OPAMPS... im get way ahead of my self now...

[hamish_gill]

hello im new to this diy stuff and brand new to this forum so any help and patience would be greatly apreciated

i have posted the following on another forum but had no response so have come to a more specialist place for advice

...


my upstairs hifi has in the last few days turned into tweeky crazyness

i have a beresford tc-7520 on its way and after reading that these LM4562 opamp thingys are in many peoples words a 'no brainer' i now have a pair of them wraped in a little bit of plastic.
im not going to put them in straight away i want to get to know the dac before i decide to upgrade it.

and this is why im getting ahead of my self, i recently bought a firestone tubehead pre-amp. i got it cheepy cheepy whilst looking for something to esentially just add an input to my tripath.

when i first got it i plugged it in and didnt like it,i left it to burn in for a bit with no real joy. i decided to sell it but in the mean while i plugged it into another system just for the hell of it really. it sounded ok but was no major improvement. after left there turned on for a week or so it obviously gave it more of a run in as when i just plugged it back into the tripath today it sounded a lot better than before and def seemed to add something.

the bass is still the major week point of the system though. there is just not a lot of it and its rather ill defined and muddy

i have read that these firestone things are a tweakers paradise and after opening the top on it today a can see there are 2 pairs of switches. one that changes gain, and one that change how the volume control works. fun fun fun fun ... no change to bass on the different settings though

first question: are these switches in pairs because there are 2 channels

second question: the other thing i notice are a pair of opamps (i think) one has

0720
jrc5021g

printed on it, the other has

opa2604ap
74w64db

can i upgrade these to something that might improve the bass


i guess i wont do anything until the beresford has burned in and i can hear what benefits that brings. but like i said im getting ahead of my self.

i think i have just opened a can of hifi tweeking that my non techy mind can fathom and i want to know more more more

[Fenris]

What Tripath do you have? There may be an input filter on it that blocks the bass (the Sonic Imapct amp were known for this).

The 2604 is a pretty decent op-amp already, depending on it's application. You might get a small improvement with the 4562, but it may be worse to your ears as well. If it's socketed, it's easy to swap out and try.

NJR opamps have a pretty poor reputation as the cheapest thing out there. I'm not sure what the 5021 is though, it's not one of the standard audio opamps I've seen.

[jaycee]

probably a TL072

be aware that the LM4562 requires good supply decoupling or it will oscillate. If the original circuit's provision for this is not good enough, you will degrade performance, not improve it.

[Bonsai]

Quote
be aware that the LM4562 requires good supply decoupling or it will oscillate. If the original circuit's provision for this is not good enough, you will degrade performance, not improve it.
Unquote

Applies to all op-amps.

[AndrewT]

It's probably not the opamp that is curtailing the bass.
It much more likely to be the implementation that has that effect.

[hamish_gill]

are you saying it is just going to be down to the combination of equipment. i am sure that is the case i was just wondering if there was a little tweak to add a bit of definition to the bass