Good day, I would like to increase the gain of my riaa mm. The amp only uses two twin tubes (ecc83+ecc88). Is there any way of doing that ? Unfo I cant find the schematics of the riaa anywhere even if I am pretty sure is taken from the riaa of Audio Innovation P2 using same devices. So let's presume the schematics is the below, what would u suggest in order to increase the 37db gain of present scheme ? Many tnks beforehands.
Ciampa.
Ciampa.
An externally hosted image should be here but it was not working when we last tested it.
Hi Ciampa. How long are your cables? That design does not work well with long cables as it is.
Replacing the E88CC with another high MU triode will definitely require an additional cathode follower. You could use a MOSFET to do that if space is limiting and we could set it so the circuit draws similar current as it now does. but if you really have an M2 then you have lotsa space to work with.
If your cables are long, then test it with really short ones... less than 15 cm. If that sounds decent, but you really need to use long cables, then we can easily try a MOSFET follower after the E88CC.
Ian
Replacing the E88CC with another high MU triode will definitely require an additional cathode follower. You could use a MOSFET to do that if space is limiting and we could set it so the circuit draws similar current as it now does. but if you really have an M2 then you have lotsa space to work with.
If your cables are long, then test it with really short ones... less than 15 cm. If that sounds decent, but you really need to use long cables, then we can easily try a MOSFET follower after the E88CC.
Ian
if you want to swap the E88CC then I would also suggest we calculate a correct bias point and appropriate anode load.
A high MU triode like ECC83 as a differential amplifier will not drive anything alone. It needs a follower.
BTW - the combination of ECC83 and E88CC should yield enough amplification for MM. This is why I asked about the length of the cables...
You could replace the E88CC with something else though.. like maybe 5751. but its NOT a drop-in replacement.
A high MU triode like ECC83 as a differential amplifier will not drive anything alone. It needs a follower.
BTW - the combination of ECC83 and E88CC should yield enough amplification for MM. This is why I asked about the length of the cables...
You could replace the E88CC with something else though.. like maybe 5751. but its NOT a drop-in replacement.
Last edited:
Yes I am. The PSU is different and implement two tubes (ecl82 + 6X5).
Wdould the ECC81 be a direct replacement w/out changes eventually ? I have a pair of 12AY7 whc shd have higher mu (45 instead of 44 of the ecc88). would this tube have low impedance enabling to drive a line without a follower ?
Otherwise I am wllng to rewrite the entire RIAA with the limit of the PSU Heater filaments whc is limited (I beleieve) to only two devices.
Yes the cable are short.
No, the heater connections would need to be re-wired. However, the ECC85 would work -it is a 12AT7 with an ECC88 pinout. If that circuit is correct you can just plug it in and try it without making any immediate changes. If it basically works well enough for you, then you could adjust (reduce) C3 and maybe increase R7 to 820R.
Probably not, and the gain would not be much higher than the ECC88 anyway.
Last edited:
Actually was a typo, 33 of the ECC88 vs 45 of the 12AY7 (6072). Do u reckon I cd give a try with an ECC85 ?
The ECC88 needs 6.3V between pins 4 and 5.
The ECC81/12AT7 needs 12.6V between pins 4 and 5, or 6.3V between pins 4+5, and pin 9.
So the ECC81 heater is not pin compatible with the ECC88. The ECC85 is compatible -they're probably quite cheap too, so yes you can give it a try.
Correct, didnt think about it ! Well tnks, will try to find an ECC85 then. Otherwise plate load/polarization all the same or ?
Right, if the above is the right circuit... however Audio Innovations and Audionote have been sharing similar philosophy for the past and cant find many others phono using the combination (ecc83/ecc8) other than M2 Riaa and AI P2.
Will def take the chance. Thks a lot !
Ciampa.
Ok, I don't consider myself an audio snob. But every time I have tinkered with 12at7 and it just never sounded right.
The ECC85 is basically a 12AT7 on a ECC88 base.. its a variable transconductance tube. It works very nice in the AGC circuit in VHF/UHF tuners. I just don't consider it for Hi-Fi any more.
I wouldn't want to mod a really nice audio-note phono amplifier this way. Your choice.
Is your cable long or short? Consider that simply trying a shorter cable might be even easier..
The ECC85 is basically a 12AT7 on a ECC88 base.. its a variable transconductance tube. It works very nice in the AGC circuit in VHF/UHF tuners. I just don't consider it for Hi-Fi any more.
I wouldn't want to mod a really nice audio-note phono amplifier this way. Your choice.
Is your cable long or short? Consider that simply trying a shorter cable might be even easier..
Attachments
This is a very unconventional topology!, you could get 38dB gain from two ECC88 tubes, without the use of the ECC83, and the passive network they employed!!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.