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Tube PP amp for subwoofer

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J

jev

Member
Joined 2004
Hi, at this moment I am using these woofers as subs next to my full range speakers: SW312TU01

Only now I blew one of my Hypex sub-amps (while experimenting with a tube based sub-filter, also burnt one voice-coil) and I am not very happy about this :mad: So i am thinking of building sub-amps with tubes. Since these amps will be more robust and repairable for me. These woofers have quite a nice sensitivity and I have 2 woofers in a not too big room

My guess is ~40 watts should be fine. I am thinking of push-pull with Toroidy transformers. is this a suitable design?: OddWatt Audio 5751 SRPP / KT88 Push-Pull Monoblock Tube Amplifier Kits

Or may be a push-pull EL34 since these tubes are cheaper ..? I like a simple design without to much silicon
 
Bfpca

Bfpca

Member
Joined 2007
Sorry to hear about the damage to amp and driver. Do you know what caused the failure? Typically, most people would not use a low power class A tube amp to drive a subwoofer. That's a lot of work and expense to get 40w for a subwoofer. There are lots of easy and reliable solid state solutions out there including used hifi or pro amps.

I use a Crown pro amp to drive 2 15" sealed subs in my main system. Unless you are really set on a tube amp I think you should take a look at pro amps, new or used they offer great value. The Crown I have is a CDI1000 270/500/700 /ch at 8/4/2 ohms. If you use the DSP it can do basic crossover and delay functions as well. Reliable amp with a quiet fan and it has built in protection for any mishaps that may occur. SS amps generally have lower output impedance than tube amps which is an important consideration for a subwoofer amp.

Depending on the size and efficiency your driver/ enclosure setup 40w may not be enough. To get 40w from an oddwatt you would need KT120 or 150 tubes which are expensive and will run hot in class A. If you must have tubes a class AB UL amp would be a better choice from an efficiency standpoint.
 
J

jev

Member
Joined 2004
The tube based filter puts out dc while warming up. I know the UCD modules did not like this but completely forgotten about this. Also I only measured dc output after the filter was warm (and there was almost none) ;-) So now I am working on a delay circuit behind the filter to postpone signal for at least 10 seconds or so

Thanks for the reply. I am really willing to invest in a tube amp because I like tubes and I like the idea ...
 
kodabmx

kodabmx

Member
Joined 2011
Why not capacitor couple the filter?

My favourite amplifier I've built uses 6P45S in triode connection for ~80W output. The only issue you might find is finding a 1k3:4R OPT.
 

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Lingwendil

Lingwendil

Member
Joined 2008
Look to horizontal sweep output types, there are a handful of affordable, high quality ex-soviet types (6P45S, like above, being a good one) that would work well, in addition to the usual television types. It's not unusual to see the output up around 100 watts out of a pair if the output iron is up to snuff. Design with parallel output tubes and stay conservative on the idle biasing for long life, and they should be very reliable long-term.

I wouldn't bother with expensive audio-type tubes for such a use. You can do better for cheaper. Pentode connected, cross coupled feedback.
 
kodabmx

kodabmx

Member
Joined 2011
jev said:
There is a capacitor on the output but still there is DC at startup? I use this circuit Tube CAD Jounal: Tube-Based Crossovers and Filters

Yes please share the schematic. But I do like very simple circuits and no silicon if possible
Click to expand...

Try lowering the 1M resistor on the output to 47k-100k. A 1uF cap will take time to charge up through 1M. Or, as Lingwendil said, short the cap to ground through a time delay relay circuit. One of these per channel set at the longest delay is a cheap and easy way to implement: NE555 DC 12V Delay Relay shield Timer Switch Adjustable Module 0 To 10 Second | eBay
 
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J

jev

Member
Joined 2004
I have my eyes one something from Toroidy. I have good experience with their power transformers and chokes. But not yet with the OPTs. And their products are relatively payable

And I am buidling a 6V based relay because I do not have 12V readily at hand in the power supply

Those Ebay circuits I already have and they are fine although only for 1 channel per print and up to 11 sec. max. (I measured)
 
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