Salas, working on second preamp build, would 1.74k be alright for gain resistor ? To get 4x plus ? 3 x feeding burning amp Wide open is normal listening level. Need just a little more. Also what is the lowest resistance you would go to get close to unity gain when driving an F5. Try around 400 ohms? Thanks Mark
1.74k will give ~4.5x gain. It won't oscillate with more than usual gain setting, its ok.
499R would be the lowest. 2x gain. Further down its dangerous to act up. I don't guarantee it will stay stable. Unity it does not do for sure. You could try push it to 1.5x but you should fully check on the bench it still works calmly with gen & scope on sine and square.
P.S.
The gain formula is 1+(R6/R7)
499R would be the lowest. 2x gain. Further down its dangerous to act up. I don't guarantee it will stay stable. Unity it does not do for sure. You could try push it to 1.5x but you should fully check on the bench it still works calmly with gen & scope on sine and square.
P.S.
The gain formula is 1+(R6/R7)
There was a KT88 trioded tube amp I had actually designed 
Many speakers also. Including professional installation types
Anyways, for electronics I generally designed what I missed or to put interesting or expensive lying around parts in use. Power amp solid state designs are so proliferate and accessible that I always had something satisfying on the rack. But I may try my hand on one sometime too just for grins
Many speakers also. Including professional installation types
Anyways, for electronics I generally designed what I missed or to put interesting or expensive lying around parts in use. Power amp solid state designs are so proliferate and accessible that I always had something satisfying on the rack. But I may try my hand on one sometime too just for grins
Attachments
I've suggested that in the past but I must admit that power amplifier is a different case and might be less popular than this preamp. I mean people with horns and panels might have the same preamp but certainly not the same amp.
Hi! I want to show you my second dcg3 which I made by myself. The first one i did not make all by myself.
It is a "by the book" version that works flawlessly, I mean no hums no buzz, dead quiet, sounds wonderful!
Many thanks to Tea Bag and of course to my friend Nick for their precious help.
I used two toroidy transformers and a 20k log pot from tkd.
The input selector is Salas and the power supply is dcstb.
It is a very accurate,wonderful sounding preamp for my second system that is driving benchmark ahb2 amp and blumenhofer fs3 horn speakers.
The other one dcg3 is a balanced version with khozmo pot that is driving bryston 4b cubed and my pmc ib2i monitors.
It is a "by the book" version that works flawlessly, I mean no hums no buzz, dead quiet, sounds wonderful!
Many thanks to Tea Bag and of course to my friend Nick for their precious help.
I used two toroidy transformers and a 20k log pot from tkd.
The input selector is Salas and the power supply is dcstb.
It is a very accurate,wonderful sounding preamp for my second system that is driving benchmark ahb2 amp and blumenhofer fs3 horn speakers.
The other one dcg3 is a balanced version with khozmo pot that is driving bryston 4b cubed and my pmc ib2i monitors.
Attachments
Last edited:
By the way he brought it over yesterday for a quick check and I was surprised to only see 0.15dB output signal difference between channels when he uses a TKD 2CP-2511 20k conductive track log pot. Not a switcher with precision resistors.
I compared sine waves on the scope fed trough his DCG3 channels from one same generator output at low left turn, quarter left turn, half turn, and at the unity gain quarter past twelve pot positions. Its curve opens slower than classic 20k log, which is at unity at about 2 o'clock in the DCG3.
Can someone with same pot in DCG3 repeat the test? Because I remember track resistances by channel weren't as greatly close when I had measured it like a pot alone (post #4266).
The sound was also very OK in this combination, clean but relaxed and open as others had mentioned before. Given that there is also a 40ish Euro 2CP-601 TKD model better avoid an ALPS RK27 altogether. Its surely veiled in comparison, at least in this preamp, and there are also many RK27 fakes in circulation.
I compared sine waves on the scope fed trough his DCG3 channels from one same generator output at low left turn, quarter left turn, half turn, and at the unity gain quarter past twelve pot positions. Its curve opens slower than classic 20k log, which is at unity at about 2 o'clock in the DCG3.
Can someone with same pot in DCG3 repeat the test? Because I remember track resistances by channel weren't as greatly close when I had measured it like a pot alone (post #4266).
The sound was also very OK in this combination, clean but relaxed and open as others had mentioned before. Given that there is also a 40ish Euro 2CP-601 TKD model better avoid an ALPS RK27 altogether. Its surely veiled in comparison, at least in this preamp, and there are also many RK27 fakes in circulation.