Radford TT100 - the saga begins...?

[nickbaba]

I took delivery of a Radford TT100 hybrid solid-state/valve amp today.

The last amp Radford made, solid state (FETs) inputs, valve output stage with 4x KT88s. Rated at 100w pc.

The price was low enough to tempt me to take a punt on it, sight unseen. The guy who sold it to me claims (!) he tested it and had it working before it was shipped to me, but tbh I daren't turn it on to test it before having it thoroughly checked over.

As you can see it looks very much in, shall we say, original vintage condition. It even has a funky old round-pin 3-prong plug on it. No idea what to do with that. The amp looks like it might have been recovered from a house clearance or something like that.

Sitting in the back are 4 original GEC Gold Lion KT88s, that have probably been in it since it was new! Most likely completely shot, I would guess.

Sadly the arrangements I made to have to shipped to me went horribly wrong - I booked a guy to collect it by hand and deliver it door-to-door by van. This guy then decided to book a courier for the job, without telling me, and pocket the difference as profit. What a scam. So the amp arrived by commercial courier, which is exactly what I wanted to avoid, and who knows how it was treated on the way? I can hear something loose rattling round inside the case. No idea what - best case scenario it's just a loose screw.

This kind of feels like it could be the start of a saga... I won't know until it gets checked over. It'll go off to David Coe at AD Audio for a thorough going over and I will report back after that.

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[Edward]

I'm surprised about the claim of it being tested as the tester presumably had to remove the old style plug to test. Why put it back on knowing it will not work.

Shocking behaviour on the part of the so called personal courier.

Hopefully David Coe will be able to bring it up without too much trouble and work.

I think the circuit diagram is on the Radford Revival website.



Via Tapatalk

[nickbaba]

I suspect the claim of testing prior to shipping to be untrue!

[montesquieu]

I think your instincts are spot on - that plug looks like it belongs in a museum. Definitely have it checked out.

I've heard of that sort of scam with these sorts of informal couriers - I was lucky enough to get a pair of Eatons hand-delivered from Glasgow in perfect order but I checked with them what the arrangements would be first. Mind you they took two weeks longer than promised but better that than trashed.

Will at Radford Revival has all the bits for these if it needs anything.

[montesquieu]

I'm surprised about the claim of it being tested as the tester presumably had to remove the old style plug to test. Why put it back on knowing it will not work.

Shocking behaviour on the part of the so called personal courier.

Hopefully David Coe will be able to bring it up without too much trouble and work.

I think the circuit diagram is on the Radford Revival website.



Via Tapatalk

I heard that David had just acquired some Tannoys, for which this amp should be just perfect ... Nick might be lucky to get it back ;)

[Edward]

I'd be tempted to open it up and have a look at the guts. Hopefully the loose item is just a stray screw or something like that. Also you can see if any obvious blown caps etc.

Via Tapatalk

[Edward]

I heard that David had just acquired some Tannoys, for which this amp should be just perfect ... Nick might be lucky to get it back ;)Yes indeed and I've seen a pic of said Tannoys. :) somewhat of a bargain I'd say.

Via Tapatalk

[nickbaba]

Oh - what Tannoys did David get? I must ask him about that.

(I love my RFC Cheviots and just got another pair of 12" HPDs to put into custom cabs to use as recording studio monitors.)

[WESTLOWER]

Oh - what Tannoys did David get? I must ask him about that.

(I love my RFC Cheviots and just got another pair of 12" HPDs to put into custom cabs to use as recording studio monitors.)

Canterbury SE

[Primalsea]

Nice one. I dont know what you paid for it but it doesn't look like it will be too hard to get it running like new. You never know, the KT88 might be worth testing, if you know someone with a valve tester. They may be OK and possibly worth something on ebay.

