That worked, thanks for the tip 

 

In other news, I fixed the offset-issue. Didn't have to do anything except realize that the servo op-amp is a dual-OP and not the usual OP27   Note to self, read the schematic properly FFS!

 

 

//UFN

what value of input pot should be used on squarewave klone? read 10K somewhere before but I can't find it

 

or maybe should use higer value like 50K/100K since it's fet input? thanks

Edited June 18, 201511 yr by ang728

well I do 10k, just because I don't want too many different versions in stock.

 

but 50k or 100k works fine for this

Thanks !

 

well I do 10k, just because I don't want too many different versions in stock.

 

but 50k or 100k works fine for this

finally finished the build with some sp style wiring 

 

 

I like that one a lot!!    I have a pile of these that I need to finish at some point as it is a really good amp. 

 

Any troubles with that feedback switch? 

I like that one a lot!!    I have a pile of these that I need to finish at some point as it is a really good amp. 

 

Any troubles with that feedback switch? 

Thanks!

 

besides not as "hi gain" as I thought , actually they work well .Love that sound with switch on 

 

btw,I am curious about how does this feedback design work in the circuit , any paper or keywords that I can learn from ?

Edited October 9, 201510 yr by ang728

What would the current draw be for a balanced version? Inside or outside GRLV range ( think I saw 1,5 amps somewhere)?

 

26 minutes ago, MLA said:

What would the current draw be for a balanced version? Inside or outside GRLV range ( think I saw 1,5 amps somewhere)?

I put them on lab bench psu before,can't remember what's exact number of current draw,but I'm sure under 1.5A

then built a slimmer case version a while ago using orginal GR and works pretty well

Edited April 5, 201610 yr by ang728

Brilliant, thanks!

On 2 december 2014 at 10:03 PM, kevin gilmore said:

about 120ma, measure across the 10 ohm resistors

Just double checking: 120ma, not mv? Can't get near the ma version, so thought I'd ask before pulling things apart...

120ma thru 10 ohms is... 1.2 volts

at least that is what I remember

 

39 minutes ago, MLA said:

Just double checking: 120ma, not mv? Can't get near the ma version, so thought I'd ask before pulling things apart...

YES,it's 120mA,you should have 1.2V reading across 10R

but 100mA-110mA sounds best IMO

Great, thanks! Can't get more than halfway there, so I've screwed up somewhere... Makes for a nice evening of troubleshooting

Ok, not so long evening, a bad solder joint it was. Nice and steady at 120 ma now. Guess I have to go watch a movie instead. Boring

Many thanks for both of your very quick responses!!!

Edited September 2, 201610 yr by MLA

Sorry for refloating this thread.

I'm listening to my "SquareWave KG latest version" in SE configuration. (Thanks Dr. Gilmore)

It works great and is very simple to assemble. I have regulated the BIAS @ 120mA without problems and could even raise it much more.

I have used a 100K resistor to make the servo act as fast as possible and from the beginning the offset is 0 Vdc so I don't need wait for listening music. I matched all the transistors as best as possible but with the MJE200 and MJE201 it was impossible to find an identical pair. ?

The next step is to install it in a box but I'm hesitating, Is it worth making a balanced version? Is there much difference between the SE vs. Balanced version?

I have enough material and pcb´s to do this without problems but if this does not make sense, I'll leave it in SE configuration.

Edited October 7, 20187 yr by jose

probably not worth making a balanced version, the output impedance is not super low.

Thanks Dr. Gilmore. 

 

 

Yesterday I was listening to the Square Wave with different headphones (hd800, W5000 ....) and I was wondering if the output impedance changes when changing the gain (Low to High)?

I understand that if he does it, I do not know exactly how much or if the change is very radical.

Just warmed this up, sounds terrific. Think I'll populate the other two boards for a balanced Squarewave.

 

I'm glad to see another Squarewave alive. 

Sorry how does this amp sound compared to the dynalo? 

19 minutes ago, Rossliew said:

Sorry how does this amp sound compared to the dynalo? 

mostly the same

The Squarewave does not sound bad but IMHO dynalo is superior: More balanced, more musical ...

 

Thanks. Thought the Squarewave would be a nice complement to the Dynalo.