Next suggested build after F5

[anilva]

Folks,

I have just finished building an F5 amp. Very happy with the entire process as well the outcome in terms of sound quality. I will post the pictures of the completed amp in the pictures section soon.

My question is what is the next logical build after a F5 build? It would help if the next amp has higher wattage and a different sound signature. I am not scared of build complexity. My sources are analog as well a digital. My speakers are Fostex full ranges, Altec Onkens and Tone tubby OBs.

Thanks in advance.

Cheers.

[anilva]

No volunteers for giving advice?

[Russellc]

Originally Posted by anilva

No volunteers for giving advice?

Im in the same boat, I have completed F-5 and am looking for whats next. My considerations are:

1 I have Peter Daniels Aleph J boards,

2 several of BrianGTs Aleph boards, Aleph 30 or Mini Aleph

3 And most interesting, is EVULs Balanced F-5 thread, thats
what Im going for next!

Also, Have boards for more F-5 builds, altering feed back will give more gain. Also in the quest for more F-5 gain, I have ordered ZenMods Pumpkin Pre amp.

Russellc

[EUVL]

Circlotron.

I have published a circuit a while ago.

The New-Tron

Complexity is not in the amp, but in floating power supplies.
Yes, I have build a few versions, using 2 pairs 2SK1529's and also 2 pairs IRFP250's.

F5-X after F5 is no challenge.


Patrick

[Melon Head]

Hi Rusellc

Have you tried connecting your cd player directly to the amp (F5).
I did this just the other day and the volume is more than what my wife could put up with. I don't have efficient speakers either (somewhere between 87-90 dB).
I think I have changed my philosophy about this. Instead of increasing the gain of the amp, I am actually considering reducing the gain of the amp so I can connect directly from my cd player.
My plan is to have two gain settings - ie stock setting of 6 and another reduced setting possibly 4.3.
To get the gain setting of 4.3 I am planing on putting another 100 Ohm resistor with a switch in parallel in the feedback path this will drop the resistance from 50 to 33, when switched on. This will allow me to switch between the two settings depending on the situation. I find I rarely adjust the volume much anyway so I don't really need a pot. Two settings is probably enough for me.

Back to topic
My vote also goes to circlotron, if you can wait a bit Nelson will be releasing a circlotron, so you possibly might like to combine some of the ideas of Patrick's version with Nelson's version.

I would also consider F3 even though you say you want more power.

[Tea-Bag]

The F3's gain is less than the F5 for sure. I've listened to it, and prefer the F5 on full rangers with OB. F5 makes a good bass amp too.

The F5 is a super fine sounding amp.

One of the finest and simplist amp's I've built is a D-Lite using a SemiSouth R100.
It's not as precise, but the tone is really good. You just have to wire as a enhanced mode, not depletion FET.

[EUVL]

The idea of a direct connection to source is OK, but you should consider some form of volume control at the source, e.g. by changing the R of the IV converter.

Changing the gain of the F5 through the feedback resistors has 2 effects. It increases the NFB, and hence reduces closed loop THD. But it also reduces your stability margin. See e.g. a OPA637 which is not unity gain stable, compared to a OPA627.

There is already not a lot of stability margin in the F5.


Patrick

[Melon Head]

Yes I understand all of that, and I will be checking it in the lab for stability.
I like to try different things, the traditional attenuator while practical is a boring solution. If I have to use an attenuator I will, but I am determined to try this idea.

The idea of changing the gain out of the cd player is also a good idea (one which I have already considered), but at the moment i am not in a position to try this. I need to build a DAC first.

[massimo]

Originally Posted by Melon Head

My vote also goes to circlotron, if you can wait a bit Nelson will be releasing a circlotron, so you possibly might like to combine some of the ideas of Patrick's version with Nelson's version.

Really?

[Melon Head]

Yes,
He will probably only release a basic circuit though, but that doesn't mean we can't work off that to build our own creation.
The thing that I am most interested in is he how he will manage to overcome the poor PSRR of the circlotron.