The circuit I copied from the amp itself! With great difficulty!
Its a basic design really few caps 2x opamps ne5534 and a huge toroidal. I dont understand the rest.
I'm not fitting anything just trying to improve whats there already in the amp. Just sounds a but bright and low bass. Both me and my pal like warm amps so adjusting to both our taste
Thanks!! I have been electrocuted 4 times from same amp before!! I try to limit my efforts lately due to potential death of not knowing LOL
Ahh, i see.. youre modifying a circuit in place..
wow.. 15dB is a LOT of gain.. i'd be tempted to VASTLY reduce this down to 6dB and with lower overall resistance values. I reckon that'd probably improve the quality alone, and your volume control on the amp would be MUCH less fierce. I bet it's very twitchy as it is now.
This amp might well date from before CD players... tuners for example only output a relatively quiet 300mV RMS compared to the 2V RMS most CD players and other "line out" sources can generate.
wow.. 15dB is a LOT of gain.. i'd be tempted to VASTLY reduce this down to 6dB and with lower overall resistance values. I reckon that'd probably improve the quality alone, and your volume control on the amp would be MUCH less fierce. I bet it's very twitchy as it is now.
This amp might well date from before CD players... tuners for example only output a relatively quiet 300mV RMS compared to the 2V RMS most CD players and other "line out" sources can generate.
The circuit I copied is the preamp section with no mods as I have:
1, never copied a circuit before with such accuracy!
2, have no idea what does what!
All I want is to reduce high frequency and increase low frequency. And I believe the solution was presented by increasing 30k to 100k (which did add bass)
and 2, to increase 220pf to something higher to reduce high frequency (yet to be tested)
Volume is actually quite gradual and fine!
OK, well.. here's the original circuit modelled in spice, with an AC analysis graph:
The -3dB frequencies are 2.37Hz, and 152KHz. Not too bad. There's only about 3.2mV of output offset which is also low. Not bad considering there is no blocking capacitor in the feedback path.
The -3dB frequencies are 2.37Hz, and 152KHz. Not too bad. There's only about 3.2mV of output offset which is also low. Not bad considering there is no blocking capacitor in the feedback path.
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I've been eagerly waiting on your expertise and from what you say for me to get the desired sound "warm" would be to try increase c2. Hoping the less treble will appear to sound as more bass!?
Bit confused by this. The 2.2uf is bipolar film and is audio input from volume control pot
No.. the -3dB HF is not really a treble boost or cut, it is a bandwidth limit. What you might find on older gear is that high frequency crap from things like mobile phones can get in and distort the signal. Limiting the HF bandwidth of the circuit can help with this. If that's not an issue, I would leave it alone.
OK, i showed an electrolytic capacitor as that's commonly used. It doesnt really matter.
Try a 4u7 polyester cap such as a Wima MKS2. I think that will give you a result you are happy with.
Ok. This will give me lower frequencies?
But can I still add a few pf to the 1pf to reduce high frequency?
4u7 for C1 will give you a -3dB LF cutoff of 1.12Hz. Much lower than the original. I'd say you'll be happy with that.
If you REALLY want to play with C4 id suggest a 2p2 capacitor of good quality. I wouldn't use a silvered mica as they are physically large and you'll have more problems with stray pickup. Use a ceramic capacitor with NP0/C0G dielectric.
Likewise, if C2 is a ceramic capacitor, change it out for a 220pF ceramic with NP0/C0G dielectric. If it's a film capacitor, leave it alone.
OK. I don't even know if I have anything of that low value. Yes its some form of film with no brand. Again!
It is a decent amp just bright that's all! Go maplins if I get a chance! Thanks for advice
Forget Maplin.. theyre a load of **** for parts these days. Try Electronic Components from Rapid - the Electronic Parts Specialist | Rapid Online
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