[nickbaba]

So... here's a quick update. I had the cover off this afternoon and took some pics inside. It all looks quite a mess to me but I don't really know about these things, or what constitutes reasonable condition in an amp of this vintage? Certainly a lot of grime and fluff in there. Maybe someone here could take a look at the pics and tell me what they reckon as to the state of the important bits.
The loose part rattling around was just a screw. It may have been part of fixing the 4 blue capacitors (I assume) in place, as that whole assembly has come loose and is wobbling about quite freely. The 4 blue tubes were all blue-tacked together presumably to hold them in place. In fact there's quite a lot of blue-tac in evidence inside.
The chap who sold it to me told me he tried it out by putting a modern plug on it, then replaced the vintage one to 'keep it original'. When I told him I was getting it checked out by a qualified tech to make sure it was working as advertised, he started getting a bit upset and implied I was trying to make trouble (!) and maybe I should just return it to him.
It's booked in for a visit with David next week. What do you think, should I stick or twist?

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[spendorman]

Did you buy on ebay? If so, and sold as used, it must be working, otherwise a refund is in order.

I guess the transformers are the most important parts.

[Wakefield Turntables]

See what David has to say. The TT is a very rare amp and probably one of the best. It's not a STA100 but a later update if you like. My Sondex S100 is another update from your TT100 and my Sondex ain't going anywhere so it migfrht be worth while getting a report from David, use this as a bargaining chip and see if you can get some more money from the seller, it may just pay for your repairs (if you need them). There should be NO blutack in that amp whatsoever. :nono:

[Edward]

Hopefully the transformers are still good to go. But even then Will at Radford Revival probably still has details of the original windings and can have new ones made up but ££.

Point David to the following page at RR which has schematics etc.

http://www.radfordrevival.co.uk/literature/tt100/
(http://www.radfordrevival.co.uk/literature/tt100/)

[Primalsea]

It loks like possible capacitor (4) and resistor (1) replacement, plus a bodged DIY upgrade with the yellow capactitors. Its a 600VDC circuit, so I think your right to get it checked out. I suspect the blue capacitors are replacements that are physically larger than the orginals and didn’t fit in the holders, so a bit of Bluetack was used.

With 600 volts running through there I’m astonished that anyone would do that. Amazing what goes through some peoples heads!

[nickbaba]

No. I didn't buy through ebay but I made sure to pay by Paypal with buyer protection (even though seller insisted on Friends & Family, make of that what you will).

I will definitely get it looked at by David before making a decision. As it is i would be nervous about even switching it on, it looks like a fire hazard to me!

[spendorman]

No. I didn't buy through ebay but I made sure to pay by Paypal with buyer protection (even though seller insisted on Friends & Family, make of that what you will).

I will definitely get it looked at by David before making a decision. As it is i would be nervous about even switching it on, it looks like a fire hazard to me!

Best tested with a light bulb is series with the mains, or a variac to bring the voltage up gradually.

[AD Audio]

Thanks for all the pointers for circuit diagrams etc guys. I'm looking forward to sorting this one out! And yes what better once sorted to test it on than some Tannoys!
Davidhttps://uploads.tapatalk-cdn.com/20180508/67e8c28c4c896f8ffa2d42b9d5d623b5.jpghttps://uploads.tapatalk-cdn.com/20180508/fd07904a71f06faf9f860871538b3376.jpg

Sent from my ONEPLUS A5000 using Tapatalk

[nickbaba]

oooh lovely, David! Hope to hear them one day!

[montesquieu]

With friends and family you have no protection at all ... though as Andrew says above this is a very rare amp and well worth getting sorted. Will is actually very reasonable when it comes to parts should they be necessary.

[nickbaba]

Yes, Tom, that's right.
The seller was insisting on a F&F payment (or bank transfer) he said because he didn't want to lose any money covering the Paypal fees, but I added the 4% onto his price to cover the fees myself and made sure I got buyer protection.
When I made that clear to him he wasn't best pleased about it, and tried to tell me that I was somehow in the wrong for having the temerity to try and protect myself and my money while buying vintage hifi off a stranger on the internet!

[nickbaba]

But agreed, I won't be returning the amp if there's any way David can restore it to its former glory. And it sounds like he's up for the challenge!

[Radford Revival]

Just for the record I have all the specs for these transformers if need be. As it happens I actually have a NOS pair of TT100 output transformers and a pair of newly wound ones to the same design (originally intended for another application).

