Joe Malone wrote:
glbaudio wrote:I'm working on a couple of Mac + INX5 with a Lundahl LL1539 (wired as 1:1) and a 2520 DOA clone on output...
I'm watching about the differences between the INX5 and the LA500...
- i see in the LA500 R4 in an half of R3 (as R6 is an half of R5), this means that the gain of the input stage is an half
Yes as it sets the input headroom to be correct. You will have unity in and out at the moment as you are using a 1:1 instead of the 1:2 fro output transformer. But it is best to drop the input 6dB when it changes from balanced to unbalanced so clipping doesn't occur in the input stage. But when you do this you will need to add 6dB gain to the output amp due to the 1:1 output transformer by changing the gain pot to 10k rev log.
- R13 is 470R instead 51R in the INX5
should i do those changes in my 2 INX5?
It should actually be changed to 1k like in the MAC kit to limit the makeup gain to 20dB (1k due to R16 = 20k on INX5. 470R due to 10k on LA500)
Do u think i still need the RV2 Gain?
No the makeup pot on the front panel is RV2
P.S. the pict is old, now i've substited the led (now wired to the VuMeter Led) with a switch...for the link!
tnx Joe, done all the changes, but the out was really strange (35dB less), so i have shorted the trafo and the difference is much less: 4,6dB (measuring with Pro Tools and an M-audio Firewire410, generator on one track, and reading value on another track, in bypass i read exactly the gerator value). Still strange.
This means my trafo is wired uncorrectly or broken...ok
this the datasheet: how should i wire it?
Anyway, actually with the makeup pot at 10K (this unit have the double track, wired only one) and R16 at 20K, i can trim the VuMeter only with "digital" signals, if i try to trim it with analog value (-20dB/-18dB digital) is not possible...
i'm using OPA2604 in input and a cloned 2520 DOA in output
The VU meter is a Nissei TR-35 0dB=1.288V DCR= 650Ω If=450uA