the horizon
as a future project .

Title: Re: Headphone connection
Post by: Doc B. on July 14, 2022, 05:54:46 AM

Wow that's kinda historical. Mid-late 90s.

Title: Re: Headphone connection
Post by: Anaconda on July 15, 2022, 03:10:36 AM

A top view