UcD400OEM upgrade

[leams]

Hello everyone,

I’m new on this forum and a novice regarding DIY audio stuff.

I recently bought a Polk R700 and a MiniDSP flex TRS which I love but then had not enough money for the amplifier. I started to look for cheap amplifier with clean output and around 200w@8R.

I came across Hypex NCore, IcePower and Pascal but even those where to costly to afford in kit. I started to look in old amps and by chance read about the Monacor IMG stageline STA800D (dual mono hypex UcD400OEM) and was able to buy one for 350€ new.

I would say that I’m 80% satisfied with the sound but that I would prefer to have a little more of “air” and resolution from the amplifier. I also want to keep THD and noise as low as possible until fed to the UcD400 module. I immediately thought of replacing the TL072 on the hypex integrated input buffer by the OPA1612 which has this slightly “airy” presentation as well as a lower THD than what the MiniDSP output is capable of.

But I don’t know anything related electronic schematics and choice of components. This is why I would be grateful if someone could look at UcD400OEM and tell if replacing TL072 with OPA1612 would work ?

 

[Koifarm]

Hypex have upgraded other UCD models with lm4562 and low noise power supply. And you can replace the elco coupling caps for filmcaps.

But start with a schematic of the Monacor amp.

 

[leams]

I looked at the buffer detail at page 6 but it's not clear if the LM4562 (https://www.ti.com/lit/ds/symlink/lm4562.pdf) can replace the TL072 (https://www.ti.com/lit/ds/symlink/tl072.pdf) in the buffer. Do you think that the LM4562 would work with no other change ?
I don't have the schematic of the monacor amplifier but it's a full hypex amp (UcD400oem+smps400a400) with a simple desymmetrizer (JRC4558) for volume followed by a symmetrizer (JRC4558) before entering in the hypex buffer.

PS: a few pictures of the amplifier and of the hypex buffer
http://dctech.fr/public/WIN/STA-800D/STA-004.jpg
http://dctech.fr/public/WIN/STA-800D/STA-008.jpg
https://www.diy-hifi-forum.eu/forum/attachment.php?attachmentid=54768&d=1589270400

 

[Koifarm]

Are you shure they use the hypex buffer? Most oem builders use their own buffer.

 

[pguerin]

Hello,

STA 800D use a custom buffer, quoted from another audio forum :

800d model
Power amplifier based on Hypex modules
Power supply: 2 Hypex SMPS400 V14 modules
Final modules: 2 Hypex UcD400OEM V7
Rated power: 250W 8 Ω 1% THD, 400W 4 Ω 1% THD
This is a completely dual mono final, each channel has its own Hypex SMPS400 power supply (V14) in the version with ± 62V DC output voltage that powers a Hypex UcD400OEM (V7). Between the power supply and the end, two 4700 F 80V parallel capacitors are inserted in parallel.
The signal, from the balanced (XLR) or unbalanced (RCA) inputs, enters a buffer made with JRC 4558DD operationals, passes through the potentiometers, and is sent to the Hypex UcD400OEM. The amplified signal passes through a stage that implements the protections: presence of DC in output, ...) and is sent to the terminals, both normal for stripped wire or bananas, or Neutrik type.

Some users are very satisfied from this amp, maybe some work on your speaker could add more "air" to your sound.

 

[Koifarm]

So changing the tl072 will not change anything. Change the 4558 for a lm4562 or opa1612.
The 4558 is not so fast , the other opamps will give you more detail.

 

[Koifarm]

 

[leams]

Are you shure they use the hypex buffer? Most oem builders use their own buffer.

I'm not sure about this. I'll need to check on the STA 800D custom board to confirm.

Hello,

STA 800D use a custom buffer, quoted from another audio forum :



Some users are very satisfied from this amp, maybe some work on your speaker could add more "air" to your sound.

Thanks for the infomation. I'll change the 4558 for a lm4562 or opa1612 first.
To be honest I'm very satisfied about the STA 800D especially at the price I paid, but my speaker (polk R700) should welcome a bit of "air" in its mid range and treble performance

 

[tigeranand]

Hi Leams Did you try try the change how did it work out