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Old 5th December 2003, 09:41 PM   #11
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Thanks. That's pretty interesting, and it's a big plus that I can buy the PCBs from him. I'm not sure if I understand one part of it though - he says the voltage gain is 1x, and he uses the tube amp's driver stage for the voltage gain? I'm not sure how I would make that work. The way I see it, the output of the linestage goes into the crossover, and then each output of the crossover goes to an amp. So my tube amp wouldn't be seeing the bass frequencies at all. I guess he has the filters after the tube amp's driver stage. I could make that work if I knew my XO points, but I want to use an outboard XO to play with this and see the effects of changing XO parameters. I'd like to try a digital XO too. So, I'm not sure if I'll be able to make this work.
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Old 8th December 2003, 04:17 PM   #12
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Ahh, I had overlooked the unity voltage gain of the TUMOS. It would need a single stage voltage amplifier to drive it. TUMOS needs about +/- 20 Volts input. If CD is your main source then a gain of, say, 15 would work nicely.

cioa

James
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Old 8th December 2003, 09:07 PM   #13
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Thanks, that's what I figured too. I'll keep that in mind.
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Old 22nd January 2004, 03:21 AM   #14
Morse is offline Morse  United States
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Hi Saurav:

Saurav: >>>...How good are they, really? (gainclones/chipamps)...<<<

Morse: >>>...Some time in the next 3 weeks I should have a small TDA2030 ...ready for general purpose listening and I'll post my results and comparisons then...<<<

Wow! 3 weeks stretched a little, but I've got a TDA2030 up and running into a pair of RS40-1354 DIY speakers. Now, this is NOT technically a gainclone...but I think that the observations here may still be relevant.

Overall, the sound is "listenable" and nonfatiguing, but not anything to rave about...my 2A3 mops the floor with it out pretty thoroughly. In general, I'd classify it as smooth with decent bass, but limited in detail and treble extension. Moreover, there's a tendency for the midrange to become somewhat "cluttered" particularly at elevated listening levels. However, it's an easy notch above the usual "big box store" mainstream tripe - and it can be built in an afternoon once you've got practice point to point wiring chips (and the experience to get a reasonably hum-free layout; believe it or not, that was one of the biggest parts of the learning process - these chip thingies are rather touchy about hum and oscillations - more so than valves).

Even so, it's cheap thrills (cost of the whole kit and kaboodle is less than a single halfway decent OPT), and if you're looking for something a little different it might be just the ticket. Buy a few extra chips in case you trash one or two (or in case one of your buddies decides he wants one....). Just don't expect better sound than you'll get from a good DIY valve amp - because you won't get it. At least if my experiences are anything to judge by.

Later I will post a followup on this thread, when I get a chance to build a "true" gainclone. That won't be for a while though.....I've got some LM1875's in with a general order of parts, and it won't be 'till after I get some of those to play with that a GC can take shape. Frankly, if $$ permits, I really want to get one of my stalled valve projects off the ground! The spirit is willing, but the wallet is weak.....

Ja mata,
Morse
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Old 22nd January 2004, 03:49 AM   #15
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I know I'm jumping into this thread late, but I thought I would put a good word in for the gainclones. While the gainclone I built wasn't as nice as my normal tube amp (6AS7 OTLs) they were better than several budget tube amps I have built in the past. If the budget is tight they are definitely worth trying out, as in my experience you would be very hard pressed to beat a gainclone with an equally priced tube amp.

Doug
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Old 22nd January 2004, 04:13 AM   #16
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Hi Doug;

Sorry, I didn't mean to make it sound like I was belittling the GC - particularly since I technically did not build one! That will be a forthcoming project though....

>>>...If the budget is tight they are definitely worth trying out...<<<

Absolutely! Any chance to make solder fumes is taken over here, and it certainly has been a fun little project. And, for those on a really tight budget, or looking for an "expendable" amp (office, dorm room, etc), they certainly bear looking into.

>>>...as in my experience you would be very hard pressed to beat a gainclone with an equally priced tube amp...<<<

Yep, I don't think I could have built a valve amp on the under $45USD (including tax!) that it cost me to put together this little chipamp - OTOH, my 6BM8 Gnat definitely outdoes it in midrange and treble "rightness", although admittedly the TDA2030A has better bass (I attribute that to the $9 OPT's!).

All the best!
Ja mata,
Morse
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Old 22nd January 2004, 05:57 AM   #17
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Thanks guys, that's a good point of reference. I plan to try biamping with my 2A3 SET on top and something more powerful on the woofer. Of course, that also means building an active line level XO, so this is on my 'long term plans' list.
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Old 23rd January 2004, 09:09 AM   #18
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Hi Saurav;

Here's an update on the TDA2030A chipamp.

The "audio mud" in the midrange cleared somewhat after about 24 hours of burnin time. A much larger improvement in midrange clarity and upper midrange "snap" was made by snubbing the FR305 diodes that I used for my rectifier bridge (usually I snub all ss diodes as a matter of course, but as an experiment I left these "fast recovery" diodes unsnubbed at first). Anyway, the snubbing caps have cleared the midrange mud to the point that it's gone from a fun toy to a moderately serious piece of gear (no, it doesn't have the midrange "magic" of a 2A3 or the "sweetness" of a 6BM8 or 6V6; but for ss kit it's really rather charming in it's fashion) - particularly when the low $$ aspect is taken into account. I'd classify it as being serious enough that I could see myself using one as a standin piece of gear for when the 2A3 is down for upgrades.

DEFINITELY snub your diodes on chipamps - they really do seem more sensitive to the effects of these sorts of things as are valves. And, though I will admit to not doing the experiment on this particular amp, given the improvements I've heard in valve amps with the fitting of a UL Listed "X" cap to the AC mains as an interference suppressor, I would also go with that from the first - I did.

If you're going to build one for a dedicated subwoofer driver, you ought to try your hand at building one as a general purpose amp first in my opinion. Then experiment around a little with how much capacitance you want for the PS filter, get your layout so that oscillation and hum are not issues, etc. Particularly since it sounds like a long range project for you, you have time (and the LM1875's are about $2.5 each at Digikey, so you won't go broke experimenting!).

Good luck and all the best!
Ja mata,
Morse
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Old 23rd January 2004, 02:12 PM   #19
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Not a subwoofer driver, but a woofer driver - 100Hz to about 2.2KHz.
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Old 23rd January 2004, 02:28 PM   #20
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What type/value caps did you use for the snubbers?

Come on, share..............
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