Modding for Helix A4 Competition

[chris m]

Hi all! i have a Helix A4 amplifier and i want to change the opams for better sq. The amplifier have a 17 opamps NE5532. i decided to make a swap for all the opams but i'm not sure what to put. I have in mind a few opamps like AD8066, OPA2134, LME49720. I like the AD8620 but the cost it's expensive for all 17 pcs.
If you have another option i'm verry opened. i put a few pics of the helix.

[luka]

I guess something like AD or OPA should be even better, but that alone will not change this amps sq like day and night... xou might need to tweak some other things... also, you would need NE footprint compatible replacements, are those OPA and AD just that?

[Perry Babin]

I know this isn't what you want to hear but... It's likely a waste of time. The 5532 is a very good op-amp. If you replaced all of them with the most expensive/best op-amps you can buy and did a blind A/B test with a non-modified amp, it's unlikely that you could tell the difference between the stock/modded amp.

[chris m]

luka - the voltage is like that - NE5532- 5-15/ OPA2134- 2.5-18/ AD8066- 5-24/ AD8620- 5-13/ LME49720-2.5-17.
i want to replace all 9 crapy caps(capxon) with Rubycon ZL(470uF)



Perry Babin - for now i have only 3 AD8066 and my first step will be to change the input opamps and that 4 which are surrounded by MKT(MKP) caps and all 9 caps
14 AD8066 and 10 caps Rubycon ZL cost about 70 euros with shipping.
So, if i sell the A4 and put not 100, not 70 euros what amp i buy better than A4? none!

[1moreamp]

I would just change out the Capxon caps with high grade audio rated and then do a Mylar bypass across them. I have a huge bag of failed Capxon caps hanging near my bench. they must be the worst cap ever made bar none.
This helps restore the leading and trailing edges of difficult waveforms like square waves and it can be seen on a scope how it improves this fact. Also maybe some cap bypassing in the power supply to help remove any harshness and noise in the DC rails.

Weather or not you individually can hear the difference is still open as I am unaware of your hearing characteristics and abilities. < Some folks got hearing like dogs and cats and can hear things others can not, and some folks have very poor hearing and any mod will not make a difference to them.

We were all put here with many differences. One of those being how we hear and see the world around us....Perception is as individual as each and every person is....

I looked at some of the AD chips your thinking about using and you have selected across a wide variety of devices and I think you will find some circuit incompatibility issues looming on your horizon. Let alone the wide voltage ops that they all seem to have.
The amp has set rails inside of it and unless your altering the supply rails you will need to be able to at least put in devices that operate safely at those rails.
The AD8620 will most likely NOT work due to its rail supply ratings, it is a low power op-amp meant for headphone and battery ops. And although it is highly touted as being very SQ device it is meant for other services then what your thinking of. < IMO >

I have done OPA2134P change outs and the overall SQ does appear to change to me. But this is what I thought I heard.
Perry is correct about the venerable NE5532. It has been used for years with much success as general purpose op-amp, this and it jelly bean price makes it and a few others the main op-amps used by the industry.
Recently I have been wanting to try the National Semi chips to see what they have to offer but I am worried about high frequency stability. As these seem to offer a clear advantage they also come with possibly new issues after install. Issues like turning a single gain stage into a oscillator circuit and what not.
Its never as simple as it all seems changing out active parts and not knowing what the result will be.... I hope it all works out for you and your project.....

[chris m]

i olso want to swap the 4 caps Audiotech-Fischer 3900uF with Evox-Rifa 4800uF but i think is too big. it has a 9,2 amper Evox-Rifa | Passives | Capacitors | Aluminium | PEG 225 Series |PEG225HJ4480QE1
the AD8620 is too expensive and my first intention is to AD8066
i swaped a 4580 with LME49720 in my sound card (Audigy 4) - i found a better sq and just a few minutes ago with AD8066. again i found better sq. is a good detail. i like it and it's not burning out like 49720
i still intend to swap 5532 with 8066. i think the 8066 is better then 5532
i'm not make it a

[hc_TK]

Did you finish the mod on the helix? Was theire any improvment?
I have a couple of these amps myself, and Im thinking about changing the opamps to. and adding som capacitors on them

Cant find any Capxon caps on mine. how to they look?

[chris m]

i finished a long time ago, and was an improvement, it more impact and controls better the speaker. the is better too especially to the tweets

[hc_TK]

thats good to hear!
What did you change? Got pictures of this?

[chris m]

no, don't have any pics
changed all op-amps and caps, jamicon 470@35v with panasonic fm 470@35v
bigger then 470 it does not fit
after the mods it look like it has more power, my micro-precision serie 7 it is verry well controlled
the a2 was on the sub, you should listened.... more bass and lowest freq