[newzooreview]

You could just give Acopian a call. They make everything at their facility in Pennsylvania (or Florida, near NASA) and are likely to have the missing part.

https://www.acopian.com/

[bbaker6212]

Tried the SX52 op amps and found that OPA1656 sounded more clear in the mid-range with comparable bass response, at half the cost.
In my experience, the discrete op amps cost too much and don't contribute a proportional improvement in sound quality.
The Douk A5 is a remarkable small amplifier that performs well above its price class and is replacing a high bias class AB amp in my own system.
For under $130 total with upgraded op-amps & 36v power supply, it is hard to beat.

what front-end/DAC and speakers were you using?

[NXSTUDIO-DRUMMER]

Watched a YT review, mentioning a nice budget 6SN7 tube preamplifier, that mates up well with solid state amps, providing that tube warmth, by adding 2nd harmonic distortion flavor, complimenting a Class D amp, such as the A5. Stephe doesn't sugar coat her reviews either. She's a straight shooter, and she doesn't get paid to review and promote products. When I watched this video, I thought maybe someone here may be interested in using alongside the A5 amp. I personally favor the sound of octal tubes. It does use a 6Z5P rectifier tube.

It's a Chi-fi amp with cheap tubes that come with it. She recommends replacing with a Matched pair Shuguang Treasure CV181-Z Vacuum Tube.
https://www.youtube.com/watch?v=9LVVyzgnpmA&t=84s

This is the 6SN7 TUBE PREAMP






















Pricing for Preamplifier including shipping and the upgraded Shuguang tubes totals $361.81 currently as of 12-16-25.

https://www.aliexpress.us/item/3256808576299109.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.1.358eIKgdIKgdhP&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=515f22e6-ff7d-4733-8b2c-0b08651c3342&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:515f22e6-ff7d-4733-8b2c-0b08651c3342,tpp_buckets:668%232846%238107%231934&pdp_ext_f=%7B%22order%22%3A%221%22%2C%22eval%22%3A%221%22%2C%22sceneId%22%3A%2230050%22%2C%22fromPage%22%3A%22recommend%22%7D&pdp_npi=6%40dis%21USD%21197.94%21150.43%21%21%211386.11%211053.44%21%402101dedf17659200668748996eb892%2112000046561959852%21rec%21US%216363125716%21X%211%210%21n_tag%3A-29919%3Bd%3A5de7f213%3Bm03_new_user%3A-29895&utparam-url=scene%3ApcDetailTopMoreOtherSeller%7Cquery_from%3A%7Cx_object_id%3A1005008762613861%7C_p_origin_prod%3A


Suggested Tubes Reviewer Highly Recommends With This Tube Preamp.
https://www.ebay.com/itm/274866891035?chn=ps&mkevt=1&mkcid=28&google_free_listing_action=view_item&srsltid=AfmBOorBBvGXV-XTOtOWYhzWxP__iJU-_xnD907a_8_Mkpso4N_Yxg4_EIQ


Unusual to hear a critical reviewer, such as stephe, claim this little 6SN7 tube preamp, performs well selling at a reasonable price.

It's not going to compete with my older Don Sachs D2 6SN7 Preamplifier, nor does it cost no where near as much either. The little preamp sounds promising though.