[struth]

Very much a botched cap replacement but should be easily enough fixed by someone who cares. If its anywhere near fixable its worth spending a bit of money on

[Bigman80]

I hope this gets fixed, I think it will be worth it, even just for to boon of owning it.

Good luck!

[Bigman80]

For interest

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.it%2Fulk%2Fitm%2F232 748598271

Decent pictures of the guts.

[nickbaba]

Thanks for the kind offer of help, Will - you have a PM.

[Firebottle]

I doubt you will have much trouble in getting this amp back to perfect condition.
Here is hoping anyway. Good find from a 'questionable' seller, best of luck with it. :)

[AD Audio]

Had a look at the pictures this morning: blue tac......what can you say? I had a pre in a year or so ago whose innards were held together with Blue Tac. Any shock and there was a risk of something moving and shorting.......
David

[nickbaba]

For interest

https://rover.ebay.com/rover/0/0/0?m...2F232748598271

Decent pictures of the guts.

Hope my one will look like that one day!

[Bigman80]

Hope my one will look like that one day!Keep the faith. It will!!

[snowman_al]

It looks in fair condition to me. A couple of odd ripples in the top cover (was it upside down with the courier - you might have a claim?) and some scratches but that is its history.
Some less than perfect repairs / mods, but obviously someone has cherished it in the past and they are easy to correct / restore.
What are the circuit boards like underneath by the way?

The KT88s may be the icing on the cake. The original MO made ones last for ages, I've seen them with the base ring split open, no lettering left and nearly all the silver gettering has turned brown and they still function reasonably well! So those look in good order...

You asked, keep it or send it back? If you really want a more pristine or fully working one, send it back now. If you paid a reasonable price 'unseen' for it and factored in repair costs, stick with it (I would), where will you find another one?

Yes, again ''it will''.

[walpurgis]

Dents and other deformations in equipment casework can be dealt with by a good car restorer or bodywork specialist if you ask them nicely.

[nickbaba]

The dents/ripples in the top case were there already - I could see them in the photos used for the ad.

I'm very curious to get the 4 Gold Lion KT88s tested - if they're in good working order they are probably worth what I paid for the whole thing. But I'm not betting on it!

The price 'unseen' was definitely very reasonable, and leaves a healthy potential budget for work/restoration, bearing in mind prices I've seen for rare fully-restored and working examples.

[Edward]

Hope my one will look like that one day!

I've seen and heard some of David's work. Had a 300B amp of his here for a while. His work is of the highest standard - Rolls Royce standard.

[nickbaba]

Here are the 4 Gold Lions out of the TT.

Middle 2 look almost new - nice shiny silver getters sides and top. 1 on right looks OK on top, but the side getters are brownish, and on the 4th the getters look worn away/transparent. Black bases, look to be in good condition.
But looks can be deceiving, won't really know until they are tested.

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[Firebottle]

The look of the getter is pretty insubstantial in giving indication of the valve quality.
Unless it has turned white or a milky shade that indicates a leak or poor vacuum.
I have valves that have either almost no silver getter but are absolutely fine.

[nickbaba]

The TT was delivered to David today. The project has begun!

[nickbaba]

So... there is news, and it's not all bad!

Initial tests have been done and there is life in the old beast! Some bits were bodged by the previous owner(s) e.g. things stuck together with blu-tac instead of properly secured inside, and some parts need to be replaced due to age (old capacitors) but the good news is that the transformers test well and are working fine.

The scariest part was that apparently the power supply board had come completely loose inside and could have shorted 600v into the metal case if it were plugged in... :(

Anyway David gradually introduced voltage up to full power and all went well - he even said it doesn't sound too bad... at least for a first test.

So things are looking very hopeful.

[Primalsea]

That’s great news. Overall the amp looked fairly solid and build quality seemed good enough that it was an amp built to last, just had a few issues due to age and a bit of bodging, but don’t we all!

