So wondering if it's best to:
1) use a 1:1 IT and a 1:2 step up at input
2) use a 1:2 IT and no step up at input
3) use a choke load and cap and a 1:2 step up at input
Will be for a triode 6V6 input stage for a SS amp.
Looking for gain if 15- 20 ish.
Concerned about how to maximize bandwidth and also minimize noise and microphonics.
I already have a choke that will work with the 6V6 (EP 30mA 100H choke)
Thanks!
Thanks!
1) use a 1:1 IT and a 1:2 step up at input
2) use a 1:2 IT and no step up at input
3) use a choke load and cap and a 1:2 step up at input
Will be for a triode 6V6 input stage for a SS amp.
Looking for gain if 15- 20 ish.
Concerned about how to maximize bandwidth and also minimize noise and microphonics.
I already have a choke that will work with the 6V6 (EP 30mA 100H choke)
Thanks!
Thanks!
Use a choke loaded el84 for 20ish gain. I think 100H choke is fine.
Regards
Regards
Because I want to. LoL. I don't know... Just really want to use 6V6 triode mode. There are a million 6V6 varieties and I have read good things about sound out of 6V6 triode.
Sorry.
What will feed this stage i.e. a source or a pre? And output impedance for the source or the pre.
Regards
What will feed this stage i.e. a source or a pre? And output impedance for the source or the pre.
Regards
Member
Joined 2009
Paid Member
factor of two not worth all the pain, just use with choke load for gain of 9.5 and it will be fine. An extra few dB gain will not make much difference.
your source, if modern, likely puts out more than enough signal to the input
keep that choke away from any power transformers, best if inside a steel box (many options from Hammond) in order to avoid hummmmmmm
your source, if modern, likely puts out more than enough signal to the input
keep that choke away from any power transformers, best if inside a steel box (many options from Hammond) in order to avoid hummmmmmm
A CD player or network player through a TVC volume control to the amp. So no gain on preamp. Output stage is a MOSFET power follower. A 6V6 running 30mA should easily be able to drive it.
My initial thoughts are to go with the 1:2 input transformer and use the 100H choke and cap couple it (2.2uF).
Just need to find a nice 1:2 input transformer.
My initial thoughts are to go with the 1:2 input transformer and use the 100H choke and cap couple it (2.2uF).
Just need to find a nice 1:2 input transformer.
Yeah I could just do the choke load and no input transformer and it may be all the gain / power I need.
Member
Joined 2009
Paid Member
for input transformer I would go with Tamura, Sowter or Lundahl. But you may not want one at all and do you really want to feed a nice tvc into a step up ? With all those transformers it should be possible to avoid a coupling cap.
Also: check the spec on your source, it’s likely putting out at least 2Vp-p (and likely closer to 3Vp-p) which after your choke loaded tube stage gives your MOSFET 19Vp-p. Allowing for, say, 5V across the FET for good performance that means you’ll be able to fully exploit your amp with up to +/-24V rails or single 48V rail (less if choke loaded too). That’s a lot if you consider you’ll be running more than 3A through it for an 8R resistive load and more needed for most speakers - I mean it’s going to be dissipating lots of heat already.
Also: check the spec on your source, it’s likely putting out at least 2Vp-p (and likely closer to 3Vp-p) which after your choke loaded tube stage gives your MOSFET 19Vp-p. Allowing for, say, 5V across the FET for good performance that means you’ll be able to fully exploit your amp with up to +/-24V rails or single 48V rail (less if choke loaded too). That’s a lot if you consider you’ll be running more than 3A through it for an 8R resistive load and more needed for most speakers - I mean it’s going to be dissipating lots of heat already.
Last edited:
It will be a choke loaded mosfet with 24v supply. Cap coupled to speakers.
So maybe just go with the choke on 6V6 and cap couple it to the mosfet.
So maybe just go with the choke on 6V6 and cap couple it to the mosfet.
Sounds impressive. Where is the evidence you built this?
Or abandoned again as were many of your other dreams. And on & on.👎
The triode wired 6V6's plate impedance, rp, has to drive the MOSFET's varying gate capacitance versus signal swing.
You might experience early high frequency rolloff; also the gate's capacitive load impedance at high frequencies might cause the 6V6 to distort.
A triode wired 6V6, its plate that is loaded by a very high impedance load, has a gain of about 9 or 10.
YMMV (Your Mileage May Vary).
If you post a schematic, it is worth 1000 words.
You might experience early high frequency rolloff; also the gate's capacitive load impedance at high frequencies might cause the 6V6 to distort.
A triode wired 6V6, its plate that is loaded by a very high impedance load, has a gain of about 9 or 10.
YMMV (Your Mileage May Vary).
If you post a schematic, it is worth 1000 words.
I can try to come up with a schematic. For now:
But essentially it would be a 6V6 with say a Sowter 9525. The output stage would be the MoFo Mosfet Source Follower:
https://6moons.com/audioreviews2/mofo/mofo.pdf
I would need to figure out how to connect them. Thoughts are to pull that 2.2uf coupling cap. Put the bias circuit on one end of the IT transformer secondary and the other to the gate of the Mosfet.
Input capacitance of a mosfet source follower is:
- Ceffective =approx= CGD + {CGS * (1 - Gain)}
I know I have another thread about parallel 6v6 as an output stage... I just throw around the idea of both of these. Not sure if one is better than the other. Not built either yet. I have built tube amps and also have built a source follower based on an IRFP240N and a Nelson Pass CCS. Both sound awesome. Also heard about how the 6V6 triode sounds stellar and has extremely low distortion.
So thats where I am at.
I love to bounce ideas off the group here as it gives me inspiration to move forward with a project. Sometimes I have too many projects and ideas though. lol.
Thank you for the understanding.
Richard