Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Instruments and Amps Everything that makes music, Especially including instrument amps.

Building a pair of valve combo-practice-amps
Building a pair of valve combo-practice-amps
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd February 2018, 01:14 AM   #21
thoglette is offline thoglette  Australia
diyAudio Member
 
thoglette's Avatar
 
Join Date: Dec 2008
Quote:
Originally Posted by Bigun View Post
For learning, I expect it to be mostly clean.
If you can find a Vox Pathfinder 15R cheaply, grab it.

It's got some of the best clean tones you'll find at a budget price point. With tremolo and an OK spring reverb thrown in.

Yes, your valve amp will sound better. But if you're anything like the rest of us it'll be constantly on the bench being "improved"

Quote:
Originally Posted by Gnobuddy View Post
Check out Gilmourish.com
+1 gilmourish.com is a damn good read even if you're not interested in Mr Gilmour.

Last edited by thoglette; 22nd February 2018 at 01:19 AM. Reason: Fix spelling!
  Reply With Quote
Old 22nd February 2018, 01:34 AM   #22
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Building a pair of valve combo-practice-amps
No, I can't go buying an amp now, I'd never finish the darn thing I've started ! besides, I have a Traynor on loan from a buddy.

Now the sides are glued on. The box is one solid piece of glued up wood. Well, it's hollow. Nice chunky pine and a pair of boxes 17.5" x 16" x 8.75". I think that's a good size.

Thanks for the encouragement Gnobuddy and the link to Gilmourish is great ! much for me to mine from there although I don't think my Tele is the best starting point necessarily but who knows what might be possible :-)
Attached Images
File Type: jpg final glue-up.JPG (845.1 KB, 90 views)
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

Last edited by Bigun; 22nd February 2018 at 01:56 AM.
  Reply With Quote
Old 22nd February 2018, 02:58 AM   #23
Gnobuddy is online now Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by Bigun View Post
I don't think my Tele is the best starting point necessarily but who knows what might be possible :-)
On DVD, I've seen Gilmour play half a dozen different electric guitars during a single show. If you're not looking, you may not hear a change of guitars at all. Gilmour with an electric guitar in his hands always sounds like Gilmour.

I bet if you gave David Gilmour a tennis racket for a guitar, and a fifty-cent coin for a guitar pick, he would still manage to produce sounds so beautiful they make our noisy minds go quiet for a second.

It's only us lesser mortals that feel we need to have exactly the right equipment to get anywhere!

That said, IMO, the most useful guitar pedal you can own is a graphic EQ. It's astonishing how much you can change the sound of a guitar (or an amp, or an FX pedal) with one.

It looks like your amp is coming along fast, nice work!

-Gnobuddy
  Reply With Quote
Old 22nd February 2018, 03:05 AM   #24
thoglette is offline thoglette  Australia
diyAudio Member
 
thoglette's Avatar
 
Join Date: Dec 2008
Quote:
Originally Posted by Gnobuddy View Post
I bet if you gave David Gilmour a tennis racket for a guitar, and a fifty-cent coin for a guitar pick, he would still manage to produce sounds so beautiful they make our noisy minds go quiet for a second.
There's a nice video of DG playing a solo on an acoustic guitar on Seymour Duncan's
How to sound like David Gilmour page.

Yes, he still sounds like him. (He does crack out a pedal for the solo)
  Reply With Quote
Old 22nd February 2018, 05:47 PM   #25
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Building a pair of valve combo-practice-amps
I need to pick a power transformer. As my sister is in the UK it means one that works with both Canadian and UK supply voltage & frequency. Locally I can get Hammond iron. There seems to be two choices

a) 260A ($60) 200-0-200 @40mA and 6.3 @1A
b) 369EX ($65) 190-0-190 @75mA and 6.3 @2.5A

The first one is lighter in weight (I think) which is a benefit. Nothing to choose based on price difference. But I fear the first one doesn't have the VA for the job as I'll be using all of it's current capacity and plus I plan to use a capacitor input filter after the rectifier so the transformer really should be rated at more current. My experience with Hammond power transformers is that they run really hot if pushed. So I'm seeing the 369EX as the only option here. Unless you know otherwise ? (Edcor say, in not so many words on their website that most of their transformers are build to order so they have long lead times and I'm not that patient).
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 22nd February 2018, 09:00 PM   #26
Gnobuddy is online now Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by Bigun View Post
So I'm seeing the 369EX as the only option here.
The schematic you posted uses a 250-0-250 transformer secondary, and a full-wave rectifier. I can't for the life of me think of a good reason to do that, when you can use a single 250V secondary and a diode bridge to get the same DC voltage.