[AD Audio]

So... there is news, and it's not all bad!
The scariest part was that apparently the power supply board had come completely loose inside and could have shorted 600v into the metal case if it were plugged in... :(

Anyway David gradually introduced voltage up to full power and all went well - he even said it doesn't sound too bad... at least for a first test.

So things are looking very hopeful.

Nick's post is spot on in that the sound quality is very promising. A lot of lazy bass power and dynamics evident but the valves were new so it would be unfair to judge the remainder of the frequency range too critically. But in addition to the loose /Blue Tack mounted high voltage components the earth wire in the plug had come adrift, so any short could have resulted in a live chassis. And 600v could be fatal........

[AD Audio]

....... just had a few issues due to age and a bit of bodging, but don’t we all!

!!!!!!! :eyebrows:

[nickbaba]

the earth wire in the plug had come adrift, so any short could have resulted in a live chassis. And 600v could be fatal........

We can definitely say it was in a shocking state ;)

[AD Audio]

So, work is well underway on this beast! I've got my head around the mindset of the previous modder. As they say, a little knowledge is a dangerous thing and as the previous modder would say 'a lot of Blue Tack is a good thing!' I've pulled out enough to run a sales conference for a fair-sized company!

Apart from creating multiple ground loops in places, our modder made quite a few mods that nowadays you'd pick up from the internet, and applied them with pseudo knowledge and scant disregard for safety considerations. I'll be really interested to hear how this sounds once complete. I never thought I'd shed a tear for Maplins, but they were darn useful for sundry audio parts that now have to come from E Bay and Amazon.

Sent from my ONEPLUS A5000 using Tapatalk

[tapid]

Good luck with it David. Hope you can fit me A/I 500 in at some stage over the next few weeks or so for repair/ service ?, no rush though. b w

[AD Audio]

Thanks Brian and I could fit you in week after next if that works for you. The TT100 is all coming together now and will soon be ready for some testing. The modified power supply has all been ripped out and rebuilt to spec. Interestingly, the modder had converted the psu to choke input without changing the choke, resulting in a large voltage sag on the HT. In the original design, there is also a fuse carrying the 600v ht mounted on the chassis side, which I've now mounted internally as that was a bit of a safety hazard as somebody curious could simply unscrew the fuse holder cap and touch the live end of the fuse. Ouch! One of the 35 year old regulators had given up the ghost and so I've also rebuilt the driver stage power supply back to its original specification.

[tapid]

Thats great David, thanks. Confirm with you next week.

[nickbaba]

I was over at David's place today and heard the TT100 working for the first time. Very exciting. It was still on his workbench, and it was only with his phone as an audio source, and through unfamiliar speakers, but still... for the first time it played music!
And played it remarkably well, I thought. I'm saving any serious judgement for when I hear it at home with my Tannoys at last, but... it lives! David has done an amazing job restoring this amp to its former glory!

[WESTLOWER]

I was over at David's place today and heard the TT100 working for the first time. Very exciting. It was still on his workbench, and it was only with his phone as an audio source, and through unfamiliar speakers, but still... for the first time it played music!
And played it remarkably well, I thought. I'm saving any serious judgement for when I hear it at home with my Tannoys at last, but... it lives! David has done an amazing job restoring this amp to its former glory!

I hope the blutac came in handy elsewhere...but not in the Amp! ;)

[nickbaba]

The amp is officially blutac free. I imagine David won't need to buy any for a while.

[AD Audio]

Yep, I've got enough for a large scale conference tho when old it loses it's stickiness somewhat. Imagine, you have to service your amp not because the electrolytic are knackered but because the Blue Tack holding the thing together is failing.......

It does sound glorious even with reduced bias on one channel and I can't wait to test it out fully either! Just waiting for some replacement bias pots from Will, as these were a casualty of whatever burn out had occurred in that channel. Otherwise, the pcbs have been well patched, the solid state devices-two op amps, 4 transistors-have all been replaced and its raring to go. Transistors at 50p a pop really out the price of valves to shame!

