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post #1051 of 1686
Can I use SOHA as a preamp?
I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
Thanks.
post #1052 of 1686
How do you know which way to face the BD139's, the lettering toward the alps pot or toward the heatsink? This is bottom mounting the heatsinks.
post #1053 of 1686
I'm pretty sure it is towards the front/pot.
I was just about to solder them so this is a good question =]

Edit: Comprehension failure. You're bottom mounting. Would they not face towards the heatsink then?
post #1054 of 1686
Quote:
Originally Posted by nattonrice View Post
I'm pretty sure it is towards the front/pot.
I was just about to solder them so this is a good question =]

Edit: Comprehension failure. You're bottom mounting. Would they not face towards the heatsink then?
Don't know very confusing.


Also is a 100 n capacitor big enough for the coupling C1's ?
post #1055 of 1686
For standard ECB devices such as BD139, MJE243, 2SC3422…:

- the lettering should faced the front side of the PCB (Alps pot) when top mounted, and...
- the lettering should faced the back side of the PCB when bottom mounted

Regarding the smaller value of C1, the HP filter is mainly determined by C1 = 0.22uF and R15 = 1MΩ.
With C1 = 0.1uF instead of 0.22uF, the corner frequency will be shifted a couple of Hz but a can work.
post #1056 of 1686
I noticed that my R15 from JRossel was only about .8 Mohm, I have a good fluke meter so I better go with the bigger cap. I have some russian 1 uF pio caps that I think I can make fit in the hammond.
post #1057 of 1686
Thread Starter 
There are mouting diagrams on the Cavalli Audio website under the Instructions/Device Mounting section.

These show top/bottom as well as different pin arrangement devices.

Gotta get you guys to read the website.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #1058 of 1686
Haha I've been at the bijou website for the past 2 days and didn't think of navigating to the soha2 page to check (palm to face).
post #1059 of 1686
Ask this question again. If it works, I can save money for a preamp and space.

Can I use SOHA as a preamp?
I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
Thanks.
post #1060 of 1686
Thread Starter 
Yes.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #1061 of 1686
Quote:
Originally Posted by yzriver View Post
Ask this question again. If it works, I can save money for a preamp and space.

Can I use SOHA as a preamp?
I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
Thanks.
You can of course, but do you want a pre-amp with a gain of 10+? My understanding is that pre-amps are usually unity gain.
post #1062 of 1686
Quote:
Originally Posted by rds View Post
You can of course, but do you want a pre-amp with a gain of 10+? My understanding is that pre-amps are usually unity gain.
The power amp is unit gain, and preamp has some gain. Am I wrong?
post #1063 of 1686
Quote:
Originally Posted by yzriver View Post
The power amp is unit gain, and preamp has some gain. Am I wrong?
That is possible I guess. But if an "amp" has unity gain then technically it's not an "amp", but a buffer instead.
My understanding is that a pre-amp attenuates the signal before it is fed to an amplifier. Hopefully someone more knowledgeable will answer this for you.

EDIT your GFA-5300 has a 29dB gain
post #1064 of 1686
Quote:
Originally Posted by rds View Post
That is possible I guess. But if an "amp" has unity gain then technically it's not an "amp", but a buffer instead.
My understanding is that a pre-amp attenuates the signal before it is fed to an amplifier. Hopefully someone more knowledgeable will answer this for you.

EDIT your GFA-5300 has a 29dB gain
you are right. I should be careful to use SOHA II as a preamp, at least to GFA5300.
I have a DAC, which output is 3.2V peak to peak. I think this output will blow away my power amp. Probably the SOHA II at here should be used as a attenuator.
post #1065 of 1686
Quote:
Originally Posted by runeight View Post
There are mouting diagrams on the Cavalli Audio website under the Instructions/Device Mounting section.

These show top/bottom as well as different pin arrangement devices.

Gotta get you guys to read the website.
But it doesn't show which side is which on the BD149's, the datasheet is no help either.
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