DCG3 is very good. Very, very good. I have one.
Gain at 3X w/F5 (no turbo, 15x gain) was just about clipping with all sources at max volume on the dial. I am using 5X now. Probably 4X would have been better. 5X is too much for most headphones as well. And the DCG3 is a very good headphone amp.
I think with 22db gain in the amp 3X (9db-ish) will be just about perfect.
DCG3 exhibited no more noise at 5X than it did at 3X but more gain sounds a little and makes me a little more comfortable with the low-gain F5.
Gain at 3X w/F5 (no turbo, 15x gain) was just about clipping with all sources at max volume on the dial. I am using 5X now. Probably 4X would have been better. 5X is too much for most headphones as well. And the DCG3 is a very good headphone amp.
I think with 22db gain in the amp 3X (9db-ish) will be just about perfect.
DCG3 exhibited no more noise at 5X than it did at 3X but more gain sounds a little and makes me a little more comfortable with the low-gain F5.
I see DCG3 feedbacks and I'll assemble one, no questions. I need it for headphone purposes mainly. I'm just waiting for Tea-bag's PCBs. One more month hopefully... Back to Gain, I'm still to not get the math behind your advice. I need not to exceed 1.42v input since I'm clipping above it. So, my delta is 1.42v-0.7v (source output) = 0.72v. It is about 1.7x from preamp. If I'm right, with Gain 3x I will get to the clipping at 1/2 of volume. Please correct me if I'm wrong.
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I am not sure your math is correct regarding the half volume figure. If your amp clips at 1.42V then all you need is a buffer, assuming your source puts out 2V-ish. This is the math.
Math is one thing, real life is another. I can tell you an f5 driven with a buffer won't play nicely into 90db-ish speakers. Sounds thin and lifeless. Also, I can say dynamics and drive are increased with an active pre. Keep in mind my speakers are 89db 3-ways and I listen to mostly vinyl.
With the non-turbo 15db gain F5 I could push the amp to clipping with 3X in the preamp but it took almost all the volume pot. That's a total system gain of 24db (15 + 9db). I am much happier with a bit more gain in the preamp for recordings that are lower in volume and flexibility with different sources. Right now I have about 30db system gain (15 + 15) which seems like a good compromise.
I am not sure but maybe ask Salas if the DCG3 is stable at 2X if you are worried about it. 2X may not be enough for some headphones like AKG though.
With the F5t you have 22db of gain. Ad 9 more db with the DCG3. I do't think 32db of system gain is unreasonable...in fact it's quite normal. Pass products like the X.5 series have 30 db gain in the power amps and 10db of gain in the preamps. That's 40db of system gain.
I too built my DCG3 as a headphone amp primarily. But now I never use it for headphones...it stays in my speaker system. Prior to assembling the DCG3 I was using the BA-3 front end which has 20db or so of gain. It's also very good sounding but not quite as refined and quick as the DCG3.
Math is one thing, real life is another. I can tell you an f5 driven with a buffer won't play nicely into 90db-ish speakers. Sounds thin and lifeless. Also, I can say dynamics and drive are increased with an active pre. Keep in mind my speakers are 89db 3-ways and I listen to mostly vinyl.
With the non-turbo 15db gain F5 I could push the amp to clipping with 3X in the preamp but it took almost all the volume pot. That's a total system gain of 24db (15 + 9db). I am much happier with a bit more gain in the preamp for recordings that are lower in volume and flexibility with different sources. Right now I have about 30db system gain (15 + 15) which seems like a good compromise.
I am not sure but maybe ask Salas if the DCG3 is stable at 2X if you are worried about it. 2X may not be enough for some headphones like AKG though.
With the F5t you have 22db of gain. Ad 9 more db with the DCG3. I do't think 32db of system gain is unreasonable...in fact it's quite normal. Pass products like the X.5 series have 30 db gain in the power amps and 10db of gain in the preamps. That's 40db of system gain.
I too built my DCG3 as a headphone amp primarily. But now I never use it for headphones...it stays in my speaker system. Prior to assembling the DCG3 I was using the BA-3 front end which has 20db or so of gain. It's also very good sounding but not quite as refined and quick as the DCG3.
Yes, the right concern would be headphone Gain too (two birds with one stone: preamp and headphone amp). I'll consult with Salas about headphone and I do have AKG K701.
I'll probably going to buy parts from Tea as well. I have quite big stock at my home, particularly for 2SK170BLs, but less headache with his kits.... I didn't read manual in details yet, so are these NEC fets are needed to be matched? Can you send the link to reliable supplier on eBay. I heard it was no high demand on these in the past and no fake ever were made.
