Wanting to increase bass response in KEL84

[robaustralia]

I built a KEL84 2 years ago and have upgraded to the Alps Blue pot which is sounding great.
I have just built a high quality VAF speaker kit with a very flat response from 40kz up. At medium volume the sound is magic and the bass is present but it lacks weight. These speakers are renowned for their bass response.
I've been told that replacing C3 (100mfd) with a 220mfd or 470mfd will beef up the bass without affecting the transparency.
Will this help?

Thanks,
Rob

[jimangus]

Hi rob in oz,

i have just replaced c1,c2 and c3 with high ripple low esr type 150mfd caps in my kel. The effect is that bass is a little more prominant however i would say it has more of an effect on the bass grip, this inturn helps with the seperation of instruments. I don't know about putting something as large as a 470mfd in there would be advisable, on the old bb some one did tell me it can have a detrimental effect if you go too large.

Replacing all the power caps is a worthwhile mod. Do it and tell us what you hear.

Jim

[Greg.]

Hi Rob/Jim,

Hmmm, I know the specific application is relative, but my understanding is that generally, the lower the value of the coupling cap, the more bass will be exposed. Are we talking coupling? have I got this completely wrong?

Best wishes,

Greg

[david counter]

Greg
I think they're talking power supply

[jimangus]

Originally Posted by Greg.

Hi Rob/Jim,

Hmmm, I know the specific application is relative, but my understanding is that generally, the lower the value of the coupling cap, the more bass will be exposed. Are we talking coupling? have I got this completely wrong?

Best wishes,

Greg

Hi greg,

yes c1 to c3 on the kel are the power caps.
However interesting piont made about the coupling caps, does changing this value have any other effects? Perhaps using some 0.2uf reasonable quality coupling caps as aposed to 0.22uf may be an option, if it turns out disasterous he could then bypass with a suitable small value (poss silver mica) cap to make up the value.



Rob,
in order to fully advise could you let us know what the current state of modification of your amp ?


regards
jim

[robaustralia]

Hi Jim.

The only mod I have is a 22mfd 630V Poly in parallel with R28 which makes the sound a little warmer with the AlpsBlue pot.

Unfortunately, I'm 150kms from Brisbane and can't get any exotic components so I'll try with what I can get.

Cheers,
Rob

[jimangus]

Originally Posted by robaustralia

Hi Jim.


Unfortunately, I'm 150kms from Brisbane and can't get any exotic components so I'll try with what I can get.

Cheers,
Rob

Hi rob,

you must be able to get bits from rs or farnell delivered?

Ok mods using rs components or farnell,
replace d1-d4 with suitable 1000v 3a schotckies.
replace c1-c3 with 150uf high ripple caps
build the shotckies bridge rectifier mod
lower the feed back as per the faq
replace those coupling caps c8-c11 with some polypropes

to make it a bit warmer you could strap it to triode operation, this will only give you about 6watts but the sound ill be lovely.

Can anybody remember how to do this ???

Jim

[robaustralia]

Hi Jim.

I managed to find the only 220Mfd 400V Electrolytic within 150kms. No idea what make but it cost AUD$9.
I just replaced C3 in the power supply and bingo.
An extraordinary transparent almost subniminal bass has appeared. Not muddy or tiring just another layer of exquisite sound. No doubt I could do more but I'm a happy chappy now.
Thanks.
Cheers,
Rob

[jimangus]

Thats fantastic news rob.

How long untill you get itchy fingers again is another thing however

You could try making it into a pentode at some point as this doesn't require any component. Look at the faqs for info.


Shurely someone must remember how to do the triode mod on the kel. I may try it again if my grey cells will recall it.