$30 amp upgraded

[Kensai]

Its been a few days, so what's the word here?

MEXXX have you received your amps yet? Hope you get them in good order.

I haven't been able to find anything locally (St. Louis metro), but I've got someone looking in the Chicago area for me. I'm probably too late to find any like that.

To you folks who can mod these things (don't think I can, since I've never touched a soldering iron before), and especially those who have been in the guts of one of these units in particular, I'd like to pose a question. Would it be possible to:

Remove the pot/switch entirely

Somehow sum or combine the input to make it take in only one channel via a 1/4" unbalanced jack

Sum the output to one decent set of terminals

Possibly beef up the connection to the power supply jack (I'll be wanting to run them this way instead of via any battery solution)

I'm effectively wanting to make one of these into a monoblock power amplifier. I'm not sure what sort of power you would get from one of these with the channels bridged, but I'm hoping that would be enough headroom to power one of my OBs. I'm actually thinking of tacking one of these (probably even sans any casing) to the back of each of my OBs and just running power and signal cables to each. I'm planning on using a Presonus HP4's monitor outs to control volume.

Does this sound doable? If so, anyone up for doing it for me? Possibly even providing the amp from their own stash (I just want 2 done up like this)? How much would you be willing to do this for, parts & labor?

Kensai

[tiroth]

You can't bridge a full bridge output.

[amt]

You cant bridge this amp unfortunately. So that being said, if you need more power, you might look at the Teac A-L700P. Its a Tripath based 30 wpc three channel amp that is suppose to sound pretty clean and is also dirt cheap. $100. It is not quite as good a performer as the SI, from what I can gather from other forums, but is still an awesome value. The center channel board is actually a stereo board with one channel just not connected. So you really are purchasing 4 channels of ampification.

As to the other questions, you can remove the pot/switch, wire the power input differently, etc but if you dont like digging into the guts, research the Teac. Two for $200 will get you 6 channels of 30watts with 2 more available with modding.

http://www.jr.com/JRProductPage.process?Product=3668124

amt

[Kensai]

Good to know. Thanks guys.

I still want to hear one of these. I may have to break down and order one full price from PE or wherever. If I can pull the nasty old Pio 411 receiver out of my office rig for $30-$60 and end up with even marginally better sounding stereo output, I'll be happy.

One more question . . . if I've got 4 (or more) amp channels available, and I'm only trying to get stereo output, is there any advantage or harm in feeding identical signals to a pair and then routing the output of both channels to single speaker? Will I be getting more output/headroom, or will I just be mangling the sound or risking mangling my gear?

Kensai

[Variac]

OK, I just broke down and ordered one.
I hope more appear in the trading post so I can make a multi channel amp.

One review said it sounds very very good- not as good as a Bel Canto, but very very good.

Well I say: Why the hell doesn't it sound as good? Where are the digital geniouses around here telling us how to make 'em super!

[Vinnie R.]

Originally posted by Variac
OK, I just broke down and ordered one.
I hope more appear in the trading post so I can make a multi channel amp.

One review said it sounds very very good- not as good as a Bel Canto, but very very good.

Well I say: Why the hell doesn't it sound as good? Where are the digital geniouses around here telling us how to make 'em super!

Head over to audiocircle.com
The SI and Teac are discussed a lot



-Vinnie

[KT]

Here are some more tweaky observations regarding something I posted about in another thread. Namely, out of the four SI amps I bought, the three that I've listened to sound substantially different from each other.

Take this as food for thought as these amps should sound the same and some people will think I'm imagining things for hearing such differences.

I noted when I first received the amps that of the three I auditioned, one sounded quite shrill and agressive in the treble, one sounded more balanced but much more muted, and the third sounded substantially more involving than these first two, with better bass definition, pacing, and tautness in the sound, while still sounding warm.

I was a little concerned because I hate finding differences like this when there should be none - makes me neurotic about getting the best sounding samples! I don't want to have to cherry pick through a bunch of amps to find the best ones when they should sound the same. What a waste of time. But, alas, I did observe these differences.

I figured everything would sound the same after burn-in, so I didn't worry about it too much.

I changed out the pot in the trebly one with a 50k Alpha pot and ran it in for about 12 hours before sending it off to my brother. It smoothed out a bit but still had a rough quality to it. Again, I figured this would work itself out with more time.

I also put a 50k Alpha in the muted sounding one and used it as my main amp.

I listened to this amp for at least 70 hours, and it did seem to get a little more involving. I enjoyed it but wasn't absolutely thrilled with it. It sounded good, but not great.

Well, just for a yuk I decided to gut it and put it in a new plastic box with better binding posts, etc.

