Headphone output on Tascam 122b

[jjones1700]

This isn't a major issue as it doesn't affect the output to tape, but I'm just curious what might be wrong.

When I playback on the 122b deck and listen with the headphones, there is an awful lot of hiss. I listened to the tape I recently recorded with it on my MR-2 deck and all sounds good, so it's just the headphone preamp portion I'm assuming. Any solutions/suggestions? Should I even bother? I noticed that when I changed the belts not too long ago that there were some discolored sections on one of the boards. Perhaps this is the effect from that?

 

[Dr ZEE]

... it's just the headphone preamp portion I'm assuming?

- Headphone power amp IC, that is.

Any solutions/suggestions?

-To ignore it if you can, or to replace the headphone amp circuit with something different, if you feel like DIYing some

As I recall, evm1024 has done something about it (on tascam 32???), or at least was working on it. Or am I wrong?

 

[Jidis]

JJones-

Yes, it's noisy as crap.

If it's the same as mine (original 122/dual speed) the hiss is so bad that I looked up the amp chip to see if it could be swapped or something, but I don't have time to mess with it now. I think there's another old Tascam here which is just as noisy (Porta Two maybe), but IIRC, my newer 122mkII was much cleaner there. I guess they figured nobody would care about the quality of the phone signal.

I'm with Dr. Zee's suggestion. I think these things may have been made back before all the cheap dedicated amp chips showed up. If you were really careful about the current and voltage matching, you may be able to stick something like an LM386 circuit in place of it. Of course there's always the possibility that the signal feeding that amp circuit is just noisy to begin with.

Take Care,

George

 

[jjones1700]

Thanks for the info. It's not a big issue, it just caught me off guard when I actually tried to monitor through the deck instead of the mixer. As long as the main I/O is unaffected, I can live with the noisy headphone amp circuit. One of these days I'll get around to snapping up a mkII or mkIII so I can have built-in dbx.

 

[sweetbeats]

I thought the mkII's were Dolby B/C/HXPRO decks...

 

[Jidis]

Indeed they were (at least up to the mkII). There's a Teac here which does dbx (435X), but only regular speed and there may be others, but an outboard 224X is just about as cheap. I just won a second one on eBay for $22.50 (for a 4-track machine). I think the heads or circuitry may have improved slightly after that original 122/122B though. I remember the high frequency limits were a bit lower on the old one unless you ran high speed. - this is judging by Tascam's specs.

Take Care

George

PS- Keep in mind every single thing from back then will probably have trouble in 2009 unless it's been serviced over the past few years. I've got five of theirs sitting here now and not a single one is running properly. It's all just the usual rubber crap though and I should have my belt order put together over the next day. Just be careful and figure that into the cost if you don't like going inside them yourself.

 

[jjones1700]

Sweet, you might be right. I'm guessing as to which one had the dbx built-in. I could have sworn at least one of them had it. Then again, I keep forgetting about the dbx 224x units. I need to keep an eye out for one of those.

As for the limited range on the first gen 122, I honestly couldn't tell you. I haven't put it through it's paces just yet. I replaced the belts not too long ago and haven't had much time to work with it since then. Something about having to go to work and paying bills. I hate that. Don't you?

I'm here to learn from you guys.

 

[sweetbeats]

According to the manual for the 122mkIII and the 112mkII, both those decks were Dolby B/C/HXPro decks and single speed at 1 7/8ips. Was one of the 100-series decks hi-speed? i.e.:

I remember the high frequency limits were a bit lower on the old one unless you ran high speed. - this is judging by Tascam's specs.

 

[Jidis]

Was one of the 100-series decks hi-speed?

Yes, the "old" 122 that he and I have. I think the 122b is the same but with balanced XLRs on the back along with the RCA jacks. There's a sister deck under the Teac name called a C1 which looks just like it (actually there were two colors of that), but it looks like it only did regular speed.

JJones, in the 122/122mkII specs, it looks like for CrO2 tapes they have the 122 listed as 35Hz to 14kHz, while the mkII goes down to 25 and up to 19k. The 122 is supposed to hit 20k on high speed, but then you've got a weird tape that nobody else can play.

BTW- It looks like quite a few of the Teac models from the late 80's or so had dbx. If you ever needed one with that onboard, look around for stuff in the R-400-500 series or D-400-500. Mine is an R-435X. That stuff's nowhere near as heavy or expensive as the rackmount Tascams, but it sounds decent when working properly.

George