Physical capactor sizing
Physical capactor sizing
(OP)
Hello,
I have acquired a vintage (1970s) transistor amp (Sinclair Project Stereo 60). Its a 50W stereo amp kit for general use.
Docs say it needs an output capacitor on the line out of each amp and the cap specified is 1000uf 63V "anything less may cause a reduction in bass".
The artwork shows a mighty large 1000uf cap (appx 100mm x 35mm, with axial leads). I'm a bit new to this but can I not just use a physically smaller 1000uf/63V capacitor, modern technology being able to scale size down over the last 30 years or so?
If its a ripple current thing, I have NO idea what ripple current is applicable on this unit.
Any help anyone?
Chris
I have acquired a vintage (1970s) transistor amp (Sinclair Project Stereo 60). Its a 50W stereo amp kit for general use.
Docs say it needs an output capacitor on the line out of each amp and the cap specified is 1000uf 63V "anything less may cause a reduction in bass".
The artwork shows a mighty large 1000uf cap (appx 100mm x 35mm, with axial leads). I'm a bit new to this but can I not just use a physically smaller 1000uf/63V capacitor, modern technology being able to scale size down over the last 30 years or so?
If its a ripple current thing, I have NO idea what ripple current is applicable on this unit.
Any help anyone?
Chris





RE: Physical capactor sizing
If your question is about the current handling capabilities of the capacitors for the audio, then - yes, it is worth checking the specs for each capacitor.
I wonder why these necessary parts weren't included in the box in the first place?
RE: Physical capactor sizing
RE: Physical capactor sizing
You are right - its in series with the speaker!
The big cap has no "markings" so I have little to go on when I'm looking at specs.
The parts were not included "since it is a bulky component and inclsing it in the Z50 [the amp] would substantially increase its size, In addition the output can be selecetd for the loudspeaker chosen and there are certain applications where an output cap is not required..."
Not a lot of help I guess!
Chris
RE: Physical capactor sizing
Thanks for the maths! That may help a lot, partic the 50W into 8ohms part. I'll have a look to see what caps I can get that are dinky, good quality and can handle that current rating.
Chris
RE: Physical capactor sizing
The most available electrolytic types today are radial lead. You can replace your axial electrolytic with a radial electrolytic as long as you observe polarity, insulate the longer lead, and secure it mechanically. You can also use a capacitor with a higher voltage rating.
RE: Physical capactor sizing
This is an electrolytic, most definitely, as polarity is marked on the cap in the diagram with axial leads...
RE: Physical capactor sizing
RE: Physical capactor sizing
Higher ripple current ratings tend to come with two other factors: lower ESR and ESL, and larger physical size. If you can accomodate 2200uF or 4700uF in the same space, do so. Modern capacitors have a far better capacitance per unit volume, so it should not be a problem.
If you are looking for excellent quality capacitors, Evox-Rifa's PEH 169 and PEH 200 series are both very good industrial grade types which we use as standard fitment for equipment on severe service duty.
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If we learn from our mistakes,
I'm getting a great education!
RE: Physical capactor sizing
I ceratinly have no great expecttaions on quality from this vintage amp - though when I used one through the 70's as a guitaer practice amp, it was the dog's nuts!
The cap (ScottyUK) was a 1000uf, not 10,000uf, so I'll be heading on a 1000-2200uf flavour based on current remarks.
Evox-Rifa ... is there a UK distributor/retailer for these? RS Components, Farnell?
Thanks all
Chris
RE: Physical capactor sizing
RS Components P/N's & approx. can sizes for the PEH200 series screw terminal industrial capacitors:
4700uF 63V, RS189-765, 35mm dia x 51mm high
2200uF 100V, RS189-822, 35mm dia x 60mm high
4700uF 100V, RS189-838, 35mm dia x 95mm high
There is a datasheet available on the RS website.
My reference to a 10,000uF cap was just my opinion on the suggestion in your original post that this size was required for decent bass response. I think that a 10,000uF cap is excessively large for the output of a 50W amp, but it is not going to have a detrimental effect if it can be physically accomodated. It will just cost more and in all probability will not give any discernable benefit.
Hope this helps,
----------------------------------
If we learn from our mistakes,
I'm getting a great education!