So that I could listen to music while I worked, I replaced the muted sounding amp with the third amp, the one I found so involving and, lo and behold, it was still so much more involving. I couldn't believe it.

Bone stock with no more than 30 minutes total play time on it, it still sounded so much better than the muted sounding amp, which had 70 hours of burn-in time and a better sounding Alpha pot in it.

As I was listening, I though to myself "I could be totally happy listening to this amp stock without changing a thing." I was that happy with the sound. I experienced a totally different level of engagement with the music, that's how much better it was.

So what the hell's going on, here? Why does this third amp sound so great while the muted sounding one, with it's better sounding pot and 70 hours of burn-in, merely sounds good?

I'd like to think this is still a burn-in thing, but 70 hours seems like enough time for thing to at least get close. The third amp sound so much better than the other two that if forced to, I would take just that one amp versus five or six of the other ones.

Again, this is pretty tweaky so go by your own experiences, of course. But this is just confounding me. I want all of them to sound the same - great. Instead I have one great sounding amp and two others that may or may not get there.

I just want them to all sound really good, that's all I ask.






Anyone experience anything similar?

Best,
KT

[Variac]

Vinnie,
Much as it pains me to admit, the audiocircle.com folks do have so interesing stuff going on.
Thanks,

Variac.

[amt]

The differences between the amps is quite interesting and not something Ive noticed. Ive got two that both sound pretty close to each other and I attribute the differences to one being an "integrated" and one a poweramp feed by an Adcom GFP-750 preamp.

Ive also sold two poweramps that I listened to for a couple of hours each and neither sounded much different nor have the customers say anything. I will say that Ive little experience with the stock amps since I immediately liberate the boards from the chassis, so all Ive really listened to is upgraded versions.

Ive not an EE or advanced student of circuit design, so my assumption would be that the TA2024 is not to blame UNLESS overdriving them has nasty consequences similar to chip amps. If not, it has to be the passive components, soldering quality or the sum of the crappy stock case and connectors AND poor assembly.

My amps are of different production runs and sound very similar. I am waiting for another batch and will listen very closely to each as well as closely scroutinize the boards.

Vinnie, have to noted any substantial differences in your amps before parts replacement? And do the brand or quality of the passives seem to change from amp to amp?

amt

[KT]

amt and vinnie,

Thanks for keeping your ears open about the sound differences.

I mentioned earlier that I had replaced the pot in in the muted sounding amp with a 50k log Alpha. I did that by removing the original pot from little circuit board, splaying the legs of the Alpha pot, and soldering it in place. I had to cut a little bit of plastic off of the little mounting ring since the Alpha pot sits lower and the clearance requirements are different. Well, having done that, I now have a little mounted potentiometer that can be swapped out by changing out the mounting ring/circuit board assembly from amp to amp. This is connected to the main board via a detatchable socket and cable.

Just to try it out, I swapped out the stock pot of the "good" sounding amp with the Alpha pot. Well, it seems to me that the sock pots are not too bad at all. Or at least they mate well with the sonic character of the amp in question.

The stock pot exibited more drive and drama, with more highlighting of the upper mids, giving voices a more prominent and "driving" quality. It worked well with this particular amp sample. The sound was still a little rougher, but it had only been played for an hour or so total. Maybe this roughness will work itself out.

I'd say the Alpha was more liquid and smooth, but seemed more recessed in the mids and lacking in "bite." It sounded mellow and laid back with more transparency, but with a more distant and slightly smaller perspective. Perhaps more neutral, as well. It sounded more refined overall, but didn't have the grip and traction on the transients like the stock pot did. I would say it sounded something like "slippery" - liquid and smooth, but exhibited a slight lack of grip. Pleasant, but not dramatic.

I noticed this same quality when I replaced a Noble pot with an Alpha in my Berning Micro-ZOTL. I noticed the slight recessed and distant quality in the mids, but the Alpha sounded nicer overall in the Micro than the Noble did, so there it's going to stay.

I'm going to listen to the Alpha pot for a few weeks and then swap back to the stock pot to see which one I ultimately prefer in the SI. Right now I'm leaning towards the stock pot, but I want to get some long-term impressions on the Alpha first. I'll keep you posted.

PS - even with a different pot, I can definitely hear the characteristics that led me to prefer this sample of the SI over the other two. So I don't think it's solely the pot.

PPS - Did you notice any dramatic differences changing out the electrolytic cap? After I took out the main board, I realized there's only one cap, the other cylinders being coils. That's pretty cool that you don't have to replace 4 or 5 caps.

Best,
KT