Hafler TA1600 recapping... looking for more bass

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I have a TA1600 thats starting to give off some hissing like a waterfall so I'm going to try to recap it. I'm a newbie to diy amplifiers but have a little knowledge. I'm thinking of recapping the unit but was wondering if it were possible to increase the bass response. If I increase the main caps uf would that help? I've noticed a deterioration in sound and also the bass is becoming almost non-existent. I have the scematic for some reference but it's too big to attach. These are some other things I would like to try in the future:
1)Putting a cap on the on/off switch and power and also putting a cap on the iec.
2)Removing the volume pot all together or find a way to bypass it.

It's a cheap little amp so I'm not afraid of ruining it. I thought it would be a good amp to start my diying on it. Thans for any help...JohnnyP.
Hi, I am definitely not an expert on this subject, but I do own a Hafler amp, and I do have a similar 'lack of bass' experience.

djk is right, on my amp, it is a 6.3V 1000uF cap.

If you do not already have a .01uF 1KV ceramic across the power switch, put it in (and replace the power switch if necessary).

The only other thing I have to add here is that it could also be your big main caps showing their age. Testing for ripple is a good first step.

Hello to all. I am a newbie to the site although I have followed many of the posts on various forums for quite some time!

I also have one of the Hafler TA1600 amps. I just picked it up as a running amp but although it works it have pretty low output on both channels and next to no bass output at all. :bawling: Any idea where I should start on this? I checked the output voltage on both of the large 3300 caps it is 41VDC. Nothing appears to have physical damage. Any chance someone has had this problem as well and figured out what is wrong? Also any chance someone may have a service manual available?

Any suggestions would be greatly appreciated, Thanks! :)
Sorry to bring this back from the dead but Im having this exact same problem. bass is very weak and the mid-highs sound overdriven and practically hurts to listen to. Any suggestions? i'm going to to try to bust it open and look for blown fuses, and I'll try to identify the feedback loop transformer like someone mentioned. Any help is appreciated.
I have not seent he schematics for the 1600 but i am working on a TA-1100 that i bet is similar. I found lots of bad Electrolytic caps on the amp boards! the amp sounded overdriven and had visable distortion on a O-scope. there is an Op-amp with two caps back to back that connect from the negative input of the op-amp to its output forming a filter. this is connected in the Negative feedback loop of the amp. the back to back caps were bad causing an open loop condition in the op-amp and this was then injecting distortion into the NFB loop of the amp!

Check all the El caps in the amp. I bet you find a bunch of bad ones!

Hi, I am glad to see some interest in this thread again!
I had so many other projects going that I had just put the 1600 aside waiting for the schematic or some suggestions. I have yet to find a schematic for this model. If anyone happens to have one or even one for the 1100 model that would be greatly appreciated. Sounds like checking all the caps would be a good start. I will post any findings here after I check them out. Thanks for the suggestions. :)
Im too new to email, but i would like the schematic. Please mail it to "iplayintraffic2(at)gmail,com" Thanks.

Techgadget, it reads like our problems are identical. Do you have piercingly loud highs and mid-highs, with almost no midrange or bass? Sometimes the highs sound mudded together or "waterfally." Also as i increase power, it seems like the lows stay at a constant volume while the highs increase dramatically. Also for some reason it seems very quiet unless i give it a heavily preamped signal. Line level or headphone out should be sufficient for this correct? Sorry, Im new to this style of power amplifier.

Does anyone know if JohnnyP00 ever recapped his or got his working?
Did recap it but to no avail.
The biggest problem for me was too many on board components to check. It's too hard, darn things are just too small.
The right channel ended up blowing and I had to toss it, but on the good news bought another one from ebay for $100 :)

I'm thinking of trying to recap this one down the road.... JohnnyP.
JohnnyP00 -

thanks for the offer. It would be great if you can send the service manual & schematic along. I still am getting the "your account is under moderation" message. I have been a member here for quite some time but have not posted much. Hopefully I will be able to send emails to fellow members soon. Anyway if you can PM or email me that would be great. I can then reply directly to your email.


Yes! it does sound like the problems are identical. Looking at the reply by Zero Cool it looks like I will be removing all the caps and testing them. I hope this is the cure as it will be fairly easy. This amp got many great reviews so it would be nice to have it working again. I never really drove it much after my initial test revealed this condition so it's been shelved.

Zero Cool: Thanks for your insight and feedback on this. Is your amp now working correctly? I am going to look at the caps ASAP! Hopefully put some time into this in the near future.

If anyone does some more work to your 1600 or 1100 please let us know your results!
Yes my amp is now working correctly now!

make sure you scrub the boards well after removing each cap. electrolyte can leak. if you get a fishy smell when unsoldering, that's the electrolyte! I scrubbed using a q-tip and alcohol. scrub well!

BTW....I ordered Panasonic brand replacement surface mount caps. there were a lot of options available. is there such a thing as a good or better grade surface mount cap???
I got the caps from Digi-key. they are pretty small. I'm getting better at SMD rework. I just applied a very small amount of solder to the pcb pads, then held the cap in place and tacked one leg down, then tacked the other leg down and then went back to the first leg again and that seemed to work well. I just made sure to let the cap cool a bit in between. didn't want to over heat it.

I had no information as to what to set the bias to? So i injected a 20khz sinewave and set the level control to obtain a 2.83V output into an 8 ohm load and adjust the bias up from minimum until the crossover notch went away. I then checked the dc current draw and it was about 50-56ma and i adjust that up to 60ma and left it.

BUT. I observed an problem!! I let the amp run at 1/3rd power for about 15 minutes. the heatsinks got warm but not hot. then both channels stared to oscillate! if i lowered the level of either channel it went away. It seems to be ground related. If i connected a clip lead from the point where the ac line is grounded to the chassis to the point where the PCb is grounded to the heatsink. it went away. also if i disconnected the 8 ohm load from either channel. the oscillations went away....

I think....the LM317/LM337 V-regs are oscillating when they get hot? need to do some more work and see what i can figure out on that! now i know why the damn thing burnt up in the first place...man, these things are just not designed well....
Hafler TA1600. The same problem as other people have found. No bass, or for that matter midrange at all.

The 10uF/16V electrolytic capacitors (C21 and C22) on both channels were bad (pF range). Swapped both of those out, the amp works perfectly now.

Attached is a before and after frequency response measurement. Quite a difference.


  • Hafler TA1600 frequency respons.pdf
    10.7 KB · Views: 301
Hi guys,

I am also trying to get a TA1600 working as well as it should. Even thought I have the schematics of the amp,
I don't know how to set the bias, as I am every bit af a newbee. Could anyone help me on this (where I should measure and what value I should set)?
Thanks for any help,

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