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Author Topic: Noticeable hiss in Tech 21 tm60  (Read 5701 times)

Wuchi

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Noticeable hiss in Tech 21 tm60
« on: November 06, 2011, 02:40:50 PM »
Hi!

I bought used tm6o and it has noticeable hiss even when all volumes are down. Does this mean that power supply electrolytics should be replaced?

Thanks!

Edit. The amp is older version. It has 2112-A speaker.
« Last Edit: November 06, 2011, 03:03:45 PM by Wuchi »

J M Fahey

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Re: Noticeable hiss in Tech 21 tm60
« Reply #1 on: November 06, 2011, 03:10:17 PM »
Don't think so; bad power supply caps (not too likely in a relatively new amp) would rather bring hum with them, or instability problems, not specifically hiss.
Do you still hear it if you plug a spare cable in the power amp in or loop return, killing the preamp?

Wuchi

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Re: Noticeable hiss in Tech 21 tm60
« Reply #2 on: November 06, 2011, 03:25:26 PM »
Don't think so; bad power supply caps (not too likely in a relatively new amp) would rather bring hum with them, or instability problems, not specifically hiss.
Do you still hear it if you plug a spare cable in the power amp in or loop return, killing the preamp?

If I put a cable in power amp in (effect loop return) there will be quite loud buzz. If I put the cable in Pre amp out (Send) there is this same hiss, and the turning channel volume increases the hiss.

Also noticed that when guitar cable is not connected, touching the chassis will decrease the hiss.

J M Fahey

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Re: Noticeable hiss in Tech 21 tm60
« Reply #3 on: November 06, 2011, 04:20:37 PM »
Hissssssssssssssssssssss ! or hummmmmmmmmmmmmmmmmmmmm ! or Bzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz ?
Not the same.
If it were a Power supply capacitor problem it would not change by touching the chassis.

Wuchi

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Re: Noticeable hiss in Tech 21 tm60
« Reply #4 on: November 06, 2011, 04:26:16 PM »
Hissssssssssssssssssssss ! or hummmmmmmmmmmmmmmmmmmmm ! or Bzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz ?
Not the same.
If it were a Power supply capacitor problem it would not change by touching the chassis.

When amp is normally on (no spare cable in effects loop) the sound is hiss (maybe buzz when volume is full but I can't try it now because kids are sleeping).

When I put the spare cable in effects loop (power amp in) the sound is Buzzz

No Humm, or if there is, the hiss and buzz are louder and humm can't be heard.

mojah

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Re: Noticeable hiss in Tech 21 tm60
« Reply #5 on: November 06, 2011, 08:18:23 PM »
I picked up a another cheap old PV a month ago ( it's an addiction for me ) and had all sorts of strange buzz's and noises but worked otherwise. I took the chassis out of the cab, pulled the pc board and cleaned everything, I mean everything, pots, jacks even the board it's self. I paid special attention to the switching contacts on the jacks. Some jacks may ground to the chassis, make sure that area is cleaned. Contact cleaner, scotchbrite, and q tips. Check the solder connections at the input jacks, I'd reflow them while it's apart anyway. Be careful with the Tech 21 board I've heard that they are muti layer, I've never seen one.

J M Fahey

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Re: Noticeable hiss in Tech 21 tm60
« Reply #6 on: November 06, 2011, 11:19:34 PM »
Quote
No Humm, or if there is, the hiss and buzz are louder and humm can't be heard.
Looks normal to me.
Anyway some pampering as mojah suggests, never hurts.

phatt

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Re: Noticeable hiss in Tech 21 tm60
« Reply #7 on: November 07, 2011, 08:28:18 AM »
I agree with *Mr Fahey's* observation,, the amp is likely normal.

I did hot rod a few tricks into a trademark 60 a while back and they like a lot of hot gainy Amps do hiss.

From memory the Reverb comes after the EFX loop return (before power amp) and the pickup side of reverb's is often noisy.

If you play these amps in bedrooms then yes it becomes annoying but trust me,,, on stage you will never notice it. ;)
Don't worry 40 years ago even the best Valve amps had worse noise problems and yet some of the greatest modern rock songs where made and played on those amps.

Cheer's,,, Phil.

songofthewind

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Re: Ho trodding Tech 21 tm60
« Reply #8 on: January 08, 2012, 05:16:42 AM »
Hi Phil
I'm intrigued: what tricks did you apply to your TM 60? I've got one and I love it, but I'm always intertested in something more.

All the best

phatt

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Re: Noticeable hiss in Tech 21 tm60
« Reply #9 on: January 08, 2012, 08:44:16 AM »
@ songofthewind,
                       Long time back and I doubt I could recall all in detail now but the Amp was insanely harsh and had awful imbalance between the 2 channels. xP

The Owner wanted a warmer tone so I simply replaced the Factory speaker with a much warmer driver.
This reduces the *Perceived* wattage but makes the OD much more controlled.
Big improvement.

The owner (still not happy with the imbalance between the channels) basically said use it for parts and build me a new amp.

But over time I realized that I could access the Return section which still allowed access to the master volume and the spring reverb.

In the end I built him a new preamp and installed an insert to break the internal preamp.

Simply by removing the plug returned the amp back to standard. (I always try to consider resale if it can be done)

I did a couple of tricks to the internal preamp but can't remember those.

Be aware that There is no Schematic for that Amp that I'm aware of and the fancy bits are covered in black goo with no names,,, the board is also double sided with Very fine tracks so if you mess up then the amp is likely junked. 8|
Phil.


songofthewind

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Re: Noticeable hiss in Tech 21 tm60
« Reply #10 on: January 09, 2012, 06:57:19 AM »
Thanks for that, Phil. I have an Award-Session JD-10 which I often run through the FX return of the TM60. That can also sound a bit harsh at times, depending on the room.

I like your speaker replacement idea-most people go for a more powerful speaker upgrade. I tried running the TM 60 into my Blues Cube with a vintage sounding 12" speaker, sounded good but not loud, just like you said.