[montesquieu]

Yep, I've got enough for a large scale conference tho when old it loses it's stickiness somewhat. Imagine, you have to service your amp not because the electrolytic are knackered but because the Blue Tack holding the thing together is failing.......

It does sound glorious even with reduced bias on one channel and I can't wait to test it out fully either! Just waiting for some replacement bias pots from Will, as these were a casualty of whatever burn out had occurred in that channel. Otherwise, the pcbs have been well patched, the solid state devices-two op amps, 4 transistors-have all been replaced and its raring to go. Transistors at 50p a pop really out the price of valves to shame!

In a way the TT100 is a footnote to history, Radford moved to solid state in the early 70s with the ZD (Zero Distortion) series but despite their stellar measurements, these were not as good sounding as the earlier amps (I owned one briefly). The TT100 came after these fully solid state amps and was a return to valves in the output stage, though it kept solid state for the input.

As I understand it, there's little difference on the output side between it and my earlier STA100, so it would be interesting to compare the whether there's any sonic difference between the later amp with the op amps and transistors, and the earlier one where the input side is the signature Bailey/Radford asymmetric splitter/driver arrangement essentially similar to rest of the classic STA series. I would expect them to sound pretty much the same.

[nickbaba]

Yes indeed - I'd also be very interested to hear the two side by side. Most hybrid designs favoured valves on the inputs and solid state on the outputs, but not Radford.

[montesquieu]

Yes indeed - I'd also be very interested to hear the two side by side. Most hybrid designs favoured valves on the inputs and solid state on the outputs, but not Radford.

Makes sense to me that it might work better the other way round especially with Radford's capability at output transformers .. of course solid state output is generally a lot cheaper to implement than doing valve output properly.

[nickbaba]

Well, not long now before I can strap it to the Cheviots and see what's what... did you get your STA100 back from Will yet, Tom?

[Wakefield Turntables]

I really love to see how the TT100, my Sondex S100 and the STA100 all compare against each other. Would be fun to have a bake-off! :lol:

[montesquieu]

I really love to see how the TT100, my Sondex S100 and the STA100 all compare against each other. Would be fun to have a bake-off! :lol:

... if only to agree 'yup all good' and just have some tunes ....

Mine got held up at the paint shop but Will has it back and and I'm hoping in the next couple of weeks.

[AD Audio]

What surprises me is how valve-like Radford have managed to make the op amp input stage. And the amp is uncannily quiet too. You are right Tom the other solid state bits are effectively mimicking the tube long-tailed pair phase splitter arrangement

Sent from my ONEPLUS A5000 using Tapatalk

[nickbaba]

So, I finally collected the TT100 from David yesterday, with great excitement. It's now home, hooked up to my Tannoy RFC Cheviots, EAR 834p and SL-1210.
I've been waiting to hear this amp since I bought it more than 2 months ago... no idea what to expect, beyond a brief audition at David's with his phone as the source. I was told that Radford's are a great match for Tannoys, but never heard one in action before.

And what's the verdict? Well, I'm happy to say it sounds phenomenal!
It is in pretty serious company, as it's on the heels of an EAR 890, my recently sold John Wood KT88 and going head-to-head with my trusty old McIntosh MA7000, but in my opinion the old TT holds its own with ease against those beasts.

Plenty of headroom with its 100w, and it has that valve-y liquid sound in the mid-range, like pouring velvety paint into my eardrums... vocals sound amazing, real presence and smooth flow in the mids, but lacking nothing in the bottom end. Perhaps not quite as pin-sharp and defined as the solid state MA7000 in the very top and bottom, but more than compensated for by the overall musicality of the sound.

Still plenty of listening to do, only had a couple of hours with it so far, but it put a big smile on my face for sure. I think its still going to be a while before it comes completely on-song, plenty of new and replaced parts that need to bed-in and get settled, and I think the presentation could get a little 'looser' and more relaxed with time, but even at this point it sounds very very lovely.

I'd like to thank David for the amazing job he did restoring this amp to its former glory, he went above and beyond the call of duty and really worked some magic on it. He certainly knows his stuff and no mistake, and it was a pleasure to deal with him at every step of the process. He took the amp from being basically a blu-tack'd together 600v deathtrap to a thing of beauty that will give many more years of top quality listening pleasure.

