Very Simple Hybrid Ampifier

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#301
Hi Guys

Jfets DO age if you run them too warm or too close to their voltage limits. Most hifi designers know to keep them cool and well within other limits. It is always a good idea to keep input devices cool anyway if not just for DC stability.

Toshiba has a warning in most of their data sheets that the device performance will be greatly compromised if operating die temp is higher than lower, and this is applied to chips as well as single devices.

Have fun
 
#302
Hi Borys,

Have you progress on 12AU7 and ECC88 IPS? You have talk on small Update. I recieve my two transformer for tube heater.
 

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#304
maxwell007 said:
What can I do with this ? 😀😀😀😀😀😀
Click to expand...
Dual triodes are always nice. But you europeans love the E88CC,
while we yanks lover out12AU7s. I like tubes also, so I have a
small stash.

I need two more KT77s for an amp. These are the oricinal GEC KT77.
If anyone finds some good stock at a good price please PM me.
I'd be willing to pay, or trade, tubes, caps, parts, etc.

Cheers,

Sync
 
#305
I have the ECC88 IPS playing every day in my workshop. I will have to finish up the enclosure to do the A/B test on both IPS boards. The ECC88 (siemens one) rocks on bass, the bottom end is really powerfull. I got some dead Yamaha receiver for parts, the transformer have already 7V for tube heaters (I will add only small resistor to lower it a bit). There is plenty faulty stuff on ebay for few $$, some of them are really good for DIYers.
Ill keep U posted.
 

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#309
borys said:
Terry
I am not using any delay circuit. All the supply goes at the one time, DC protect circuit does the job, after 5-6s the DC at the output is stabilised and speaker relay kicks in.
Very basic and simple circuit, never failed me down.
Click to expand...

I tried turning it all on at one time and the offset goes almost full rail. If you turn on the heater first for about 6-10 seconds the offset is only 2V or less and settles quickly. I'm not sure but it seems pushing voltage the wrong way through electro caps, even for a few seconds has to take its toll after a while.

How do you compare what you are seeing from the ECC88 compared to the 12AU7?
 
#310
Yes, there is full DC at the output for first few seconds but DC protection is doing the job OK.

Now I like more the ECC88, very pleasen sound with briliand bass, I have not tested the compensation as OS mentioned few posts back (but I am going to do thad anyway).
The hum spikes at the FFT are completly gone to compare to 12au7.
I will finish the enclosure and do the direct test.
Bot tube versions IPS are giving lot of background details but I think there is more in 12au7 tube.
 
#313
AKSA said:
Most hybrid amps need a separate, expensive power supply for the tube. This circuit does not, and is very easy to build. The only concern is the switch on, which is at least 11 seconds to stabilise the offset. Accordingly, I would suggest a single 100V rail, and this would require a coupling cap at the output - ensuring offset controls during switch-on AND speaker protection is incorporated in the design very simply. It could then permit a whole series of other triodes since the Vak would now be around 100V.

Cheers,
Hugh
Click to expand...

Hi, I like this idea (+100 V single rail), but there are a lot of fruity things that stick at a -45V rail. Is as simple as to refer all these to 0V and put an output cap, or some -Ve supply will still be needed?
 
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