If you're willing to provide the heater power from a cheap switch-mode DC power supply, use a bridge rectifier, and settle for 230V AC (rather than 250), this might be an option, at half the price of the Hammond: A41-43-230 Bel Signal Transformer | Mouser Canada

The datasheet is here: https://www.mouser.com/ds/2/643/A41-1131073.pdf

In the USA, wire both primaries in parallel and both secondaries in series to get a nominal 230V AC. In the UK, wire both primaries in series, and also both secondaries in series, so you have a 1:1 ratio, 230V:230V transformer.

There is a beefier (80VA) version as well, but the price difference from the Hammond vanishes: A41-80-230L Bel Signal Transformer | Mouser Canada

I would expect somewhere between around 330 - 350V DC using a bridge rectifier and capacitor with a 230V secondary. That seems about right for a 6V6, at least in my world (not Leo's.)

Something like this ( TRG1506-A-11E02-Level-VI Cincon | Mouser Canada ) should happily supply the heater power you need for an EF86, a 12AX7, and an EL84 or 6V6.

With DC heater power, you no longer need black magic to get hum-free performance. In 1930 you had no choice, but here in 2018, DC heater power from a switch-mode power supply makes so much more sense than the ancient alternative.

You may be able to tweak the nominal 6V DC up to 6.3V DC - there is often a trimpot inside these switching power supplies.

Alternatively, you can use a supply that puts out more than 6.3V, and drop the excess voltage in a power resistor. I use a Sony 8.4V switching power supply in one of my amps, with a series resistor to drop the voltage down to 6.3V at the heaters.

-Gnobuddy
  Reply With Quote
Old 22nd February 2018, 10:32 PM   #27
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Have you looked at the Hundred Buck amp thread here? You might find some tips to cut costs.
  Reply With Quote
Old 22nd February 2018, 11:15 PM   #28
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Building a pair of valve combo-practice-amps
Hi Guys,

some interesting options !

I must admit I'm wasn't feeling comfortable with the SMPS option simply because I wanted to build with parts I can see and touch and repair rather than use modules that are essentially a black box - it's not so much a rational issue as an emotional issue !!!

Cost is not a prime driver, but I like the 'challenge' of using up parts and materials I have at hand and then buy the minimum to achieve the goal. It's a perverse pleasure really since I could easily buy an amp and have done with it but I like to make things.

I could go with the Bell transformer you recommended and add a Hammond 266JB6 heater transformer for a traditional supply. The total weight is about the same as a single 369EX and the cost a bit less but not enough to worry about. The advantage of the separate heater supply is no rectifier pulses from the HT supply leaking into the heater circuit. The advantage of the 369EX is that it's encased and therefore a much safer option for anybody sticking their hand up inside the box when the power is on.

Gnobuddy - good catch on the schematic as I hadn't notice the supply voltage. Most of the other AC4 circuits seem to aim around 250V but the one I posted is closer to 300V (allowing for the 50V drop across the power supply 1k series resistor). I guess anywhere in this range is going to do the job.


My guitar teacher has asked me to practice with a metronome. It has been a most irritating experience, like being micromanaged or something - I bet Gilmour didn't have to do it.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 22nd February 2018, 11:52 PM   #29
LeftHandFool is offline LeftHandFool  United Kingdom
diyAudio Member
 
Join Date: Oct 2017
Location: Carlisle, UK
Quote:
Originally Posted by Bigun View Post
My guitar teacher has asked me to practice with a metronome. It has been a most irritating experience, like being micromanaged or something - I bet Gilmour didn't have to do it.
I'll bet he did...

Regardless, practicing to a metronome is something you'll thank yourself for persevering with in the long term.
I'd been 'playing' for well over a decade before I knuckled down and learned to play in time. Boy, were those bad habits hard to break!

Do yourself a favour and do it right from the off. Trust your guitar teacher, they know best .

Matt.
__________________
www.falderguitars.com
  Reply With Quote
Old 23rd February 2018, 12:02 AM   #30
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Quote:
Originally Posted by thoglette View Post
There's a nice video of DG playing a solo on an acoustic guitar on Seymour Duncan's
How to sound like David Gilmour page.

Yes, he still sounds like him. (He does crack out a pedal for the solo)
I like this one: YouTube
  Reply With Quote

Reply


Building a pair of valve combo-practice-ampsHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Kicking a dead pig - upgrading low-end practice amps ericj Instruments and Amps 30 30th June 2017 01:30 PM
Less than 1w practice guitar amp Tube Valve tehmessiah Instruments and Amps 11 20th December 2016 03:01 AM
Digital source and valve amp combo. Good or bad set up? matt scarlett Digital Source 17 18th May 2015 06:11 PM
TAD TH-4001 horns plus a pair of Brass tweeter combo danVeyron Vendor's Bazaar 1 4th May 2014 02:14 PM
Building combo amp for stage piano MBAnderson Construction Tips 4 29th July 2012 09:15 PM


New To Site? Need Help?

All times are GMT. The time now is 05:35 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki