Replies to This Discussion

Permalink Reply by Anthony Tucker on March 6, 2017 at 4:56am

Yeah i think i am going to go this route as well. I like the idea of having it as a separate preamp or even building it into my amp enclosure then putting it on the CBG itself. I just dont think i would like the look of it my CBG.

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Permalink Reply by David McQueen on March 6, 2017 at 6:35am

I have a couple of the guitar preP/equalizers. Be aware that they are designd for guitars with rod piezo's ... And do sound great with them. For disk piezo, the inputmis not high enough impedance and it still sounds harsh.

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Permalink Reply by David McQueen on March 6, 2017 at 6:38am

Thanks for the preamp link. Imhave bookmarked that. Here is the amp board I am thinking for using

http://www.ebay.ca/itm/DC-12V-TDA7377-35W-35W-2-0-Channel-Dual-Ster...

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Permalink Reply by Timothy Hunter on March 7, 2017 at 2:27am

are you going to use this as a 2 channel amp with 2 inputs? or are you going to bridge the inputs? 

2 x 35 watts is going to be loud!  i built myself a 100W amp back in the 80's and used 2 x 12"speakers scavenged from broken guitar amps. the thing was so loud i dont think it was ever used past 5.....lol  

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Permalink Reply by David McQueen on March 7, 2017 at 6:33am

I figure on having two inputs, run them through individual preamps with their own tone controls, also,each through a cheap reverb board I found, then combining inputs and sending both altered inputs to both channels ... So yes ... As loud as I want :-). At the other end, I would really like to combine the output to one speaker. From what I can find, the fact that I combined them and sent the combined signal through both channels mey allow me to recombine them at the speaker end. This is another amp designed for auto audio, so I am planning on using cheap auto speakers with enough power handling capacity. I am still thinking this through.

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Permalink Reply by Timothy Hunter on March 7, 2017 at 10:44pm

its not quite as easy as that. you cant bridge a class D  amp speaker output. besides you will get a little more power if you are feeding the altered signal to both channels than if you tried to bridge the speaker output. factor in the added cost of a higher wattage speaker needed to handle the bridged output. 

plus you will need another board before the power amp. you need to invert the signal to say the left channel and feed the normal signal to the right channel this will drive the left channel full negative swing and the right channel full positive swing effective giving you twice the voltage swing across the speaker.

actually i just checked the TDA7377 amp chip on that board and its an interesting chip..  it can be set for 4 in 4 out. and in the configuration of this amp it is 2 in 2 out and the outs are already bridged internally.... so you definitely cant bridge the two outputs....

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Permalink Reply by David McQueen on March 8, 2017 at 4:11am

Darn ... You actually know what you are doing. Before the discussion on preamps, I was looking at using the 35 watt per channel board directly, just as I am the 15 watt per channel amp. I think they are by the same manufacturer. I really like the sound from the 15 watt smp board. I was hoping to get the same, except louder and add a passive tone board and a karioke reverb board I found on line.

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Permalink Reply by Anthony Tucker on March 7, 2017 at 7:51am

check out this preamp board. This might be interesting as a tube preamp.

https://www.amazon.com/Qianson-Pre-amp-Amplifier-Headphone-Circuit/...

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Permalink Reply by Timothy Hunter on March 7, 2017 at 10:35pm

requires a 12 AC power supply to work. that might present some problems....

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Permalink Reply by Anthony Tucker on March 8, 2017 at 2:09am

Yeah I noticed that. Would have been cool. I did a quick look into a DC to AC inverter but didn't have a lot of luck, may not be worth the trouble

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Permalink Reply by Timothy Hunter on March 9, 2017 at 2:17am

wrong way to look at it. you can get wall warts that output AC. you could try to find one with 12V AC output feed that to the preamp and also feed that into a 4 diode rectifier then add a few Caps to filter it then feed the resulting ~ 16 V DC to the amp if it can take it or a voltage regulator down to 12 V DC if needed....

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Permalink Reply by Anthony Tucker on March 10, 2017 at 2:06am

That is a good idea.  For this build want to keep it as simple as possible and was hoping to use the power supply i already have since I am still very new to all of this. If this one is successful i am going to attempt to use the tube preamp on my next one since I think that will give me more of the sound i am going for.  When start that build I may have questions for you. Thanks

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