Search found 15705 matches

by Nick
Thu Mar 28, 2024 9:21 am
Forum: Everyones Projects
Topic: GM70 Monoblocks’
Replies: 12
Views: 541

Re: GM70 Monoblocks’

I would hazard to suggest the el34 would be better than a DHT, far less microphonic as a driver valve. Why not just do what Phil does, make your existing amp the driver, replace the output TX with the interstage, then just add the gm70 output stage. At least as a prototype.
by Nick
Thu Mar 28, 2024 8:54 am
Forum: Everyones Projects
Topic: GM70 Monoblocks’
Replies: 12
Views: 541

Re: GM70 Monoblocks’

I think they can, though, I would think you might want to run that o/p stage b+ via a variac partly for the valve, and partly for room temperature. 125W in winter, maybe a bit less in summer (+ 60W heater power as well). In the amps I built Colin way back, that Andrew has now, I used a similar circu...
by Nick
Wed Mar 27, 2024 4:48 pm
Forum: Everyones Projects
Topic: OK…so I’m on wi’ summat
Replies: 149
Views: 30826

Re: OK…so I’m on wi’ summat

Oh, and I was quoting Mr Sowter "Junior". I used the past tense as he has now retired and Sowter Transformers sold.
by Nick
Wed Mar 27, 2024 4:46 pm
Forum: Everyones Projects
Topic: OK…so I’m on wi’ summat
Replies: 149
Views: 30826

Re: OK…so I’m on wi’ summat

Wound components these days are not wound for 243 volts as theyre imported and we said to the rest of europe our voltage is 230. But it isnt. No wound components from cheap sources have any reserves. More true for chokes you want to use as choke input. Mr Senior Sowter is right. Well, to be picky, ...
by Nick
Wed Mar 27, 2024 3:49 pm
Forum: Everyones Projects
Topic: OK…so I’m on wi’ summat
Replies: 149
Views: 30826

Re: OK…so I’m on wi’ summat

Yep its often ignored that the entire AC component of the rectified sine wave is applied directly across the choke (the coupling cap being a short at AC). The effect of that instantaneously being stopped at some point in the 100Hz cycle when its turned off is never going to be trivial. Brian Sowter ...
by Nick
Mon Mar 25, 2024 12:25 pm
Forum: Everyones Projects
Topic: Directly Heated 1619 SET
Replies: 18
Views: 461

Re: Directly Heated 1619 SET

Yep, anywhere from 600v-1200v and a GM70 in A1 is just a "simple" way of getting a bit more Set power. Once you get over the heater requirement its a nice more powerful cross of a 211 and a 845. I think a 7k load works well with it, but its generally ok with anything from 5k to 12k.
by Nick
Sun Mar 24, 2024 1:24 pm
Forum: Everyones Projects
Topic: OK…so I’m on wi’ summat
Replies: 149
Views: 30826

Re: OK…so I’m on wi’ summat

However after calculating distortion at youre operating point 2nd h is only 3.9%.
Just to put this in perspective, when I talked about high 2nd I was thinking 0.5% at most. Beyond that I would start to consider it a guitar effects box.
by Nick
Sat Mar 23, 2024 10:51 pm
Forum: Everyones Projects
Topic: Directly Heated 1619 SET
Replies: 18
Views: 461

Re: Directly Heated 1619 SET

Yes, I keep forgetting about the MoFo, a great and relativity simple power buffer that with the right speaker will sound exactly like whatever it is you put before it.
by Nick
Sat Mar 23, 2024 10:20 pm
Forum: Everyones Projects
Topic: Directly Heated 1619 SET
Replies: 18
Views: 461

Re: Directly Heated 1619 SET

But I do know the 300b has more 2nd distortion. I did a rough sketch in a hurry, I’ll find it and put it below in an edit. But I could only make 6 watts into 4K7 Again, just my take on this, but IMHO, I think comparing or even considering what the distortion is at full swing is misleading and missi...
by Nick
Sat Mar 23, 2024 6:51 pm
Forum: Everyones Projects
Topic: Directly Heated 1619 SET
Replies: 18
Views: 461

Re: Directly Heated 1619 SET

I see the strange 2nd harmonic reduction found in A2 operation because the left most curves pich together similarly to the right mose curves Yes, that's true, but what is going on is that you are getting more 3rd harmonic being generated. I found with the A2 211, that you needed a driver stage to g...
by Nick
Fri Mar 22, 2024 9:49 am
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9387

Re: 6550 SE Amplifier

by Nick
Fri Mar 22, 2024 9:18 am
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9387

Re: 6550 SE Amplifier

Eric has cap coupled to the A2 output stage which is supposed to cause “blocking distortion” in A2 Yep, it is a bit ugly that output stage. No need for quotes around blocking distortion, its a real thing and it will happen in that amp. he has tried to avoid it by using as big a coupling cap as prac...
by Nick
Sat Mar 16, 2024 12:21 pm
Forum: Solid State
Topic: Germanium Amplifier
Replies: 162
Views: 80900

Re: Germanium Amplifier

Just for reference, it's pretty much based on this - the 'Burns Orbit', which was a guitar amp apparently - I think -
What I love about that circuit is how much you can see valve thinking. Its basically a valve amp circuit with lower voltages and transistors.
by Nick
Fri Mar 15, 2024 6:46 pm
Forum: Everyones Projects
Topic: 6550 SE Amplifier
Replies: 110
Views: 9387

Re: 6550 SE Amplifier

I dont hear any 2nd so maybe the ecc88 is cancelling the worst of it? Answeers on a postcard.
I find in the absence of test kit, the clarity (or lack of) of the voice in this is a good measure.

by Nick
Thu Mar 14, 2024 8:32 pm
Forum: Assorted Stuff
Topic: Road vehicle fires.
Replies: 157
Views: 153645

Re: Road vehicle fires.

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