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Old 26th Feb 2011, 11:51 pm   #1
MrElectronicman
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Default Valve tremolo circuit

Does any one remember a circuit for a valve tremolo, that may have been published in Practical Wireless, or some of the other magazines.
I remember building one when I was in secondary school, and the design may have come out of one of the Practical Mags, it would have been in the mid to late 1950's.

I have various designs using both triodes and pentodes but I cannot remember much about the one I built, it was a long time ago, and I would like to try to build it again.

Thanks for any insight.
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Old 27th Feb 2011, 10:56 am   #2
Mike Phelan
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Default Re: Valve tremolo circuit

If no luck with finding the circuit referred to, most of these used in electronic organs used a Wien Bridge as an LF oscillator, typically using a double triode.

Hammond used a set of LC sections scanned using a motor.

Note that tremolo is not the same thing as vibrato. Tremolo is an amplitude variation, vibrato is a frequency variation.
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Old 27th Feb 2011, 10:57 am   #3
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Default Re: Valve tremolo circuit

I have a copy of Babani Press No12 (HiFi, PA & Discotheque Amp Designs) which has designs for a 2 valve tremelo unit 1 x ECC82 & 1 x ECL86 and also a combined tremelo and vibrato unit using just 1 ECC83. Any use?
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Old 28th Feb 2011, 12:14 am   #4
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Default Re: Valve tremolo circuit

Thanks for the feedback.

The unit I had built those many year ago was only a tremolo, not a vibrato. As I recall there were two valves one of which was a pentode, and I think it may have been an EF80, I know this is an RF valve, but EF80's were everywhere, and thus cheap.

Anyway, I am going to go with one I have found that uses an ECC83 as a phase shift oscillator, and an ECC82 as a cathode follower, and see out it works out. It helps that I have a number of ECC8_'s and the 12A_7 equivalents to play with.
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Old 28th Feb 2011, 1:21 am   #5
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Default Re: Valve tremolo circuit

I wonder if this was part of the circuit used in the "PW Guitar Amplifier"? That certainly used an EF80 oscillator valve, as a phase shift oscillator I think.. The main amplifier used two 807's, and I think it dated from about 1965, plus or minus a bit.

If so, I have a very tatty PW "blueprint" somewhere. I will try and find it if that's the one, and happily scan it... it's a big sheet and in many shreds but the circuit should be recoverble at least.
Pete
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Old 28th Feb 2011, 11:05 am   #6
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Default Re: Valve tremolo circuit

The Wem dominator had a tremolo effect on it using an ECC83 I think.Quite a simple circuits as I recall,Andy
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Old 1st Mar 2011, 12:14 am   #7
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Default Re: Valve tremolo circuit

Hi DangerMan,

I would like to the see the cct. Might bring back some memories.
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Old 1st Mar 2011, 9:25 am   #8
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Default Re: Valve tremolo circuit

Hi MrElectronicman,
I've scanned the circuit diagram of the preamplifier and also, for what it's worth, the main amp. Now I just hope I've attached them successfully!
Pete
Attached Files
File Type: pdf DOC005.PDF (146.1 KB, 659 views)
File Type: pdf DOC006.PDF (130.2 KB, 532 views)
File Type: pdf DOC007.PDF (157.6 KB, 538 views)
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Old 1st Mar 2011, 9:12 pm   #9
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Default Re: Valve tremolo circuit

Hi DangerMan,

Thanks for the diagrams, they came through just fine.

I now have to find a good EF80, I had one in my box but when I looked at it closely the tip must have broken and the vacuum has gone.

The pre-amp looks very much like I one I am looking for, but in the mean time I have made a lash-up, and I mean a lash-up, using the ECC83.