[montesquieu]

Awesome result - though not unexpected :)

[Edward]

Love to see some pictures ....

[Firebottle]

So, I finally collected the TT100 from David yesterday, with great excitement. It's now home, hooked up to my Tannoy RFC Cheviots, EAR 834p

I see you are using an 834P. Now you have a stellar power amp the 834 can be improved quite dramatically as well with some simple mods, see http://theartofsound.net/forum/showthread.php?58388-Phonostage-Bake-Off-08-07-18-Penkridge-*NOW-CONFIRMED*&p=993563#post993563

[WESTLOWER]

So, I finally collected the TT100 from David yesterday, with great excitement. It's now home, hooked up to my Tannoy RFC Cheviots, EAR 834p and SL-1210.
I've been waiting to hear this amp since I bought it more than 2 months ago... no idea what to expect, beyond a brief audition at David's with his phone as the source. I was told that Radford's are a great match for Tannoys, but never heard one in action before.

And what's the verdict? Well, I'm happy to say it sounds phenomenal!
It is in pretty serious company, as it's on the heels of an EAR 890, my recently sold John Wood KT88 and going head-to-head with my trusty old McIntosh MA7000, but in my opinion the old TT holds its own with ease against those beasts.

Plenty of headroom with its 100w, and it has that valve-y liquid sound in the mid-range, like pouring velvety paint into my eardrums... vocals sound amazing, real presence and smooth flow in the mids, but lacking nothing in the bottom end. Perhaps not quite as pin-sharp and defined as the solid state MA7000 in the very top and bottom, but more than compensated for by the overall musicality of the sound.

Still plenty of listening to do, only had a couple of hours with it so far, but it put a big smile on my face for sure. I think its still going to be a while before it comes completely on-song, plenty of new and replaced parts that need to bed-in and get settled, and I think the presentation could get a little 'looser' and more relaxed with time, but even at this point it sounds very very lovely.

I'd like to thank David for the amazing job he did restoring this amp to its former glory, he went above and beyond the call of duty and really worked some magic on it. He certainly knows his stuff and no mistake, and it was a pleasure to deal with him at every step of the process. He took the amp from being basically a blu-tack'd together 600v deathtrap to a thing of beauty that will give many more years of top quality listening pleasure.

Very well done! It Takes Nuts to purchase such a poorly conditioned Amp in the first place, no matter it's reputation. David Coe's work, commitment to a project and passion is top notch and I know he wouldn't rest until he'd cracked it and had it seriously singing.
10/10 all round chaps! Picture please!

[AD Audio]

Thanks for the compliments Guys. It was a great fun project, and, I too, was surprised by the sound quality produced by this beast. I've got some photos of the insides which I'll post when I get a chance. I'd like to thank Will at Radford Revival for lending a friendly ear for advice along the way! The biggest challenge was actually something stupidly simple: the bias voltage was incorrect on one channel which had had a meltdown previously. It's a simple circuit and despite replacing all the solid states bits it just wouldn't produce the correct bias. It turned out after a detailed comparison between the working and non working channels that it all boiled down to one transistor which was new......I had been supplied a BC213A and not a BC213L. These are essentially identical but with different pin outs:lol: And the print is only visible with a magnifying glass!

Pics to follow

[AD Audio]

I see you are using an 834P. Now you have a stellar power amp the 834 can be improved quite dramatically as well with some simple mods, see http://theartofsound.net/forum/showthread.php?58388-Phonostage-Bake-Off-08-07-18-Penkridge-*NOW-CONFIRMED*&p=993563#post993563

Certainly agree with this: the 834 is very modable for improved performance!

[nickbaba]

Not much to show pics-wise from my end - it's a big black box! But here's a couple, one round the back showing the 4 NOS GEC KT88s currently singing happily...
I'm sure David will post some shots of the juicy stuff inside in due course... I don't want to mess with the cover which is screwed into place and quite awkward to remove.

