Pumpkin Preamp - Perfect for F4

[3GGG]

Nah, some di*k put the led's in reverse. Need to order more IRF510's. Need to diagnose what else may have been damaged :-(

 

[Andy5112405]

Correcting the LEDs may not have caused any further damage.

Mine had track shorts around the LEDs and, once corrected everything was fine.

 

[3GGG]

Definatly need to get two new matched pairs of IRf510's. Both are shot.

 

[Zen Mod]

yup

LED CCS , without other current path , tried to fill their gates with 3-5mA , and pull them all way up

so - they go poof because of excessive Ugs , not because of excessive current

 

[3GGG]

How hard are these to match, if I buy 10 should I get two matched pairs if from the same batch or is it a bit more variable than this. Everything else looks ok I think.

 

[Zen Mod]

10 will suffice , considering that those are for CCS load duty ;

just for fact - upper ones (9510) are more important , matching wise

 

[3GGG]

Thanks Zen. The 9510 look ok, touch wood.

 

[3GGG]

I put some IRF840's in and the unit test's fine(very brief test). I have 15 IRF610's coming from an Aussie eBay dealer so hopefully they will come within a few days.

All i need now is a pot, I am thinking could I use part of the lighternote I have currently in use? One concern is the minimun volume setting as I am building 110db sensitive horns?

 

[Zen Mod]

lighternote ?

link please

 

[3GGG]

sorry
Lighter Note Kit - ALL YOU NEED

Udailey's take on the Lightspeed

 

[Zen Mod]

what gain you need from ?

 

[3GGG]

Not sure, I am not that smart or knowledgable, still learning.

Amp's are Aleph J's which are nearly finished.

Out of interest the complete system will be as follows
Diy Slate and acrylic TT
http://www.diyaudio.com/forums/analogue-source/168284-my-tt-build-3.html
Dl103R Cart

HPS 5.1 Phono
http://www.diyaudio.com/forums/analogue-source/167360-hps-5-1-a.html

Pumpkin

Aleph J's

4 Way horns
Fane 8m, 200hz LeCleach
Yamaha 6681b 400hz LeCleach
Fostex T500A MKII
Bass TBA

I hope to avoid digital X-Over so am looking at Passive line level for X-Over.

 

[jacco vermeulen]

I am not that knowledgeable - Diy Slate and acrylic TT - HPS 5.1 Phono

Could have fooled me.

 

[3GGG]

Could have fooled me.

My skills are best used on the hands on building part. The technical side is where I am laccking and slowly learning.

So what gain should I set Pumpkin to and how do I go about working this out.

Cheers

 

[Zen Mod]

set Pumpie for - say - 4x gain

meaning - input resistors in range of 15K , feedback resistors in range of 62K-68K

 

[3GGG]

thanks again Zen

 

[tonimxp]

Here's my Shuntky / Pumpkin Stereo Pair

All I can say is ABSOLUTELY STUNNING

The GREEN GROUND wire that you see at the top left was experimental during build, it was eventually tidied away but connected to the IEC socket instead of the screw hole used in the photo.

Zen-Mod is wonderful and very helpful, I had a few problems which were quickly and easilly resolved. That is the DIY spirit.

An externally hosted image should be here but it was not working when we last tested it.

Incidentally the two transformers were not used, one for each channel. I just happened to have 2 x 50VA 20-0-20V Transformers which were perfect for 40-0-40V use.

Hi Andy and good year !Please why did you use that connection between the heatsink and chassis? You've got yourself a problem of background noise initially? It seems to me that by touching with my hands sinks the noise varies, please could you give me some advice?

Thanks in advance

Antonio.

 

[lhquam]

What is the preferred front-end (voltage gain stage) for a single-ended F4?

I am looking at the BA3 FE, Pumpkin, Blowtorch, and various opamps. The difficulty is getting enough voltage swing and a voltage gain of 6x or better with low distortion, particularly higher order harmonics.

 

[Zen Mod]

if you ask me - BA3 Bal FE , or

 

[3GGG]

Did anyone use Pumpkin to power high efficient speaker, e.g. 110db+
I have a 98% built pumpkin and might try it with my horn rig.