Hi ammel68 hope fully you can see this it is basically how it is connected.
I simply took the front end from Robert Nee Dance's preamp in Audioxpress and mated it together with the F6. The F6 I use the 9.1Volt Zeners for the Gate drive and I have used +- 20Volts for the supply to the HA5002 incredibly simple and effective.
I simply took the front end from Robert Nee Dance's preamp in Audioxpress and mated it together with the F6. The F6 I use the 9.1Volt Zeners for the Gate drive and I have used +- 20Volts for the supply to the HA5002 incredibly simple and effective.
No Mishkaa your eyes do not deceive you it is that BIG!
I have a confession to make it is actually a 600V to 120V 120V but supplied with 110volts so outputs 24V 24V. It was a spare transformer that was not doing anything but gathering dust on a shelf at work so I could not resist.
I have a confession to make it is actually a 600V to 120V 120V but supplied with 110volts so outputs 24V 24V. It was a spare transformer that was not doing anything but gathering dust on a shelf at work so I could not resist.
Hello,
Okay...so you have several different voltages powering the circuit...+-18V going to the HA5002, 38V going to the JFET's drain through R4 and +-33V powering the F6 circuit?
Sounds like that's going to call for more than one power supply.
Does the 5002 not run too hot with 18V supplies? I see on the data sheet that 22V is the maximum.
Is the 50K trimmer for controlling offset?
I assume it's okay to hang a volume pot on the end of R34?
Thanks...
Second F6 Build
Thanks to Mr. Pass and forum members and this thread, I have been able to complete my 2nd F6 build. This time I built with IR MOSFETs unlike the first one with Semisouth ones.
I re-purposed a F5 chassis. The chassis design has a fan pushing air thru back to back connected heatsinks.
The amp is biased at 680mV measured on 0.47 ohms resistor, going close to target 1.5A bias current. Offset is stable around 4 mV. The fan design is quite efficient and there is luke warm heat on the heatsinks. I used the 9.1v zeners in this.
Quickly connected up and heard the amp. It has the F6 sound signature that I am used to. Clean, detailed with very high resolution. No hum or hiss. No startup or power-off thumps or cone movements. Cannot make out the difference between the Semisouth and IR based builds. To my ear, they sound similar.
Attached are some pictures taken in a haste. They are not fugly. I need to tidyup my wiring.
Thanks for all the help.
Cheers
Anil
Thanks to Mr. Pass and forum members and this thread, I have been able to complete my 2nd F6 build. This time I built with IR MOSFETs unlike the first one with Semisouth ones.
I re-purposed a F5 chassis. The chassis design has a fan pushing air thru back to back connected heatsinks.
The amp is biased at 680mV measured on 0.47 ohms resistor, going close to target 1.5A bias current. Offset is stable around 4 mV. The fan design is quite efficient and there is luke warm heat on the heatsinks. I used the 9.1v zeners in this.
Quickly connected up and heard the amp. It has the F6 sound signature that I am used to. Clean, detailed with very high resolution. No hum or hiss. No startup or power-off thumps or cone movements. Cannot make out the difference between the Semisouth and IR based builds. To my ear, they sound similar.
Attached are some pictures taken in a haste. They are not fugly. I need to tidyup my wiring.
Thanks for all the help.
Cheers
Anil
Attachments
Have a look at the home site of the DIY Audio shop supplier - they have "spare" radiators.
Take this one, their biggest: Heatsink 300 X 40 H 210 mm at € 35 (USD 38?) it looks like a bargain !
Yes you are correct the preamp part of the circuit does indeed have various voltages. In fact the 38V is now 40V and the supply to the HA5002 is +-20V and they barely get warm.
I have been using this preamp for over a few months without issue. I will caution anybody working with these HA 5002 buffer chips they love to oscillate so careful grounding is needed. Since the Jensen transformer has winding resistances of 600 Ohm we are not driving the buffer too hard. Just a good clean sound is heard.
I have been using this preamp for over a few months without issue. I will caution anybody working with these HA 5002 buffer chips they love to oscillate so careful grounding is needed. Since the Jensen transformer has winding resistances of 600 Ohm we are not driving the buffer too hard. Just a good clean sound is heard.
xformer is declared as 600:600 , center tapped ....... when appropriately loaded
so , that's more as 150+150:150+150
however , loading here is much greater than 150 per secondary , and with unity transfer ..... go figure what's buffer loading
so , that's more as 150+150:150+150
however , loading here is much greater than 150 per secondary , and with unity transfer ..... go figure what's buffer loading
What Lundahl to choose?
this one looks good: LL1527 (1+1 : 1+1) +16 dBU or the LL1527XL +19 dB.
The LL1524 is of a different league: an output transformer (and that looks like what we are doing after the buffer?)
Who has hands-on experience? Glad to hear.
this one looks good: LL1527 (1+1 : 1+1) +16 dBU or the LL1527XL +19 dB.
The LL1524 is of a different league: an output transformer (and that looks like what we are doing after the buffer?)
Who has hands-on experience? Glad to hear.
Thank you for the link to the spare heatsinks.
As you stated, they look to be about 38 USD each and just $29 shipping for 2.
It looks like Europe is becoming competitive again !!! 🙂
I plan to also use their "economico" line of cases for an amplifier to which I will put the heatsinks and capacitors on top, not on side.
I can´t find the vishay RN55 RN60 any more.
Has anybody used the CMF series. The funny thing is that the CMF in the same size as the RN are rated to to double the power rating.
Has anybody used these? Which would you use for the F6.
The CMF55 are so small but rated at 0,5W at 70°C and 0,25W at 125°C
Has anybody used the CMF series. The funny thing is that the CMF in the same size as the RN are rated to to double the power rating.
Has anybody used these? Which would you use for the F6.
The CMF55 are so small but rated at 0,5W at 70°C and 0,25W at 125°C
The diff in rating is a mil-spec thing. They're suppose to be
the same:
http://www.vishay.com/docs/31018/cmfind.pdf
("Except for marking, the Industrial and Military versions are exactly the same")
Dennis
Well I finally got a set of boards, so ready to build minus power transformer. Try as I might I don't see where the recommended VA is listed? I'm building as stereo PS. Is there a Antek that will work?
AS-3218 - 300VA 18V Transformer - AnTek Products Corp
My understanding is this is the minimum which is out of stock. I used the 500 VA because that is what I had on hand of which they show out of stock also. They do show the 400 VA.
AS-4218 - 400VA 18V Transformer - AnTek Products Corp
My understanding is this is the minimum which is out of stock. I used the 500 VA because that is what I had on hand of which they show out of stock also. They do show the 400 VA.
AS-4218 - 400VA 18V Transformer - AnTek Products Corp
Much - much easier to avoid ground loops if you build the thing as dual mono. I.e. 2 transformers...
This implies the Lundahl transformers I mentioned look similar LL1527 (600 ohms, 1+1 : or the similar but higher voltage LL1527XL , but specifically not the LL1524.
Also LL1532 might be aa cheaper option.
The LL1527 core is a high permeability mu metal core. The transformer is housed in a mu-metal can. That is advantageous.
It would be good one too to interface witha DAC !
I sent an email to Per Lundahl about LL1582 and LL2811 regarding a possible group buy.
It would be possible to get the transformers directly from the factory if big enough order.
The cost would then become around 50e/pc.
Anyways, I would need to make a prototype to test it first.
The problem is, there is no such a thing as a free sample from Per and the cost of just one tranx is 100e...
We also must forget a JFET buffer if the xformers in question was used.
I was therefore thinking something like LME49610 or something...