2. amps-preamps
  3. 161362-152909

Budget system for building retro look console

Hello Audiogon,

I brand new to audiophilia.  I got into restoring tube radios recently and had some success; and just loved the analog (tube) sound, which then sparked my interest in consoles.  I priced vintage consoles and found them to be cost prohibitive so because I am pretty handy at building cabinets i figured I'd build one myself and utilize vintage hi-fi components.  So far I assembled the separates (Hafler DH-100 pre, Speakercraft BB275 amp, Phillips 777 TT,  Denon DCM-340 CD changer, and a Yamaha TX-900 tuner).  I got everything used from ebay for $50 or less,  except the pre-amp , which i paid a bit more for.  I also built some kit speakers (Tritrix MTMs).  I re-capped and replaces the ICs in the Hafler DH-100 from kits I got on ebay.  After being reworked, the pre-amp has a lot of (too much?) bass response that is muddy (not crisp/clean).  Both channels and all input modes have this problem; my guess is that there is a power supply problem.  How bad this problem is really depends on the source, some music and recordings sound okay (like jazz or acoustic music), while rock and soul and busy (fuller) types of music generally sound pretty muddy.  My ears aren't what they once were so I not sure if I'm just pumping too much base into the 5" woofers or if I have a bit of distortion on the lower bass frequencies.  I can play my MP3 player directly through the amp and speakers and the bass is at a normal level and sounds cleaner, although the overall sound is very thin from the MP3 (as you would expect).  I don't pretend that I'm good at soldering so I'm wondering if bad solder joints could cause this type of problem.  Also, I noted that the positive power and negative power are not balanced (14.85, -15.15); pretty close but?  I've checked ohms and voltages all around and did not find any balance issues other than that.  My next step is to replace the JFETs (again) and put sockets on them so I can pull the JFET leads and bypass the muting circuit, which I read could be problematic.  Any suggestions on what else I can do to diagnose this issue?  

Thanks 
wgh64

Showing 2 responses by wgh64

wgh64 OP
28 posts
 
I'm pretty limited on spare equipment but i've done enough testing to be confident there is something going on in the pre-amp.  I disconnected the muting JFETs and it reduced the distortion but there is still some distortion and an abnormal amount of bass, particularly low frequency bass.  I'm starting think maybe a combination of solutions are needed.  So my plan of attack at this point is to troubleshoot the pre-amp muting circuit and get it back online and go back resolder some of the not so pretty solder joints.  I also noticed that the left channel drops off at very low volume so I'll likely also change the volume pot if I can find a new one (I already tried Deoxit).   If that cleans it up great but if not I'll get my hands on some spare equipment and do some testing.  I'm having fun learning this stuff and tinkering.  It's also nice to dust off my old record collection.  

Thanks.   
wgh64 OP
28 posts
 
Latest update.  I took millercarbon's advise,  I picked a cheap receiver and set of speakers to use for reference to troubleshoot my setup (Pioneer VSX 3600 and Kenwood KS-31s).   The VSX is in very good condition and sounds swell; the KS-31s are near mint and sound very good as well.   By taking advantage of the tape output (record) features of my pre-amp and the reference VSX receiver,  I could compare my set up with stuff that works correctly.  I learned that my Tritrix MTM speakers and Speakercraft BB275 amp both sound good (better than the VSX/KS-31 setup) and my Hafler DH-100 pre-amp is the source of my problem.  It is changing the sound.  I have read that I should expect this to a small degree; particularly at high output levels.  But what I am hearing is a substantial increase is bass frequencies and it sounds a bit muddy and compressed (i think those are words people use) at all levels.  For reference to my listening preference, when tone control is available, I normally bump the bass up a little and leave the treble flat or backed off a touch.  With my pre-amp in line, I have to turn the bass down almost all the way to get even a marginally listenable sound.  I've re-capped and replaced all of the op-amps, ICs, regulators, diodes, JFETs, etc.  I had a power supply imbalance (15.15, -14.85) but I bought a handful of regulators and socketed them on the PCB so I could balance the power supply; I now have 15.06, -15.06.  It has new 5532LN op-amps, but the old 5532 op-amps have the same issue. I socketed the JFETs so I can pull them and bypass the muting circuit; bypassing the muting circuit doesn't correct the sound.  I have also checked all of the resistors and only found 1 that was out of spec (but I tested them in circuit so I have to desolder one of the leads to check it properly).  I am just about down to the pots being the only thing left to replace.  Could one of those cause this type of problem?
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