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GM70 an 813 strapped in SE-UL - circuits?

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Mush

Mush

Member
Joined 2005
I have admired and learned from your page for years. I need to thank you for this. Thank you Sir.

I have studied your 845 (all of them), GM70 and 813 designs. They are beautiful.

I still can't figure out which tube to use. Graphite GM70 costs almost nothing. Some people hate it, some love it. Copper GM70 costs a fortune. 813 has a plate cap and that's terrifying. 845 now costs a fortune. Which one will sound good, cost little and last for years?

Unfortunately your designs cost much more than I can afford. Even Lundahl costs too much. I am in the Edcor $83 range. Is there a cheap alternative to the Bartolucci interstage?

Thanks very much and I hope you are doing wonderfully.
 
A

audiodesign

Banned
Joined 2005
The 845 ampl. is still in progress and until now I don't have found a valid interstage so I will continue to test some protopytes by Bartolucci.

In all these 3 amp. the most of the cost is not in the tubes but in the trasformers.

900 euro for the less expensive version of Bartolucci is not a few money but these components are better than the more expensive Tango 2500$ or Audionote.

There is no other less expensive components on the market with the same characteristics.

Here we are speaking about a no compromise project to get the best performances never ear.

The GM70 copper and 813 RCA are both valid choices to create a reference amp. to drive any kind of loudspekers.

I am testing some custom power supply transformers designed on my specification by F.I.A.T. with a low cost.
 
B

Bandersnatch

Member
Joined 2003
Cobra2 said:
I like the designs, but it would have been more interesting for the DIY-world if the interstage-trafos could be replaced by some cheaper sollution.
Maybe a "PowerDrive" (TubeLab-style).

Arne K
Click to expand...

hey-Hey!!!,
Look at Pete Millett's site, and look up his AudioXpress article on the E-Linear KT88 amp. I have gone PP, and found the topology *VERY* scaleable. I have some built with type 4E27 which upon rigging for 10V filament supply will take type 813 directly.

http://www.pmillett.com/
http://www.pmillett.com/elinear.htm

cheers,
Douglas
 
A

audiodesign

Banned
Joined 2005
I cannot consider as valid the Powerdrive:

http://www.tubelab.com/powerdrive.htm

It is and hybrid circuit with many limitations.

To skip the interstage trasformer cost there are 2 real solutions:

1) interstage capacitor and inductance load
2) direct coupled with stacked power supply and inductance load

In both the cases we need a good inductance near to 70-80 euro each so 150 euro for a pair instead of 300-350 euro for a pair of Bartolucci interstage transf.
 
otto88

otto88

Member
Joined 2007
Andrea

“To skip the interstage transformer cost there are 2 real solutions:
1) interstage capacitor and inductance load
2) direct coupled with stacked power supply and inductance load”

The lower cost is attractive.

Can you elaborate a little on those two, in particular how would the sound quality of these alternatives be, and would the first be simpler?

Overall would you recommend either the interstage capacitor or direct coupled.

Thanks
 
A

audiodesign

Banned
Joined 2005
Are you sure these two options are cheaper ?

In both these two cases it is necessary a choke per channel

http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_PLATE_CHOKES_22.html

110 euro each

and in the first case also a good cap like

Mundof Supreme
Auricap
Audyn Cap Plus
Jensen Copper Film paper in oil

20 euro each

so we have 2x110+2x20=260 euro

Both the intestages cost only 300-350 euro and no capicitor can give the same neutral sound
 
Gluca

Gluca

Member
Joined 2004
A choke is much cheaper than a transformer and a direct coupled stacked supplies amp does sound much better than an interstage coupled amp. Been there, seen there. I tried the the 813 as well a couple of years ago and I liked it. I preferred graphite anodes (GE) to metal anodes (RCA).

As said, you have two supplies and it would take 5mins to convert that amp to a DC amp recycling the interstage as a choke *without* any capacitor. And, frankly speaking, a cap is free of the many drawbacks the interstage transformers have.

Gianluca
 
kevinkr

kevinkr

Administrator
Joined 2004
kta-hifi.net
Paid Member
Gluca said:
A choke is much cheaper than a transformer and a direct coupled stacked supplies amp does sound much better than an interstage coupled amp. Been there, seen there. I tried the the 813 as well a couple of years ago and I liked it. I preferred graphite anodes (GE) to metal anodes (RCA).

As said, you have two supplies and it would take 5mins to convert that amp to a DC amp recycling the interstage as a choke *without* any capacitor. And, frankly speaking, a cap is free of the many drawbacks the interstage transformers have.

Gianluca
Click to expand...

Except if you want to run A2 then capacitors have big drawbacks..
 
Gluca

Gluca

Member
Joined 2004
kevinkr said:


Except if you want to run A2 then capacitors have big drawbacks..
Click to expand...

:D

That amp won't like A2, just like mine. My point is that an interstage is not an easy piece of iron to wind, much easier and cheaper is a choke and Andrea's amp has two separate power supplies: I see only good reasons to stack them and direct couple the stages. But this is just my take on the subject.

gianluca
 
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