I'm not going to start the thread yet - I need to build some tube pre-amp for whatever I end up with and eventually it will be a pair of F4's run balanced if necessary or I might try to find another way that doesn't require me to bypass the crossover networks in my speaker cabinets.
Crippled won't work with my inefficient speakers. The entire reason I started taking this route is because they are difficult to drive, more current needed. I am unable to test the impedance curve of the speakers because of the crossover network and four drivers per cabinet - I suppose I could pay the person that has done refoaming and other speaker work for me, but he assured me these dropped below 2 ohms at times. Sounds like a half a day labor to pay for which I would rather spend on other audio gear, plus the risks of transporting heavy speakers across the city.
I didn't know the price of torroidial transformers had gone up so much so I'm going to have to do the F4 builds very slow. For now it looks like I'm going to pick up a used Adcom amplifier from craigslist which should get me by while I save my lunch money - and still get some type of tube pre-amp even if it is some ebay chinese junk.
I understand Jackinnj not wanting to sell to a newbie (he didn't refuse, just hinted in this forum), if I do place an order it's because I talked my uncle into helping his poor, stupid nephew out. Ahem, if he is reading this... I probably won't ask. And if he is reading this, he should show some of his projects off. He don't need no stinkin' PCB's! I just saw the first pictures of them a few days ago.
Jackinnj, you posted a photo and instructions for modding for parallel. Can you point out what needs to be done to run them balanced as in this if it isn't the same? The example is for a pair of 8 ohm speakers, hope it is not a mistake to assume it will work just fine for 4 ohm speakers... Best to find out now rather than 6 months down the road.
https://docs.google.com/spreadsheets/d/1p2bfkhoGji-dwjsf0tMBUPm6kHZDIK14C2UMdGlf2w8/edit?usp=sharing
Yes, unusual way of sharing a photo but it seems to have worked. Time for me to make a donation for image hosting space...
Crippled won't work with my inefficient speakers. The entire reason I started taking this route is because they are difficult to drive, more current needed. I am unable to test the impedance curve of the speakers because of the crossover network and four drivers per cabinet - I suppose I could pay the person that has done refoaming and other speaker work for me, but he assured me these dropped below 2 ohms at times. Sounds like a half a day labor to pay for which I would rather spend on other audio gear, plus the risks of transporting heavy speakers across the city.
I didn't know the price of torroidial transformers had gone up so much so I'm going to have to do the F4 builds very slow. For now it looks like I'm going to pick up a used Adcom amplifier from craigslist which should get me by while I save my lunch money - and still get some type of tube pre-amp even if it is some ebay chinese junk.
I understand Jackinnj not wanting to sell to a newbie (he didn't refuse, just hinted in this forum), if I do place an order it's because I talked my uncle into helping his poor, stupid nephew out. Ahem, if he is reading this... I probably won't ask. And if he is reading this, he should show some of his projects off. He don't need no stinkin' PCB's! I just saw the first pictures of them a few days ago.
Jackinnj, you posted a photo and instructions for modding for parallel. Can you point out what needs to be done to run them balanced as in this if it isn't the same? The example is for a pair of 8 ohm speakers, hope it is not a mistake to assume it will work just fine for 4 ohm speakers... Best to find out now rather than 6 months down the road.
https://docs.google.com/spreadsheets/d/1p2bfkhoGji-dwjsf0tMBUPm6kHZDIK14C2UMdGlf2w8/edit?usp=sharing
Yes, unusual way of sharing a photo but it seems to have worked. Time for me to make a donation for image hosting space...
Looks good -- you should probably check the temperature of the depletion MOSFETs (no fingers! use a non-contact IR thermometer)-- I haven't had to heat sink mine, but if the voltage coming off the regulator is too high they give up the excess in heat. I think the voltage drop is ~80V @8mA = 0.64W.
Thanks to both of your reply.
I could use this altec lansing vs4121 from my PC just to test this preamp.
So, it means I could not hear it from unpowered speaker?
I'll build 4-channel F4 to mate this in balanced stereo but it will be a while.
I hope I could still test single ended.
I could use this altec lansing vs4121 from my PC just to test this preamp.
So, it means I could not hear it from unpowered speaker?
I'll build 4-channel F4 to mate this in balanced stereo but it will be a while.
I hope I could still test single ended.
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I had to put a small wing of aluminium on mine to keep them warm as opposed to hot.
You don't need a preamp with a gain of 30-40 in front of a class D amp that has an input sensitivity of no more than 2V to full power.
The impasse was made to drive a buffer power amplifier that has no gain, and to convert single-ended (RCA) to balanced output, and add a ton of gain. This really isn't the preamp for your needs.
The impasse was made to drive a buffer power amplifier that has no gain, and to convert single-ended (RCA) to balanced output, and add a ton of gain. This really isn't the preamp for your needs.
You're right again, I ordered cinemag 15/15B and have it on hand, but, I think (not totally sure) that the input impedance is even too low for this transformer, better to have a buffer in between (THAT1646 has output impedance only 50 ohm).
Another option I'm thinking is the BA-3, what do you think? I'm sure you know it very well
Another option I'm thinking is the BA-3, what do you think? I'm sure you know it very well