Thanks for the tip regarding the EAR 834p. As far as I know its un-modded, altho' it does have rolled tubes, which were in it when I bought it from RFC Paul. A Mullard and a couple of triple mica Philips 12AX7s if memory serves. I tried Telefunkens in it but didn't hear much of a change tbh.

I'll look into the Thorsten mods. David is currently building me a SUT with Hashimoto HM3s which I'll use to bypass the 834 MC input/internal trannies and go through the MM in. I'm keeping him busy this summer!

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[AD Audio]

Hi All,
Some pics attached. The main work undertaken was:

1. Replace mains lead and plug, inc. lead retention.

2. Replace mains cable currently used as speaker cable with correct cable from output transformers to sockets.

3. Replace 4 x main smoothing capacitors.

4. Install correct mounting brackets for main pus caps

5. Replace 11 other old electrolytic capacitors

6. Replace cathode bypass capacitors with Elna Cerafines

7. Remove and rebuild the driver boards adding correct insulation on 8 coupling caps to make safe and reliable

8. Re-wire and improve earthing arrangement (currently made through oxidised tag connectors)

9. Remove and rebuild power supply board with correct mounting on new brackets and stand offs, replacing capacitors and adding insulation where necessary

10. Replace cathode resistors with Mills audio grade non inductive

11. Re-wire and insulate mains switch

12. Re-bias amp for current tubes

13. Replace broken regulators in driver power supply and rebuild to original specification

14. Replace indicator light and reconnect power supply inc. mounting power supply board correctly

15. Reflow all connections on two driver amp boards

16. Replace bias pots

17. Trace bias fault on one channel

18. Replace faulty transistors and op amps in that channel

19. Repair broken tracks and reflow entire driver board on faulty channel

20. Upgrade coupling capacitors to Leclanche /Mundorf ZNs

https://farm2.staticflickr.com/1807/29495764668_6dcac9dcb3_t.jpg (https://flic.kr/p/LWrvdG)Rad3 (https://flic.kr/p/LWrvdG) by David Coe (https://www.flickr.com/photos/123420230@N05/), on Flickr

https://farm1.staticflickr.com/926/42649124034_99b8e1af6f_t.jpg (https://flic.kr/p/27YKUGJ)
rad2 (https://flic.kr/p/27YKUGJ) by David Coe (https://www.flickr.com/photos/123420230@N05/), on Flickr

https://farm2.staticflickr.com/1770/28496871977_ae5e71599a_t.jpg (https://flic.kr/p/KqaVdV)rad1 (https://flic.kr/p/KqaVdV) by David Coe (https://www.flickr.com/photos/123420230@N05/), on Flickr

Happy to answer any questions!
David

[Edward]

Good grief - that looks like pretty much like a rebuild.

Amazing quality David. I've had the pleasure of hearing some of your work and I have no doubt this Radford is similarly out of this world.

Are you inspired to do a build using similar circuitry to the Radford TT100?

Edward

[AD Audio]

Hi Edward, I was very impressed with the sound quality and very low noise of the circuit and in particular there was loads of grunt with my fussy Tannoy Canterburys. But being a valve man I'm thinking of doing something with the all valve STA circuit and seeing what that does with a pair of Tannoy Canterburys!

It's been really interesting turning some of my holy cows on their udders so to speak. Eg I'd always thought no feedback amps were my favourites and solid state driver stages-who'd want them in a valve amp? So seeing what Radford and others can do with properly implemented feedback and solid state opamp input stages has been a real eye-opener!

[Edward]

Yes that I believe Arthur Radford was so successful in his design in being able to reduce distortion to to vanishingly small levels via feedback - and oh yeah the iron grip his push pull ideas have on speakers such as Tannoys.

Edward

PS: Need to chat sometime with you on the PSU thing (the one Adam brought over) but no rush on that.

[nickbaba]

Yes the work was extensive, to say the least. However, sitting here listening to it right now I can say it was worth it, imho. Luckily David was up to the challenge, and the cost, while not insignificant, was still less than even a second-hand EAR or similar quality of amp.