A 2 or 3-channel SE 'Horn-amp'

IslandPink · Post by **IslandPink** » Thu Jan 30, 2014 6:54 pm

Hi Romy
Thanks for the interesting comments.
There are quite a few, so I'll respond to them piece-wise , as I get time.
Firstly, have no fears over the phono amp, I will get you a link to the circuit somewhere, but that is shown elsewhere , briefly it's a passive RIAA design with Tribute 1:10 step-up on the input, then D3a/RIAA/D3a. The signal for this amplifier hence comes in at around 2V RMS typically .
However- this is not a low Z-out high drive pre-amp like yours, so it is not appropriate for my power-amp circuit to use the passive crossover elements on the input, like yours .

The later circuit, as-built, is on page 3 of this thread. There were a couple of useful changes/refinements .

Rest assured the amps have often been breadboarded in messy temporary fashion, and the other 300B amp remains in that fashion after 5 or 6 years to be honest. The implementation and valve choice for this amp has come from many experiments over the last 12 years of ( mainly) SE use.
One of the last changes was the use of the 4P1L - DHP - , which is the best driver I've found so far, after having tried C3m pentode, C3g pentode, and various triode drivers including a three-stage amp with ECC40-DCinto - 45(choke-loaded) - 300B for instance . I have heard the 6E5P in a local guy's amps , and quite like it , but I feel the 4P1L has many of the same advantages ( eg. up to 35ma driver current ) with the advantage of direct-heating ; although the advantage required us to develop an improved DHT filament supply to get the best out of it . This supply out-performs the Tentlabs and Coleman DHT supplies, and to some extent confounds your theory that this forum is a low-level sort of place.
More soon....

Romy The Cat · Post by **Romy The Cat** » Thu Jan 30, 2014 7:30 pm

IslandPink · Post by **IslandPink** » Thu Jan 30, 2014 8:07 pm

I think you occupy a different reality to me . That's your business and I'm fine with that, but I'll continue to work on the design & sound of my amps to acheive my goals. The other guys on here who are interested in amp building and are also friends of mine will continue to build some excellent amplifiers which may or may not inspire me to make changes on the circuit when I listen to them at our regular meetings.

Cressy Snr · Post by **Cressy Snr** » Thu Jan 30, 2014 9:27 pm

Romy The Cat · Post by **Romy The Cat** » Thu Jan 30, 2014 10:04 pm

IslandPink wrote:I think you occupy a different reality to me . That's your business and I'm fine with that, but I'll continue to work on the design & sound of my amps to acheive my goals. The other guys on here who are interested in amp building and are also friends of mine will continue to build some excellent amplifiers which may or may not inspire me to make changes on the circuit when I listen to them at our regular meetings.

Someone have interest in creating Sound by audio means. Somebody even knows why and for what. Somebody have interest to endlessly build senseless audio components. Someone have interest to use soldering, oscilloscopes, tube swapping and records polishing to furnish own social life. There is nothing wrong with all of it but they are of cause different realities, implying different objectives, different method and different reference points. It looks like your your friends do fine self diagnosing themselves. They shall switch to stamp collecting or accumulating of vintage pipe tobacco - there are many great male hobbies.

rowuk · Post by **rowuk** » Sat Jun 14, 2014 10:48 am

IslandPink wrote:The sound is getting better but I will have to get rid of the hum a.s.a.p. tomorrow morning !
See pic -

Is the hum gone? How does it sound? How did you end up implementing the crossover?

IslandPink · Post by **IslandPink** » Sat Jun 14, 2014 11:47 am

Yeh let me think . Hum I got rid of by changing the filament supply or something about the way I was using it - I forget !
It sounds fine, but wasn't used a lot before I went back to the 'workhorse' 300B amp ( using the two channels for upper/lower speaker ) to continue working on the speaker options. Since then I've had a total about-turn on the speaker concept . This will require some small re-working of the 2-channel amp when i get back to using it . This amp will now be driving a compression driver at 114db/w and an OB midrange speaker at ~97db/w . So, there'll have to be some thought about how best to attenuate the horn channel . Some of it will be done with some series resistance at the driver - maybe 8 to 15R , I've trialled this with non-inductive planar resistors .
Also, I might alter the upper channel on this amp to use a 45 .
Plus I need to install one or more of Andrew's final versions of the DHT filament supply .
So - still a work in progress, but this is the amp ( and I need to build a second one ) I will eventually use for the upper 2 ( most likely 3 - bullet tweeter coming in at eg. 8kHz with simple passive crossover ) in the final set-up .

IslandPink · Post by **IslandPink** » Sun Jul 20, 2014 12:06 pm

Ping ! Nick or Stephen ( Izzy Wizzy ) probably .
I'm going to use a pair of the K&K Audio CCS boards as anode loads in a small pre-amp for the bass channel ( to feed the Pass F4 ) .

Having built up the boards yesterday almost entirely, and drilled the holes, I'm now trying to find the circuit diagram and some application notes ... and failing .
On the PCB there is an adjustable 1k resistor ( supplied ) and a space ( part not supplied ) for 'Rset' . 'Rset' appears to be in series with the output ( neg terminal ) and searching suggests that part quality is important here.
I just need to know how to set the value .
There is a probably a similar resistor in the Gary Pimm SB CCS's, I remember chooing a MIlls WW in there, but at least Gary had a guide and equation to set the value of that .

pre65 · Post by **pre65** » Sun Jul 20, 2014 12:17 pm

I think that board uses a 10M45s chip, heres how I wired mine up. I usually use a 1K carbon for the grid stopper, and Rk from the chart on the 10M45s data sheet, but enlarge the graph if you want to read it accurately.

What ma are you aiming for ?

IslandPink · Post by **IslandPink** » Sun Jul 20, 2014 12:31 pm

Thanks Phil . The board uses two IXYS ( or DN2540 ) items, but your circuit is probably right for the lower Mosfet . K&K supply two-off 900R resistor which are I guess for setting the Mosfet bias(es) . Then there's an adjustable 1k and the 'Rset' . I'll be running about 15mA in these units supplying a 6N6P or a 5687 .

pre65 · Post by **pre65** » Sun Jul 20, 2014 12:33 pm

Mark, I edited my post above while you were posting.

IslandPink · Post by **IslandPink** » Sun Jul 20, 2014 12:35 pm

Have I made a mistake in using two of these IXYS things, just replacing the two DN2540's in the K&K boards ?
If the IXYS is an all-in-one CCS maybe I don't need two of them ?

pre65 · Post by **pre65** » Sun Jul 20, 2014 12:48 pm

I use just one on the anode of GK-71 driver.

slowmotion · Post by **slowmotion** » Sun Jul 20, 2014 12:50 pm

Which K&K boards do you have?

IslandPink · Post by **IslandPink** » Sun Jul 20, 2014 1:02 pm

They are the (small) cascode boards for DN2540.
I've built up two boards with DN2540's , and two with IXYS .
The IXYS devices Nick has given me are IXTP08N100D2 ; IXYS TS1223 S7206 .

audio-talk

A 2 or 3-channel SE 'Horn-amp'

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