I have akg 272 and have tried 701. 3x is good. Too loud at about 3/4 of the volume dial. It gets more complicated if you have akg, grado and AT like me...then you have sensitivity all over the map.
The UPA68h does not need to be matched. But the bf256b do.
Any supplier on eBay is probably fine. I think I bought from Utsource. Hard part to fake and not expensive enough.
Hikari1: thanks for that info sharing.
Andrew, would you advice to increase PSU DC output a bit to raise the Gain/Wattage? I have 57W into my 6R speakers now.
So, I use MUR3020T in rectifiers now (same diodes as in amp). I can go for MBR3020 or similar (Schottky) with lower Vr. To change trany will be $$$ and I have 2 of these (monoblocks). I assume that I can reach 35-36 VDC with Schottky under load.
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Andrew, would you advice to increase PSU DC output a bit to raise the Gain/Wattage? I have 57W into my 6R speakers now.
So, I use MUR3020T in rectifiers now (same diodes as in amp). I can go for MBR3020 or similar (Schottky) with lower Vr. To change trany will be $$$ and I have 2 of these (monoblocks). I assume that I can reach 35-36 VDC with Schottky under load.
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57w into 6r0 is equivalent to 18.5Vac (26.15Vpk)
Your "Gain is 18.5(outputV)/1.44)InputV)=12.85(DeltaV)=22.2dB."
That makes your input sensitvity for maximum unclipped output equal to 18.5Vac/18.5gain = 1Vac
Any signal more than 1Vac (1.414Vpk) will clip your power amplifier.
Any signal that cannot reach 1Vac at maximum peak transient will never clip the power amplifier.
Do you have any sources that have a maximum output of less than 1Vac?
Your "Gain is 18.5(outputV)/1.44)InputV)=12.85(DeltaV)=22.2dB."
That makes your input sensitvity for maximum unclipped output equal to 18.5Vac/18.5gain = 1Vac
Any signal more than 1Vac (1.414Vpk) will clip your power amplifier.
Any signal that cannot reach 1Vac at maximum peak transient will never clip the power amplifier.
Do you have any sources that have a maximum output of less than 1Vac?
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Interesting method... However, in order to make it right, I need to take my drivers out. I can't do that since they are still under warranty. Second, I'm sure they can handle much more power which is not the point. BTW, my leaving room is about 12mx15m. Thank you for that info too.
Andrew:
We are kind of repeating our simple calculations forward and back:
All my sources can deliver V in range 0.6-0.7Vac RMS
Max input V = 1.42Vac RMS
Max output V = 18.5Vac RMS
The GAIN = 18.5/1.42 = 13 times = 22.3dB
Wattage = 18.5²/ 6R (speakers) = 57W
Preamp calculated Gain needed = 1.42/0.7 = 2 times = 6dB
I’m sharping my question:
I might need 3x preamp in order to satisfy my headphones and 3x might be a little more than my amp need now with 1.42Vac input.
Does it make sense to increase VDC on PSU by probably 5-8% to minimize 3x small overload with current setup.
I can replace my rectifier diodes (MUR3020) by some Scottky type with 0.6 Vrev and safe a bit V-loss?
I might gain 3-5 addition VDC for the amp.
We are kind of repeating our simple calculations forward and back:
All my sources can deliver V in range 0.6-0.7Vac RMS
Max input V = 1.42Vac RMS
Max output V = 18.5Vac RMS
The GAIN = 18.5/1.42 = 13 times = 22.3dB
Wattage = 18.5²/ 6R (speakers) = 57W
Preamp calculated Gain needed = 1.42/0.7 = 2 times = 6dB
I’m sharping my question:
I might need 3x preamp in order to satisfy my headphones and 3x might be a little more than my amp need now with 1.42Vac input.
Does it make sense to increase VDC on PSU by probably 5-8% to minimize 3x small overload with current setup.
I can replace my rectifier diodes (MUR3020) by some Scottky type with 0.6 Vrev and safe a bit V-loss?
I might gain 3-5 addition VDC for the amp.
You don't probably need that much space for leaving. Doors are big enough for that. Better make all that space your living room
This calculation is OK with 0dB recordings. But you know that there are many good recordings made at max. -6dB or less. So having some additional gain at your disposal is not a bad thing...
You don't probably need that much space for leaving. Doors are big enough for that. Better make all that space your living room
That is the one of many benefits of living in USA Wild-West rural locations. Expensiveness and big home sizes... Disease of "Giantizm" - it is a general phenomenon in countries like US or Russia. Everything is big...
Agree, and I'll go for 3x. Any way, I would like to squeeze MAX out for my giant amp without changing PSU tranys. Andrew is quite about my diodes inquiry, so I nee to find out that empirically.
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