2. amps-preamps
  3. 125863-85386

Replace C28 with... ?

In my previous thread regarding a power amp, some of you commented that replacing the McIntosh C28 preamp would make a huge difference. However, what was missing was any elaboration how why you made the recommendation, and with what to replace it.

So, let’s get down to it.
McIntosh C28
HiFiBerry DAC+ Pro (Yes, I know... sacrilege, but it’s all I’ve got for now)
Bryston 4BST
Dahlquist DQ10
Polk PSW650 sub

Need guidance from you guys on whether I ought to be looking at SS, Tube or even a Passive unit. Since I have some skill with a soldering iron, I'm not above entertaining the idea of a kit.

I’ve seen the Tortuga LDRx and that concept looks pretty interesting. My worry is that the DQ10s can be a bit aggressive on the high end with that ribbon tweeter, so I’d like to hear your thoughts.

Thanks again in advance!
parabolic
parabolic OP
99 posts
 
I was just about to click in here when mhztweaker posted the above.  Like him, I want a certain experience, but can't afford it new, so I have to look at (very) pre-owned equipment.

Just pulled the trigger on a KRC-3.  It's the earlier style with the more 'industrial' less streamlined faceplate, but the innards ought to be the same.

After all of this, I can only hope that a near 40 year-old C28 will be outperformed by a 20 year-old KRC-3.

Per the suggestion by auxinput, I might try to recap the unit, though that will have to wait until I can afford to do so.

Thanks to all for the very insightful input, it's been quite helpful!
timlub
1,649 posts
 
The difference it tight bass, detail and top end extension will be dramatic,  you will loose your bloom.  They will definitely sound different,  you'll figure out your taste very quickly.  Purchasing used,  no matter what, you shouldn't get hurt and should be able to move one preamp without issue. 
Enjoy
auxinput
1,538 posts
 

You'll have to let us know how the KRC-3 sounds. 

I agree with mhztweaker on the caps.  I have spent the last several years modifying audio circuits and have gone through a great selection of capacitors.  The Nichicon Muse KZ are the absolute best, in my opinion.  They are extremely fast and very neutral (and provide very detailed sound).  Otherwise, if the KZ do not come in the proper rating or physical size, choose other Nichicon caps (like KW or ES, etc.).  Do not use any of the 105 degree and above caps.  The 85 degree actually sound the best.  I had several people at DIYAudio tell me to use 105 degree caps.  However, they really sounded bad - had some bigtime electrical resonance happening.  The 85 degree caps, and especially the Muse KG, are built to reduce electrical resonance as much as possible.  This is extremely important in audio circuits.  The 105 degree (and up) caps are built to operate in a higher temp situation (like in a car or industrial machines) and do not focus on electrical resonance.

I did not like the Nichicon Fine Gold FG series - they pushed the upper midrange too much for me.

The re-capping with Muse and other Nichicon will make a significant difference in your preamp.  Don't be afraid to increase the capacitance of the two main power supply caps (if you can).  However, the smaller pre-regulator caps should not be larger than about 330uf.  The small caps around the audio circuits themselves should not be larger than 47-68uf.  Putting large caps here will make the sound more laid back with less midrange.  Even 100uf is too large and too slow to respond to the upper midrange transients (you'll even lose some midbass because it's just not fast enough).

parabolic OP
99 posts
 
I'll report in when I get the unit and have a chance to listen for a while.

In a world of disposable equipment, it's amazing to think that some components were built to last and are worthy of this sort of attention.  My philosophy has always been: "buy it once, buy it right".

Not sure if I'm comfortable doing the recap work myself.  Soldering new components?  Check.  Removing solder?  Not so much.  I guess I'll live with it for a while and see what happens.

Quick question on the KRC-3...

How would you attach the Polk PSW to the preamp?  I read the Krell manual and it says that both the balanced and single-ended outputs are active at the same time but that it wasn't advisable to connect both at the same time to a preamp.  Does that also apply to the Sub?  My plan was to connect the two RCA leads to the inputs on the Polk, and use balanced going to the Bryston.

Your thoughts?
auxinput
1,538 posts
 

Not sure why the Krell manual states that both should not be used at the same time.  It looks like the traces on the board just connect the two outputs together (like a Y-splitter cable) as shown in the upper left part of the following picture:  

http://img.usaudiomart.com/uploads/large/1027567-krell-krc3-vintage-preamp-at-its-best-legendary-krell-sound.jpg

It may be an issue with driving two different types of amplifier impedances, not sure. The other alternative would be to use a Y-splitter cable, which is doing the same thing and you have multiple cable connectors that are degrading the audio quality.  I say that you should just try connecting both XLR and RCA outputs and see how it goes.

I suppose you could use the RCA input/out of the Polk subwoofer to connect on to the Bryston amp, but you'll definitely be losing sound quality here.

If you have any interest, I would be willing to do the re-cap job for the cost of the components plus shipping plus $100-150 labor (depending on what you wanted done).  It's probably a couple hours of work for me.  If you don't have a good desoldering gun, it can be extremely difficult to remove solder and dis-attach the capacitors.  It is easy to pull up traces on the circuit board if you are not able to melt the solder enough - and you've just destroyed a $1000 item. lol. Sometimes you have to re-apply new solder and re-melt the contacts to get all the solder hot enough so that it lets go of the capacitor leads. 

Oh, expect to have a burn in time of about 250 hours with those Muse capacitors. 

More to discover