When I left the UK many years ago now, I threw out most of my Practical Wireless and Practical Television magazines, and only kept a few. Unfortunately years later we had a flood in the basement and that put paid to the rest.
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Old 3rd Mar 2011, 11:30 pm   #10
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Default Re: Valve tremolo circuit

Wow this looks interesting iI would like to see Tterry Bbull,'s diagrams and am interested in getting a copy of his book. Danny.
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Old 4th Mar 2011, 11:18 am   #11
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Default Re: Valve tremolo circuit

I am sure any small signal pentode would do or even triode.
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Old 4th Mar 2011, 11:31 am   #12
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Default Re: Valve tremolo circuit

Quote:
Originally Posted by Danny View Post
Wow this looks interesting i would like to see terrybull,s diagrams and am interested in getting a copy of his book. Danny
Me too.

Al
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Old 4th Mar 2011, 11:46 am   #13
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Default Re: Valve tremolo circuit

You may be interested in also having a look at the tremelo circuit of the Heathkit PA-1 amplifier.
I posted the manual for it here : https://www.vintage-radio.net/forum/...2&postcount=13
It uses half an ECC83 as a phase-shift oscillator to modulate the screen grid of an EF86.

Andy
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Old 4th Mar 2011, 7:48 pm   #14
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Default Re: Valve tremolo circuit

Here is a pdf of the tremolo circuits I previously referred to. A couple expressed interest. I apologise for the poor quality but my scanner is not here at present so they were done quickly on a phone camera. You can just about make out the detail. If anyone wants a better scan send me a PM and I'll sort it out.
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Old 4th Mar 2011, 9:25 pm   #15
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Default Re: Valve tremolo circuit

Looks as if I have started something here. I now have a circuit working using an ECC83 and ECC82, and I am now going to try using an EF80.

I found these diagrams at following website, they look much like the ones in terrybull's pdf.

http://www.triodeel.com/studio.htm

There are some interesting circuits that use a phase shift oscillator to directly modulate the drive current of a couple of EL84's in push-pull. A bit of overkill if you ask me.

I like the idea of using a ring modulator for the vibrato, so I might try to incorporate this option as well.
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Old 4th Mar 2011, 9:36 pm   #16
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Default Re: Valve tremolo circuit

You are right MrElectronicman. The link you posted look precisely like scans from the Babani book and my pdf
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Old 9th Mar 2011, 10:31 pm   #17
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Default Re: Valve tremolo circuit

Hi There,

I’ve attached a picture of a Tremolo project in the Feb 1961 copy of Practical wireless; it may be the one you’re after?

If it’s the one I can do a better scan/copy for you.

I also remember Practical Wireless doing a complete valve guitar amplifier project in 1964. This used 807’s and the Radiospares De-Luxe output transformer.

Regards
Terry.
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Old 9th Mar 2011, 10:53 pm   #18
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Default Re: Valve tremolo circuit

Hi Valvepower.

A very elegant implementation there, using the variable slope characteristics of the EF80. To my mind it should sound very good.

Al
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Old 10th Mar 2011, 4:15 am   #19
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Default Re: Valve tremolo circuit

Hi .. mm very interesting - F J Camm's usual ingenuity, but its got to be mentioned the EF80 ISN'T strictly a Vari-Mu type - so by all means build the circuit, but then perhaps try popping in an EF85 or EF183 for smoother operation ?

BTW, Tremolo Pedantry:- SOME people used the term to mean pitch bend (eg a 'Tremolo arm') though it IS actually 'Vibrato' (says Wikipedia and the dictionary)

The only serious attempts at THIS (using, phase-rotation) are the aforementioned Hammond scanner - (wonderful ol' thing with a spinning 'distributor arm') and Magnatone guitar amps http://www.vibroworld.com/magnatone/ (DO read the diagrams - great stuff!) - who I suspect had shares in a Valve company, due to the mega preamp arrangement - Vox and fender used something far simpler, and concentrated on raw power !

Just my .02 worth - F J Camm Lives !
Pete G
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Old 10th Mar 2011, 11:05 pm   #20
MrElectronicman
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Default Re: Valve tremolo circuit

Hi Valvepower,

That's the circuit I was looking for, I see It was in PW in 1961, so it's about the right date give or take a couple of years.

Can you do a better scan? or shall I PM you?
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