Hafler DH-200 only plays low

[Charlie Lamar]

I purchased a used DH-200 to be the focal point of a 2 speaker system that I am building. My goal is to modify each component to be custom and provide high quality performance. I pulled the trigger on the DH-200 because it was very affordable and could be modded easily, especially if I decided in the future to purchase a second one and make it into a dual mono amp set up. OK so I finally got a preamp and with the volume turned all the way up the sound is relatively low. I checked it with a receiver with pre outs and same thing. I then took it to my high end audio shop and tested with a luxman pre and a vintage HK pre and still low sound. No fuses blown, no caps swelled and nothing looks odd. The amp is clearly a professionally built model so I don't see any shoddy workmanship. I posed the situation to the ebay seller Qua-Co (He sells upgrades for all hafler and Dynaco products)(Former Hafler Engineer) and he said check the fuses (Did and their good) then he recommended changing the caps on both boards. Only $30 for the cap kit, just curious if anyone has an opinion before I pull this trigger. Any help would be great.

BTW, not using a Phono just digital media, CD's and Phine, Itunes etc...

 

[Charlie Lamar]

OK So I am going to recap the boards I was hoping for some guidance

 

[TLS Guy]

OK So I am going to recap the boards I was hoping for some guidance

I highly doubt that will do squat.

You really can't service like that.

Anyhow what do you mean by "plays low?" Do you mean the volume is low, or that it only plays low frequencies? In addition is the sound distorted?

You need a scope signal generator and VOM. You need a service manual.

First check that the voltages are correct. If both channels have low output, then I strongly suspect something is wrong in the power supply.

If the power supply checks out, then you will have to use the generator and scope to see at which stage things go adrift.

You can download a service manual here.

 

[Charlie Lamar]

Well I am going to upgrade the board caps and transistors. With my limited skill set this is the consensus from my brain trust. I could not get the service manual to download. This is a sixty dollar blind stab. If someone can get that service manual to download, please send it to calpbs@hotmail.com

 

[slipperybidness]

Well I am going to upgrade the board caps and transistors. With my limited skill set this is the consensus from my brain trust. I could not get the service manual to download. This is a sixty dollar blind stab. If someone can get that service manual to download, please send it to calpbs@hotmail.com

$60 could be used for a function generator......1 of the tools needed to troubleshoot and diagnose rather than blind stab / shotgun approach.

 

[Charlie Lamar]

I may not be cut out for this

 

[slipperybidness]

I may not be cut out for this

It's certainly not for everyone. But, if you will follow advice, then TLS will absolutely get you going.

Or, bite the bullet and take it to a professional for troubleshooting and repair.

Or, you know, just buy a new and/or functional unit from the beginning and save yourself the headache.

EDIT: If you are still wanting custom, but less hassle, then you could look at some ready-made kits that have all the parts, then you can construct the kit to your desired look. If you want to go that route, I can send you some links for kits.

 

[Charlie Lamar]

yes please

 

[slipperybidness]

yes please

Now we're talking!

Do you have your speakers picked out already? Choice of speakers will likely point you towards the amp type that you want.

Do you have a preference for tubes vs SS? In general, I rec SS. SS will typically be cheaper and offer more power and performance.

If you go SS, then the question becomes ChipAmp or Discrete Amp.

So,

1) What speakers?
2) Tubes or SS?
3) What is the budget for the amp?

 

[Charlie Lamar]

Well. SS makes the most sense, I listen to 60's, 70's, 80's rock and some modern stuff (Girlfriend). I have a pair of Boston Acoustic monitors (VR-M60's) and I am about to refurbish a pair of ESS 1AMT's. Long term I will build a pair of custom speakers but these two options are what I am working with right now. Not sure of a budget for the amp. I have the option to send this amp off and have the JFET mod done for $500. This is a stepping stone to build two dh-200's and convert them to monoblocks, which is sort of the foundation of my two speaker system from the beginning. So I am not sure what I am doing. I am looking for options and advice.

 

[slipperybidness]

Well. SS makes the most sense, I listen to 60's, 70's, 80's rock and some modern stuff (Girlfriend). I have a pair of Boston Acoustic monitors (VR-M60's) and I am about to refurbish a pair of ESS 1AMT's. Long term I will build a pair of custom speakers but these two options are what I am working with right now. Not sure of a budget for the amp. I have the option to send this amp off and have the JFET mod done for $500. This is a stepping stone to build two dh-200's and convert them to monoblocks, which is sort of the foundation of my two speaker system from the beginning. So I am not sure what I am doing. I am looking for options and advice.

OK.

These guys are at the top of my "want to build" list. I have not built any of these or heard any of these. But, their products certainly seem to check all of the right boxes and I see many items on their site that gives me some confidence in the company:
http://ampslab.com/

Then, you have the Hypex NCore modules. These things measure silly good and pretty much have a cult following (I have yet to hear or build one)
http://www.hypex.nl/product/2012-11-23-13-41-35/nc400.html

There are some very good ChipAmp kits on the market:

I have not heard or built this one, but again the specs are just silly good and there is an AH member currently building one.
http://www.neurochrome.com/modulus-86-rev-2-0/

These I have heard and they sound good.
http://akitika.com/GT101.html

This one isn't high power, but it is a good amp (but mine does have an audible thump when you shut it down, I used a speaker protection circuit with relay to avoid that). I measured it at about 18Wpc rms if I remember correctly:
https://www.boxedkitamps.com/gobo-stereo-audio-amp-kit

I also did a high power chipamp build from scratch (meaning I chose the chip, the PCB, the components and layout, etc), I could supply info on this if you are interested
http://forums.audioholics.com/forums/threads/new-chipamp-project-thread.92513/

If you want less DIY, then consider this:
http://www.classicaudioparts.com/index.php/electronic-parts/bang-olufsen-icepower50asx2-module.html
or this
http://www.classicaudioparts.com/index.php/electronic-parts/icepower-170w-amplifier-module-complete-with-power-supply.html

Or look at amp boards from PE
http://www.parts-express.com/cat/audio-amplifier-boards-modules/3464

 

[Charlie Lamar]

Well in a slightly bolder move I purchased the upgrade kit from Qua-Com off ebay that employes the JFET technology. I know it makes it a whole new amp and well, that's what I did. We'll see how it works out. I have my brother (Electrical Engineer) interested in my quest and we are considering building some ESL's from scratch. This is getting fun.