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Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Tue Nov 18, 2025 8:26 pm
by n8nagel
Good evening

Back at it again, testing an Adcom GTP-450 tuner/preamp that I picked up off FBMP in a package with the ACE-515 that I really wanted (will likely sell the GTP-450 for cheap or gift to a friend) just trying to make sure I advertise this correctly and disclose any functional issues, so of course I ended up back here

I don't have the original remote (RC-45 II)

worse, I seem to have lost two of my Harmonies, one that I could find (650) has a bunch of dead buttons, cracked open a NOS 700 and it seems to be DOA :/

well anyway I was able to determine from my very partially functional Harmony 650 that it was NEC1, device 26 which matches the posted upgrade for the GTP-550 and 600. All those OBCs worked great (except for the ones that don't apply of course as this is just a stereo tuner/preamp) so I can say when I post this unit for sale for cheap "works with remote" :)

Just curious, I brute forced some but nowhere near all of the code set and found nothing, does anyone know if there's any discrete remote codes for:

- Power on and power off (guessing no, but it's worth an ask)
- FM tuning seek/manual (this isn't on the original remote, but it really seems like it ought to be, the switch on the unit itself is not latching but momentary)

Thanks guys! and it's great to have the forums back.

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Tue Nov 18, 2025 9:30 pm
by The Robman
How did you "brute force"? Did you create test upgrades with all of the OBC? If not, that's the way to do it, to easily get through all 256 buttons, even less if you leave out all of the known buttons.

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Tue Nov 18, 2025 9:53 pm
by n8nagel
Yes but I only did 127-215ish. I was having lots of fun testing this thing, a nearly new interconnect fell apart causing me to waste time troubleshooting that, the volume pot motor was stuck so that wasted more time, plus looking for my old Harmonies. Managed to kill a whole evening for a preamp that I'm probably going to sell for $40 or so :/

If I have time later this week I'll try to figure it out but this is a low priority as the only other remote controllable Adcom gear I have is one CD player that I'm not currently using (and I figured out all the codes for that one)

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Fri Nov 21, 2025 8:26 am
by n8nagel
I actually wrote to the current iteration of Adcom and they sent me two documents for their old remote codes. So while the new Adcom is not the same as the old they apparently inherited some of the docs. Didn't there used to be a space in the file section to upload stuff like this? I didn't see it on the github site. I do remember making a spreadsheet for Denon AVRs after getting a doc from Denon, although their tech support people were pretty surly.

Unfortuntely, it appears that there are no power discretes :/

Oddly, it appears that Adcom used the same code set for their tuner/preamps and CD players. Verified by looking at the upgrade I made years ago for a GCD-700.

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Fri Nov 21, 2025 7:07 pm
by n8nagel
All right, I think I have a spreadsheet made for various Adcom products based on the first doc (just converted binary to OBC and input all the data). Cross checking with what info I have from various upgrades I think it's right, although since I manually entered everything I'll have to go back and check it again to make sure no errors.

If anyone wants it and the Adcom PDFs before the file section comes back up, PM me. There's a second Adcom doc with codes for the GDD-1, GTP-740, and GTP-750, but since I own none of those I'm not inclined to invest the time in transcribing that one since I cannot test the results. I do not really know how to interpret their "Custom Code". On the first doc it is 1AE5h and that appears to correspond to NEC1, device 26. The second doc is Custom Code 1AE8h. There is an old upgrade for a GTP-740 but it doesn't have any of the non-device 26 codes.

Oddly there is an upgrade for a GTP-602 on GitHub using the same code set which is a tuner/preamp that is not on the docs I got from Adcom. That one uses some codes that are NEC1, device 26, subdevice 232. I would have to do the spreadsheet to see if they correspond to any codes on the second doc however.

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Sat Nov 22, 2025 9:23 am
by The Robman
as a temporary measure, you could add it as an attachment to this post

Re: Adcom GTP-450 (and 550, 600) tuner/preamp

Posted: Sun Nov 23, 2025 1:08 pm
by n8nagel
I want to proofread the spreadsheet again before I post it. I already found one error. I was going to post the .pdfs as attachments to this post but I am getting "Error - Invalid file extension: Remote Codes.pdf" I tried changing the extension to .txt and got the same error.