Whistle Rock RED-25 Discrete Opamp - First impressions

[dissonantdissident]

So, I just got my pair of RED-25 opamps, which are brand new to the Whistle Rock line.  They're a great, easy project, since the SMT parts are already mounted.  Each one only took me a few minutes to solder the through hole parts, and these guys were ready to rock.  I want to note that the matched transistor pair and the two really big(140/139) transistors were identical to the ones used in the GAR2520/1731s I've got, if memory serves me. 

So, I popped them into my trusty CAPI VP26 and checked them against my GAR2520, in that preamp, since this would be the closest relative.  My basic experience is that the RED-25s seemed cleaner with more high and low end detail, but less mid-focused punch.  This actually seems to be what folks say about his ML2520s, so I think Whistle Rock's being honest, when they say it matches performance(on the bench).

For those that own both the VP26s and VP25s, with GAR2520 opamps, I found that the VP26 with the RED-25 sounded remarkably similar to the VP25 with the  GAR2520.  Hopefully that can help some folks understand the difference in how the opamp's particular response interacted with the VP26 circuit/transformers.

Despite the similar PCB color, these are not DIY SL Red Dots.  In fact, I think these are probably closer to being DIY Blue Dots, tone-wise. All that being said, these things are cheap, super easy to assemble, and really sound great.  I've gotta tip my hat to Whistle Rock for coming up with a super affordable 2520-style opamp, which I really think should find a following.  I'm going to be trying them in a few different spots and preamps, but I can envision them ending up in either my drum channels or in one of the positions of a VP28.  I think the smart money is on kick drum, for sure.  With the big bass and crisp high end, I think it'll give me plenty of boom and snap.

glenn

 

[mikefatom]

Hey Glenn,

Thanks for the nice review of the RED-25!  I spent a lot of time listening to the different transistor options.  I had no particular tonal goal in mind and this started more as a research project.  I wanted to see if I could put something like this together.

Some folks seem to have a negative opinion of SMT for high-end audio.  I just happen to work with SMT a lot at my day job and thought that there is no reason why they couldn't work for a 2520 clone (others have done it), as long as I was careful with my parts selection.  To be honest, my main concerns were the thermal distortion of the resistors and the uncertain suitability of the SMT transistors available for this project.

For this reason, I went straight for the Susumu resistors (low temp-co thin film) and started experimenting with various transistors.  Turns out they can make a huge difference!  I only settled on the best sounding combination.

I ran the RED-25 through an AP and although the performance is not mind-blowing (none of the 2520s are),  it is absolutely respectable and right on par with my other DIY 2520s from various sources.  I will say however that the ML2520,  ML918 and BLU-18 seriously outperform the other 2520 clones in my collection by a long shot.

But in the end, none of this matters because they all sounds fantastic in their own way.  It always comes down to what your hears tell you, not what the AP says.

Cheers!

Mike

 

[dissonantdissident]

Cheers, Mike!  I'm really happy with the purchase.  I'm waiting for the pots and transformers to come back into stock at their various suppliers, and then I'm going to do the Studer-EQ project that pcbgrinder makes boards for, and I'm considering giving the blu-18s a try in those.  I know the Jensen family of opamps is considered the cleaner lineage, and that might make sense(in an eq circuit).  A lot of folks seem happy with just 5534s, though.

To me, what's great about these kits is that they take so little time to assemble that I'm going to just try them in different spots.  Not having to spend hours with a magnifying glass over the tiny pcb makes it more likely that I'll at least try the discrete opamps option on the EQ project.